Heater Calc

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bascom

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Gentlemen,
I am hooking up three single phase 480VAC 5000W resistive heaters in a delta configuration to a three phase contactor and breaker in an industrial control panel fed by 480VAC. Am I correct in calculating the three phase load at 18.1 amps? One of my electricians thought that it might be different result for resistive and inductive loads connected this way. Thanks
 
Re: Heater Calc

Bascom:
The answer to your post should 6.0 amps per line.

I=5000 divided by 480 times1.732 equal 6.0 amps

the numerial value of the sq root of 3 is 1.732
The heater are connected in a 3 phase delta configuration.

Phil c
 
Re: Heater Calc

phil,

The batteries in your calculator must be in backwards,

5000x1.732/480 = 18A

I think you divided by 1.732.

rattus

[ February 25, 2005, 11:30 PM: Message edited by: rattus ]
 
Re: Heater Calc

It must be really late back East. I believe I see 3 ea of 5000va heaters connected in a delta. That would make a total of 15,000va on a 480 3 ph system.

15000va/(480*sqt(3))= 18.042A per line or
5000 va single phase load/480v=10.416A

then add the vector load of the next single phase load, 10.416A* sqt(3)= 18.042A

It all comes out the same.

Garrett

[ February 26, 2005, 01:59 AM: Message edited by: grlsound ]
 
Re: Heater Calc

Thanks for your replies folks. I would like to close this topic now, but I couldn't find anything in the FAQ to tell me how. Thanks for your help.
 
Re: Heater Calc

Thanks for your replies folks. I would like to close this topic now, but I couldn't find anything in the FAQ to tell me how. Thanks for your help.
Click to expand...
Oh no. You don't get to close the topic. Nobody gets off that easy! We get to keep giving you free advice weather you want it or not :D

Steve
 
Re: Heater Calc

I think an important consideration in the formulas presented is that grlsound presented it correctly. The order of operations must be taken correctly.

15000VA / 480V * 1.732 = 54.125A (incorrect)
15000VA / (480V * 1.732) = 18.043A
15000VA / 480V / 1.732 = 18.043A

Bob
 
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