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Table 1 — Physical Data
LEGEND
*Evaporator coil fin material/condenser coil fin material.
†Weight of 14-in. roof curb.
**Circuit 1 uses the lower portion of condenser coil and lower portion of evapora-
tor coils, and Circuit 2 uses the upper portion of both coils.
††Due to belt and pulley style, pulley cannot be set from 0 to 1
1
/
2
turns open.
UNIT 551A
155 180 240
NOMINAL CAPACITY (tons)
12 15 20
OPERATING WEIGHT (lb)
Unit
Al/Al*
1575 1650 1750
Al/Cu*
1725 1800 1900
Cu/Cu*
1855 1930 2030
EconoMi$er
80 80 80
Roof Curb†
200 200 200
Perfect Humidity™ Dehumidification Package
40 40 40
COMPRESSOR
Quantity...Model (Ckt 1, Ckt 2)
1...ZR72KC, 1...ZR57KC 1...ZR94KC, 1...ZR72KC 1...ZR125KC, 1...ZR108KC
Number of Refrigerant Circuits
22 2
Crankcase Heater Watts
70 70 70
Loading (% of Full Capacity)
0, 56, 100 0, 60, 100 0, 60, 100
Oil (oz) (Ckt 1, Ckt 2)
60, 66 85, 60 110, 110
REFRIGERANT TYPE
R-22
Expansion Device
TXV
Operating Charge (lb)**
Circuit 1
20.7 19.5 18.5
Circuit 2
11.9 13.45 13.3
CONDENSER COIL
Cross-Hatched
3
/
8
-in. Copper Tubes, Aluminum Lanced, Aluminum Pre-Coated,
or Copper Plate Fins
Rows...Fins/in.
4...15 4...15 4...15
Total Face Area (sq ft)
21.7 21.7 21.7
CONDENSER FAN
Propeller Type
Nominal Cfm
10,500 10,500 14,200
Quantity...Diameter (in.)
3...22 3...22 2...30
Motor Hp...Rpm
1
/
2
...1050
1
/
2
...1050 1...1075
Watts Input (Total)
1100 1100 3400
EVAPORATOR COIL
Cross-Hatched
3
/
8
-in. Copper Tubes, Aluminum Lanced or Copper Plate Fins, Face Split
Rows...Fins/in.
4...15 4...15 4...15
Total Face Area (sq ft)
17.5 17.5 17.5
EVAPORATOR FAN
Centrifugal Type
Quantity...Size (in.)
2...10 x 10 2...12 x 12 2...12 x 12
Type Drive
Belt Belt Belt
Nominal Cfm
5200 6000 8000
Std Motor Hp
2.9 5 7.5
Opt Motor Hp
3.7
Motor Nominal Rpm
1725 1745 1745
Std Maximum Continuous Bhp
3.13 6.13 9.47 [208 v], 10.33 [230 v and 460 v]
Opt Maximum Continuous Bhp
4.38 N/A N/A
Motor Frame Size
56H 184T 213T
Fan Rpm Range Low-Medium Static
834-1064 873-1021 1002 -1151
High Static
1161-1426 1025-1200 1193-1369
Motor Bearing Type
Ball Ball Ball
Maximum Allowable Rpm
1,550 1,550 1,550
Motor Pulley Pitch Dia. Low-Medium Static
3.1/4.1 4.9/5.9 5.4/6.6
High Static
3.7/4.7 4.9/5.9 5.4/6.6
Nominal Motor Shaft Diameter (in.)
7
/
8
1
1
/
8
1
3
/
8
Fan Pulley Pitch Diameter (in.) Low-Medium Static
6.0 9.4 9.4
High Static
5.2 8.0 7.9
Nominal Fan Shaft Diameter (in.)
1
3
/
16
1
7
/
16
1
7
/
16
Belt, Quantity...Type...Length (in.) Low-Medium Static
1...BX...42 1...BX...50 1...BX...54
High Static
1...BX...42 1...BX...48 1...BX...50
Pulley Center Line Distance (in.)
13.5-15.5 13.3-14.8 14.6-15.4
Speed Change per Full Turn of Movable Low-Medium Static
58 37 37
Pulley Flange (Rpm) High Static
67 44 44
Movable Pulley Maximum Full Turns
From Closed Position
4†† 4†† 4††
Factory Speed
3.5 3.5 3.5
Factory Speed Setting (Rpm) Low-Medium Static
978 965 1095
High Static
1327 1134 1303
HIGH-PRESSURE SWITCH (psig)
Cutout
426
Reset (Auto.)
320
LOW-PRESSURE SWITCH (psig)
Cutout
27
Reset (Auto.)
44
FREEZE PROTECTION THERMOSTAT (F)
Opens
30 ± 5
Closes
45 ± 5
OUTDOOR-AIR INLET SCREENS
Cleanable
Quantity...Size (in.)
2...20 x 25 x 1
1...20 x 20 x 1
RETURN-AIR FILTERS
Throwaway
Quantity...Size (in.)
4...20 x 20 x 2
4...16 x 20 x 2
Al —
Aluminum
Bhp —
Brake Horsepower
Cu —
Copper
TXV —
Thermostatic Expansion Valve