Mee - Elevator.pdf

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Chapter 32╇ Vertical Transportation: Passenger Elevators

load‐weighing control, door and platform detection beam equipment, speech synthesizer (if used), and visual displays.

ELEVATOR S ELEC TI ON   32.28╇GENERAL CONSIDERATIONS The selection of elevators for any but the simplest buildings requires the simultaneous consideration of several factors: adequate elevator service for the intended building usage, economics, and the architectural integration of spaces assigned to elevators, including lobbies, shafts, and machine rooms. In large buildings, many combinations are possible because these factors are interdependent. The selection of an optimum system for such buildings is most practical and accurate with the aid of a computer or simulator, and their use has become standard practice in the industry. Hand computation, following certain guidelines, can yield good results for small, straightforward buildings and reliable preliminary data for almost all buildings. The design criteria usually used in determining elevator service quality are

• • •

Interval and average waiting time Handling capacity Travel time

The elevator system selection process, either by hand or computer, involves matching these three criteria with estimated performance values. Design intent (for example, acceptable service or excellent service) will inform the choice of numeric values for the criteria.

32.29╇DEFINITIONS Fig. 32.17 Typical car operating panel. Designs of these panels vary widely, but the essential components are as shown.

Definitions of important terms, including variant usages, follow. Average lobby time or average lobby waiting time. The average time spent by a passenger between arriving in the lobby and leaving the lobby in a car. This is a key selection criterion.

HANDLING CAPACITYâ•…1477

Handling capacity (HC). The maximum number of passengers that can be handled in a given time period—usually 5 minutes, thus the term 5‐minute handling capacity. When expressed as a percentage of the building’s population, it is called percent handling capacity (PHC). This is a key selection criterion. Interval (I) or lobby dispatch time. The average time between departures of cars from the lobby. Registration time. Waiting time at an upper floor after a call is registered. Round‐trip time (RT). The average time required for a car to make a round trip—starting from the lower terminal and returning to it. The time includes a statistically determined number of upper‐floor stops in one direction and, when calculating elevator requirements based on up‐peak traffic, an express return trip. Travel time or average trip time (AVTRP). The average time spent by passengers from the moment they arrive in the lobby to the moment they leave the car at an upper floor. This is a key selection criterion. Zone. A group of floors in a building that is considered as a unit with respect to elevator service. It may consist of a physical entity—a group of upper floors above and below which are blind shafts—or it may be a product of the elevator group control system, changing with system needs.

32.30╇INTERVAL OR LOBBY DISPATCH TIME AND AVERAGE LOBBY WAITING TIME In an ideal installation, at least from the riding public’s point of view, a car would be waiting at the lower terminal on the rider’s arrival or would be available after a short wait. Because cars leave the lobby separated in time by the interval (I) and passengers arrive at the lobby in random fashion, the average waiting time in the lobby should be half (50%) the interval. Field measurements show, however, that it is actually longer than this. The figure most often used in the industry is 60%—that is, Average lobby waiting time = 0.6 × I

Table 32.4 lists intervals and suggested values for office buildings and the related average waiting

TABLE 32.4╇ Recommended Elevator Intervals and Relateda Lobby Waiting Time Interval (sec)

Facility Type

Waiting Timea (sec)

OFFICE BUILDINGS 15–24 25–29 30–39 40–49 50+

Excellent service Good service Fair service Poor service Unacceptable service

9–14 15–17 18–23 24–29 30+

RESIDENTIAL Prestige apartments Middle‐income apartments Low‐income apartments Dormitories Hotels—first quality Hotels—second quality aBased

50–70 60–80 80–120 60–80 30–50 50–70

30–42 36–48 48–72 36–48 18–30 30–42

on the relationship: waiting time = 0.6 × interval.

time based on the foregoing relationship. Because some control systems zone the building in such a way that some cars do not return to the lobby, the interval as a figure of merit may be somewhat misleading in such buildings. The table also lists recommended intervals for other types of buildings. With intervals in the recommended range, riders are not conscious of any irksome delay in elevator service. Consciousness of delay is considered a major drawback in rental desirability and should be avoided for all traffic conditions except morning and evening peaks, when a certain delay is expected and therefore tolerated, however grudgingly. Even in peak periods, any modern group supervisory system will recognize a timed‐out call—that is, a call with a registration time exceeding 50 seconds—as a priority call. Priority calls are answered by the first available car, usually within 15 seconds. If a considerable amount of interfloor traffic is expected during peak periods, as may be the case when a large company occupies several floors of a building, elevator capacity should be increased by 20% to 40% over the capacity otherwise calculated, to maintain proper intervals.

32.31╇HANDLING CAPACITY The frequency, or interval, with which a car appears at the main building lobby is one of the two factors that determine the passenger capacity of an elevator

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Chapter 32╇ Vertical Transportation: Passenger Elevators

system. The other is the size of the elevator car. The system’s handling capacity is completely determined by these two factors—car size and interval—and is independent of the number of cars. This can be best understood by visualizing an elevator system as a single set of doors that opens periodically (the interval) to remove a given number of passengers (the car capacity) from a patiently waiting group of would‐be passengers. Whether the set of doors represents a single car or many cars that take turns is immaterial. The only factors that determine the handling capacity are passenger load (car capacity) and frequency of loading (interval) (Table 32.5). Note is taken of the fact that during peak traffic periods, cars are not loaded to maximum capacity but typically only to about 80%—a figure determined by actual count in many existing installations. As a convenient measure of capacity, the handling capacity of a system for 5 minutes is taken as a standard. This is because a 5‐minute rush period is historically used as a measure of a system’s ability to handle traffic. This may be expressed thus: handling capacity (HC) = passengers/car × cars/sec × 5 min × 60 sec/min

Because the number of cars per second is the reciprocal of the interval (e.g., 30 seconds between cars is the same as 1⁄30th of a car per second), this equation reduces to HC =

passengers/car interval × 300

HC =

300p I

or

TABLE 32.5╇ Car Passenger Capacity (p)

a

Elevator Capacity lb (kg)

Maximum Passenger Capacity

Normal Passengera Load per Trip

2000 (907) 2500 (1134) 3000 (1361) 3500 (1588) 4000 (1814)

12 17 20 23 28

10 13 16 19 22

The number of passengers carried on a trip during peak conditions is approximately 80% of the car capacity.

TABLE 32.6╇ Minimum Percent Handling Capacities (PHC) Percent of Population to Be Carried in 5 Minutes

Facility

OFFICE BUILDINGS 12–14 11.5–13 14–16

Center city Investment Single‐purpose RESIDENTIAL Prestige Other Dormitories Hotels—first quality Hotels—second quality

5–7 6–8a 10–11 12–15 10–12

aDue to more urgent traffic demands, particularly at the school and work exodus.

where p is car loading (number of passengers/ car). When the interval is 30 seconds, the system’s handling capacity is 10p, a convenient figure to remember. To establish a figure of merit for building service, system HC must be related to building size. This is normally done by establishing the minimum percentage of the building population that the system must handle in 5 minutes, called PHC. A good system for a diversified office building will handle no less than 12% of the building population. Similar values are shown in Table 32.6 for various types of facilities. In planning a building’s elevator requirements, its population must be estimated. This is particularly difficult in speculative‐type, diversified‐use buildings. However, based on rental cost, area, and building type, a fair estimate can be made. Population estimates for office buildings are based upon net area—that is, actual available area for tenancy. Table 32.7 gives suggested density figures, and Table 32.8 gives average office building efficiency values for use in calculating net area.

32.32╇TRAVEL TIME OR AVERAGE TRIP TIME The average trip time (or time to destination) is the sum of the lobby waiting time plus travel time to a median floor stop. Car round‐trip time is also used as a performance criterion, but it is not as meaningful as trip time. In a commercial building

ROUND‐TRIP TIMEâ•…1479

TABLE 32.7╇ Population of Typical Buildings for Estimating Elevator and Escalator Requirements Building Type OFFICE BUILDINGS Diversified (multiple tenancy) Normal Prestige Sing∫le tenancy Normal Prestige HOTELS Normal use Conventions HOSPITALS General private General public (large wards) APARTMENT HOUSES High‐rental housing Moderate‐rental housing Low‐cost housing

Net Area FT2 PER PERSON (M2/PERSON)

110–130 (10–12)a 150–250 (14–23) 90–110 (8–10) 130–200 (12–19) PERSONS PER SLEEPING ROOM 1.3 1.9 VISITORS AND STAFF PER BEDb 3 3–4 PERSONS PER BEDROOM 1.5 2.0 2.5–3.0

aDensity

may vary for different floors. Clerical and stenographic areas may have a population density as high as 70 ft2 (6.5 m2) per person.

bIf

visiting hours are restricted, the visitor population will determine elevator requirements. If visiting is not restricted to a certain few hours, staff requirements may determine elevator design. Where traffic is heavy, a combination of passenger cars and larger “hospital” cars should be used to provide optimum service.

context, a trip of less than 1 minute is highly desirable, a 75‐second trip is acceptable, a 90‐second trip is annoying, and a 120‐second trip is the limit of toleration. In the more relaxed atmosphere of a residence, where interval alone can account for

a minute or more of trip time, these maxima are revised upward. Figure 32.18 shows that the 2000‐ and 2500‐lb (907‐ and 1134‐kg) cars used in residential buildings can have a 17‐story rise, even with a 60‐second interval, without excessive trip time. The 3500‐lb (1588‐kg) car, however, which is almost universally used in office buildings (Fig. 32.19), is limited to a maximum 16‐floor local run before exceeding the 90‐second limit and to about 6 to 8 floors to stay within the 75‐second criterion. An important reservation on the foregoing statements must be noted. The curves presented in Figs. 32.18 and 32.19 are based upon statistical calculations, empirical data, and field observations, as discussed in the next section. This being so, the average values that these curves give should be considered to be ±15% accurate, and borderline cases can be shifted either way. Designs that show high travel time on paper frequently work out well in the field, because lobby loading is often less than 80%, upper‐floor stops take less than the statistically predicted time due to groups of people going to the same floor, and staggered working hours relieve traffic peaks. Also, a feature called high‐call reversal takes account of the fact that cars do not travel to the top of the shaft on each trip, but reverse at the topmost call. This can reduce the average trip time by 5% to 10%. Finally, sophisticated solid‐state traffic controls allow for rapid acceleration and deceleration without discomfort, variable door‐closing time, and very efficient selection of landing call responses, all of which can further reduce the trip time by another 5%.

