Help solve an "argument" about a DPST thermostat for my ceiling heat?

Discussion in 'HVAC Heating & Cooling' started by Blind Frog, Aug 23, 2012.

  1. Blind Frog

    Blind Frog New Member

    Messages:
    3
    Location:
    Western Ohio
    My electrician buddy was admiring my new Honeywell LineVolt Pro 8000 (TL8230A1003) as we prepared to install it. This is a DPST model (two red/two black). I told him I would like to find similar models for my SPST units (One red & one black wire) for my smaller rooms. He said that since I got the thermostat at a great price, I should just do all the rooms with the same DPST model. He said I should simply pigtail both reds and both blacks (Line & Load) and then tie into the existing wiring. I told him this either could NOT be done or it would shorten the life span of the stat. He says I am an idiot. :p We have a pitcher & pizza riding on it.
  2. jimbo

    jimbo Plumber

    Messages:
    8,997
    Location:
    San Diego
  3. Blind Frog

    Blind Frog New Member

    Messages:
    3
    Location:
    Western Ohio
    jimbo - HEY!!! At first I was worried you were saying he was right and I was wrong...then I noticed you are a PLUMBER and not an electrician, so I know you are all wet and your answer can be flushed down the drain!:rolleyes:
  4. Chad Schloss

    Chad Schloss Member

    Messages:
    330
    Location:
    USA
    Check out this image and you surmise who is incorrect :)

    Attached Files:

  5. Blind Frog

    Blind Frog New Member

    Messages:
    3
    Location:
    Western Ohio
  6. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,313
    Location:
    New England
    I do not agree with the drawing of the DPST switch above! A double pole (two paths), single throw (essentially an on/off switch) is commonly used to break BOTH leads of a 240vac device...it is essentially a two pole on/off switch. It is safer since it actually removes power entirely from the device, whereas a SPST switch on a thing like a 240vac heater does stop it from operating, but there's still voltage applied to the device. If it developed an internal short, or you touched something in it and were connected to ground, you could fry yourself. SPDT and DPST are reversed in the drawing.
  7. Chad Schloss

    Chad Schloss Member

    Messages:
    330
    Location:
    USA
    Yep. These look better. Copied that image from google...

    http://www.kpsec.freeuk.com/components/switch.htm
  8. jimbo

    jimbo Plumber

    Messages:
    8,997
    Location:
    San Diego
    I was a Master Chief Electronic Technician in the Navy, couple that with on a submarine everyone learns about everything, I feel eminently qualified to comment on switches!
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