A few days ago I posted a question about sharing a neutral in a single phase system between a 240 firaeplace and the 102 v living circuit(someone pulled a 12-2 instead of a 12-3 and robbed a nuetral from the 120 cir.)Can someone give their opinion on the potential problems here?

A safety problem at the breaker panel or any intervening boxes for one thing. If you are working on the 120v circuit and trip the breaker you will assume there is no current on the neutral. That could be a deadly assumption. There is also the inductive heating problem 300.20.

So the 220 v fireplace needs a neutral? Generally that kind of heater is a 220 single phase, two hots and a ground.

If the fire place is only 220,then no. If it is 110/220 then yes.

I responded to this post twice in the first post. I agree with the three members above. If you rob a nuetral from another circuit, you will still have current present in the fire place connection box when the power is secured or the breaker trips. There will still be current in the connection box because of the current still present on the living-room circuit. 220v with a neutral sounds like it has other bells and whistles on the fire place, like a remote or circuit card. Usually it is 2 hots and a ground. I would run a new 12/3 back to the panel if it indeed needs a nuetral. Since this is a repost with the same question, could you please let us know the make and model of the fireplace. Someone from the forum could probably could answer your question on in one reply. Good Luck.

Sorry,been busy.Thanks for your responses.Yes the fireplace has remote but I don't know if it has to be 240 to use the remote.I can get the info when the trim starts.I only read enough when it was wired to keep someone from burning it up.Also,you know the old saying about keeping multi-wire circiuts sharing a neutral on oppisite phases?Seems impossible here:(