RCD tripping problem

[markmcke]

i've been asked to look at an installation that was rewired a couple of years ago. it is a split board and the RCD has started tripping out. the owner said that previously he would maybe have an issue if a standard lamp blew etc but now something is leaking to earth. it all tests out fine. i have a suspicion that it will be one fo the kitchen appliances. probably the microwave but i don't think it is enough to trip on it's own. anyone any other ideas??

further to that, it happened at 7.30pm, 1am and 6.30am. he only had the fridge, oven, combi boiler, fish tank and cordless phone switched on. if the pipework for the combi were becoming clogged would this cause the pump to work harder and cause a spike in the current, resulting in increased earth leakage?

 

[UNG]

Where the times you quote all in the same 24hr period. Never known a heating pump trip an RCD because of clogged pipework

Could be the auto defrost heater failing on a fridge or freezer had this quite a few times

 

[markmcke]

yes, last night at 7.30pm and then this morning at 1.30am and 6.30am. sounds like the freezer is the culprit. i believe it is relatively new maybe a year old.

i think i'll move the MCCB for the kitchen sockets over to the non RCD side and see if it clears the problem.

 

[Kiers1970]

my Worcester 24cdi Pump starts automatically every few hours for a minute or so to push the water round the system, is the ch boiler connected to the the RCD? Just an idea.

 

[malcolmsanford]

yes, last night at 7.30pm and then this morning at 1.30am and 6.30am. sounds like the freezer is the culprit. i believe it is relatively new maybe a year old.

i think i'll move the MCCB for the kitchen sockets over to the non RCD side and see if it clears the problem.

:nono:..................................... perhaps finding the fault might be a better alternative

 

[ianphilip007]

yes, last night at 7.30pm and then this morning at 1.30am and 6.30am. sounds like the freezer is the culprit. i believe it is relatively new maybe a year old.

i think i'll move the MCCB for the kitchen sockets over to the non RCD side and see if it clears the problem.

if its an earth leakage problem on an appliance connected to the kitchen socket circuit then yes its going to clear the problem, but only because there will be no RCD monitoring the earth leakage. The fault is still there either on the circuit or on a connected appliance. does the rcd hold with all appliances unplugged?? if so then its a case of tracking down the faulty appliance. putting the kitchen sockets on the non protected side can only be a temporary measure surely ??

 

[markmcke]

it would only be a temporary fix to prove that the freezer was causing the tripping fault. unfortunately it is very sporadic and to leave it unplugged for a considerable length of time is not an option. i may just leave the door open and wait for the temp to increase and ultimately switch on.

 

[MarkieSparkie]

Of all the appliances you suspect, the fridge is the most likely culprit, either the compressor breaking down due to overheating or defrost heater as stated above.

 

[Top Cat]

I would be interested in seeing the IR readings. You say it all tests out fine but if you have poor IR readings (but within the correct limits) over a few circuits, the combined can make an RCD trip as you described especially a N-E fault.

Sorry if i am teaching a granny to suck eggs but with a post count of 3 it is hard to tell how experienced you are.

 

[andydj99]

Have you tried a Ramp Test ?
Sounds like a faulty 61008 rcd switch to me

 

[markmcke]

understandable, i'll post them and let you see when i get a chance.

 

[HandySparks]

I would be interested in seeing the IR readings. You say it all tests out fine but if you have poor IR readings (but within the correct limits) over a few circuits, the combined can make an RCD trip as you described especially a N-E fault.

I can see what you're saying, TC. But if all IR values are over 1Mohm, the maximum leakage (not counting capacitive) is 0.23mA on a 230V supply. So you'd need a lot of marginal final circuits on one RCD to have a significant effect.

 

[Top Cat]

In theory yes, but i know in practice, lots of 1Mohm readings add up to tripping problems. Have you done L-E, N-E on the complete instillation?

I would be worried if each circuit had readings of 10 - 30 Mohms.

 

[markmcke]

problem solved, fridge freezer as predicted. switched everything else off and left the door open for 5 mins. RCD tripped. it's under warranty so the couple are calling the manufacturer. all the circuits were reading well over 1M but nowhere near 10M.

 

[nickblake]

well thats good i would sugest that the RCD is Ramp tested mind just to see what current its tripping at they normally trip around the 24ma but i have found them tripping at 8 or 9 ma