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.