Johnson Controls
5513350-JTG-1018
In order to determine the electrical service required for the
NexusPremier
™
rooftop unit, use the appropriate calcula-
tions listed below from U.L. 60335-2-40. Based on the con
-
figuration of the unit, the calculations yield different mini-
mum circuit ampacity (MCA) and maximum overcurrent
protection (MOP).
67
Electrical Data
Electrical Service Sizing
Use the following calculations to determine MCA and MOP
for units supplied with a single-point power connection:
MCA = (1.25 x Load1) + (1.25 x Load3) + Load2 + Load4
Exception:
Load3 may be multiplied by 1 if the elec-
tric heater is greater than 50kW
MOP = (2.25 x Load1) + Load2 + Load3 + Load4
Use the following calculations to determine MCA and MOP
for units supplied with a dual-point power connection:
Electrical circuit 1: compressors and crankcase heat
-
ers, condenser fan motors, electric heat (MCA 1 /
MOP 1)
Electrical Circuit 2: supply fan, return/exhaust fan,
energy recovery wheel, 120V transformer for lights/
UV lights/convenience outlet, and 24VAC control
transformers (MCA 2 / MOP 2)
Use the formulas above to calculate MCA and MOP for
electrical circuits 1 and 2.
For single/dual point power connection, if the MOP does
not equal a standard current rating of an overcurrent pro-
tective device, then the marked maximum rating is to be
the next lower standard rating. However, if the device se
-
lected for MOP is less than the MCA, then select the lowest
standard maximum fuse size greater than or equal to the
MCA.
Fixed Speed Compressor Data
Table 33:
Standard Efficiency/Standard Capacity Compressor Electrical Data
Model
Compressor
Nominal Voltage
208-230/3/60
460/3/60
575/3/60
RLA
LRA
RLA
LRA
RLA
LRA
25
1A
34.0
240.0
16.0
140.0
12.9
107.6
2A
18.1
137.0
7.8
52.0
5.8
38.9
2B
25.0
164.0
12.2
100.0
9.0
78.0
30
1A
25.0
164.0
12.2
100.0
9.0
78.0
1B
25.0
164.0
12.2
100.0
9.0
78.0
2A
22.4
149.0
10.6
75.0
7.7
54.0
2B
27.6
191.0
12.8
101.0
9.6
78.0
40
1A
48.1
245.0
18.6
125.0
14.7
100.0
1B
22.4
149.0
10.6
75.0
7.7
54.0
2A
28.2
240.0
14.7
128.0
11.3
93.7
2B
34.0
240.0
16.0
140.0
12.9
107.6
50
1A
29.5
195.0
14.7
95.0
12.2
80.0
1B
55.8
340.0
26.3
179.0
23.7
132.0
2A
34.0
240.0
16.0
140.0
12.9
107.6
2B
48.1
245.0
18.6
125.0
14.7
100.0
Using the following load definitions and calculations, de
-
termine the correct electrical sizing for the unit. All concur-
rent load conditions must be considered in the calculations,
and the highest value for any combination of loads must
be used.
Load Definitions:
•
LOAD1
is the current of the largest motor – compres-
sor or fan motor.
•
LOAD2
is the sum of the remaining motor currents
that may run concurrently with LOAD1.
•
LOAD3
is the current of the electric heaters – zero for
cooling only units.
•
LOAD4
is the sum of any remaining currents greater
than or equal to 1.0 amp.