TABLE 32.8╇ Office Building Efficiency Building Height 0–10 floors 0–20 floors 0–30 floors 0–40 floors

Net Usable Area as Percentage of Gross Area Approximately 80% Floors 1–10 approximately 75% 11–20 approximately 80% Floors 1–10 approximately 70% 11–20 approximately 75% 21–30 approximately 80% Floors 1–10 approximately 70% 11–20 approximately 75% 21–30 approximately 80% 31–40 approximately 85%

Source: Reprinted from G. R. Strakosch, Vertical Transportation, Elevators and Escalators, 2nd ed. John Wiley & Sons, New York, 1983. Note: Applicable to buildings with 15,000 to 20,000 gross square feet (1394–1858 m2) per floor.

32.33╇ROUND‐TRIP TIME The value for round‐trip time during up‐peak traffic conditions, used for calculating elevator requirements, is composed of the sum of four factors: (1) time to accelerate and decelerate, (2) time to open and close doors at all stops, (3) time to load and unload, and (4) running time (Figs. 32.20–32.22). Physically, round‐trip time is the time from door opening at the lower terminal to door opening at the same terminal at the end of a round trip. Because the actual number of stops made by a car is unknown, a statistical probability value is used, based upon the passenger

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Chapter 32╇ Vertical Transportation: Passenger Elevators

No. of local floors 5

6

7

8

9

10

11

12

13

14

15

16

17

18

80 75

9' 6'' (2.9 m) floor to floor 2000-lb (907 kg) car

Seconds

70

250 fpm (1.27 m/s) 300 fpm (1.6 m/s) 350 fpm (1.8 m/s) 400 fpm (2.0 m/s) 500 fpm (2.5 m/s)

65 60 55

(a)

50 80 75 Seconds

250 fpm (1.27 m/s)

9' 6'' (2.9 m) floor to floor 2500-lb (1134 kg) car

300 fpm (1.6 m/s) 350 fpm (1.8 m/s) 400 fpm (2.0 m/s) 500 fpm (2.5 m/s)

70 65

Average trip time

60

(b)

55 90

250 fpm (1.27 m/s)

85

9' 6'' (2.9 m) floor to floor 3000-lb (1360 kg) car

Seconds

80

300 fpm (1.6 m/s) 350 fpm (1.8 m/s) 400 fpm (2.0 m/s) 500 fpm (2.5 m/s)

75 70 65

(c)

60 100 95

9' 6'' (2.9 m) floor to floor 3500-lb (1588 kg) car

Seconds

90

250 fpm (1.27 m/s) 300 fpm (1.6 m/s) 400 fpm (2.0 m/s)

85

500 fpm (2.5 m/s)

80 75

(d)

70 5

6

7

8

9

10

11

12

13

14

15

16

17

18

No. of local floors

Fig. 32.18 Plots of average trip time for various car speeds and capacities with a 9‐ft, 6‐in. (2.9‐m) floor height and a 30‐second interval.

capacity of the car and the number of local floors above the lower terminal. In calculating this round‐trip time (RT), it is assumed that a car will depart the lower terminal when loaded. No intentional delay is included at either the lower or upper terminal. The RT thus calculated is a median figure, with any single actual round trip

taking more or less time. In detail, RT consists of the time expended in 1. Loading at the lobby 2. Door closing at the lobby 3. Accelerating from the terminal and from each stop

ROUND‐TRIP TIMEâ•…1481

No. of local floors 5

6

7

8

9

10

11

12

13

14

15

16

17

18

90 250 fpm (1.27 m/s)

85

12' 0'' (3.7 m) floor to floor 2500-lb (907 kg) car

Seconds

80

300 fpm (1.6 m/s) 350 fpm (1.8 m/s) 400 fpm (2.0 m/s) 500 fpm (2.5 m/s)

75 70 65 60

(a)

55 95

250 fpm (1.27 m/s)

12' 0'' (3.7 m) floor to floor 3000-lb (1134 kg) car

90

300 fpm (1.6 m/s) 350 fpm (1.8 m/s) 400 fpm (2.0 m/s) 500 fpm (2.5 m/s)

Seconds

85 80 75

Average trip time

70

(b)

65 100 95

Seconds

90

250 fpm (1.27 m/s) 12' 0'' (3.7 m) floor to floor 3500-lb (1360 kg) car

300 fpm (1.6 m/s) 350 fpm (1.8 m/s) 400 fpm (2.0 m/s) 500 fpm (2.5 m/s)

85 80 75

(c)

70 250 fpm (1.27 m/s)

12' 0'' (3.7 m) floor to floor 4000-lb (1814 kg) car

105

300 fpm (1.6 m/s) 350 fpm (1.8 m/s) 400 fpm (2.0 m/s) 500 fpm (2.5 m/s)

100

Seconds

95 90 85 80 75

(d)

70 5

6

7

8

9

10

11

12

13

14

15

16

17

18

No. of local floors Fig. 32.19 Plots of average trip time for various car speeds and capacities for a 12‐ft (3.7‐m) floor height and a 30‐second interval.

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Chapter 32╇ Vertical Transportation: Passenger Elevators

4. Decelerating at each stop 5. Passenger transfer at each stop 6. Door operations at each stop 7. Running time at rated speed between stops 8. Return express run from the last stop These figures are obtained as follows: 1. Field observations: Items 1 and 5 are based upon a 3‐ft, 6‐in. (1.07‐m) door opening. A smaller door opening increases passenger transfer time. 2. Calculations: Items 2, 3, 4, 6, 7, and 8. Door‐ closing time is based on a 3‐ft, 6‐in. (1.07‐m) center‐opening door with adjustable speed. Acceleration and deceleration times are calculated with a maximum of 4 ft/s/s (1.2 m/s/s) because anything beyond that results in physical discomfort to the passengers. Running time at rated speed takes place after the car has accelerated and before it begins to decelerate. Considering that it takes between 20 and 30 ft (6–9 m) to accelerate to 700 fpm (3.6 m/s), depending upon the rate of acceleration, in local runs a car never gets to the rated speed. It simply accelerates and decelerates. Higher‐speed equipment with a larger motor accelerates more quickly and gives some time advantage on the return express run, but it has no great time advantage over all. This accounts for the small reduction above 500 fpm (2.5 m/s) seen in Figs. 32.20 and 32.21. In calculating RT for cars in upper zones, it is necessary to know the time required to traverse the express floors. This may be obtained from Fig. 32.22. The times given there are for one‐way express runs. Thus, to calculate RT for an upper‐ zone car, take the RT corresponding to the upper local floors and add twice the figure obtained for express run time from Fig. 32.22.

RT AVTRP I D PHC

round‐trip time, in seconds average trip time, in seconds interval, in seconds population density, in square feet (m2) per person percent of the population to be moved in 5 minutes, and expressed as a percentage

Now that the definitions of interval, handling capacity, average trip time, and round‐trip time have been presented, the interrelationships among these quantities can be demonstrated, along with other equations governing the remaining factors that define elevator systems. Handling capacity HC is determined by car capacity p and interval I: HC =

In a system consisting of a single car, the interval (I) is equal to the round‐trip time (RT). In a system with more than one car, the interval is reduced in proportion to the number of cars. Thus, I=

The symbols that will be used in describing elevator calculations are: p h N HC

individual car capacity, equal to 80% of the maximum during peak hours 5‐minute capacity of a single car number of cars in a system system 5‐minute handling capacity, expressed in number of persons

RT (32.2) N

The 5‐minute handling capacity (h) of a single car is then h=

300p (32.3) RT

remembering that for a single car, its interval is its round‐trip time. It follows that if the handling capacity of a single car is h, then the handling capacity of N cars is N times as much. Thus, HC = N × h

or N=

32.34╇SYSTEM RELATIONSHIPS

300p (32.1) I

HC (32.4) h

32.35╇CAR SPEED The selection of car speed to be used is a matter of trial and error, the final selection being that required to give an RT that in turn gives an acceptable interval. In order to establish a starting point, however, it has been found that a minimum car speed corresponding to a given building height—or, in elevator parlance, rise—can be established. Similarly, although car size can be selected at any value, it has

CAR SPEEDâ•…1483

5

6

7

8

9

No. of local floors 10 11 12 13

14

15

16

17

18

170 250 fpm

160

9' 6'' floor to floor 2000-lb car

150

300 fpm

Seconds

Round-trip time

140

350 fpm

130

400 fpm

120

500 fpm 700 fpm

110 100 90 80 (a)

70 190 180

9' 6'' floor to floor 2500-lb car

170

250 fpm 300 fpm

160

350 fpm 400 fpm

140 Seconds

Round-trip time

150

500 fpm 700 fpm

130 120 110 100 90 80

(b)

70 5

6

7

8

9

10 11 12 13 No. of local floors

14

15

16

17

18

Fig. 32.20 Plots of round‐trip time for various car speeds and capacities with a 9‐ft, 6‐in. (2.9‐m) floor height and a 30‐second interval.

