tripping rcd

[tommy-trucker]

Hi All
been asked to check out my friends flat his rcd is tripping all the time even when he's not there all seems fine apart from the insulation resistance on the lighting circuit is slightly low but unable to currently get to the connections as they are spots and cannot get to the junction boxes but when i was changing the shower switch back box the whole system tripped this circuit was connected at the time but not on(added that bit on just in case someone thought i was working on a live one)but the rest of the system was on so i could have lights on in the bathroom this is the first time i've come across something like this so any help would be grateful if i don't get back to you tonight with any questions you have i'm of to work, but i will answer you
cheers Tom

 

[acat]

Is he on a split board or is this a recent fault.



Chris

 

[tommy-trucker]

recent fault not split board only 3 circuits shower,sockets and lights

 

[acat]

The most likely suspect on a lighting circuit is a flourescent light the older types when they start breaking down cause all sorts of havoc does he have one or more of them.


Chris

 

[tommy-trucker]

no all spots about 30 of them in a 1 bed flat.more info that i found out last night when it was refubished a couple of years ago they had the same problem back then the earthing was not good enough through tn-s so an earth rod was put in

 

[Sintra]

Hi All
been asked to check out my friends flat his rcd is tripping all the time even when he's not there all seems fine apart from the insulation resistance on the lighting circuit is slightly low but unable to currently get to the connections as they are spots and cannot get to the junction boxes but when i was changing the shower switch back box the whole system tripped this circuit was connected at the time but not on(added that bit on just in case someone thought i was working on a live one)but the rest of the system was on so i could have lights on in the bathroom this is the first time i've come across something like this so any help would be grateful if i don't get back to you tonight with any questions you have i'm of to work, but i will answer you
cheers Tom

When you were working on the circuit you may have touched N & E together even if this circuit was not on it would trip the RCD.

no all spots about 30 of them in a 1 bed flat.more info that i found out last night when it was refubished a couple of years ago they had the same problem back then the earthing was not good enough through tn-s so an earth rod was put in

You have stated IR low on lights this could be due to a cable that is touching a lamp and starting to melt causing The RCD to trip.

I don't think that the earth rod is related to your problem.

 

[tommy-trucker]

all bulbs were taken out trying to find junction boxes and did not notice any damage to any of the cables

 

[SirKit Breaker]

Have you checked the RCD trip times and current, they do go faulty.
When you say the IR test result was low, how low?
Is there any damp present in the atmosphere especially in the vicinity of the CU, or has any liquid been spilt on or around a socket?
Have any metal back boxes corroded away due to moisture, common in cellar conversions.
Is water getting into the shower?
Has anything been replaced recently like a light switch, socket, or shower switch, look for loose or corroded connections.
Are the connections in the CU in good condition and secure?
I once had a problem due to the socket behind the washing machine coming loose from the wall due to the machine vibrating against it and eventually the vibration caused the cable to chaff through tripping the RCD as it didnt have a grommet fitted.

I ask these questions because i have been to faults on RCD's and found the cause to be one or a combination of the above.

Cheers..........Howard

 

[tommy-trucker]

IR was 179 as to the rest of the questions the answers are no apart from an outside light was changed recently but the connections are now fine as it was disconnected for the test

 

[beanzntoast]

hI tommy don't know if this helps.i did a CU change,all tests satisfactory before did the change,fitted new CU.RCD kept tripping out at 5 minute intervals turned out to be 1 of 4 old double pole socket fronts,changed them to new single pole fronts, job sorted.must have been arcing between poles on sockets but didn't show up in the tests.just trying to give you other ideas
cheers jason

 

[tommy-trucker]

thanks for all your info still trying to sort it out but done a earth resistance yesterday and it came back with 265 could this be the cause and if so how do i get it lower
cheers tom

 

[beanzntoast]

thanks for all your info still trying to sort it out but done a earth resistance yesterday and it came back with 265 could this be the cause and if so how do i get it lower
cheers tom

Hi tom. By earth resistance do you mean a ZE on your earthrod,just so we're clear

 

[tommy-trucker]

yes i do
sorry to confuse you and me

 

[Smugley]

tommy, as sintra stated in an earlier post, your earth impedence is not related to the reason your RCD is tripping. If you look at a circuit diagram of how an RCD works, this will be clear. If the RCD is tripping it usually means your earth is good enough, though not necessarily good enough to trip overcurrent protective devices quickly enough, but that's another story.

(A missing earth connection may be a reason for an earth fault condition NOT tripping an RCD. In other words, a circuit is not completed, therefore the current has nowhere to run, and therefore no load is possible to unbalance the coil).

 

[beanzntoast]

A high ZS on whichever circuit that is the problem would have the opposite effect on an RCD ie would not trip because the resistance is too high making the leakage current too low.IMO I think your looking in the wrong place &if it was me I would test all the circuits again just in case something was missed cheers jason
DAMN too slow ha ha