A colleague of mine posed this question to me today. He is doing a side job for a friend. He has to hook-up a 40A 240V single phase spa. He is running (2)#6's but found out that he had to up the neutral size to #4 (per manufacture - owners manual). Not sure why he had to. Is there any reason to have the neutral larger than the other ungrounded conductors? I told him I have not run across any situation where the neutral had to larger in any circumstance. He told me he ran a "high" harmonics xfmr which needed a larger neutral? Any responses appreciated.
My question is why the need to oversize the neutral, 240 volt residential, the neutral will the 'difference ' of the two legs, ie 20 on A and 25 on B then the total on the nutral will be 5 amps. The heaters are generally 240 volts on both and the neutral is not involved, balance. What am I missing here, it doesnt make sense to oversize the neutral in this case. Right ???!!
Re: neutral for hot tub#10982 06/26/0208:26 PM06/26/0208:26 PM
The high harmonics xfmr was just another instance where he had to up the neutral. The hot tub is another situation. ( i don't see the reason to up the neutral (secondary) in the xfmr situation either!!
Re: neutral for hot tub#10983 06/26/0208:39 PM06/26/0208:39 PM
menegt Some of these hot tubs have two heating elements that use the neutral and if one of them opens then all of the load is thrown on the neutral most of these self contained hot tubs are set up to be connected to 110v by changing the hookup cord and not useing both heating elements and the motors also are 110v
Be Fair, Be Safe Just don't be Fairly Safe
Re: neutral for hot tub#10986 06/29/0201:00 AM06/29/0201:00 AM