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Thread: 24 V circuit breaker for thermostat transformers

  1. #1
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    24 V circuit breaker for thermostat transformers

    What's a good circuit breaker to use on the 24 V circuit of small transformers that are typically used for thermostats, sprinkler controls etc?

    It's easy to find circuit breakers and fuses for automotive and "marine" use, but their amp ratings seem too high for the job.

  2. #2
    Normally residential HVAC controls use a 3 amp fuse. I don't think I've ever seen a circuit breaker. The problem with a breaker is that it's not always reliable in low current ranges, or high for that matter. Fuses are reliable. Either way, a look in McMaster Carr should turn something up.

    What are you after exactly?

  3. #3

  4. #4
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    Quote Originally Posted by Stan Coryell View Post
    What are you after exactly?
    After a fuse blows at 4:15 in the video https://www.youtube.com/watch?v=r0r3ayKcq3s the technician puts what he calls a "little popper" in the circuit at 4:41.

  5. #5
    Something like this? The voltage shouldn't matter.

    Blade-Style DC Circuit Breaker, Vibration-Resistant, Push Button Style, 48V DC

    https://www.mcmaster.com/4212T4

  6. #6
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    the technician puts what he calls a "little popper" in the circuit at 4:41.
    It's actually - a Li'l Popper - made by ESP :

    https://www.trutechtools.com/ESP-Lil...-Breaker-3-amp That's the Pop3 (3 amp) model. They also have a Pop5 (5 amp).

    Our furnace guy uses one. I wanted to get one to have in the car for emergencies, but, then I realized what a waste of money that would be. (Like I'm going to fumble around and try to find and repair a short in my car's wiring... )
    My granddad always said, :As one door closes, another opens".
    Wonderful man, terrible cabinet maker...

  7. #7
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    How much trouble are you having with that fuse? The only time I've ever heard of one blowing was from someone changing the thermostat without pulling that fuse first.

  8. #8
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    Quote Originally Posted by Tom M King View Post
    How much trouble are you having with that fuse? The only time I've ever heard of one blowing was from someone changing the thermostat without pulling that fuse first.

    I agree with this. For a couple pennies for a fuse and if they are blowing alot then there is something wrong even a breaker is not going to fix. Tape a couple spare fuses in cover or some place convient to always have on hand.
    John T.

  9. #9
    Quote Originally Posted by John Terefenko View Post
    I agree with this. For a couple pennies for a fuse and if they are blowing alot then there is something wrong even a breaker is not going to fix. Tape a couple spare fuses in cover or some place convient to always have on hand.

    A "couple of pennies" for a fuse? You have not bought many fuses recently.

  10. #10
    Most boats are loaded with these, they work--

    boatCB.jpg
    -right on the breaker it's stated 124/240V - 32VDC,
    ========================================
    ELEVEN - rotary cutter tool machines
    FOUR - CO2 lasers
    THREE- make that FOUR now - fiber lasers
    ONE - vinyl cutter
    CASmate, Corel, Gravostyle


  11. #11
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    Why not a breaker on the 120 input side? Too low of an amp draw?
    Bill D

  12. #12
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    As already mentioned, the automotive blade type is easy to solder to. Size it at 2x the normal current. Fuses do go bad without issues causing it. Metal fatigue is visible on some blown fuses rather than the molten explosion type residue caused by a short.

  13. #13
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    Fuses will often test good with a meter and almost no load but fail under load.
    Bill D

  14. #14
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    Quote Originally Posted by Rollie Meyers View Post
    A "couple of pennies" for a fuse? You have not bought many fuses recently.

    If you are talking those barrel fuses or even the automotive blade stab ins they yes Pennies. Look on Amazon. They also have circuit breaker setups for autos that you could use.
    John T.

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