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Dehumidifier - compressor stall?

Discussion in 'Electronic Repair' started by N_Cook, Dec 6, 2012.

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  1. N_Cook

    N_Cook Guest

    As a sealed unit I suppose there is nothing other than banging the
    compressor housing to reset the problem. Sometimes it will start properly so
    not permanently seized. Control board fuse of 1.6 amp (240V supply) has
    never blown but stall? current must be something more than 1 amp.
     
  2. Ian Malcolm

    Ian Malcolm Guest

    Got a hard start kit on it?
     
  3. N_Cook

    N_Cook Guest


    Would that be inside the black plastic cowling to the side? otherwise just 2
    wires going to the compressor + grounding wire
     
  4. nesesu

    nesesu Guest

    If the 'off' time is too short, the compressors will often not be able to start into the back pressure that has not bled off yet. On my dehumidifiers that seems to take about 5 minutes. If the compressor is capacitor start [external capacitor] then I would also check that the cap is not worn out. Asyou surmise, the motor current is not passing through that small fuse on the control board. Even at 240V the compressor stall current will probably be well over 5A since I am guessing that my 120V units are drawing 10-12A atstart stall.

    Neil S.
     
  5. N_Cook

    N_Cook Guest

    compressor housing to reset the problem. Sometimes it will start properly so
    not permanently seized. Control board fuse of 1.6 amp (240V supply) has
    never blown but stall? current must be something more than 1 amp.

    If the 'off' time is too short, the compressors will often not be able to
    start into the back pressure that has not bled off yet. On my dehumidifiers
    that seems to take about 5 minutes. If the compressor is capacitor start
    [external capacitor] then I would also check that the cap is not worn out.
    As you surmise, the motor current is not passing through that small fuse on
    the control board. Even at 240V the compressor stall current will probably
    be well over 5A since I am guessing that my 120V units are drawing 10-12A at
    start stall.

    Neil S.

    ++++

    No capacitor seen.
    2 wires to the compressor and under the cowling one wire goes to what I'd
    have guessed to be a bimetal thermal cutout attached to the compressor body,
    any markings obscured by metalwork. The other goes to one spade of a 3 spade
    terminal , at first sight looks like a 25 amp triac. 2 spades unconnected
    and ohmic between all 3, also connected to the main body.
    Marked QP2-22 , this being the nearest to a datasheet that I've found

    http://www.hctemp.com/product_thermal_0_73.htm
    2. QP2-22
    Norminal resistance : 22O±2%
    Max voltage:350V
    Max current:8A
    Tripping time: 0.3?0.8S
    Reset time:<=100S
    Power dissipation: <=3.5W
    pic
    http://t1.gstatic.com/images?q=tbn:ANd9GcTMStB_nFYcKOiiUT6WAP5NNyjEdY7VfGwWY
    kqvMokiphwHHFgn9hJi9A
    I wonder what the other spades are for

    I'll try monitoring this current a bit better than variac meter but it does
    not seem to drop away within 1 second but 100 second reset time sounds like
    your situation
     
  6. N_Cook

    N_Cook Guest

    That 1.6 amp fuse is just for the fan and electronics .
    I tried heating the QP thing with hot air but did not see any hint of
    resistance change.
    Put a .6R 20W in line to the motor and monitored the voltage over. In stall,
    6amps initially and then dropping under the action of the QP and then a
    click as the cutout triggers. Then a matter of waiting until it clicks back.
    1.1amp in normal running.

    The other lump under the cowling , I can just make out some markings on the
    other side, Klixon on some metal and 4TM on the "kettle" white plastic so a
    thermal cutout
    http://www.datasheetarchive.com/klixon+4tm-datasheet.html
     
  7. N_Cook

    N_Cook Guest

    I've now seen the owners manual , from the owner. No mention of this stall
    procedure business. With the fan noise an owner would not necessarily
    realise that the start sequence can repeat multiply through this stall/lock
    out/ /cool/reset / start, rather than just start.
     
  8. N_Cook

    N_Cook Guest

    This is a GET DHMD10/2 . I will monitor what voltages appear on pins 1 and 3
    of the QP2 device and maybe add a suitably dropped neon (what are those
    other 2 pins for normally?) , so the owner can at least monitor , at switch
    on, how often the motor is stalled .
     
  9. N_Cook

    N_Cook Guest

    I burrowed into an older working dehumidifier I could wreck if I needed.
    This is aWDH -101B with a P330MC PTC start themistor .
    There is a schematic for this in use in an LG NS30LAEG out there so I could
    see how the run/start circuit works.
    Unfortunately need to cut a corner off that PTC (not 3 exposed terminals , 2
    others are sockets underneath for pins from the 2 coils) to expose the other
    terminal for the other side of the disc thermistor that connects to the run
    coil.
    Not enough discrimination in voltage drop to use a neon across the PTC. But
    a 240V neon from this exposed contact and the commoned feed to both coils at
    least shows when the cut out is activated as 240V across then. 4V
    (centrifugal switch ? so presumably induced voltage) across in normal
    running of the motor and 58V across in stall so the added indicator neon is
    out in those situations. At least then an owner knows that despite the fan
    noise , the pump is not running as this neon would continuously cycle 3
    minutes on , 5 seconds off, ...
    Now to add a neon to the GET machine
     
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