# single-pole double-throw switch

Discussion in 'Electrical and Wiring' started by kentannenbaum, Dec 27, 2010.

1. Dec 27, 2010

### kentannenbaum

#### Member

Joined:
Oct 31, 2010
Messages:
17
3
I just ran a 12-3 line for 240v baseboard heaters and now want to use one of those lines for an A/C in the same room during the summer. The switch is really expensive, but is there anything wrong with using an in-line SPDT 20amp switch that CLEARLY would cut half the power to the heaters during the summer only? The switch has center "off" position and two "on" positions to channel current one way or the other. Thanks.

Last edited: Dec 27, 2010
2. Dec 27, 2010

### kok328

#### Well-Known Member

Joined:
Nov 20, 2007
Messages:
2,755
249
Is the A/C 120V or 240V?

If 120V, where you getting your neutral & ground from?

To the best of my knowledge a SPDT will cut both legs of power in a 2-pole circuit.

3. Dec 27, 2010

### kentannenbaum

#### Member

Joined:
Oct 31, 2010
Messages:
17
3
This is a 12/3 cable. My plan for the 120v A/C WAS to use the white wire as neutral and of course the copper as ground AND to use the SPDT to split one of the hot wires which goes to the baseboards in winter and use that "split off" leg for the 120v A/C in summer.
BUT, I decided to run a dedicated 12/2 cable to the A/C which doesn't exist yet. Too bad I didn't think to go to an electric supply house a use 12/4. Would have saved a lot of time. Again thanks.

4. Dec 28, 2010

### JoeD

#### Well-Known Member

Joined:
Mar 16, 2006
Messages:
1,528
273
SPDT = Single pole double throw. Single pole means it only cuts on leg.
If you want to cut both legs you need a DPDT.Double pole double throw.

Not sure how the code feels on this but a normal three way switch could work. Put one hot on the common and the heater on one traveller and the AC on the other traveller. Only one device will be able to be on at any time.

5. Dec 29, 2010

### speedy petey

#### Lic.Electrical Contractor

Joined:
Mar 15, 2006
Messages:
470
44
6. Jan 28, 2011

### ajaynejr

#### Member

Joined:
Jan 28, 2011
Messages:
8
0
An ordinary 3 way switch is a single pole double throw switch.

Be sure that the switch current rating is sufficient before using it to control a heater.

7. Jan 28, 2011

### kentannenbaum

#### Member

Joined:
Oct 31, 2010
Messages:
17
3
Actually, I decided to run another separate line for the A/C. Thanks very much for the insight.

Title
Replies Views
Last Message

Replies:
4
Views:
70

Replies:
2
Views:
17

Replies:
0
Views:
7
4. Sticky