Supply Power Wiring; Lug Sizes For Single Disconnect Or Power Block - McQuay SWP 018 Installation And Maintenance Manual

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 nonconcurrent
electric heat capability:
In the cooling mode, the loads will be composed of sup-
ply 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 running 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.
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.
16
Lug Sizes For Single Disconnect or
Power Block
Table 10. Single Disconnect
UNIT VOLTAGE
018-028 208/230
018-028 400/460
018-028 575
035-040 208/230
035-040 400/460
035 575
040 575
045 208/230
045 400/460
045 575
055-070 208/230
055-070 400/460
055-070 575
080-095 208/230
080-095 400/460
080-095 575
095-105 (6 Comp) 208/230
095-105 (6 Comp) 400/460
095-105 (6 Comp) 575
a. Disconnect is 250 amps with electric heat.
Table 11. Lug Sizes For Single Disconnect
DISCONNECT SIZE
100
150
225
250
400
600
Table 12. Lug Sizes For Power Block
UNIT VOLTAGE
018-045 ALL
055-105 400/460/575
055-105 208/230
Note: Use copper wire only.
SIZE (AMPS)
225
100
100
225
150
100
150
400
a
150
150
400
250
150
600
250
250
N/A
250
250
LUG SIZE
#6-2/0
#2-3/0
#3-300 MCM
#4-350 MCM
250 MCM-500 MCM
250 MCM-350 MCM
LUG SIZE
#6-400 MCM
#6-400 MCM
1/0-600 MCM
IM708