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RCD in consumer unit difficult to switch on

Alan B

Just as I arrived at a customers house there was a power cut because the DNO was working on a substation near by. It wasn't expected back on until midnight tonight meaning that I could only do dead tests.

When the power cut the main RCD in his CU also tripped and it was quite difficult to get it back to the on position. I am aware you can get latching RCD's in plug sockets but not normally in domestic CU's.

This leaves me wondering if the lack of power on the supply side or maybe some disturbance on the lines was making the RCD difficult to set or if I had a faulty RCD and need to start hunting down an RCD for my return trip.

There was a single RCD protecting all circuits and switching all the circuits off made no difference. I am assuming it doesn't change the operation of an RCD  but the CU was mounted upside down.

Welcome your thoughts

Thanks

 

Alan

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    Dead does not normally make an RCD harder to reset - it feels stiff and grauchy then something inside is failing. 

    But why were you there ? Was there an RCD problem already or is something else wrong?

    Mike.

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    Perhaps if the RCD had been exercised quarterly* by the pressing of the test button all would have been well.

    *until 2018

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    Failure due to power cut - rcd disconnecting whilst heavy load still connected. Could it have been a ‘one last time’ scenario? End of life due to historical excess faults.

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    Having just one R.C.D. protecting all outgoing circuits is not a good design regarding reliability. I would install a new R.C.D. and advise the house owner to consider a new all R.C.B.O. consumer unit.

    314.1

    Z.

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    difficult to switch on

    As it took a lot of force to move the toggle, or it moved OK but refused to latch reliably?

    If the latter, I might suspect a grumbling fault within the installation - in odd cases it's actually quite easy to trip RCDs with a very small voltage if it's unbalanced (I can easily trip some of my RCBOs by applying a multimeter on Ohms range between the two N terminals). If the supply is dead but not entirely isolated but picking up a few volts from somewhere - perhaps N is a couple of volts higher than normal - circumstances could conspire to give that sort of effect.

       - Andy.

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    Maybe need better description of the RCD in question or photo or make model/type? I have had RCD units protecting either full or split consumer units and the ones with a lever action i.e rotary action can and are quite stiff to reset compared to those with just an up/down action, there are of course just one or two odd ones out there that require the lever to be “Reset” by pushing fully to the off position where it resets then it will move back to the on position. Cant tell the issue from the initial description.

     

    GTB

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    Thanks for your thoughts.

    I was on site to resolve a flickering light which I think was due to poor connections in the lamp holder. Still waiting to find out if the problem was resolved when power came back on.

    The rcd is a leaver type it felt a but stiff to push on but the main concern was that it didn't latch reliably.

    Just to clarify again the installation was not powered as dno was working on the substation, therefore problem unlikely to due to fault in the installation.

    The rcd was a GET 80R30.

    I agree that the customer could do with a new consumer unit which I will advise on my return visit. I am going back because I felt the light installation I was working on needs replacing because of modifications that are potentially dangerous. 

  • 0

    Alan B: 
     

    Thanks for your thoughts.

    I was on site to resolve a flickering light which I think was due to poor connections in the lamp holder. Still waiting to find out if the problem was resolved when power came back on.

    The rcd is a leaver type it fel

    Just to clarify again the installation was not powered as dno was working on the substation, therefore problem unlikely to due to fault in the installation.

    The rcd was a GET 80R30.

     

    I would renew the R.C.D. and see what happens. G.E.T. was a seller of “economy” electrical products, the full company name = Great Eastern Trading.

    Z.

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    AJJewsbury: 
     

    difficult to switch on

    As it took a lot of force to move the toggle, or it moved OK but refused to latch reliably?

    If the latter, I might suspect a grumbling fault within the installation - in odd cases it's actually quite easy to trip RCDs with a very small voltage if it's unbalanced (I can easily trip some of my RCBOs by applying a multimeter on Ohms range between the two N terminals). If the supply is dead but not entirely isolated but picking up a few volts from somewhere - perhaps N is a couple of volts higher than normal - circumstances could conspire to give that sort of effect.

       - Andy.

    I believe that the offending device would not easily switch to the ON position dead. So the issue is probably mechanical inside the cheap R.C.D.

    Z.

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    Some older rcd's need pushing down to reset before pushing up to set. The older MK ones did, don't know about GET.

     

    Gary

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