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Registered: ‎03-01-2016
Message 11 of 14 (104 Views)

Re: Superhub causing RCD to trip


Clint_Flick wrote:

My point is that there is no return path (it is a plastic pin from a plastic case) other than the neutral, so an out of balance cannot occur.


However... it is very common for antenna screening to be connected to the 0v rail in equipment. It is also usual for screening to be connected to earth in earthed equipment. If isolation has failed this can provide quite a low impedance earth path.

It's rare but not impossible.

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It'd be interesting to know if the OP has got it solved. 

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Registered: 3 weeks ago
Message 12 of 14 (96 Views)

Re: Superhub causing RCD to trip

Hi

Yes, nuisance tripping from DC sources used to be quite frequent. 

I did consider the fault path. There is no earth connected, therefore no leakage to earth is possible.

To find an earth return path mine would have to go back thru the co-ax that VM installed, and/or through an ethernet cable to my PC and then exit via the casing.  Other ethernet cables go to nowTV box, no earth connection and occasionally my laptop, yet again no direct earth path for a fault.

In the old days of ELCB's voltage operated trips, you could hear a faint hum sometimes when a device was leaking a tiny amount, enough to vibrate the trip coil but not trip it.  A common source of earth "faults" were Baby Belling cookers that had the 'oven on' light connected to earth.

I would test one with a 500 volt megger and it failed 1st time, 2nd time it passed because the bulb had blown.  Tick the box.  Then a coupla weeks later a ticket to repair the oven light on a BB cooker.  And so it went on.

 

And as you say, "in earthed eqipment".  And as I said  "However I do not exclude the remote possibilty of a DC current somehow leaking through and causing nuisance tripping without frying the superhub."

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Registered: ‎20-05-2014
Message 13 of 14 (89 Views)

Re: Superhub causing RCD to trip

Is the screen on VM co-ax cable at earth potential?
Is there any isolation provided in the internal connecting box/socket?


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Superuser
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Registered: ‎10-07-2014
Message 14 of 14 (69 Views)

Re: Superhub causing RCD to trip

[ Edited ]

Theres an isolator in your internal wall point. Thats why its so difficult to recess the boogers...

 


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