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Chapter 32╇ Vertical Transportation: Passenger Elevators

5

6

7

8

9

No. of local floors 10 11 12 13 14

15

16

17

18

200 190 180

25

300

170

150 Seconds

fpm

fpm 350 fpm 400 fpm 500

160 Round-trip time

pm

0f

9' 6'' floor to floor 3000-lb car

140 700 fpm

130

800 fpm

120 110 100 90

(c)

80 210 200

9' 6'' floor to floor 3500-lb car

pm

0f

25

190

300

180

fpm 350 fpm 400 fpm 500

170 160 Seconds

Round-trip time

fpm

150 700 fpm

140

800 fpm

130 120 110 100 (d )

90 5

Fig. 32.20 (Continued)

6

7

8

9

10 11 12 13 14 No. of local floors

15

16

17

18

CAR SPEEDâ•…1485

No. of local floors 200 12' 0'' (3.7m) floor to floor 2500-Ib (1134 kg) car

190 180

(1.27 m/s)

pm

(1.6 m/s)

fpm

(1.8 m/s)

fpm

(2.0 m/s)

0f

30

170

350

160 Round-trip time Seconds

pm

0f

25

400

150 140 130 120

700 fpm

(3.6 m/s)

110 100 (a)

90 80 220 210

Round-trip time Seconds

200

pm

(1.27 m/s)

fpm

(1.6 m/s)

fpm

(1.8 m/s)

fpm

(2.0 m/s)

0f

25

12' 0'' (3.7m) floor to floor 3000-Ib (1361 kg) car

190

300

180

350

170

400

160

500

fpm (2.5 m/s)

150 700 fpm

140

(3.6 m/s)

130 120 110

(b)

100 90

5

6

7

8

9

10

11

12

13

14

15

16

17

18

No. of local floors Fig. 32.21 Plots of round‐trip time for various car speeds and capacities with a 12‐ft floor (3.7‐m) height and a 30‐second interval.

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Chapter 32╇ Vertical Transportation: Passenger Elevators

230 220

12' 0'' (3.7m) floor to floor 3500-Ib (1588 kg) car

210

(1.27 m/s)

pm

(1.6 m/s)

pm

(1.8 m/s)

pm

(2.0 m/s)

fpm

(3.15 m/s) (3.6 m/s)

fp

m

(1.27 m/s)

fpm

(1.6 m/s)

pm

(1.8 m/s)

pm

(2.0 m/s)

fpm

(3.15 m/s) (3.6 m/s)

0f

30

200

Round-trip time Seconds

pm

0f

25

0f

190

35

180

40

170

500

0f

160 150

700 fpm

140 130 120 110

(c)

100 250 240

12' 0'' (3.7m) floor to floor 4000-Ib (1814 kg) car

230

0

25

220

0 30

210

0f

35

200

0f

40

Round-trip time Seconds

190

500

180 170 160 150 700 fpm

140 130 120 110

(d)

100 5

6

7

8

9

10

11

12

13

No. of local floors Fig. 32.21 (Continued)

14

15

16

17

18

CAR SPEEDâ•…1487

48 One-way express running time as a function of car speed. Does not include time for stops at terminals. For round trip, double time figures shown.

44

One-way express run time–seconds

40

0f

30

36 32

pm

6 (1.

s)

m/

) m/s 1.8 ( fpm ) m/s 350 (2.0 m fp 400 ) m/s (2.5 m p f 500 m/s) (3.15 m p f 600 ) 6 m/s m (3. p f 0 70

Low-speed cars

28 24 20 16 12 8 4 5

6

7

8

9

10 11 12 13 14 No. of express floors (a)

15

16

17

18

19

/s m .1 5 (3 60

One-way express run time–seconds

High-speed cars

0

m fp

70

40

30

pm

0f

0 10

(3

pm

0f

0 12

m

0 (5.

)

/s

m fp

.6

0

50

One-way express running time as a function of car speed. Does not include time for stops at terminals. For round trip, double time figures shown.

)

60

s)

m/

/s)

1m

(6.

20

10

10

20

40 30 No. of express floors (b)

50

Fig. 32.22 One‐way express running time, not including terminal time; (a) low‐speed cars, (b) high‐speed cars.

60

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Chapter 32╇ Vertical Transportation: Passenger Elevators

TABLE 32.9╇ Elevator Equipment Recommendations Car Capacitya Building Type

lbâ•…â•…â•…kg

Office building

 2500   3000  3500 

Hotel

 2500 1250     3000 1250 

1250 1250 1600

Minimuma Car Speed

Rise

    

ft

m

fpm

0–125 126–225 226–275 276–375 Above 375

0–40 41–70 71–85 86–115 >115

350–400 500–600 700 800 1000

As above

m/s 2.0 2.5 3.15 4.0 5.0

As above

0–20 21–30 31–40 41–55 56–75 >75

150 200–250 250–300 350–400 500–600 700

0.63 1.0 1.6 2.0 3.15 4.0

Hospital

 3500 1600     4000 2000 

0–60 61–100 101–125 126–175 176–250 >250

Apartments

 2000 1000     2500 1250 

0–75 76–125 126–200 >200

0–25 26–40 41–60 >60

100 200 250–300 350–400

0.63 1.0 1.6 2.0

Stores

 3500   4000  5000 

0–100 101–150 151–200 >200

0–30 31–45 46–60 >60

200 250–300 350–400 500

1.0 1.6 2.0 2.5

aCar

1600 2000 2500

    

capacity is determined by building size, and car speed by rise.

been shown that for certain facility types, specific‐ size cars are indicated. These recommendations are given in Table 32.9. Bear in mind that elevator equipment falls into distinct speed categories. Thus, most manufacturers use geared equipment through 400 fpm (2 m/s) and gearless equipment thereafter. The next category is 500 fpm (2.5 m/s) gearless, followed by 600 fpm (3.0 m/s) to 700 fpm (3.6 m/s), and so on. It is wise to avoid moving into the next higher— and more expensive—equipment category if possible. This may mean exceeding the recommended interval or dropping slightly below desired handling capacity. It will be found, however, that this can usually be done without injury to the elevator system performance, provided that a high‐quality group supervisory control system is employed.

EXAMPLE 32.1 Office building, downtown, diversified use, 14 rentable floors above the lobby, each 12,000 ft2 (1115 m2) net. Floor‐to‐floor height—12 ft (3.7 m). Determine a workable elevator system arrangement. SOLUTION From Table 32.6, recommended average HC is 13%. From Table 32.4, the maximum recommended interval is 25 seconds. From Table 32.7, average population density is 120 ft2 (11 m2) per person. Trial 1 Building population: 14 floors at 12,000 ft 2 = 1400 persons 120 ft 2 per person (14 at 1115/11 ≈ 1400 persons)

32.36╇SINGLE‐ZONE SYSTEMS Having established the relationships that govern the design and performance of an elevator system comprising a single zone, it would be helpful to follow through an illustrative example.

Suggested minimum handling capacity: PHC = 13% HC = 0.13 × 1400 = 182 persons rise = 14 floors at 12 ft (3.7 m) = 168 ft (51m)

SINGLE‐ZONE SYSTEMSâ•…1489

From Table 32.9, select a car size of 3500 lb (1588 kg) at 500 fpm (2.5 m/s).

