circuit selector switch

Discussion in 'Electrical Forum discussion & Blog' started by beekerc, Oct 13, 2008.

  1. beekerc

    beekerc IT Consultant / Network Engineer

    Messages:
    94
    Location:
    Seattle
    is there such a thing as a switch that would allow an A/C circuit branch to connected to two different circuits from the main panel? Obviously not at the same time.
  2. Speedy Petey

    Speedy Petey Licensed Electrical Contractor

    Messages:
    1,000
    Location:
    NY State, USA
    WHY would you possibly need to do this??? :confused:

    Is this a 240v or 120v circuit?
  3. Chris75

    Chris75 Electrician

    Messages:
    608
    Location:
    Litchfield, CT
    The only time I see this come up is with a landlord that owns a 3 family with only 3 meters and no house meter and a well. :D
  4. Thatguy

    Thatguy Homeowner

    Messages:
    1,459
    Location:
    MD
    DPDT?
    3PDT?
    It might be cheaper to use a SPST switch controlling a 3PDT relay with a 120vac coil.
  5. Bill Arden

    Bill Arden Computer Programmer

    Messages:
    584
    Location:
    MN, USA
    You could use a generator panel to switch between two sources.

    I hope you aren't trying to bypass a off-peak or "cycled AC" reduced rate meter.
  6. beekerc

    beekerc IT Consultant / Network Engineer

    Messages:
    94
    Location:
    Seattle
    circuit switch

    I have a generator with a limited number of circuits that it can feed. one of them is the exterior security lights, currently 10A of max load on a 15A breaker. They are quartz/halogen lamps (i'm told these don't have the same in-flow spike as incandescents, but i don't know if this is true) and only come on at night. I have a set of lights in the attic (4 CFL's, so pretty low load, but I also have outlets for power tools). Originally I had made this part of the security lights branch, but I also have just pulled a fresh line (not an easy task) into the attic to service the microwave (long story as to why i had to do that) and I was thinking of switching the attic lights and outlets to the microwave circuit. the chances of the microwave being engaged while i'm using power tools in the attic is zero. However, in the event of a power outage, I'd like to have lights in the attic if i need to go up and check anything out. I'd like to be able to switch the attic circuit from the microwave to the line feeding the security lights (on the generator).

    One thought is to run a set of outlets to the microwave circuit and just include the 4 CFL's on the security lights circuit, but that would require tearing down the whole attic run and redoing it, especially replacing the light fixtures that have outlets in them with keyless (i think they're called) sockets. it's not the cost, it's the level of effort and pain (scraped knuckes and hands) that was incurred in the initial installation, and then having to distribute new receptacles to those same locations so i have the same coverage. i know i could just cap/tape the existing outlets, but when i sell the house, i don't want to have to worry about the new owner simply removing the cover, plugging in and tripping the breaker.

    Okay, so the prudent/wise thing would probably be tear it down and rebuild it. i'm looking for a more expedient solution, provided that it's code compliant.

    Thanks
    BeekerC
  7. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    27,247
    Location:
    Cave Creek, Arizona
    switch

    heavy duty DPDT switch with the feed to the AC off the center common terminals and a feed to each end of the switch would do it. You would not want to make the switch over under load, however.
  8. beekerc

    beekerc IT Consultant / Network Engineer

    Messages:
    94
    Location:
    Seattle
    switch

    Thought it might be something as simple as that, and while i know a few things about electricity and wiring, i am far from an expert. when you say "over/under load" do you mean that the switch is rated for the amperage of the lines? or something else?

    both feeds are 15A, the circuit branch is 15A, so as long as i get a 15A rated switch I'm okay.

    with regard to the a/c feed, it think what you described is backwards (unless i've misinterpreted your words). I have two hot feeds and the switch determines which one the end circuit is attached to.


    what i need

    panel ---- microwave --------+
    ..............................\
    ...............................\
    ................................0----- attic lights


    panel ---- security lights -----+
    (line covered by backup gen)

    so when the power goes out i can throw the switch over and run the lights off the gen circuit

    <please ignore the dots. they're place holders, i couldn't figure out how to insert a non-breakable space into the message>

    Last edited: Oct 17, 2008
  9. Thatguy

    Thatguy Homeowner

    Messages:
    1,459
    Location:
    MD
  10. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,313
    Location:
    New England
    A single pole, double-throw wall switch should work fine if you want it manually controlled. If you want a little more margin, get a 20A switch. Those should break before make, or to ensure that, get an on-off-on switch where you have a definite off position in the middle. If you need to switch the neutral, too, you'd need a double-pole, double-throw switch.

    try this http://www.leviton.com/OA_HTML/ibeCCtpItmDspRte.jsp?item=2968&section=10046
    Last edited: Oct 17, 2008
  11. Thatguy

    Thatguy Homeowner

    Messages:
    1,459
    Location:
    MD
    If you can find a relay with a 24vac coil that can control this much power you can mount the relay-controlling switch in a convenient location. The NEC rules are much relaxed about running wires for voltage & current this low.
  12. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    27,247
    Location:
    Cave Creek, Arizona
    circuit

    If by A/C you meant an airconditioner, then I would assume that would be 220/240 volts in which case you would need a DPDTswitch. A center off position would prevent switching under load but would also increase the cost of the switch. If this is a 120 volt circuit then a SPDTswitch will be all that is necessary and that is what a 3 way switch is.
  13. brownizs

    brownizs In the Trades

    Messages:
    196
    Location:
    Springfield, IL
    We used to use them for supply power to different branch circuits on the same panel *A circuit/B circuit.
  14. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    27,247
    Location:
    Cave Creek, Arizona
    switch

    A three way switch with the generator to one traveler terminal and the main power to the other. The common terminal goes to the lights. One way the generator is connected, switch it over and the main power runs them.
  15. beekerc

    beekerc IT Consultant / Network Engineer

    Messages:
    94
    Location:
    Seattle
    circuit switch

    thanks to all for the good information. i actually stumbled across a much simpler solution. probably due to jostling by the painter, a 4 of the 10 halogen lamps that comprise my exterior security lights burned out and needed to be replaced. i discovered that for this bulb format (GY8.6) there were lower wattage bulbs than the 100watt that came with the fixtures. (should have figured this out on my own, but for some reason......) decided to try a pair each of 50's and 75's. as it turns out a i really can't distinguish between the 50's and 100's. so, i just plan to replace 8 of the 10 lamps with 50's and that cuts my load by 40%. plenty of extra capacity now.
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