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RCD Keeps tripping, may be 8.5 kW Shower?

Discussion in 'Electrics UK' started by otisthecat, 13 Mar 2012.

  1. otisthecat

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    Hi Everyone,

    I wonder if you can point me towards a solution to my problem?

    I have no experience with wiring and the homecare electricians I've called out so far have not fixed the problem.

    I had a 9.5kW shower installed for around 4 years. In the last few weeks tennants in my flat noticed 5 mins in to a shower and the RCD circuit was tripping taking the shower and sockets off.

    (From the picture above - it was and is the large blue RCD that is tripping and not the actual shower circuit which is no1 on the picture. no1 was switched off in the picture by us )

    I'm with BG Homecare and had an engineer sent out. I was advised the 9.5kW shower was too powerful for the cable in use. I asked why it had been working for 4 years and I was told that it had been made to work by putting a 40mA RCD on the circuit to accommodate it.

    I've replaced the shower with a 8.5kW model hoping this would solve the situation. Unfortunately my tenants have reported the same thing happening.

    I went over to see myself and I had the shower running for 15 minutes on two occasions, but sure enough on the third occasion the circuit tripped after the shower had been running for maybe 5 or 10 minutes.

    As the shower was not constantly tripping I advised the tennants to keep a record of occurences until I could investigate further.

    The tennants have since had reports of the circuit tripping with the shower off once and now they can simply trip the circuit by switching the power to the shower on. (The ceiling switch)

    I have had an electrician from BG back and he's not really been much help. He told me the 40mA braker should be donwgraded to a 32mA one - but as it is a WYLEX fuse board his company won't do this and he'd have to change the whole fuse box.

    He replaced the ceiling switch as he thought it could be steam in the electricals (something which we had previously ruled out).

    Still - as soon as the ceiling switch is turned on - even if the shower is off - the RCD trips. I'd say this also ruled out "steam in the switch"

    Now I work out that an 8.5kW shower needs around 35mA protection, meaning a 40mA breaker would be right for the job. This however seems to contradict what two BG electricians have told me.

    I definattely need to get another electrician out - but I'd like to be a bit more clued up as nothing is making much sense so far.

    Thanks to all

    Dan
     
  2. Taylortwocities

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    You are getting confused between what an RCD does and what an MCB does.

    The RCD will be 30MILLIAMP, period. That is what you have got. That's the big one on the right hand side with the TEST button. It doesnt need changing, leave it alone.

    The 40AMP MCB is borderline for a 9.5KW shower but (as you rightly say) its worked for 4 years.

    If the everything holds in OK with the shower ceiling switch off the problem is the shower itself.

    The RCD will still trip with the shower MCB off because the MCB still leaves the neutral conductor connected and the RCD will still see the fault.

    You need a new shower. Get BG back to replace it if it is under their guarantee - or you'll need a spark/plumber to do the deed.
     
  3. holmslaw

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    ..
     
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  4. holmslaw

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  5. otisthecat

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    Apologies, I'm rapidly learning about all this stuff.

    Its the RCD that trips. It does happen to be 30mA but I am not talking about changing this and I don't think the sparkies were either.

    The shower MCB never trips. This is currently 40mA and what I have apparently been told should be 32mA.

    The RCD only trips when the shower MCB is on.

    I replaced the shower only last week with an 8.5kW model - it was tested and was working fine for long periods at first.

    Now the RCD trips immediately when the shower ceiling switch is turned on.

    Maybe the shower has now broke due to the fault, but it can't be the actual fault.
     
  6. Adam_151

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    That will be 40A and 32A. mA is milliamp, A is amp, the former is one thousanth of the later.

    Its not relevant though, whether its 32A or 40A will not result in the issue you have

    Would seem to suggest that the fault was not in the shower unit, or that the new one somehow developed the same fault which seems unlikely

     
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  7. yorkspark

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    Your 40amp not mA as you keep saying is ok for an 8.5kw shower, it sounds like you have a cabling issue and that's what needs testing between the db and switch and switch to shower










    Beaten to it damn!!
     
  8. 17thman

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    A fault between the shower switch and the showers seems likely, I should only take a decent sparky half an to sort that particular fault diagnosis out. There is another factor here in that you may have a combined earth leakage from circuit cables on other circuits and or appliance or equipment supplied protected by that rcd. A few milliamps of leakage of various circuits totalling 30 mA will cause it to trip considering it seems a little intermittant
     
  9. otisthecat

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    Well it turns out that the immediate trip being caused by the ceiling switch was caused by:

    drumroll - the British Gas Homecare guy had all the wired crossed togeather in the switch!

    Are they homecare or are they there for sabotage? I'm lost for words. I will be complaining first thing tommorrow.

    I went over with my father (a qualified electrician) and as soon as the ceiling switch was wired correctly the shower is working again.

    Now the original problem may still be there - we currently think it's an issue with a surge in the power demand caused by switching the shower on at full temperature. Apparently the older WYLEX boards are not good with surges and may need some extra protection.

    We are not ruling out anything thats been advised here either.

    Thanks to everyone for the help and clearing up some confusing BS being spouted by BG!!
     
  10. otisthecat

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    Oh yes, and I shall remember. It's Amps and not MilliAmps for MCB's

    Sorry :LOL:
     
  11. 17thman

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    This is becoming a common and reoccuring complaint with British Gas, and i believe they are not paying peanuts. The next PG tips advert should include BG fitters with hi vizes and drinking the stuff "its the waste"
     
  12. sparkybird

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    BG Homecare - what a joke! Not the first time I've heard/seen/had first hand experience of these shysters

    Please DO complain really strongly and ask for compensation for completely unnecessary work - as otherwise many more people will be duped by them - they may not have the sense to post on a forum to ask advise

    Imagine if they had done the fuse board change as well - and hey presto that's still not solved the problem

    Just goes to show that not one single test was done otherwise fault would have been identified

    How they can call themselves Homecare is beyond me - Home Rip Off more like

    Well done Otis!

    SB
     
  13. krieghammer

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    [b]hello [/b]world
     
  14. IJWS15

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    There is still a chance that BG could be right about the cable - is it 6sq mm or 10 sq mm cross section?
     
  15. bernardgreen

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    The OP said the RCD tripped after few minutes of showering. That suggests earth leakage somewhere. Maybe that has been solved by the change of shower unit. It is hard to believe an "engineer" could " cross wire" a switch such that it immediately trips the MCB and then leave the premises without having tested the shower worked. ( I am not saying it is impossible, some "engineers" are capable of such crass stupidity ). Which suggests that he may not have tested anything at all. He probably did not measure the insulation resistance in the cable between switch and shower. That may still be a problem that will lead to the RCD tripping again.
     

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