RT = 143 seconds

3500 lb (1588 kg) 500 fpm (2.5 m/s) Then, from Figs. 32.23c and 32.21c: RT = 155 seconds

AVTRP = 82 seconds

h=

300(16) = 33.6 persons 143

N=

HC 182 = = 5.4 cars h 33.6

Using five cars:

Single‐car capacity: h = 300p/RT (see Table 32.5 for p): h=

300(19) = 36.8 persons 155

N=

HC 182 = = 4.9, say 5 cars h 36.8

I=

I=

5(13%) = 13% 4.9

These results are acceptable, but faster cars might reduce the interval. Select 700 fpm (3.6 m/s). Trial 2

RT = 151seconds AVTRP = 81seconds (by extrapolation)

I=

PHC =

Solution 1 2 3

N=

182 = 4.8, say 5 cars 37.7

4

I=

RT 151 30 seconds = 5 N

This solution is only marginally better than the previous 500 fpm (2.5 m/s) solution, and the increased cost would not be justified. A trial using smaller cars with shorter RT is called for. Trial 3 3000‐lb (1361‐kg) cars 500 fpm (2.5 m/s)

6 (13) = 14.4% 5.4

Both solutions are acceptable. Tabulating the calculation results, we have:

300(19) = 37.7 persons 151

5(13%) = 13.5% 4.8

RT 143 = = 23.8 seconds N 6

and

h=

actual PHC =

5 (13%) = 12% 5.4

Trial 4 Using six 3000‐lb (1361‐kg), 500‐fpm (2.5‐m/s) cars:

3500 lb (1588 kg) 700 fpm (3.6 m/s)

RT 143 = = 28.4 seconds 5 N

actual PHC =

RT 155 = = 31seconds 5 5

actual PHC =

AVTRP = 76 seconds

Cars lb (kg) 5@ 3500 (1588) 5@ 3500 (1588) 5@ 3000 (1361) 6@ 3000 (1361)

Speed fpm (m/s)

RT (s)

AVTRP (s)

I (s)

PHC (%)

500 (2.5)

155

82

31

13

700 (3.6)

151

81

30

13.5

500 (2.5)

143

76

28.4

12

500 (2.5)

143

76

23.8

14.4

Solutions 1, 3, and 4 are acceptable. Solution 2 was discounted due to the high cost. Interestingly, solution 3, using smaller cars than the corresponding solution 1, and therefore being more economical, gives better results except for HC. Although the best solution is number 4, which gives excellent interval and HC, the additional cost of a sixth car plus the revenue loss from the rentable area occupied by the sixth shaft and the cost of additional maintenance weigh heavily against this option. A trial with five 3000‐lb (1361‐kg) cars at 700 fpm (3.6 m/s) is in order, with the knowledge that a considerable cost increase would result because 700‐fpm (3.6‐m/s) cars require gearless equipment, whereas 500‐fpm

1490â•…

Chapter 32╇ Vertical Transportation: Passenger Elevators

(2.5‐m/s) cars are available in either geared or gearless format, both giving excellent service. Trial 5 3000‐lb (1361‐kg) cars 700 fpm (3.6 m/s) RT = 140 seconds

AVTRP = 73 seconds

h=

300(16) = 34.3 persons 140

N=

182 = 5.3; use 5 cars 34.3

I=

RT 140 = = 28 seconds 5 N

PHC =

5 (13%) = 12.3% 5.3

As expected, improvement over the performance at 500 fpm (2.5 m/s) is very slight: an interval of 28 seconds rather than 28.4 seconds, and a handling capacity of 12.3% versus 12%. The large increase in first cost for gearless equipment would not be justified. ■

At this point, the final selection would be made on the basis of cost. When considering cost, note that first cost is the governing factor only in a speculative venture. With an owner‐operator building, the cost comparison should be on a life‐cycle basis. Cost figures must reflect the impact of elevator space requirements on net rentable area in the building. Comparative cost figures are given in Table 32.10.

As mentioned earlier, and shown in Fig. 32.16, planners of new buildings today generally take advantage of elevator selection software provided by consultants, by manufacturers, or via in‐house capabilities. The results from one such program are shown in Fig. 32.23 (this particular analysis was prepared by Otis Elevator Co.). Note that projected system performance under a variety of operational and functional scenarios can be evaluated and compared. The round‐trip curves in Fig. 32.21 are based on a 3.3‐second door time and a 4.0 ft/s2 (1.2 m/s2) car acceleration. Note that high call reversal occurs at the top floor (13.6, i.e., 14) and that the number of up stops is 10 (9.7 from statistical calculations). The up‐peak calculation assumes no counterflow traffic (i.e., an express down run and no interfloor traffic), as shown. These can be added, however, yielding very different results, as shown in Fig. 32.23. Counterflow traffic (down stops) of only 2% and interfloor traffic of 1%, both of which are reasonable values, change the round trip time substantially and reduce the handling capacity appreciably.

32.37╇MULTIZONE SYSTEMS In general, buildings with fewer than 15 stories are elevatored with a single zone (i.e., all cars serve all floors), and buildings with more than 20 stories are split into two or more zones. Buildings in between these limits—16 to 19 stories—can go either way, depending upon the population density and the

TABLE 32.10╇ Relative First Costa Figures for Passenger Elevators of Various Speeds and Drive Systems Hydraulic fpm (m/s)

a

Geared Traction fpm (m/s)

Gearless Traction fpm (m/s)

Car Size (lb)

100 (0.63)

200 (1.0)

350 (2.0)

500 (2.5)

500 (2.5)

700 (4.0)

1000 (5.0)

1200 (6.0)

2000 (907) 2500 (1134) 3000 (1361) 3500 (1588) 4000 (1814) 4500 (2041)b 5000 (2268)b

40 43 50 58 60 70 75

80 85 90 95 100 120 130

100 115 120 125 135 150 160

130 145 150 155 165 185 200

165 175 180 190 200 225 240

170 180 185 195 205 230 250

220 235 250 265 280 300 330

235 250 265 275 300 325 350

Costs are ±10%; based on standard fixtures, cabs, and entrances, and average rise for the speed indicated.

b

Service elevator or hospital elevator.

Note: See Table 32.9 for speed/rise recommendation.

MULTIZONE SYSTEMSâ•…1491

Fig. 32.23 Printouts from a computerized elevator selection program. This analysis shows that the addition of even light counterflow and interfloor traffic can seriously affect system performance, as can be seen from the round‐trip, interval, and handling capacity figures. (Courtesy of Otis Elevator Co.)

required interval. A modern group supervisory system can automatically zone a building when traffic requires it. Such an arrangement, although efficient, is expensive in terms of both equipment and construction because it does not take advantage of the considerable savings engendered by blind lower shaftways for upper‐zone elevators. Analysis of multizone systems is complex and today is rarely done by hand. See Stein et al. (1986) for a detailed explanation of the technique involved. Most designers and consultants use one

of many available computerized simulation and selection programs. These have the advantage that, in addition to using basic criteria and building parameters, they can also consider the effect of variations in traffic control. Furthermore, the best of these programs can evaluate the engineering and economic impacts of such factors as varying rental rates for different floors, rental space, machine room and hoistway space, core layout, and the structural ramifications of the elevator system.

1492â•…

Chapter 32╇ Vertical Transportation: Passenger Elevators

32.38╇ELEVATOR SELECTION FOR SPECIFIC OCCUPANCIES (a) Office Buildings Necessary design criteria can be selected from Tables 32.4 to 32.7. Supervisory group control is normally microprocessor‐based. Approximately 1 service car per 10 passenger cars should be provided or, alternatively, one service car for every 300,000 ft2 (27,870 m2) of net area. Service cars should be 5000 lb (2268 kg) or larger without a dropped ceiling and, if also used for passenger service, equipped with wall pads. An oversized door (e.g., 4 ft, 0 in. [1.2 m] or 4 ft, 6 in. [1.4 m]) is particularly useful in handling furniture. Service elevators should have a shaftway door at every level plus easy access to the truck dock (or other freight entrance) as well as the lobby. These cars operate as service cars normally but can serve as passenger cars in peak periods to reduce congestion and delay. This fact is particularly useful in marginal service designs. See Table 32.11 for approximate building costs. (b) Apartment Buildings Studies indicate that apartment building traffic depends not only upon the population but also on the location and type of tenant. Buildings with many children experience a school‐hour peak; buildings in midtown with predominantly adult tenancy exhibit evening peaks due to the homecoming working group and outgoing dinner traffic. Where two cars are required, the second car should function both as a service car and as a passenger car. The cars may be banked or separated, as desired. If a single car is used, it should be of service elevator size. Self‐service collective control is the general choice, with provision for attendant control in prestigious buildings. With small cars and a short rise, a swing‐type manual corridor door is acceptable; in

TABLE 32.11╇ Office Buildings: Cost of Elevator and Electric Work Number of Stories Item Elevator work Electric work

20

35

60

10.9% 13.3%

11.9% 12.6%

12.2% 12.2%

larger installations, both the car and the corridor door should be the power‐operated sliding type. Service elevators must be large enough to handle bulky furniture and should therefore be at least 4000 lb (1814 kg), with a 48‐in. (1.2‐m) door and a high ceiling. Hoistways must be isolated from sleeping rooms by lobbies or other space. Similarly, machine rooms must be isolated because the starting and stopping of motors and other machine room noises are a detriment to sound sleep. Security arrangements are discussed in Section 32.47. (c) Hospitals As mentioned in Table 32.7, the governing factor in the determination of elevator requirements may be either normal hospital traffic or visitor traffic, depending upon the visiting‐times schedule. Due to the large volume of vehicular traffic such as stretcher carts, wheelchairs, beds, linen carts, and laundry trucks, hospital elevator cars are much deeper than the normal passenger type. This type of car, when used for passenger service, holds more than 20 persons and therefore gives slow service. For this reason, it is occasionally advisable to utilize some normal passenger cars in addition to hospital‐size cars, particularly in large hospitals. The use of tray and bulk carts in food service imposes a considerable load upon the elevator system before, during, and after meals, and passenger service is seriously disrupted. To reduce this congestion and delay, many architects and hospital administrators prefer the use of dumbwaiter cars or another of the many types of materials‐handling systems that can handle a 15½ × 20 in. (394 × 508 mm) food tray. These systems can also be used for transporting pharmaceuticals and other items, and are discussed in Sections 33.14–33.16. Elevators should be grouped centrally, although separated by type of use. Car control is normally self‐service collective. The population of a hospital may be estimated from Table 32.7. Experience has shown that a carrying capacity of 45 passengers in a 5‐minute period is adequate (estimating each vehicle as equivalent to 9 passengers). Intervals should not exceed 1 minute. All recommendations regarding service for the disabled should be adopted (see Section 32.14).

