# RCD Tripping - Unable to Trace



## teemyob (Nov 22, 2005)

Hello,

Nothing to do with motorhomes but I am sure there are some Expert Electricians on here?

Two days ago the area where we live had a power cut.

The Day after the Mains in our house tripped a couple of times.

Today it is constantly tripping.

I have megger tested every major appliance in the house, all okay. Even disconnected the oven, hob and extractor and tested them, all perfect. I have isolated all the external mains supplies to the heat pump, garden sockets and motorhome EHU.

Still it keeps tripping.

The RCD is about 20 years old.

I think it is of the Square D brand and is marked

Q05-M4-RC5

Could it be faulty do we think?

The House is 20 years old. 

TM


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## Techno100 (May 8, 2010)

It could very well be faulty yes. Can only be tested with an RCD test instrument that will pass fault currents at 50% and 100% of it's rating and take it's response times.


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## shedbrewer (Jan 6, 2007)

*RCD Tripping*

We had a similar thing happening in our Park Home, the swtch would not stay on, phoned my electrician son who sent one of his 'boys' over to replace the RCD switch ,,,,,,, problem gone away.Cheers, Jack & Patty, Cornwall


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## teemyob (Nov 22, 2005)

*Function*



Techno100 said:


> It could very well be faulty yes. Can only be tested with an RCD test instrument that will pass fault currents at 50% and
> 100% of it's rating and take it's response times.


I tested the RCD with a Seaward CMB-S

I can' find my instruction manual, so can't get the full results

But at 30ma test the screen shows it tripped at 21.5ma

TM


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## Techno100 (May 8, 2010)

At what percentage of the tripping current? at 50% it shouldn't trip at 100% it should trip in 300ms or better


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## clodhopper2006 (Aug 13, 2006)

Can you identify which circuit is tripping it? Try switching off one MCB at a time till the RCD stops tripping. Once we know which circuit is causing it we cab go on from there.


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## MiketheWelshman (May 1, 2005)

Hi TM, sounds like a neutral side fault to me, to trace it, disconnect each circuit in turn, both live and neutral, IR test with megger, each circuit should be 2mohm or higher. 
Hope this helps
Mike


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## clive1821 (Mar 27, 2010)

ok so if the rcd is coming out at 21mA that fine.... look at your emertion heater thats a faverate.... the usual cause is heating elements like kettles, etc... that my view to start with


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## Techno100 (May 8, 2010)

If it's tripping below 30ma it's too sensitive.


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## teemyob (Nov 22, 2005)

*faulty*



Techno100 said:


> If it's tripping below 30ma it's too sensitive.


If it is Faulty they seem hard to find replacements for.

Only one I have found so far Is on ebay

But is used and is 100ma

TM


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## Techno100 (May 8, 2010)

I would say Does your board actually need a whole board RCD? have you any rcd's for other circuits?


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## joedenise (Jul 20, 2007)

Check the main neutral connection in your box. Daughter had the same problem. Switched all breakers off, lights would work but nothing else. After finally checking everything else it was a solid main neutral cable that wasn't quite screwed up tight and was arcing out.

Joe


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## teemyob (Nov 22, 2005)

*Board*



Techno100 said:


> I would say Does your board actually need a whole board RCD? have you any rcd's for other circuits?


The Consumer unit is mixed.

Left hand side serves Lights, Immersion and one single a/c unit. No RCD just MCB's

Anything from the middle is on the RCD, so

Cooker
Downstairs Ring
Upstairs Ring
Garage/Study Extension Ring
Outside Mains and Lights
Upstairs Multi-Room Heat Pump

TM


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## Techno100 (May 8, 2010)

Yes that's a good configuration.
Really it's an obsolete board and it may not be too costly to replace the lot. Just have a gander at the likes of screwfix, a sparky shouldn't be too greedy to swap it out :roll:

Keep searching for another RCD tho just in case but I would not advise paying even a penny for a used one.


