trouble with newly installed MK c/u

[jenions]

recently changed an old fuseboard to a new MK consumer unit with 2rcbo's and then RCD with 5 mcb's on it, now i IR all the circuits and all came out at <299Mohm but since day 1 the rcd has tripped whenever a high load is switched on? i tried the up and down ring and the fridge radial on 1 of the rcbo's (40A) and they worked fine but if i put them back on the rcd side they trip. anybody got any ideas? also the test button on the rcd isnt working, now this is the 2nd rcd ive tried as i changed the 1st 1 just incase that was faulty.

 

[Knobhead]

Where the hell do outside lights come in to it!

For gods sake it’s not difficult if the RCD fails to trip on test, the faults in the RCD.

View attachment 7289

 

[jenions]

no outside lights apart from 1 on a plugtop and that isnt plugged in, can see this being 1 of those jobs

 

[jenions]

think is this is the 2nd rcd ive tried surely 2 in a row arent broke

 

[Knobhead]

No wonder I need tablets for my nerves!

 

[platty1005]

Good drawing Tony
Bottom line There are 2 faults

1) The RCD wont' trip on test button operation - check supply to RCD - Test RCD on a known good installation (own house) If RCD wired correctly it should trip SEE Tony's post
If not tripping change it again

2) The RCD trips when loads are switched on
but not when no loads connected - appliance/load problems

PS long distance fault finding is proving quite difficult

 

[mickys86]

Where the hell do outside lights come in to it!

For gods sake it&rsquo;s not difficult if the RCD fails to trip on test, the faults in the RCD.

View attachment 7289

Or the wiring beforehand

 

[sparkinlee]

I agree with Tony and others... if the test button is not tripping the RCD, that needs sorting before any other fault finding, and the test button not working would be caused either by a faulty RCD unit, or incorrect wiring configuration within the CU (but I can't think what!).

 

[Knobhead]

I’ve just re-read this thread.

I’m sorry but for professional electricians some of you should sign yourselves as “Hop-a-long Cassidy”. You condemn cowboys, but then give advice that is so off target it’s a wonder you’ve got two feet left!

A RCCD is a simple thing to figure out, if what’s going in doesn’t equal what’s going out then you’ve got a down stream fault and it trips. If it doesn’t trip on the test button then the RCCD is faulty (unless you’ve used a 4 pole 440V unit).

Sort your testing in to logical order, it’s the only way to fault find.

Sorry but people rely on you to get things right, I wouldn’t be impressed with someone constantly on their I-Pad asking advice.

Don’t get me wrong, I’ll help anyone, but you have to have the basics. Not just being able to quote regulations ad nauseum.

 

[RomRobi]

I quite agree with Tony and patty1005. I've had similar problems in the past. The RCD detects an imbalance between the line and neutral on the load side and pressing the test button simulated this imbalance to cause RCD to trip. I guess a few guys were right too, in carrying certain test and in particular trying the RCD in a complete different CCU to check its functionality.

 

[nickblake]

Where the hell do outside lights come in to it!

For gods sake it’s not difficult if the RCD fails to trip on test, the faults in the RCD.

View attachment 7289

Sorry Tony , but i have come across this before RCD trips on high loads brand new install ,the fault was caused by an incorrectly fitted lid on an outside light ,the light was half full of water ,replaced the fitting fault gone , this was the reason i mentioned outside lights

 

[ezzzekiel]

im sorry also Tony,

had a rcd that wouldnt trip, swapped for another exactly the same, swapped for the rcd in other bank which worked on one side but not the other.
removed all neutrals and it tested fine, replaced one at time until it stopped working when an old heating supply that had been fused down to supply an outside light caused the rcd not to trip and zs tests to fail, repaired the cable and then all tests came back fine.

But obviously I AM WRONG and as you say it was the rcd, next time ill leave it and tell customer the cu will only accept one rcd as all the rest in the world are broken................

and as a wise man once said and im inclined to agree with

I’m sorry but for professional electricians some of you should sign yourselves as “Hop-a-long Cassidy”. You condemn cowboys, but then give advice that is so off target it’s a wonder you’ve got two feet left!

 

[mickys86]

im sorry also Tony,

had a rcd that wouldnt trip, swapped for another exactly the same, swapped for the rcd in other bank which worked on one side but not the other.
removed all neutrals and it tested fine, replaced one at time until it stopped working when an old heating supply that had been fused down to supply an outside light caused the rcd not to trip and zs tests to fail, repaired the cable and then all tests came back fine.

But obviously I AM WRONG and as you say it was the rcd, next time ill leave it and tell customer the cu will only accept one rcd as all the rest in the world are broken................

and as a wise man once said and im inclined to agree with

Ok try that and if that don't work I'd go with the wiring beforehand haha

Maybe try the rcd connected with none of the mcb's connected? ( can't remember if this has been tried and am not re-reading all the posts again )

And as for the above..... Looks like a lot of us has learned something today

When removing all neutrals I'm guessing you mean with mcb's switched to off with the main breaker on?? Otherwise the neutrals would become live.
(just an apprentice and I like to be sure of these things!) hahaha 

 

[timo1]

RCBO's - They are the future!!! I got so fed up with RCD's and shoddy quality I only fit new boards decked out with RCBO's now, cost has come down so much its not all that much extra IMHO.

 

[topquark]

Well I'm not sorry ... well apart from the heath robinson explaination of the test circuit

 

[Knobhead]

Please supply a better drawing.

William Heath Robinson was a fantasic guy, using his methods I’ve got umpteen industrial plants going. What’s wrong with a brush stale holding a circuit breaker closed?