DIMENSIONS AND WEIGHTSâ•…1493

(d) Retail Stores Retail stores present a unique problem in vertical transportation inasmuch as the objective is partially to transport persons to specific levels and partially to expose the passengers (customers) to displayed merchandise. For this reason, modern stores rely heavily on escalators, with one or two elevators provided for use by staff and handicapped persons. When, for some reason, it is desired to equip a store exclusively with elevators, use the recommendations shown in Table 32.9, calculated for a load of 10% to 20% of the store’s population. Control should be automatic, selective collective. Cars are arranged in a straight line to facilitate loading and waiting.

P H YSIC AL PR O PERTIES A ND SPATIAL R EQ UIR EM ENTS O F ELEVATO R S 32.39╇SHAFTS AND LOBBIES Elevator lobbies and shafts are one of the major space issues with which the architect is concerned. The elevator lobby on each floor is the focal point from which corridors radiate for access to all rooms, stairways, service rooms, and so forth. Such lobbies must be located above each other. The ground‐floor elevator lobby (also called the lower terminal) must be conveniently located with respect to the main building entrances. Equipment within or adjacent to this area should include public telephones (if provided), a building directory, elevator indicators, and possibly a control desk. Lobbies should provide adequate area for the peak‐load gathering of passengers to ensure rapid and comfortable service to all. The number of people contributing to the period of peak load (15‐ to 20‐minute peak) determines the required lobby area on the floor. Not less than 5 ft2 (0.5 m2) of floor space per person should be provided at peak periods for waiting passengers at a given elevator or bank of elevators. The hallways leading to such lobbies should also provide at least 5 ft2 (0.5 m2) per person, approaching the lobby. Under self‐adjusting

Fig. 32.24 Rough hoistway dimensional data for use in schematic design. (a) I‐P elevator sizes and dimensions. (b) SI elevator sizes and dimensions.

relaxed conditions, density is about 7 ft2 (0.65 m2) per person. During peak periods crowding occurs, however, reducing this to 3 to 4 ft2 (0.3–0.4 m2) per person. An acceptable compromise is 5 ft2 (0.5 m2) per person. The main lower terminal of elevator banks is generally on the street‐floor level, although it may be on a mezzanine level when the elevations of the street entrances vary so that one side of the building is at mezzanine level, whereas another entrance is lower. Such a situation is ideal for the use of escalators, which can economically and rapidly carry large numbers of people between levels, thus making practical and efficient a single main lower elevator terminal. The upper terminal is usually the top floor of the building. Typical dimensional data and lobby arrangements are shown in Figs. 32.24 to 32.26.

32.40╇DIMENSIONS AND WEIGHTS Most manufacturers and elevator consultants will, upon request, supply standard layouts for elevators— including dimensions, weights, and structural loads.

1494â•…

Chapter 32╇ Vertical Transportation: Passenger Elevators

In line

opposing 8′-10′ Limit of inline due (2.4 m-3 m) May be to cross traffic, closed except in department store (b) Four-car groups

6′-8′ (1.8 m-2.4 m)

May be closed

(a) Three-car groups

Min. 10′ (3 m) 8′-10′ (2.4 m-3 m)

May be closed

8′-10′ (2.4 m-3 m)

Must be open at both ends

Larger space between is required for closed end plan (d) Eight-car group

(c) Six-car groups

Fig. 32.25 Lobby groupings for single‐zone systems: (a) three‐, (b) four‐, (c) six‐, and (d) eight‐car groups.

Furthermore, to assist in preliminary design, major manufacturers have agreed upon and publish a set of Standard Elevator Layouts via their trade organization, the National Elevator Industry, Inc. (NEII). One such standard is reproduced in Fig. 32.27 for 500‐ to 700‐fpm (2.5–3.6‐m/s) gearless units in the full range of car capacities. These standards are available from the NEII. As may be seen from Fig. 32.27, in providing for an elevator installation it is necessary to consider such factors as the depth of the pit, the dimensions of the hoistway, the clearance from the top of

Low Low Low

May be closed

8′-10′ (2.4 m-3 m)

Low Low Low

8′-10′ (2.4 m-3 m)

High High High

Low High High

(a) Six-car groups

(b)

Low

Low Low High High

Min.10′

(3 m)

High

(c) Eight-car groups

Min.10′

(3 m)

Low Low High High

(d)

Fig. 32.26 Lobby groupings for multiple zone systems. Arrangement (a) is preferable to (b), and (c) to (d). Groups with more than four cars in a row are not used because end‐to‐end walking time would excessively lengthen landing stops and hence total travel time.

the hoistway to the floor of the penthouse, the size of the penthouse, and the loads that must be carried by the supporting beams. The penthouse floor (and the secondary‐level floor, where required) are located above the shaft of each elevator and need approximately 1½ stories of additional height above the top of the support beam of a given elevator when it is standing at its top‐floor location. The actual floor area required by the elevator traction machine and its controls is roughly two times the area of the elevator shaft itself. The machine room contains the bulk of the elevator machinery. Because some of this equipment must be moved for maintenance, it is advisable to furnish an overhead trolley beam that can be used during installation as well. The maximum beam load is supplied by the elevator manufacturer. Some typical machine room dimensional data are listed in Table 32.12, taken from actual installations. Because of multiple drive options and flexibility in equipment arrangements, no general conclusions can be drawn from these figures; they are listed simply to give a general picture of requirements. A manufacturer’s layout giving dimensional data for the hoistway and machine room is shown in Fig. 32.28. When penthouse space is not available and a hydraulic unit is not desired, a basement traction unit, also referred to as an underslung arrangement, can be used. These units are always low‐speed

DIMENSIONS AND WEIGHTSâ•…1495

Fig. 32.27 Typical elevator installation dimensional data. (Reproduced from Vertical Transportation Standards, 7th ed., © 1992, with permission of National Elevator Industry, Inc., 185 Bridge Plaza North, Fort Lee, NJ 07024.)

1496â•…

Chapter 32╇ Vertical Transportation: Passenger Elevators

Fig. 32.27 (Continued)

TABLE 32.12╇ Typical Elevator Machine Room Dimensions Bank Description No. – lb (kg)

fpm (m/s)

Approximate Machine Room Dimensions ft (m)

2–2500 (1134) 3–2500 (1134) 3–2500 (1134) 6–3500 (1588) 6–3500 (1588) 6–3500 (1588) 6–5000 (2268)

125 (0.6) 350 (1.8) 700 (3.6) 500 (2.5) 700 (3.6) 1000 (5.1) 450 (2.3)

16 × 18 (4.9 × 5.5) 19 × 26 (5.8 × 7.9) 21 × 26 (6.4 × 7.9) 26 × 29 (7.9 × 8.8) 27 × 27 (8.2 × 8.2) 27 × 27 (8.2 × 8.2) 31 × 33 (9.5 × 10.1)

(100–350 fpm [0.5–1.8 m/s]) and are therefore applicable only where rise is limited and traffic is light to medium. Figure 32.29 shows a typical shaft section for this design with car and dimensional data.

32.41╇STRUCTURAL STRESSES For structural design, it is necessary to know the overhead load that must be supported by the foundations, by structural columns extending up to

STRUCTURAL STRESSESâ•…1497

MAX AISE (121.920 mm)

400′0′′

9′1′′

(2768.6 mm) PIT

LADDER & LIGHT SW (NOT BY OTIS)

29′0′′ (6839.2mm) TOTAL CLEAR HEIGHT

W304.8 X 38.69 W12 X 26

TOP OF MACHINE 7′6′′ CLEAR ROOM FLOOR (2286mm) 21′6′′ (65.53 2 mm)

7′0′′ (2135 mm) CL. OPNG 20′6′′ (6248.4 mm)

8′0′′ (2438 mm) CAB

TOP OF MACHINE BEAM SUPPORTS

2′0′′ (610 mm)

CONCRETE (NDT BY OTIS) 4′ (102mm)

TROLLEY BEAM

TOP FLOOR

BOTTOM FLOOR

SECTIONAL ELEVATION

Fig. 32.28 Manufacturer’s layout data for a bank of six 3500‐lb (1588‐kg), 700‐fpm (3.45‐m/s) gearless passenger elevators. Equipment shown in the machine room is the thyristor control for DC traction machines. Because each controller provides group supervisory control in this design (Otis Elevonic 411), no separate group supervisory equipment is shown. No additional space would be required if a UMV drive with m‐g sets were selected rather than thyristor control. (Courtesy of Otis Elevator Co.)

