Non-linear loads

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sjaniga

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Iam installing a 400 amp 208/120y panel in a dollar store, and am wondering if I have to count the neutral as a current carrying conductor? The flourescent lighting is approx
100 amps and the calculated load is 263 amps. 310-15(4)(c) States that if the major portion of the load is non-linear I have to derate the neutral, would 100 amps make it a major portion?
and is all flourescent lighting a non-linear load?
 
dereckbc

dereckbc

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Staff member
Location
Plano, TX
Re: Non-linear loads

SJANIQA, you will probable get two different opinions. One group will say no need to count the neutral, and another will say you should.

Consider this. If there is going to be sensitive electronic loads like cash registers, optical scanners, routers, etc I would consider using a K-4 transformer, count the neutral as a current carrying conductor, and size the neutral same as phase conductors.

On the other hand if all it is going to supply is lighting, HVAC, and general-purpose outlets, do not use a K-rated transformer or count the neutral.

It really comes down to economics. If you go the K rated route no one will question you other than economics, but no technical problems will likely occur. Go the other route, you will save some bucks, but risk problems down the road if heavy nonlinear loads develop.
 
bob

bob

Senior Member
Location
Alabama
Re: Non-linear loads

I assume that your 100 amp lighting load is the total and you would have 33.3 amps per phase. Also the total load of 263 amps would be about 88 amps per phase. If that is correct the lighting is not a major part of the load. However Derick make some good points. The Dollar Stores I've seen would not have 12kw in lighting. Thats
what the 33.3 amps equates to but I have not seen the plans.
 
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