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using timer safe?

Discussion in 'Hobby Electronics' started by rcunado, Jun 5, 2010.

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  1. rcunado

    rcunado Guest

    Hello I have a chest freezer with a faulty thermostat that is jammed on
    running flat out (better than not at all I suppose).
    I was wondering if it would be safe to use a timer so that it isnt running
    flat out 24 hours a day until we can get it fixed?
    the freezer label says: Rated current 1.3A
    Power consumption: 0.75 kw.h/24hr
    the HPM timer says: Max 2400 Watts, 10A 230-240Vac 50Hz, motor rating M40

    Is it safe to use this timer on the freezer?
    One more q: due to distance it may be some time before it could be repaired
    professionally. Age of (home maker brand) freezer is somewhere between 5 to
    8 years old. I have some experience over many years fixing basic electrical
    items. Is replacing a thermostat on a freezer a difficult job? I would
    assume it is pretty easy and was thinking about getting the part ordered in
    and fitting it myself. cheers
  2. terryc

    terryc Guest

    I can not see any problems. My guess is 15 mins per hour during day time
    and 15 min per 2 or 3 hours at night. sans details.
  3. Sylvia Else

    Sylvia Else Guest

    It certainly wouldn't bother me to be using such a timer on the freezer,
    and I can't see freezer coming to harm - turning the pump on and off is
    likely all the thermostat does anyway.

    Indeed, having the pump running continuously is probably not doing it
    any good - it wasn't designed for that.
    That's a tough one. I've found parts soldered into the circuit, and
    held in place by brackets that have been spot welded, and there was
    obviously never any expectation of a replacement. Other parts are nicely
    held in place with screws, and wired in using spade connectors.

    The only way to tell is to take a look.

  4. RMD

    RMD Guest

    I did that when my freezer stuck on. It was summer so I ran it 4 hours
    on/4 hours off while I bought another freezer. Once the freezer gets
    as cold as it can there tends to be a very light load on the
    compressor motor anyway.

    Based on freezer power measurements I've done subsequently probably a
    20% durty cycle would be fine. (1 hour on, 4 hours off.) I have a
    thermometer in the freezer to monitor temperature anyway.

    I meant to replace the thermostat subsequently, but I never got around
    to it. In the end I only kept if for an emergency freezer if the new
    freezer suddenly failed with a hard fault.

  5. Mauried

    Mauried Guest

    If the thermostat is an older style mechanical type, ie a small knob
    on a small box that has wires and a capillary tube coming from it ,
    they are easy to replace provided you can find a suitable replacement.
    If its an electronic type , they are a lot harder to fix.
  6. Martin

    Martin Guest

    Pump? What pump?
  7. Sylvia Else

    Sylvia Else Guest

    I doubt it's a thermoelectric freezer, nor one using an absortion cooler
    that takes electricity as it's heat source.

    Most likely, it's a normal compressor style refrigerator. And a
    compressor is a pump.

  8. Mr.T

    Mr.T Guest

    Not at all, harder to find perhaps. An alternative is to use a generic
    electronic temperature controlled mains switch with adjustable hysteresis,
    like the one published in Silicon Chip recently. The manufacturers
    controller is just the same but usually more expensive, and less versatile.
    (but probably smaller of course)

  9. Martin

    Martin Guest

    8<-------------------------------------------------------------------------------- > Most likely, it's a normal compressor style refrigerator. And a> compressor is a pump.>A pump is a device that expends energy to raise, transport, or compressfluids-liquids and gases. The term pump is generally used forliquid-handling or hand-operated devices, while the term compressor is usedwhen the pressure of a gas is increased in a motor-driven machine.Next you will be telling us that hot air or water rises.
  10. Sylvia Else

    Sylvia Else Guest

    So after all that, you just wanted to split some hairs on terminology.

    I wonder how you'll fit a motor operated vacuum pump into your nicely
    partitioned world.
    Or are you perhaps just trying to gloss over the fact that you didn't
    actually know how a refrigerator works.

  11. ian field

    ian field Guest

    If you're really lucky it might be welded contacts in the thermostat switch
    block, if you're even luckier still a sharp rap on the side of the switch
    block with a screwdriver handle might unstick it - good for temporary
  12. Martin

    Martin Guest

    Ah well ignorance IS bliss after all. You're the proof.
  13. rcunado

    rcunado Guest

    Thank you all very much for the good help I really appreciate it. I have
    tried a few different timer settings and the freezer seems to be holding
    steady at around -8C with the timer set for 15 minutes on, then 3/4 hour
    off, then 30 minutes on, 30 minutes off, etc. Thanks!
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