HVAC load calculation

Status
Not open for further replies.
W

wireperson

Senior Member
Location
Florida
I need to find feeder size for a panel that is going to feed 2 condensing units and 2 air handler units
the info is as follow
C.U.

compressor RLA 28
fan 1.4



total 29.4

AHU

heater + blower = 10.8kw (taken from AHU Electrical data sheet)

10.8 / 240 V = 41.6 = 42 amps



now, how do I do my load calculation from here , to determine my feeder size and OCP? do I use only the bigest load (AHU) ?
 
wireperson said:
I need to find feeder size for a panel that is going to feed 2 condensing units and 2 air handler units
the info is as follow
C.U.
compressor RLA 28
fan 1.4
total 29.4
AHU
heater + blower = 10.8kw (taken from AHU Electrical data sheet)
10.8 / 240 V = 41.6 = 42 amps
now, how do I do my load calculation from here , to determine my feeder size and OCP? do I use only the bigest load (AHU) ?
Click to expand...
Is this 2 heat pumps with 10 kw electric heat or is 2 A/C units with 10 kw
electric heat?
 
Common practice is to use the nameplate data. Art 424 & 440 both require units to be marked with minmum circuit amps and maximum overcurrent.

If you are calcualting from "raw" data be sure to taek into account that heating loads are considered continuous.
Also, you did not mention if the units are heat pumps where you might have auxiliary heating and condensors running at the same time.
 
again, nameplate data should be your guide.
That said using raw data
10.8 kw x 2 x 125% = 27 kw
29.4 x 1.25 + 29.4=16 kw
If I did the math correctly, 180 amp feeder
 
shoulnd't I use the the largest load only ? the air handling units in this case? since the condensing unit and the heater are non coincident loads?
 
correct .. my mind was thinking heat pumps as I am accustomed to them.
sorry 113 amp feeder 1/0 Romex/SE or #2 THHN
 
Status
Not open for further replies.
Top