Two SPST relays in place of a DPST relay?

Discussion in 'General Electronics Chat' started by cherynk, Feb 3, 2016.

  1. cherynk

    Thread Starter New Member

    Feb 3, 2016
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    0
    Are there any issues using two SPST relays instead of a DPST relay? I am running a 220 load through the relay and bought the wrong thing. A DPST is more expensive than two SPST so I figured Id just buy another SPST and run each leg through a separate SPST relay. The relay control is 12VDC. I would run these in parallel rather than in series, correct? There wouldn't be any issues with one relay connecting before the other, right?
    Thanks for your help.
     
  2. MaxHeadRoom

    Expert

    Jul 18, 2013
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    Normally no problem, run in parallel.
    Max.
     
  3. MrSoftware

    Active Member

    Oct 29, 2013
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    Your MTBF will be lower since you have double the mechanical parts (greater chance for failure), if that's a consideration.
     
  4. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
    4,867
    993
    There "could" be..
    But if you are just using the relays to switch each side (Line/Neutral) then it won't matter..

    Even double pole relays can have one pole that fails to switch while the other is just fine.. (VERY common on "low cost" relays... virtually non-existent on a quality relay like Omron)
     
  5. MaxHeadRoom

    Expert

    Jul 18, 2013
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    If 200v 1ph (L1&L2) as in N.Am. then you can switch both sides, if 220vac L1 & N then the N is not normally switched (or fused).
    Max.
     
  6. eetech00

    Active Member

    Jun 8, 2013
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    You should consider the failure modes of your circuit. What if one relay energizes but the other doesn't? Not saying it's a problem but should be considered.
     
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