Current Calculation for 120/240 panel

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Daniel S

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Texas, Garland
Hello Guys,

I think this question might be stupid but I am just an student :)

I have a 120/240 Panel which supplies both 120 and 240 Loads. The total load is 15.8 KVA. If it was a single phase 120 panel or a 3phase 120/208 I would know how to calculate the current, but this split phase panel is confusing for me.
shall I use 240 V or 120 V to calculate the total current of the panel? or another way?

Thanks.
 
Divide total KVA by 240 volts works unless you have significant unbalance on the 120 volt loads. Then you better figure that worst case unbalance and add the corresponding amps to one side to get a final result.

Example: say you had three identical 12 amp 120 volt loads. Two of them balance out to 12 amps @ 240 volts, but the third is an extra 12 amps on whichever line it is connected to. Generally you would provide this with a feeder capable of carrying at least 24 amps both sides even though one side is only carrying 12.
 
charlie b said:
You use 240 volts, and you get a current value of 65.8 amps. Welcome to the forum.
Click to expand...

Main breaker 200 amp
200 x 240 x 80%=3840

(5) 20 amp
5 x 20 ×120× 80%= 9600

(1) 2 pole 30 Water heater continous load
1 x 30 x 240 x 125%= 5760

(2) 2 pole 50 amp breaker
2 x 50 x 240 x 80% = 19200

Total= 19200+5760+9600= 34560

34560 ÷ 240 = 144
Require at least 150 main breaker

So i was told can use this method as a quick reference. Is this to be true
 
This thread is more than 5 years old.. I am closing it. The software is supposed to close all threads after 1 year but it apparently is not doing existing ones that were imported to the new software
 
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