SPDT double-throw switch

[Ken Tannenbaum1]

I ran a 12/2 cable to use for 240v baseboard heaters in one room and would like to split one of the legs to use ONLY during the summer for an A/C. Can I install an in-line, single-pole, double-throw 20amp
switch for that purpose? Seems right but want to do the correct thing. It's awfully expensive but should work, right?

Thanks very much.

[jbfan74]

With 12/2 cable, you only have 240 volts and not 120v.
You do not have neutral wire to use for 120v.

The only way to do this is buy a pure 240 AC unit.

[Ken Tannenbaum1]

Thanks for the response...Oops, my error...the cable is 12/3, NOT 12/2...it's got a R, B, W and copper wires. Also, nothing's hooked up to the panel yet. Now, just to be sure...at present, the two hots (B+R) run to the 240v heater + the copper ground. There is no neutral necessary from what I gather. Back to me question, can I use the white neutral and split one of the hot legs (B or R) with a SPDT 20amp switch to get to the 110v A/C in the same room? Sorry for the confusion.

[drick]

The right thing to do is pull a separate circuit for the A/C. 12/2 wire isn't that expensive.

And yes what you are suggesting would work. And SPDT 20-amp switches are more $$ but shouldn't be that expensive as they are commonly used in commercial buildings.

-rick

[Ken Tannenbaum1]

Thanks.....guess my life would have been easier if the box stores carried 12/4....I should have gone to a supplier direct. HD and Lowes also don't carry that switch.
But you probably knew that. Happy New Year.

[ballvalve]

You did not need the 12 - 3 for the heater as you discovered, 2 runs of 12-2 would have solved your issue much cheaper than 12-4.

Maybe I'm missing something, but a spdt switch isnt enough, you need a switch with two poles normally off and 2 poles normally on, so that throwing it disconnects the heater completely and engages a 120v circuit to the AC, and the two may never intermix.

But then you have a 120v circuit on 1/2 of a double breaker.

The NEC guy will likely be here soon to read you the law.

[Ken Tannenbaum1]

Yes, the 12/3 was a waste. About "missing something", you know better than me...that said, based on what you've contributed, I'm going to make another run with 12/2 and not mess with doing it incorrectly. Also, the cost of the 20amp SPDT is probably as much as or more than the 12/2 cable! Anyway, safety first...I live there!
Thanks.