1498â•…

Chapter 32╇ Vertical Transportation: Passenger Elevators

Fig. 32.29 Typical data for a basement traction machine (underslung) arrangement, used where a penthouse is unavailable or undesirable. (Courtesy of Montgomery‐KONE.)

POWER REQUIREMENTSâ•…1499

the penthouse, and by the main beams that support the penthouse floor and subfloor. These loads (reactions) are supplied by manufacturers and usually include the actual dead weights of equipment when the elevator is not in motion, plus the added weight caused by the momentum of all moving parts and passengers when the elevator is at top speed and is suddenly stopped rapidly by the safety devices.

P O WER AND ENERG Y   32.42╇POWER REQUIREMENTS The power required by an elevator drive is that which is needed to provide the necessary traction and to overcome friction. Because power is equal to the rate at which work is done, elevator motor size is directly proportional to the speed of the system. In other words, it requires proportionately more power

110

90 80 70 60 50 40 30 20 10 0

Horsepower-Gearless Equipment

Horsepower-Geared Equipment

100

92

No. of cars

84

2 3 4 5 6 7 10 15 20 25 and over

76 68 60 52

to lift a 3000‐lb (1361‐kg) car at 700 fpm (3.6 m/s) than at 200 fpm (1.0 m/s). This relationship is shown in Fig. 32.30, which shows the minimum size of a DC elevator traction motor as a function of speed for cars of different capacity. (For power data on hydraulic elevators, see Section 32.9.) As friction is higher in a geared machine than in a gearless unit, the geared machine traction motor must be larger for the same car speed. The size of the traction machine shown in Fig. 32.30 is independent of the power supply design (m‐g set, VVVF, thyristor control) because it is determined purely by traction system requirements. (In practice, however, traction motors with VVVF control are frequently smaller because they operate more efficiently.) An elevator moves only about 50% of the time, the remainder being spent standing at various landings. As the number of cars in a bank increases, the probability of all the cars being in operation simultaneously decreases, resulting in a system demand factor of less than 1.0. The factor for different group sizes is shown in Fig. 32.30.

Group demand factor 0.85 0.77 0.72 0.67 0.63 0.59 0.52 0.44 0.40 0.35

00

40

lb

b

0l

0 35

00

30

lb

0 lb

250

0 lb

200

44 36 28 20 16 12 8 4 0

100

200

300

400

500

600

700

800

900

1000

Elevator Speed. fpm Fig. 32.30 Elevator traction motor power requirements per car. An m‐g set drive (if used) is approximately 20% larger than a traction machine.

1500â•…

Chapter 32╇ Vertical Transportation: Passenger Elevators

As an example of the use of the power curves, consider a bank of five 3500‐lb (1588‐kg), 600‐fpm (3.0‐m/s) units. From Fig. 32.30, each car requires 48 hp (36 kW): group demand factor = 0.67 total instantaneous power required = 5 × 48 × 0.67 = 160 hp ( = 5 × 36 × 0.67 = 120 kW)

Note that this is the traction motor power requirements. If an m‐g set with an overall efficiency of 80% is used to drive the traction motor, the elevator system power requirement is system power =

160 hp = 200 hp 80% eff

32.2 Given a system of five 3500‐lb (1588‐kg), 600‐fpm (3.0‐m/s) gearless cars, calculate:

which must be provided by the building electrical system. If a solid‐state power supply system with a (typical) efficiency of 92% is used, the system power requirement will be only 160 hp = 174 hp 92% eff

(120 kW/.0.92 = 130 kW)

which is a 13% reduction from the previously calculated 200‐hp (150‐kW) requirement.

Power

The energy used by an elevator is essentially the system friction, including the heat generated by the brakes plus the electrical losses in the traction motor and power supply equipment (rotary or solid‐ state). The energy expended in raising a car and its passengers is simply stored as potential energy. It is returned to the power system when the car and passengers descend via the system of regenerative braking used in almost all elevator systems. Refer to Fig. 32.31, which shows the approximate efficiencies of the components of a typical system. With these data, it is possible to calculate a system’s energy consumption.

EXAMPLE

(120 kW/0.80 = 150 kW)

system power =

32.43╇ENERGY REQUIREMENTS

a. The heat generated in the machine room during peak periods; assume solid‐state control b. The approximate monthly energy cost; using a combined demand/energy rate of $0.08/kWh SOLUTION a. During peak periods, the traction motor operates approximately 50% of the time and is at standstill the other half. Assume that, while operating, it draws 90% of the full load (with a VVVF power supply, this figure is reduced

Solid-state Power supply/control minimum efficiency ~ 90%

Traction equipment efficiency Gearless ~ – 80% Geared ~ – 65% 291 W loss

0.14 hp (104 W)

0.25 hp (187 W)

1.39 hp (1.04 kW)

1.25 hp

Gearless

1.71 hp

1.54 hp

Geared

0.17 hp (127 W)

1 hp

0.54 hp (403 W) 530 W loss

Fig. 32.31 Block diagram showing losses in the system per horsepower (kW) delivered to the elevator car and the equivalent wattages. Note that the losses in a geared system are almost double those of a gearless one. Figures shown are for solid‐state thyristor controls.

ENERGY CONSERVATIONâ•…1501

considerably). Therefore, for one car, from Fig. 32.30, traction motor = 48 hp (36 kW) Total loss per machine: In controls: 48 hp × 90% load × 50% operation × 10% loss 0.9 eff = 2.4 hp (1.8 kW ) In traction motor: 48 hp × 90% load × 50% operation × 20% loss = 4.32 hp (3.2 kW) total = 6.72 hp = 17,100 Btu/h (equivalent to 5 kW) Because five elevators are operating, the total heat generated is 5 × 17,100 Btu/h = 85,500 Btu/h (equivalent to 25 kW) This is roughly the heating capacity of a home furnace. As a result, machine room temperatures in warm climates frequently reach 120°F (49°C). (No diversity is taken because all the machines are operating and the heating is additive; diversity is applicable only in calculating instantaneous load.) As solid‐state elevator equipment is much less tolerant of high ambient temperatures than the electromechanical switches and relays previously used, an elevator machine room should be held to a maximum dry‐bulb temperature of 90°F (32°C). (Temperatures above 90°F (32°C) can result in unreliable elevator system performance.) This limit can sometimes be accomplished by thermostatically controlled forced ventilation, particularly if spill‐ over air from an air‐conditioned space is available. However, because machine rooms are frequently on the building roof and exposed on all surfaces to ambient temperatures and solar radiation, air conditioning may be necessary. It is also important to prevent machine room temperature from dropping below 55°F (13°C). This can usually be done with one or more unit heaters, which will normally operate only during the winter, and then only on nights and weekends. In actual design situations, accurate heat loss values, which are available from manufacturers, would be used, along with accurate heat gain and heat loss calculations for the specific machine room being designed. Frequently, use of thermal

insulation, thermostatically controlled louvers, and sunshading can ease the thermal load and result in appreciable savings in money and energy. Because of the high initial and operating costs of air conditioning, some elevator manufacturers use control components that are tolerant of high temperatures. This point should be carefully examined with proposed elevator equipment manufacturers and the conclusions reflected in the elevator system specifications. b. To calculate a monthly energy cost, an estimate must be made of the total usage of the system. Assuming the system to be in an office building, a reasonable breakdown of operation during a 24‐hour day would be 2 hours at peak use 2 hours at 70% of peak 6 hours at 50% of peak 14 hours at 10% of peak This gives a weighted average of 30% of peak load for the elevator bank. Therefore, per car energy = 30% × total losses × 24 hours = 0.3 × 6.72 hp (or 5 kW) × 24 hours = 48 hp-h (or 36 kW-h) = 36 kWh/day/car Monthly cost would be kWh 36 × 25 days × $0.08 day = $72/month/car = $360/month for the bank This figure would be lower with a VVVF power supply and higher for a Ward–Leonard (m‐g set) arrangement. ■

32.44╇ENERGY CONSERVATION A reduction in energy consumption can be accomplished by implementing the following recommendations: For Existing Elevators 1. Increase the interval during nonpeak hours. 2. Replace m‐g sets with a solid‐state DC power supply or AC traction motors with a VVVF power supply. This conserves energy not only

1502â•…

Chapter 32╇ Vertical Transportation: Passenger Elevators

due to the higher efficiency of the power supply, but also because energy consumption of idling machines is eliminated. 3. Reclaim machine room waste heat. 4. Shut down some units completely during off hours. For a Building in the Planning Stage 1. Base the design on the maximum recommended trip time. 2. Use the lowest speeds possible within a type— that is, geared or gearless. 3. Use gearless equipment whenever possible. 4. After construction, implement the energy conservation recommendations for existing elevators. Because elevator shafts can induce a powerful stack effect, measures should be taken to counteract the potential loss of heat from the building that may occur during the heating season.

