faulty rcd

[chris troman]

At a job where using the shower trips the main rcd and two rcds under it (not on shower circuit). rcd test trips the lot at 1/2 current. When i isolate the main rcd from all circuits after it it fails to trip even at 5 x current. I suspect the main rcd to be at fault. can any one confirm this ? Also I have been told that rcds in line can affect each other. Could the two rcds away from the consumer unit have contributed to the failing of the main rcd, which was fitted after and is about 7 years old. thanks chris

 

[Pete999]

Not sure what you mean chris "the 2 RCDs under it" What sort of CU do you have, have you done any testing IR ZS etc?

 

[Octopus]

Could do with more info on the rods

 

[dazza1981]

Could do with more info on the rods

Rods ????

 

[uksparks]

Kind of sounds like one feeds another, then another then the board maybe? With no discrimination between them.

If testing at half times with no shower connected then something isnt right. Have you done a ramp test on it?

 

[Brightspark2]

Rods ????

I think he means RCDs...

Probably auto correct changed it...

 

[dazza1981]

I think he means RCDs...

Probably auto correct changed it...

Arrr yes lol.... Murdoch knows his stuff so i was thinking where has he got RODS from pmsl !!!

 

[Octopus]

Rods ????

Dam predictive text on my mobile - should have said RCD's!

 

[telectrix]

test each RCD with any others in series bridged and no circuits connected. if they trip correctly, then i suspect you have a N-E fault somewhere on the installation.

 

[chris troman]

test each RCD with any others in series bridged and no circuits connected. if they trip correctly, then i suspect you have a N-E fault somewhere on the installation.

please re read the original post. when the main rcd is isolated from the circuits it fails to operate even at five times the rated current. I would assume in anyones book that is not good. the other point is that I suspect the other rcds (originally fitted to the installation before the new consumer unit was added with an rcd covering 4 circuits) may be damaging the main rcd. thanks chris.

 

[Richard Burns]

RCDs cannot cause harm to other RCDs no matter how they are connected.
So long as the main RCD is correctly connected to the power supply and the RCD testing is done correctly then if it fails to trip under test then it is faulty, however if there is a fault in how it is connected or how the testing is done then this may not be the case.

RCDs that are connected sequentially especially if they are of the same rating (e.g 30mA) will, under fault conditions, trip randomly, i.e. it will not be possible to tell which one (or both) would trip in the case of a fault.
RCDs connected in parallel will not affect each other, although incorrect connection of the RCDs may cause tripping of another device.
Also it is possible that if a current spike occurs under fault conditions that this may affect the supply and cause an imbalance sufficient to cause an adjacent RCD to trip.

 

[davesparks]

Describe the arrangement of these RCDs for us so that we can understand how they connect to each other and what they each protect along with the rating of each one.

Having RCDs connected downstream of other RCDs will not damage them, I've done it many times with no problem whatsoever.

 

[telectrix]

please re read the original post. when the main rcd is isolated from the circuits it fails to operate even at five times the rated current. I would assume in anyones book that is not good. the other point is that I suspect the other rcds (originally fitted to the installation before the new consumer unit was added with an rcd covering 4 circuits) may be damaging the main rcd. thanks chris.

are you sure this main RCD is not 100mA and /or time delay?

 

[Badged01]

A sketch/drawing of the arrangement (if possible) would add some clarity to what the set-up arrangement is.

 

[Octopus]

please re read the original post. when the main rcd is isolated from the circuits it fails to operate even at five times the rated current. I would assume in anyones book that is not good. the other point is that I suspect the other rcds (originally fitted to the installation before the new consumer unit was added with an rcd covering 4 circuits) may be damaging the main rcd. thanks chris.

With the greatest respect, you should answer the subsequent posts to your less than detailed post! I'm still not sure what you mean!