220.61 35% Harmonic Load 120/208V 3 Phase Reduced Neutral
- Thread starter dmouz
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wirenut1980
Senior Member
- Location
- Plainfield, IN
Is the 35% harmonic load all or mostly third? Is the 35% from a specification sheet? What type of load is it? Remember that triplen harmonics add in the neutral. If I were in your shoes, I would probably try and do a quick estimate the harmonic magnitude if the loads are known, and try to get more data about the loads.
On a total wag (not recommended) if all someone told me was 35% harmonic loads, I would specify a full size neutral.
On a total wag (not recommended) if all someone told me was 35% harmonic loads, I would specify a full size neutral.
220.61 35% Harmonic Load 102/208V 3 Phase Reduced Neutral
220.61 35% Harmonic Load 102/208V 3 Phase Reduced Neutral
The engineer did break it out with quite a bit of detail, and the 35% represents the inductive lighting load. He can't fit a full sized neutral in the existing conduit. But it's only 5 feet from the building, so I'm not too sympathetic. His calculations are correct, but omitted some show window recpt.
I denied it, but i was looking for any one with additional practical experience. It was the 1st reduced neutral proposal I had seen in about 10 years.
The "Basic Calculation" in 220.61.A was correct, (based on continuious and non-continuious) and the neutral load, around 120 amps. The rest of the load was mostly for refridgeration and general use recpt's. The engineer did a good job of analysis.
It's a grocery store, so I figured they would have the possibility of addtional inductive signs and lighting for the display windows,,,,(christmas lights, etc.)
Anyway, I was also trying to remember back, to what edition the code changed, and allowed, "one or two" down sized neutral. back in the 220-22 days! I can't remember that article number.
220.61 35% Harmonic Load 102/208V 3 Phase Reduced Neutral
The engineer did break it out with quite a bit of detail, and the 35% represents the inductive lighting load. He can't fit a full sized neutral in the existing conduit. But it's only 5 feet from the building, so I'm not too sympathetic. His calculations are correct, but omitted some show window recpt.
I denied it, but i was looking for any one with additional practical experience. It was the 1st reduced neutral proposal I had seen in about 10 years.
The "Basic Calculation" in 220.61.A was correct, (based on continuious and non-continuious) and the neutral load, around 120 amps. The rest of the load was mostly for refridgeration and general use recpt's. The engineer did a good job of analysis.
It's a grocery store, so I figured they would have the possibility of addtional inductive signs and lighting for the display windows,,,,(christmas lights, etc.)
Anyway, I was also trying to remember back, to what edition the code changed, and allowed, "one or two" down sized neutral. back in the 220-22 days! I can't remember that article number.
wirenut1980
Senior Member
- Location
- Plainfield, IN
If the engineer calculated the neutral current based on the lighting and it was within the ampacity of the neutral, I feel better about the downsized neutral. But you still don't know what will be plugged into the general use receptacles. Given that it is a grocery store, I would feel ok with a down-sized neutral. But keep one question in mind...who's butt is going to be on the line if there are problems with over-heating due to harmonics in the future? Yours, the engineer's, or both?
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