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Amateur question regarding grounding

Discussion in 'General Electronics Discussion' started by mk2mark, Aug 25, 2011.

  1. mk2mark

    mk2mark

    5
    0
    Aug 25, 2011
    I'm trying to convert a fridge for curing meat which requires temperatures above what the fridge can do, but using an external controller with sensor should turn the fridge on and off to achieve the correct temp.

    Unfortunately I want to complicate things and periodically bypass the controller with a switch. The attached jpg shows as far as I've gotten, I'm not quite sure if the neutral wires are connected correctly though - something about joining the neutrals for the input and output of the controller seems wrong. I'd appreciate any help with this, otherwise I can do a less elegant solution that I know will work.
     

    Attached Files:

  2. daddles

    daddles

    443
    3
    Jun 10, 2011
    Why not use a single SPDT switch to switch the hot either between the fridge or the controller? Then there's no need for a relay.
     
  3. mk2mark

    mk2mark

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    0
    Aug 25, 2011
    That might be the best thing alright. I though a relay would be an easier option considering I'd need a beefy switch but I guess not.
     
  4. mk2mark

    mk2mark

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    Aug 25, 2011
    I've attached a new circuit, how does that look?
     

    Attached Files:

  5. Resqueline

    Resqueline

    2,848
    1
    Jul 31, 2009
    Both circuits will work (with some reservations/requirements) but first things first:
    You've used the terms "live" & "neutral", but having drawn a typical automotive relay.
    This makes me wonder if this is a mains or a 12V application.
    Next question is how much power does the fridge draw and how much power can the TCU handle?
     
  6. mk2mark

    mk2mark

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    0
    Aug 25, 2011
    Yeah I'm sorry, I'm more used to cars, hence the approach but this should be a 110v circuit. The fridge is about 10A which is at the peak of what the TCU can handle, which is why I wanted to have a relay.

    I understand I may be a little out of my depth, but I feel like it's simple enough that I should be able to work it with some guidance. I'm definitely open to any corrections.
     
  7. Resqueline

    Resqueline

    2,848
    1
    Jul 31, 2009
    Ok, no prob's. 1100VA is some fridge btw..
    Use either circuit as you like. You'll either need a 110VAC coil on the 10A relay + a small switch, or else a 10A mains rated spdt switch.
    Check that the neutral on in & out of the TCU are connected internally or that they are completely separate (isolated).
    It could be made in many ways internally, with a(n opto isolated) triac or a relay.
     
  8. mk2mark

    mk2mark

    5
    0
    Aug 25, 2011
    Ok great! Pending whether the TCU has connected internal neutral lines I'll have another question. Many thanks for all the help!
     
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