32.45╇EMERGENCY POWER Major power failures and local brownouts have demonstrated forcefully the need for a standby or emergency power source of adequate size to operate an affected building’s elevators. Few experiences are so harrowing as being trapped in the crowded confines of a small box suspended in a long vertical shaft, with little or no light, and complete strangers for companions. A common misconception about elevators is that on failure of power, the cars will automatically descend to the nearest landing, where an exit is then possible. In reality, the car brake is set immediately upon power outage and the car remains stationary. Hydraulic cars can be lowered by operation of a manual valve; small traction cars can be cranked to a landing by hand, but large cars are fixed in position. This is particularly bad for cars in blind shafts—that is, express shafts with no shaftway doors. In such cases, escape from the cars via a hatchway is not practical; when emergency power is not available, the undesirable option of breaking through the shaftway walls is the only recourse. In addition to simple inconvenience, loss of elevator service in facilities such as hospitals and

mental and penal institutions constitutes a danger to life. For this reason, most codes require that emergency power be available in specific building types to operate at least one elevator at a time, and for elevator lighting and communications. Many installations separate the emergency power functions, providing a generator for elevator traction power and separate individual elevator battery packs for communications, lighting, and, preferably, the car fan. The last two items can be furnished as an option by elevator manufacturers with their cars. The generator is normally sized to supply one elevator motor at a time, with manual or automatic switching arranged between unit controllers. Thus, each car in turn can be brought to a landing, and thereafter a single car can be retained in service. If it is desired to operate more than one car, a larger generator can be installed. This might well be the case in a multiwing building with critical service requirements, such as a hospital. The amount of power required, the size of the emergency generator, and the equipment size necessary to absorb regenerative power are all data that can be furnished by a consulting engineer and the elevator manufacturer.

S P EC I A L C ONS I D ERATI ONS   32.46╇FIRE SAFETY Most fire codes specify the procedures that elevator control equipment must implement once a fire emergency has been initiated. Details vary somewhat, but in general the actions are these: 1. All cars close their doors and return nonstop to the lobby or another designated floor, where they park with the doors open. Thereafter, they are operable in manual mode only, by use of the firefighter’s key in the car panel. 2. All car and hall calls are canceled, and call‐ registered lights and directional arrows deactivated. 3. The fire emergency light or message panel in each car is activated to inform passengers of the nature of the alert and that cars are returning to a designated terminal.

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4. Door sensors and in‐car emergency stop switches are deactivated. 5. Traveling cars stop at the next landing without opening their doors and then proceed to the designated terminal. The cars can then be used by trained personnel to transport firefighters and equipment and for evacuation. In the event of a false alarm, the emergency procedure can be overridden at the (lobby) control point, and the system can then be returned to normal while the source of the alarm is located. (This is a particularly important feature in large buildings with automatic fire alarm systems containing hundreds of fire, smoke, and water‐flow detectors.)

32.47╇ELEVATOR SECURITY Elevator security has two key aspects: physical security of riders and consideration of the elevator as a portal in a building‐access security system. (a) Rider Security This problem is particularly difficult inasmuch as a traveling elevator is an enclosed space that can be rendered inaccessible simply by pressing the emergency stop button. Thereafter, an attacker can escape at a floor of his/her choice. To reduce this danger (to some extent), elevators are equipped with alarm buttons that alert residents and security personnel (if any). Every elevator, by code, must be equipped with communication equipment. A two‐way communication system with “no‐hands” operation in the car is particularly effective for security. When a closed‐circuit TV monitor is added, utilizing a wide‐ angle camera in each car (Fig. 32.32), the security problem will have been addressed to a considerable extent. Using a communication and TV system presupposes continuous monitoring of the building security desk so that an incident will be detected. (b) Access Control This is often a matter of restricting access to (and from) a floor or car. This can be accomplished by pushbutton combination locks or coded cards, the proper use of which will permit access (see Chapter 31). However, if a second (unauthorized) person

Fig. 32.32 Wide‐angle camera coverage intended for elevator car surveillance. A prominent printed warning in the car is an integral part of the system’s effectiveness.

accompanies an authorized person, the effectiveness of this type of access control is seriously compromised. In sum, the most effective security system is a combination of automatic monitoring and access devices coupled with continuous supervision by persons who know the appropriate actions to take in an emergency.

32.48╇ELEVATOR NOISE Elevator operation, with its rotating, sliding, and vibrating masses, can be a cause of serious noise disturbance to quiet areas such as sleeping rooms, libraries, and certain types of office space. Noise and vibration can be reduced by the appropriate application of noise control strategies and vibration isolators (e.g., between guide rails and the structure), but primarily by placing noise‐sensitive areas away from shafts and machine rooms. The clatter and whirring sound associated with older machine rooms (and caused by relays, step switches, m‐g

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sets, and sliding contacts) can be entirely eliminated by the use of solid‐state equipment.

32.49╇ELEVATOR SPECIFICATIONS Two basic types of specifications for elevator equipment, as for other types of equipment, are utilized. These are the prescriptive (equipment‐based) and performance (outcome‐based) approaches. Performance specifications describe job conditions and invite contractors to submit detailed proposals that will meet explicit design criteria. The burden of comparing proposals then falls upon the owner, who—if competent to properly perform such an evaluation—would probably do better to utilize an equipment‐type specification in the first place. In recent years, the use of performance specifications has increased because of the advent of preengineered, premanufactured systems. These are supplied by the major elevator manufacturers and have the following advantages: 1. Approximately 10% lower cost than a custom‐ designed system 2. A completely engineered and tested system whose performance and cost are known exactly 3. Rapid delivery 4. Minimum supervision required by the owner and architect If architects decide to use a custom‐designed system, they must prepare detailed drawings and specifications. The specifications must include:

• • • • • • • •

Elevator type, rated load, and speed Maximum travel Number of landings and openings Type of control and supervisory system Details of car and shaft doors Signal equipment Characteristics of the power supply Finishes

The last item can be left as a dollar allowance for architectural treatment of the car interior. Because the selection of, and technical specifications for, elevators are specialized and complex, the services of an elevator consultant are usually required. In addition to the technical portions of the specifications, it is imperative that the following items be covered in detail.

(a) Owner’s Responsibility The general construction contractor (acting for the owner) normally provides the following: â•⁄ 1. The hoistway, including a properly designed, lighted, drained, waterproofed, and ventilated machine room and pit â•⁄ 2. Access doors, ladders, and required guards â•⁄ 3. Guide rail bracket supports, and support for machine and sheave beams â•⁄ 4. Electric feeder terminating in a switch in the machine room â•⁄5.  Hoistway outlets for lighting, power, and telephone â•⁄ 6. Temporary lighting and power during construction â•⁄ 7. Concrete machine foundations â•⁄ 8. Vents, holes, and other work to satisfy fire codes â•⁄9.  All cutting, patching, and fabricating of walls, beams, masonry, and so on 10. Coordination of all work 11.  Any special work, as negotiated and specified

(b) Elevator Contractor’s Responsibility The elevator contractor shall provide a complete, working, tested, and approved system in accordance with specifications, plus any special work such as painting, special tests, work scheduling, and temporary elevator service. The system is “inserted” into the building framework described in Section 32.49(a).

(c) Special Job Conditions These include work restrictions, scheduling, penalties or bonuses, test reports, and the like. In alteration and modernization work, the problems of coordination are complex, and an elevator contractor experienced in this type of work should be selected. To this end, in all elevator contract work, bids should be solicited from parties named on qualified bidder lists. A complete elevator contract includes a warranty and provisions for maintenance of the installation for a specific period after completion.

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32.50╇INNOVATIVE EQUIPMENT The elevator industry is constantly developing new equipment to improve the operation and safety of standard systems. In addition, novel designs that are essentially different from standard traction arrangements are always being developed in an attempt to increase the efficiency of space use and to decrease the high cost of standard traction machinery. Among the interesting designs being developed in the first category is one that permits a car to travel horizontally in addition to its normal vertical motion, the purpose of which is to increase the number of cars using a single shaft. The second category includes a design using a linear motor (as opposed to a rotating unit) to supply traction power. These and several other special designs are discussed in Chapter 33. A recently developed interesting variation of the conventional traction design that effects a considerable space reduction is shown in Figs. 32.33– 32.36. At this writing, its principal applications are in low‐speed, low‐rise installations now generally serviced by hydraulic elevators, but with higher speeds and rises under development. The novelty of the design lies in the use of a flat (disc‐shaped),

Fig. 32.33 Disc‐shaped hoisting motor rigidly mounted on the elevator guide rail. The AC synchronous motor is connected directly to the hoisting cable drive sheave with no intervening gears. Brakes and controls are built into the assembly.

synchronous AC gearless hoisting motor, which, due to its flat disc shape, can be mounted directly on the main car guide rail at one side of the shaft (see Fig. 32.35). This essentially removes the need for a penthouse and a large machine room above the hoistway. Due to the traction motor’s position

Fig. 32.34 Schematic (a) and pictorial (b) representations of the disc‐motor‐driven elevator arrangement.

