I would use the constant hot side at the heater for a 20 amp receptacle hot and the ground for a neutral & ground. I don't think this is proper since I have no true neutral but what is the danger?

NeedAC

Are you planning on trying to keep the 240 too? That's very dangerous to do and against code. If you are converting 240 to 120, use the black at the breaker, the white to neutral and the ground to ground.

Are you planning on trying to keep the 240 too? That's very dangerous to do and against code. If you are converting 240 to 120, use the black at the breaker, the white to neutral and the ground to ground.

I was planning on keeping the 240 VAC heater circuit operational, though that would not be in use simultaneously with the 120 VAC receptacle. I could connect to a neutral wire at an adjacent receptacle, would this make the circuit proper?

Could someone please explain the potential danger of this wiring configuration?

First, connecting a separate wire neutral is not code and unless you have a 4 wire connection with 2 hots, a neutral and ground, what you are considering is also against code and unsafe.

First, connecting a separate wire neutral is not code and unless you have a 4 wire connection with 2 hots, a neutral and ground, what you are considering is also against code and unsafe.

OK, I guess my plan to add three receptacles for window AC powered from the nearby resistance heater is a no go. Unless I use 240 V AC units, which are likely too large for the task? Thanks very much for the advice.

240VAC is just more efficient. Finding 240VAC Air conditioning units is not hard but they will be most likely larger BTU than you need. If you have space in your panel, run a couple of new lines. If you read up on 240VAC, you will see that each power conductor is phased opposite each other, even if it looks like they are on the same side of the breaker box, one side is cross connected to the other side.

240VAC is just more efficient. Finding 240VAC Air conditioning units is not hard but they will be most likely larger BTU than you need. If you have space in your panel, run a couple of new lines. If you read up on 240VAC, you will see that each power conductor is phased opposite each other, even if it looks like they are on the same side of the breaker box, one side is cross connected to the other side.

I may just bite the bullet and install 2 split AC systems, I was trying to Yankee my way out of the added expenditure.
Thanks again for your help.