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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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    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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  • 0

    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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