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2

Disk-type drive motor

T

B

E

3

MCOP 4

1

Closet for controls at top landing

CONTROLLER 34″ x 14″D x 72″ H

PIT LADDER

HPB

3′–6″ (1067)

A D

(a)

Fig. 32.35 (a) Section through the top of a hoistway showing dimensional data for a single 2500‐lb (1134‐kg), 200‐fpm (1‐m/s) installation with a rise of up to 80 ft (24 m). Note that the drive motor occupies less than 2 ft (0.6 m) in the width of the hoistway and that the elevator motion and operating controls (Section 32.4) are installed in a closet 42 in. (1.07 m) wide and approximately 20 in. (508 mm) deep at the top landing. (b) Elevator system basic data for the simplex (single) unit shown in (a). (Courtesy of Montgomery‐KONE.)

at the side of the hoistway, the car is roped in an underslung arrangement, as shown in Fig. 32.34. Additional space economy is achieved by the use of a small drive controller built into an alcove at the top landing (see Fig. 32.35). The pictorial hoistway representation in Fig. 32.36 shows the equipment arrangement, demonstrating the absence of a penthouse and the limited machine room space requirement. An additional advantage of this

Fig. 32.36 Pictorial representation of a disc‐type traction motor hoistway showing the system’s essentials.

arrangement is that the elevator loads and reactions are borne by the (stiffened) guide rail and transferred directly to the concrete pit below the bottom landing. This reduces the reactions borne by the machine room level in a conventional traction design and results in reduced structural loads. Compared to hydraulic elevators, this design exhibits considerable energy economy due to its use of a gearless traction machine.

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32.51 Case Study—Vertical Transportation Hong Kong International Commerce Center

Project Basics •â•¢ Location: West Kowloon, Hong Kong, People’s

Republic of China

•â•¢ Latitude: 22.3oN; longitude: 114.1oW; eleva-

tion: 60 ft (18.3 m) above sea level

•â•¢ Heating degree days: 425 base 65°F (236 base

18.3°C); cooling degree days: 8284 base 50°F

(4602 base 10°C); annual precipitation: 88 in. (2235 mm) •â•¢ Building type: New construction; mixed‐use composed of offices, a hotel, recreation areas, retail space, and an observation deck •â•¢ Size: 2,800,000 ft2 (260,000 m2) •â•¢ Completed 2010

Fig. 32.37 The ICC tower and its immediate context. (© SHK Properties; used with permission.)

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Fig. 32.38 Lower lobby level showing entry to the lower half of the double-decker elevator cars. (© Julia Lau; used with permission.)

(a)

(b)

Fig. 32.39 (a) Card key entry system for security. (b) Card is placed under the monitor for identification. (© Julia Lau; used with permission.)

(a)

(b) Fig. 32.40 (a) Main “double” lobby showing escalators and elevator entry. (b) Entry to elevators to specific floors. (© Julia Lau; used with permission.)

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(a)

(b)

Fig. 32.41 (a) Card reader to interior elevator lobby. (b) Multiple entries for high traffic flow. (© Julia Lau; used with permission.)

•â•¢ Client: Sun Hung Kai Properties •â•¢ Design team: Kohn Pedersen Fox Associates,

Wong & Ouyang Architects Ltd., and J. Roger Preston (Building Services Engineer) are key collaborators on the design development of the vertical transportation for the project.

Background. The 118‐story International Commerce Center (ICC), designed by Kohn Pedersen

Fox Associates (KPF), was the winning entry in an international design competition. A mixed‐use building, composed of offices, a hotel, recreation areas, retail space, and an observation deck, the ICC as a whole serves an important role in the larger Union Square reclamation project. As of 2013, it is the tallest building in Hong Kong. The ICC is embedded with intelligent elevator, heating/

Fig. 32.42 View from upper lobby to lower lobby at street level. (© SHK Properties; used with permission.)

Case Study—Vertical Transportationâ•…1511

Fig. 32.43 Shuttle lift arrangement (left) shows fast travel to specific destinations, and local lift arrangement (right) shows intermittent stops between and within zones. (© Wong & Ouyang (HK) Ltd.; used with permission.)

cooling, and water‐reclamation systems, while also being integrated into the municipal transit network. Design principles, client values, and a collaborative as well as interdisciplinary design process were important to the success of the project. Context. The ICC was designed as an iconic structure that would support high‐end finance, tourism, shopping, and hospitality. Kowloon Station, with which the ICC is closely integrated, aside from supporting eleven million passenger‐journeys per day (Malott, 2011) is linked, via high‐speed rail,

subway, bus, and ferry terminals, to both mainland China and Hong Kong International Airport. In dealing with this programmatic juxtaposition, KPF built upon precedents such as the Met Life building over Grand Central Station and the JR Central Towers in Nagoya, Japan. Anticipating 30,000 visitors per day, the ICC pursued a multi‐deck elevator system, with intelligent access controls, in order to increase the efficiency of the interior vertical transportation network, both in terms of energy expended, and time spent in the elevator.

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Fig. 32.44 Typical floor arrangements for office zones, observation deck, and the hotel. (© Wong & Ouyang (HK) Ltd.; used with permission.)

Design Intent. The design was meant to integrate high‐density development, high‐technology efficiency, and transit‐network integration. The leading principles behind the design were as follows: •â•¢ Set an iconic precedent for dense, integrated,

and sustainable development for Hong Kong.

•â•¢ Provide for the functional needs of the mixed

uses that the ICC supports.

•â•¢ Implement an intelligent elevator system that

satisfies both the expected passenger loads and the multi‐use nature of the building.

•â•¢ Use intelligent HVAC systems. •â•¢ Use water reclamation/reuse systems.

The architects came up with an effective vertical transportation strategy that provides good quality lift service, and at the same time, developed floor plans that optimize space utilization for all zones of the building. The office portion of the tower is divided into five office zones. Double‐deck elevator cabs minimize the requirement for lift shafts and are employed to serve the first four zones. Zones 1 and 2 are served from the two entry levels. Zones 3

References and Resourcesâ•…1513

and 4 are reached via the sky‐lobby. Zone 5 has an independent drop‐off with direct access via single‐ deck elevators. The Ritz‐Carlton Hotel has its own drop‐off and a distinctive hotel entrance with a magnificent view of the Victoria Harbor. Guests take the shuttle lifts to the reception area at the 103rd floor, before using local lifts to access the top‐zone guestrooms. Sandwiched between the Ritz‐Carlton and the office portion is Sky100 with two observation decks. The general public can take the shuttle lifts from the ticketing office in the podium below. Design Criteria and Validation. The project was intended to serve as a novel prototype by which skyscrapers could be designed and understood. Aside from the sheer scale of the project, the nature of its mixed‐use functions required KPF to approach the project in a collaborative manner. Kohn Pedersen Fox Associates, Wong & Ouyang Architects Ltd., and J. Roger Preston (Building Services Engineer), along with other specialist consultants, collaborated to achieve this end, and to help synchronize, more fully, the original design intent with the outcome.

system also helps to group passengers according to their destination requirements. The building contains 80 Schindler elevators, 40 of which are double‐deck elevator cars. They travel at speeds anywhere from 11.5 fps (3.5 m/s) to 29.5 fps (8.9 m/s), and cover distances from 236 ft (71.9 m) to 1555 ft (474 m) (Schindler Group). Such double‐deck systems, optimized via intelligent transit management systems, are crucial for multi‐use and super‐high structures such as the ICC for satisfying the large daily inflow of visitors, while not sacrificing rentable floor space. In dealing with buildings even taller than the ICC, consultants have proposed the use of triple‐deck elevator systems (Knight, 2005). FOR FURTHER INFORMATION

Wong & Ouyang (HK) Architects Ltd.: http://www .wongouyang.com Kohn Pedersen Fox Associates: http://www.kpf .com Sun Hung Kai Properties: http://www.shkp.com/ en‐US

Performance Data. Information available to date suggests success in a range of fields, but particularly in the areas of urban transportation integration, and vertical passenger movement. In terms of the latter, the ICC utilizes a wide variety of elevators, including double‐deck passenger, service, emergency service, VIP, and freight elevators. This helps to move an estimated 30,000 people/ day through the building in an efficient and less‐ energy‐consuming manner. In order to optimize system performance, an intelligent identification

Knight, W. 2005. “Architects Plan Kilometre‐ High Skyscraper.” NewScientist. http://www .newscientist.com/article/dn8445‐architects‐plan‐ kilometrehigh‐skyscraper.html#.UfYUZKzgeS0

References and Resources

Strakosch, G. R. 1983. Vertical Transportation, Elevators and Escalators, 2nd ed. John Wiley & Sons. New York. Strakosch, G. R. (ed.) 1998. The Vertical Transportation Handbook. John Wiley & Sons. New York.

Goetz, A. 2003. Up, Down, Across. Merrell Publishers. London. Stein, B., J. Reynolds, and W. McGuinness. 1986. Mechanical and Electrical Equipment for Buildings, 7th ed. John Wiley & Sons. New York.

Schindler Elevators: http://www.schindler.com Malott, D. 2011. “International Commerce Center,” Elevator World, May. Schindler Group, “East Meets West,” Next Floor. http://www.schindler.com/content/dam/web/us/ PDFs/NF‐References/ICC.pdf