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Thread: double pole single throw snap switch use.

  1. #11
    Join Date
    Feb 2003
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    Bremerton, Washington
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    Quote Originally Posted by qcroanoke View Post
    That can be done, we usually use 3/22 300 volt insulation for alarm wiring but we can use 12 thhn just as easily.
    But you still can't mix these circuits, see 300.3(C) and the note. We all know 300.3(C) but most miss the note.
    Moderator-Washington State
    Ancora Imparo

  2. #12
    Join Date
    Aug 2017
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    Los Angeles CA
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    No matter what the NEC says, I would not do it. Has the switch been designed so that an internal mechanical failure cannot easily short across the two poles? In a line voltage situation that would not be a big deal as the OCPD would just trip but in an LV situation?

    I would use a 120v or what ever the line voltage is relay in another box wired to follow the switch. And in that case you could get by with a single pole switch as well. A relay can also be had in two or four pole DPDT configurations which gives you much more flexibility on the LV side.

    P.S I would probably put a listed pigtail fuse on that relay coil as well inside the relay box.

  3. #13
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    Nov 2010
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    Quote Originally Posted by qcroanoke View Post
    Can I legally use a double pole single throw snap switch to control lights with one side and use the other side as a dry contact (no voltage) to send an alarm that the lights are on?
    If no please give me the reference.
    Thanks!
    Along with the issues already mentioned such as Article 725, Article 404.8(C) directly prohibits this. Also UL Product Code WJQR which covers snap switches says: Multi-pole, general-use snap switches have not been investigated for more than single-circuit operation unless marked " 2-circuit" or "3-circuit."
    Even it you found one marked for 2-circuit I think there are still issues with 725.

  4. #14
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    May 2005
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    Quote Originally Posted by texie View Post
    Multi-pole, general-use snap switches have not been investigated for more than single-circuit operation unless marked " 2-circuit" or "3-circuit."
    Does that mean I was wrong when I used a 30a 2p switch as a water heater disconnect years ago?
    Code references based on 2005 NEC
    Larry B. Fine
    Master Electrician
    Electrical Contractor
    Richmond, VA

  5. #15
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    Nov 2010
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    Quote Originally Posted by LarryFine View Post
    Does that mean I was wrong when I used a 30a 2p switch as a water heater disconnect years ago?
    I don't think so. This is one of deals that has been discussed at length with various code/NRTL "experts". They say that your water heater is one circuit. Similarly, a MWBC is one circuit. All OK on the 2 pole snap switch.
    Now, how that differs from, say, 2-240 volt circuits with a 2 pole snap switch opening 1 leg of each is beyond me.

  6. #16
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    Sep 2005
    Location
    Greenville SC
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    Quote Originally Posted by qcroanoke View Post
    Can I legally use a double pole single throw snap switch to control lights with one side and use the other side as a dry contact (no voltage) to send an alarm that the lights are on?
    Not addressing the code or safety issue, rather performance; a switch designed to switch moderate current power often works for a while with mA level loads, whether low voltage DC or 120 VAC. Be wary.

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