JOHNSON CONTROLS
74
FORM 145.05-NOM7
ISSUE DATE: 10/31/2019
SECTION 2 – INSTALLATION
ELECTRICAL DATA
Field Power Wiring
Wiring must comply with all applicable codes and or-
dinances.
A single point power terminal block is provided as stan-
dard and wiring within the unit is done in accordance
with the National Electrical Code. All branch circuits
within the control panel are individually fused. A single
field supplied disconnect is required, or a unit mounted
non-fused disconnect can be ordered with the unit.
Holes are located in the top of the control compartment
for the entry of the power wiring. There is also a 7/8"
diameter hole in the same location of the control wiring.
Disconnect
Disconnecting means are addressed by Article 440 of
the National Electrical Code (NEC), which requires
“disconnecting means capable of disconnecting air con-
ditioning and refrigerant equipment including motor-
compressors, and controllers, from the circuit feeder.”
The disconnect switch should be selected and located
with the NEC guidelines. Location requirements per
NEC are that the disconnect be located in a readily ac-
cessible position within sight (50 feet) of the unit.
Electrical Service Sizing
In order to determine the electrical service required for
the unit, use the appropriate calculations listed below
from the National Electrical Code. Based on the con-
figuration of the unit, the calculations yield different
MCA (Minimum Circuit Ampacity), and MOP (Maxi
-
mum Overcurrent Protection).
The MCA value is used to size the wire for the power
service to the unit. The MOP is used to size either the
breaker or fuse for the entire unit.
Using the following formulas, determine the correct
electrical sizing for the unit. All concurrent load con-
ditions must be considered in the calculations, and
you must use the highest value for any combination
of loads.
MCA
For units with cooling capability (all concurrent loads)
with or without hot water or steam heat:
Field power wiring connected to incoming
power termination point must be copper
conductor only. Aluminum wire cannot
be connected to the incoming power ter-
mination point.
MCA = 1.25 (largest motor RLA or FLA) plus
other loads plus 2 amps.
For units with cooling capability and non-concurrent
electric heat the following calculations are required. In
the cooling mode, the loads are composed of the com-
pressors and supply fan motor loads. In the heating
mode, the loads are composed of the supply fan motor
and the electric heaters. The MCA is calculated for the
unit in the cooling mode and in heating operation. The
highest value obtained is used for the MCA.
For unit in the cooling mode:
MCA = 1.25 (largest motor RLA or FLA) plus
other loads plus 2 amps.
For units in the heating mode:
With Electric Heater KW 50 KW or less:
MCA = 1.25 (electric heat FLA plus supply fan
motor amps) plus 2 amps.
With Electric Heater KW greater than 50KW:
MCA = 1.25 (supply fan motor amps) plus elec
-
tric heat FLA plus 2 amps.
MOP
For units with cooling capability (all concurrent loads)
with or without hot water or steam heat:
MOP = 2.25 (largest motor RLA or FLA) plus
other loads plus 2 amps.
For units with cooling capability and non-concurrent
electric heat the following calculations are required. In
the cooling mode, the loads are composed of the com-
pressors and supply fan motor loads. In the heating
mode, the loads are composed of the supply fan motor
and the electric heaters. The MOP is calculated for the
unit in the cooling mode and in heating operation. The
highest value obtained is used for the MOP.
For unit in the cooling mode:
MOP = 2.25 (largest motor RLA or FLA) plus
other loads plus 2 amps.
For units in the heating mode:
With Electric Heater KW 50 KW or less:
MOP = 2.25(electric heat FLA plus supply fan
motor amps) plus 2 amps.
With Electric Heater KW greater than 50KW:
MOP = 2.25 (supply fan motor amps) plus electric
heat FLA plus 2 amps.
Contact the factory for electric heat full load amp data.