Electric baseboard heaters

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BigMark

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Can anyone answer me this question? A commercial customer wants us to hook up three 1500 watt electric basboard heaters, 208 volts. Being that it is approximetly 200 feet from the panel one way can we run three phase power out to the heaters and connect them (1 heater) phase a to b (2nd heater) b to c and (3rd heater) c to a ? We would hook up a 3 pole breaker at the panel. The three baseboard heaters are in the same room. They will all be on individual thermostats. Based on my calculations, we would use #8 THHN copper. The local code out here also requires all electrical to be installed in EMT. 7.2 amps per heater @ 208 volts in case any one wants to know. We are trying to save space in the panel seeing that there is not to many spaces left. I can't find anything in the code regarding this type of installation. We were going to use a 20 amp breaker also. Thanks
 
Actually we were trying to keep everything in balance. That is why we wanted to run three wires out to these heaters. I guess we could pull 2 # 6s and put it on a thirty amp 2 pole breaker instead. And yes running three # 8s would cost more than running two #6s. Any thoughts?
 
BigMark said:
Actually we were trying to keep everything in balance. That is why we wanted to run three wires out to these heaters. I guess we could pull 2 # 6s and put it on a thirty amp 2 pole breaker instead. And yes running three # 8s would cost more than running two #6s. Any thoughts?
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So the phase feed-thru's have taps to the stats being series back to each heater. How would #6's be cheaper? rbj
 
Actually if we were to run 3 wires we could use #8s. If we were to run 2 wires, we could use #6s. 200 less feet of #8 if we were to run #6s.
 
Well, to make this simple and not confusing for my guys and future people trying to troubleshoot etc, I think we are going to tie these in on a two pole 30 amp breaker. I have one other question, since these draw 7.2 amps apiece, (there are three of them remember) is this breaker to large for these three together? At what point is to much breaker for loads? I can not find it in the code book.
 
BigMark said:
Well, to make this simple and not confusing for my guys and future people trying to troubleshoot etc, I think we are going to tie these in on a two pole 30 amp breaker. I have one other question, since these draw 7.2 amps apiece, (there are three of them remember) is this breaker to large for these three together? At what point is to much breaker for loads? I can not find it in the code book.
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That way might cause a violation because we must look at each one seperate and even after applying 125% because it is a heat load your now over fused. Doing that way you would need the specs on each one as to max breaker.
 
BigMark said:
Well, to make this simple and not confusing for my guys and future people trying to troubleshoot etc, I think we are going to tie these in on a two pole 30 amp breaker. I have one other question, since these draw 7.2 amps apiece, (there are three of them remember) is this breaker to large for these three together? At what point is to much breaker for loads? I can not find it in the code book.
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You're good with the three of them on a 30a breaker. 7.2a x 3 x 1.25 gets you 27a.
 
If you are going to run 2 #6's due to voltage drop and keep them off the same phased vs trying to balance them off of all 3 phases then your calculation looks good to me. For the small amount of amperage I would not be worrying about balancing out the load on the phases. You save money on wire and a 3phase breaker now that you only need a one double pole.
 
If you hook this up as A/B, B/C and A/C it will be a 3 phase 4500 watt load line currents of 12.5 amps. #10s will keep the voltage drop under 3%, and you only need a 3 pole 20 amp breaker.
 
don_resqcapt19 said:
If you hook this up as A/B, B/C and A/C it will be a 3 phase 4500 watt load line currents of 12.5 amps. #10s will keep the voltage drop under 3%, and you only need a 3 pole 20 amp breaker.
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I'm not quite sure how you come up with 12.5 amps. Could you or anyone explain? The way I was figuring it, but I could be wrong, is I was adding two heaters on each phase and just doubleing the amperage. Which is correct? Also there are going to be two pole line voltage stats for each heater.
 
BigMark said:
I'm not quite sure how you come up with 12.5 amps. Could you or anyone explain? The way I was figuring it, but I could be wrong, is I was adding two heaters on each phase and just doubleing the amperage. Which is correct? Also there are going to be two pole line voltage stats for each heater.
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You can not just add up the amps with three phase, it will not work.

You have three 1500 watt 208 volt heaters on a balanced 3 phase circuit.


3*1500=4500 watts

4500/208/1.73=12.5 amps per phase.
 
I would also label heater wiring compartment cover an thermostat what panel this is fed from an also the circuit breaker numbers for safety - example panel A circuits 2-4-6

Just my opinion
 
Jim W in Tampa said:
Yes but now we have a 1500 watt load protected by a 30 amp breaker. Can fuse it that high ?
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It looks to me according to the 2008 NEC Article 424.3 (a) we can fuse it (circuit breaker) that high, but not more unless it is fixed infared heating equipment in non-dwelling occupacies which this application (baseboard heaters) is not. Upon reading Article 424.19 Disconnecting means. Does this mean we need a disconnect switch for each heater installed.
 
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Guess I shouls look at the entire article before posting the question about disconnecting means. I found it in 424.20. Looks like I do need a disconnect and I can use the thermostat as such as long as it meets all the requirements for such.
 
iwire said:
You can not just add up the amps with three phase, it will not work.

You have three 1500 watt 208 volt heaters on a balanced 3 phase circuit.


3*1500=4500 watts

4500/208/1.73=12.5 amps per phase.
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If the three heaters are going on and off from the thermostats wired this way, is the load still balanced? or does it make a difference?
 
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