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## clive1821 (Mar 27, 2010)

The legal requirement for domestic RCD trips is no more than 30ma the higher ones are used for high current use but when terminated for protection as a final supply it must be more than 30ma as per 17th edition regs which I go by


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## Techno100 (May 8, 2010)

Yes 30 ma not 21.5. they're manufactured to trip at 30ma that's why they're expensive, it's not a thereabouts figure.
Also the IEE regs are non statutory but are used for reference by the HSE as the neccessary requirement for safety


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## Techno100 (May 8, 2010)

I appreciate the front is different but are the rear mounting and connections like this?
http://cgi.ebay.co.uk/SQUARE-D-QOE-...tBreakers_RL&hash=item41568625ed#ht_500wt_922


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## teemyob (Nov 22, 2005)

*Front*

Thanks for that, I was trying to find an image of the back.

Will check later.

Has been on since 9pm last night, tripped 9am this morning.

TM


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## Techno100 (May 8, 2010)

Interesting. Did anything get turned on about that time? something on a timer perhaps


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## SpeedyDux (Jul 13, 2007)

I had an annoying and incomprehensible trip problem that turned out to be a bit of faulty cable under the living room floor that had started to short intermittently. Not a RCD defect. Once the length of faulty cable had been isolated the problem disappeared. I had to use a qualified Sparks to track down and fix the problem.


SD


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## Techno100 (May 8, 2010)

This site says all the different styles of square D are interchangeable. "In the past the you had the QO & QOE`s there are 3 MCBs in this range which do look different, but have the same Electrical & Mechanical Fixings.
From the front: - one is black
one is grey with rounded corners
the last is grey has square corners & a yellow stripe
They are all interchangeable."
http://www.reconelectrical.co.uk/mcbs/square-d/qoe-sp/prod_27535.html

I think this has a different rear for din rail mounting so probably not the type for you
http://www.reconelectrical.co.uk/di...rcds-rcbos/80amp-30ma-rcd-kit/prod_26968.html


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## clodhopper2006 (Aug 13, 2006)

have you tried switching the mcb off one by one on these circuits?

Cooker 
Downstairs Ring 
Upstairs Ring 
Garage/Study Extension Ring 
Outside Mains and Lights 
Upstairs Multi-Room Heat Pump 


I wouldn't consider buying a new rcd until I'd done that. If the fault goes away with one of the mcb switched off then the problem is on that circuit not the rcd.


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## teemyob (Nov 22, 2005)

*work*

Just in from work, not tripped all day.

I have to go back out and do a job for my Daughter so will do some checking tomorrow.

Thanks for the great replies everyone. Very much appreciated.

TM


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## teemyob (Nov 22, 2005)

*ding*



Techno100 said:


> Interesting. Did anything get turned on about that time? something on a timer perhaps


Ice maker, I think.

Will let you know when I get time to test etc. Checked neighbours identical RCD Again and theirs is 28ma ours is showing 20ma.

Thanks Techno and all for the replies.

TM


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## TickTok (Aug 27, 2010)

I don't suppose this is your problem but I was once asked to trace a fault that was tripping the RCD and it turned out to be the capacitor that locks the washing machine door while the drum stops spinning at the end of a cycle discharging to quickly. 

Worth checking if the machine was being used. 



The thanks on your last post was a twitchy finger.


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## Techno100 (May 8, 2010)

TickTok said:


> The thanks on your last post was a twitchy finger.


No I did it on purpose :roll:


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## teemyob (Nov 22, 2005)

*Test*

Sorry I have not updated you all for a while.

Well it seems it was the Fridge/Freezer (ice maker). Though the RCD still tripped a good few times when it was unplugged.

The ice maker is on a timer/thermostat.

When the ice is ready, the thermostat starts the motor and sends power to the heater to heat to the ice mould.

However, there is a problem with the ice maker whereby the heater is not operating correctly. And instead of the paddles gently pushing the ice over into the bucket, the ice is being forced out by the paddles and the ice cubes are popping around a bit like popcorn popping.

The result is that a an ice cube or two is/are then flying up in the inside of the freezer and landing onto the water filler tube. The ice then causes the water to run off the pipe onto the cables rather than into the mould for the next harvest.

So now, I hope we have solved the problem.

THANKS Again.

TM


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