120/240 volt 3 phase service calculation condo building

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Jimmy4645

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Can I have a 120/240 volt, 3 phase panel (high phase leg) and connect (10) ten 5KW, single phase electrical wall heaters utilizing all three phases.

So, the first wall heater will be connected to AB leg, the second wall heater connected to BC, the thrid wall heater connected to CA leg and so on..

I also have a sub-feed 120/240 volt single panel that services lighting and receptacles connected to AC legs (non-high legs), which the loads is 6KW.

Is the following panel size calcualtion correct?

10 X 5KW wall heaters = 50KW divided by 240V three phase =120.4 amps
6KW lighting / receptacles = 6KW divided by 240V single phase = 25 amps

So, the total panel amps is (120.4 amps + 25 amps) =145.4 amps. I would install a 200A, 120/240V three phase panel with a 200A three pole main circuit breaker.

Is this correct??

Thanks
 
In that you are connecting 10 single phase heaters to a 3 phase panel, the load will not be evenly balanced. To be on the safe side you might look at your loading per phase.
That said, the 200 amp panel will allow for this inbalance.
A 150 amp panel would not suffice due to that inbalance.
 
If my calculations are correct. Yes a 150 amp panel would not be enough because it doesn't leave me without any future provisions too..

The most important thing is that i did the calculation correct. Having multipule 240 volt single phase loads across a 240 volt three phase panel with the high leg.. adding up all the KW and to divide by 240 volt three phase which is (240 times the square root of 3 = 415)..
 
in terms of total load, I agree with your calculations.
I was simply pointing out that your load calculation does not actually address the load per phase.
 
calculating the load per leg.

A = 20.5KW
B = 17.5KW
C = 18Kw

What will be the total amperage per leg on a 120/240V 3 phase system??
 
Jimmy4645 said:
calculating the load per leg.

A = 20.5KW
B = 17.5KW
C = 18Kw

What will be the total amperage per leg on a 120/240V 3 phase system??
Click to expand...

While it's only an approximation, divide each by (240 ? √3), or 138.56...

A = 147.95A (148.0)
B = 126.30A (126.7)
C = 129.90A (130.5)

The number in parentheses are the currents determined through vectorial summation (i.e. a more precise method).
 
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