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Compressor faults

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  • 29-08-2019 9:59pm
    #1
    Bmc17
    Registered Users Posts: 8 ✭


    I have a 200l air compressor with twin motors recently it has started tripping the Rcd.had electrician look at it and no joy he said its not onThe Rcd side of the board the compressor starts and trips the Rcd the Rcd reset and stays up any ideas on the cause


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    #2
    hedzball
    Registered Users Posts: 764 ✭✭✭hedzball


    Sounds like hard starting?? Single phase assuming I'd replace the capacitors. Capacitors generally don't go from 100 to zero but die off over time.


    Cheap to swap out so start with those.

    Also before that if they are belt driven take the belts off and try start the motors.



    'Hdz


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    #3
    Bmc17
    Registered Users Posts: 8 ✭Bmc17


    Thanks I'll try that why wud it be tripping the Rcd on start up and their not controlled by the rcd


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    #4
    2011
    Moderators, Home & Garden Moderators, Technology & Internet Moderators, Regional East Moderators Posts: 12,596 Mod ✭✭✭✭2011


    So the compressor trips an RCD for other circuits and the compressor is not fed from an RCD?

    ^^if this is correct then off the top of my head possibly there are a few issues:
    1) An earth fault at the compressor or on the compressor circuit. Carry out an insulation resistance test.
    2) That earth fault is causing an imbalance on the current flowing through the RCD. Check the integrity of the earthing and bonding of everything related to the compressor.


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    #5
    Bmc17
    Registered Users Posts: 8 ✭Bmc17


    Their was new cable fitted after this started to happening so maybe fault is with the compressor


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    #6
    2011
    Moderators, Home & Garden Moderators, Technology & Internet Moderators, Regional East Moderators Posts: 12,596 Mod ✭✭✭✭2011


    Bmc17 wrote: »
    Their was new cable fitted after this started to happening so maybe fault is with the compressor

    What does the new cable do? An insulation resistance test on that cable might be a good place to start. You may find that there is an insulation resistance issue with this cable. This may mean that a fault current is flowing from the compressor circuit and returning though the RCD causing it to trip.

    I’m only guessing. But if the compressor and it’s circuit was healthy then there would be no way it could trip a healthy RCD that feeds other circuits.


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    #7
    Bmc17
    Registered Users Posts: 8 ✭Bmc17


    Their was new cable fitted after this started to happening so maybe fault is with the compressor


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    #8
    Bmc17
    Registered Users Posts: 8 ✭Bmc17


    There was new cable fitted from fuse board to compressor after the problem started to rule that out


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    #9
    2011
    Moderators, Home & Garden Moderators, Technology & Internet Moderators, Regional East Moderators Posts: 12,596 Mod ✭✭✭✭2011


    Sorry my mistake. I misread your post and thought that the problem started after the new cable was installed. Clearly it is less likely this cable is the issue. However an insulation resistance test would still be a good starting point. I would definitely do this on the compressor and check the quality of the earthing.


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    #10
    Bruthal
    Closed Accounts Posts: 13,422 ✭✭✭✭Bruthal


    A neutral earth fault on a circuit other than the one the compressor is on is possible.

    Sometimes a neutral earth fault requires a heavy load to cause this type of tripping due to neutral earth fault on a different circuit than the item that seems to be causing it.


    A compressors starting current may be a short duration but heavy load.
    Current from this returns to the main neutral bar, and out the neutral supply. But a very small amount will go through the RCD neutral and down to the N-E fault on the RCD controlled circuit, and back to the Earth bar, then Neutralizing point, thus only on the RCD neutral side. If this is greater than 30ma, RCD trips.

    It would be expected that in such a case, a circuit with a neutral earth fault itself would trip the RCD with any load. SO its unusual to see this scenario unless the affected fault circuit has no real load on it.

    So, if a N to E fault is the cause, a load tripping an rcd that the load is not controlled by, is usually a relatively high load. Where as the actual rcd controlled circuit which has the fault, would usually be tripped by any small loads it has on it.

    Try plugging a kettle into various sockets around the house and see if the RCD trips.

    Other than that, insulation tests between disconnected individual rcd controlled Neutrals and earth would be what I'd look at first.


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    #11
    Tuco88
    Registered Users Posts: 1,051 ✭✭✭Tuco88


    Ideally if the compressor was placed on its own RCBO, it would narrow down the fault more quickly.


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    #12
    Bruthal
    Closed Accounts Posts: 13,422 ✭✭✭✭Bruthal


    Tuco88 wrote: »
    Ideally if the compressor was placed on its own RCBO, it would narrow down the fault more quickly.

    RCDs can do funny things, but if the tripping RCD is not a little faulty, my own suspicion would be that there is a fault on a circuit controlled by the RCD.

    Even a N-E short on the non RCD compressor wouldnt be expected to make any difference to RCD circuits that are fault free, and may in fact reduce the chance of a fault on an RCD circuit causing the RCD to trip, as the compressor N current divides, one half going to the N bar, the other to the earth bar.


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