Faulty pressure switch?

  1. Clarke SC200 3 phase, 200Litre.

    The compressor powers up fine and drops out when up to pressure. However it will not start up again when the pressure drops, even to zero. Do I need to replace it, or is there a simple fault?

    Are they largely universal? I have looked at Ebay and they are all from China etc, plus they don't really give the info needed. Some say 3 Phase, 4 ports. Do I need 4 ports? Should I just bend over for Clarke spares cost of a replacement? ;-)
     
  2. dobbslc

    dobbslc Forum Supporter

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    There are different sized ports on some soof them so you have to know what you need. Extra ports you can just blank off.
    Did it hum when it tried to restart?
     
    Memmeddu likes this.
  3. No, if the switch on the top is cycled, it restarts happily. It will just not start from pressure drop.
     
  4. dobbslc

    dobbslc Forum Supporter

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    Does it hiss when it reaches pressure?
     
  5. Don't know as it lives in an outdoor housing. I can test for that tomorrow though.
     
  6. hotponyshoes Member

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    The pressure switch is not that eye watering, about 20notes or so I think, changed one for a mate a while back on a sealey or something but the same thing.

    Start it up and watch it to see what it's doing.
    When it gets up to max pressure and turns itself off you should hear a hiss. That's the air between the pump and the tank discharging so there is no pressure in the pistons when it tries to restart.

    then start drawing some air out until you get to the point it should kick back in. If at that point the motor looks like its trying to start and the red button or whatever on the top pops up then it's a fault with the discharge.
    You could also try restarting manually with half a tank of air and see if it starts .
    If the tank will drain all the way down then I would guess it's the pressure switch. I think they are 2 switches in one, one to turn on below say 30 and another to turn off at say 50.
    If you pull the plastic cover off you might find its adjustable and the adjustment has just shaken loose , might be worth checking the terminals and if really keen strip it down and clean the contacts but if you can isolate the problem to the switch probably quicker to fit a new one
     
  7. It comes up to pressure and stops with a hiss. It can then drop to zero without restarting. It will always restart if the switch is cycled.

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    Memmeddu likes this.
  8. octo0072000

    octo0072000 Member

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    As said take the top off the switch should be a couple of adjusters in there see if one has come loose if not note how many turns before adjusting take pictures readjust go from there
     
  9. Well I thought it would restart everytime but it doesn't. The motor just hums for a moment then the contactor drops out again. Once in a while it will restart and come up to 6 Bar although I am sure it was doing 10 previously.
    Adjusting the current trip control upwards just causes it to hum on manual restarting. Nothing looks loose or out of place under the cover.

    The power plug is a bit black and burnt on two of the pins so I will replace that anyway presently. Not sure it has any relevance, but what do I know? ;-) It is a 4HP motor I think so perhaps 16A connectors are a bit marginal? I have ordered some 32 A replacements.

    Price is a bit Fruity! £113 for a matching one which is a Condor MDR3, data sheet here: https://www.condor-usa.com/wiring-adjustment-instructions
     
    Last edited: Sep 11, 2019
    Memmeddu likes this.
  10. Nicked form an electrical forum...

    The Condor is not just a pressure switch though, it's a pressure switch, dol starter, overload, unloader, and on/off switch all in one, and IIRC, when the thing drops out (o/l or NVR) it has to be switched off and back on again for it to-restart the unit.
    So, quite a "clever" device really, but, as far as compliance goes, I'm not convinced without looking further into it, I don't "like" them personally, but they do a job.
     
  11. brightspark

    brightspark Member

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    I use one on mine but have a separate contactor and just use the pressure switch to operate the contactor coil rather than the internal contacts as I don't think there that good
     
  12. octo0072000

    octo0072000 Member

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    if it just buzzes could be starter on motor if it has one
     
  13. MCKDAVID Member

    I just changed my MDR3 condor, due to damage not failure. You're right the price is steep, but it's a complete starter package... I got the replacement from Alpha controls in Wigan,
    I was 52 quid for the undervoltage relay, and 102 for the MDR3 including overload..

    I still have the old MDR / overload / and undervoltage relay,I'd guess they would still work electrically, but the casings are all damaged, but you're welcome to it for parts, if it helps..

    edit OL on mine was only 10A so might be a bit small, but the UV relay and mechanical parts are the same
     
  14. MCKDAVID Member

    you might want to check that all the bits are included in that price, mine were all priced seperately
     
  15. carbon

    carbon Member

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    Seems odd for a three phase motor to hum so could be one of the contacts in the pressure switch is not making a good enough connection and dropping one of the phases, then overloading and tripping the overload. If the pins in the plug look a bit burnt then it could be an issue with the socket as well. Is the socket a switched one with interlock as I went out to a machine recently that wouldn't start, that turned out to be a fault with the switched socket only turning on one of the three phases rather than a machine fault.
     
  16. This is my suspicion, which is why I ordered some 32A replacements. Do I take it that you are in that line of business?
     
  17. carbon

    carbon Member

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    Not compressors, industrial pressure washers. But have similar faults that are according to customers are the machines fault rather than there supply
     
  18. I found a five pin 32A plug that mates with a socket already wired, so used that.The compressor has never worked so well! Very high pressure (nearly off the 10 Bar clock) and it seems to restart on low pressure as it should. That saved me an expense!
     
    carbon likes this.
  19. carbon

    carbon Member

    Messages:
    1,184
    Location:
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    I don't have mine fitted with a plug, have always wired compressors with a dol starter and never touched the one on the compressor. Instruction say always turn on/off at compressor but i haven't had any issues, but my system does have a small leak that can drain the tank in two days and i don't use the compressor every day
     
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