Supply Power Wiring; Lug Sizes For Single Disconnect Or Power Block - McQuay SWT C Series Installation And Maintenance Manual

Table 9 Supply Fan Motor Data
Horsepower
3
Premium Efficiency
5
Premium Efficiency
7.5
Premium Efficiency
10
Premium Efficiency
15
Premium Efficiency
20
Premium Efficiency
25
Premium Efficiency
a. 460/60/3 motors are used. Derate nameplate horsepower to 0.83 to obtain actual horsepower.

Supply Power Wiring

1. Units require three-phase power supply.
2. Allowable voltage tolerances:
a. 60 Hertz
Nameplate 208V: Min.187V, Max. 229V
Nameplate 230V: Min.207V, Max. 253V
Nameplate 460V: Min.414V, Max. 506V
Nameplate 575V: Min.518V, Max. 632V
b. 50 Hertz
Nameplate 400V: Min. 342V, Max. 418V
3. Power lead wire sizing:
a. For units with cooling capability (all concurrent
loads) with or without hot water heating and circuits
with motor loads only:
MCA = 1.25 (largest motor RLA or FLA) + other
loads + 2 amps.
b. For units with cooling capability and non concurrent
electric heat capability:
In the cooling mode, the loads will be composed of
supply fan motor and compressors. In heating mode,
the loads will be composed of supply fan motor and
electric heater. The MCA is calculated for unit run-
ning in either mode; the highest value obtained is used
for the MCA.
(1) For unit in cooling mode:
MCA = 1.25 (largest RLA or FLA) + other loads +
2 amps.
(2) For unit in heating mode:
MCA = 1.25 (electric heat FLA + Fan FLA) + 2
amps.
20
208/60/3
TYPE
High Efficiency
High Efficiency
High Efficiency
High Efficiency
High Efficiency
High Efficiency
High Efficiency
230/60/3
FLA FLA
9.9 9.0
9.3 8.2
14.8 14.0
15.7 13.6
22.3 21.6
22.3 20.0
29.7 28.0
29.0 25.8
44.4 40.6
43.4 37.8
57.0 50.0
57.0 49.0
69.8 62.0
70.5 61.0
4. Size wires in accordance with Table 310-16 or 310-19 of
the National Electrical Code.
5. Wires should be sized for a maximum of 3% voltage
drop.
Lug Sizes For Single Disconnect or
Power Block
Table 10. Single Disconnect
UNIT
018-028
018-028
018-028
035-040
035-040
035
040
Table 11. Lug Sizes For Single Disconnect
DISCONNECT SIZE
100
150
225
Table 12. Lug Sizes For Power Block
UNIT
018-040
a
460/60/3
400/50/3
FLA FLA
4.5 4.5
4.1 4.1
7.0 7.0
6.8 6.8
10.8 10.8
10.0 10.0
14.0 14.0
12.9 12.9
20.3 20.3
18.9 18.9
25.0 25.0
24.5 24.5
31.0 31.0
30.5 30.5
VOLTAGE SIZE (AMPS)
208/230
400/460
575
208/230
400/460
575
575
LUG SIZE
#6-2/0
#2-3/0
#3-300 MCM
VOLTAGE
ALL #6-400 MCM
575/60/3
FLA
3.4
3.1
5.3
5.2
8.2
7.4
11.0
10.3
16.2
14.1
20.0
18.9
24.3
24.2
225
100
100
225
150
100
150
LUG SIZE
IM709