ECN Forum Forums General Topics of the Trade General Discussion Area Residential Multiwire Circuits

Are we talking about non linear loads in the 3 phase multiwire? That isn't good for the nuetral, but a purely resistive load shouldn't have the harmonic problems. I don't see this being an issue on a single phase service,which is a multiwire circuit by its very nature. I use multiwire circuits in rewires. Pulling 3-wire into places too small for two 12-2's in quite a labor saver.

I wish I knew more about the harmonics on a 3 phase system. However, there shouldn't be any problem with installing three duplex receps on there own dedicated 20A ciruits (phases a, b, and c) using a single neutral is there? Oh, this is on a 208Y/120 panel.

I have noticed two distinctly different approaches to residential multiwires at the DB. In south Denver, CO aluminum breaker ties are used to couple both poles and the ties are commonly available at the orange box. In northeast Nevada, no ties are used. The use of a tie-bar certainly identifies the circuits as multiwire – what happens in your area?

I appreciate everyone's input.

Roger, Iwire, under 'power quality' I was including the voltage surges that can occur in a multi-wire circuit should a shared neutral connection be disturbed, corroded, etc. I agree that harmonics are not an issue here.

The use of a shared neutral may make it a lot more expensive to later GFI or AFCI protect one of the circuits; such a two-pole breaker costs a lot more than a pair of single-poles.

I have commented often on the need to ID neutrals- something that I have almost never found. I'm not even sure that the parts houses have ever heard of white wire with a colored tracer in it!

Ever notice that whenever you make something "idiot proof." they come out with a better idiot?