Garage unit trips house consumer unit problem

[porticoman]

I'm installing a garage unit but it's tripping the (20A) house breaker. There's no load on the garage unit so I'm missing something obvious/doing something stupid. The garage has pre existing T and E powering lights and a couple of sockets which I want to modify to get a bit of practice after doing Part P. The Wylex 2 way unit (1 x 6A and 1 x 16A) and a RCD is connected as per the instructions (yes,I've read them!) Line/Neutral into the RCD, CPC into the Earth bar and the pre installed neutral link is in place. I've checked the connections to they are biting the conductor not insulation, tight etc. When it's returned back to its original format (no garage unit) it works perfectly so I'm being dense and maybe not asking the right question. Anything constructive suggestions the forum could add would be great.

Thanks

Peter

 

[porticoman]

Dunx, will do...thanks very much

The earthing is TN-S

I didn't test the sub-main. In my head the reasons were: I knew it was working and I wasn't adding extra load. In my head was obviously wrong... curse you Inside Head.

The SWA isn't earthed at the garage end. Should point out I didn't put it in!

There's some useful stuff in these replies, even the wrist slapping ones!

Ideally I'd like to have done the learning in conjunction with an experienced electrician but despite a letter writing campain no one seemed interested. Training courses just don't cover it. Sadly the only other avenue left open is to be a dangerous idiot for a while and rely on forums etc to sort out issues. Not really the way I like to go through life, so thanks to all respondents.

As an aside, as a plumber, we find that when electricians are working in premises they tend to switch the boiler off from the consumer unit along with everything else. This causes a nuisance lock-out of the boiler because water stuck in the heat exchanger continues to heat up for a few seconds after the boiler shuts down (the power to the pump having gone means it can't pull new cold water over the heat exchanger). Low water volume boilers can reach very high temps very fast, resulting in a safety cut out activating Shut it down by the programmer, switching the hot water and heating off a minute or two before cutting the power. This phased shut down allows the pump to over-run and carry the excess heat away. Happy days for the customer...

Thanks

Peter

 

[Specialist]

Dunx, will do...thanks very much

Did'nt you say you'd found out what the problem was ? If everything is working without the CU fitted & the house MCB is'nt blowing then the submain should be ok.

 

[Dunx]

Did'nt you say you'd found out what the problem was ? If everything is working without the CU fitted & the house MCB is'nt blowing then the submain should be ok.

My thoughts were to start at the beginning...sub main first, then load circuits.

 

[Specialist]

My thoughts were to start at the beginning...sub main first, then load circuits.

Yes I realise that mate, but according to the OP everything worked ok in the Garage until he disconnected whatever box was there originally & put the 2 way CU in it's place. He's removed the CU now & put things back how they were, i.e with the lights & sockets back on & no more tripping of the MCB. From what he's said so far i'd guess the feeder is ok otherwise he's still have a problem & the problem is something he did, in fact he did actually say that earlier.

 

[GLENNSPARK]

I'm installing a garage unit but it's tripping the (20A) house breaker. There's no load on the garage unit so I'm missing something obvious/doing something stupid. The garage has pre existing T and E powering lights and a couple of sockets which I want to modify to get a bit of practice after doing Part P. The Wylex 2 way unit (1 x 6A and 1 x 16A) and a RCD is connected as per the instructions (yes,I've read them!) Line/Neutral into the RCD, CPC into the Earth bar and the pre installed neutral link is in place. I've checked the connections to they are biting the conductor not insulation, tight etc. When it's returned back to its original format (no garage unit) it works perfectly so I'm being dense and maybe not asking the right question. Anything constructive suggestions the forum could add would be great.

Thanks

Peter

so you`v become part p registered.....now you want to "get a bit of practice in" sorting out a lighting circuit in a garage?....hmm....

 

[GLENNSPARK]

Dunx, will do...thanks very much

The earthing is TN-S

I didn't test the sub-main. In my head the reasons were: I knew it was working and I wasn't adding extra load. In my head was obviously wrong... curse you Inside Head.

The SWA isn't earthed at the garage end. Should point out I didn't put it in!

There's some useful stuff in these replies, even the wrist slapping ones!

Ideally I'd like to have done the learning in conjunction with an experienced electrician but despite a letter writing campain no one seemed interested. Training courses just don't cover it. Sadly the only other avenue left open is to be a dangerous idiot for a while and rely on forums etc to sort out issues. Not really the way I like to go through life, so thanks to all respondents.

As an aside, as a plumber, we find that when electricians are working in premises they tend to switch the boiler off from the consumer unit along with everything else. This causes a nuisance lock-out of the boiler because water stuck in the heat exchanger continues to heat up for a few seconds after the boiler shuts down (the power to the pump having gone means it can't pull new cold water over the heat exchanger). Low water volume boilers can reach very high temps very fast, resulting in a safety cut out activating Shut it down by the programmer, switching the hot water and heating off a minute or two before cutting the power. This phased shut down allows the pump to over-run and carry the excess heat away. Happy days for the customer...

Thanks

Peter

oh i see......its OUR fault now.....

 

[Dunx]

Yup just re-read it but I would still have started at the beginning!!

 

[micknew]

Is he a plumber or electrician?
We may never know.

 

[Specialist]

Yup just re-read it but I would still have started at the beginning!!

OK mate, but why: After being told the same by a customer out on site, the first thing i'd have been looking at was what had changed i.e the New consumer unit & how it had been fitted.

 

[Octopus]

What test equipment do you have at your disposal?

an eerie silence since I asked this question

 

[GLENNSPARK]

how do you know the garage roof hasn`t been leaking all over the CU in there n all....IP4X.....

 

[micknew]

Perhaps he's a plumber then.

 

[Dunx]

OK mate, but why: After being told the same by a customer out on site, the first thing i'd have been looking at was what had changed i.e the New consumer unit & how it had been fitted.

Cos from there you can test everything....

 

[Specialist]

Cos from there you can test everything....

But you already have part of the Answer, the system was working OK on the supply cable as fitted, without blowing the MCB. ergo no fault, CU gets fitted & MCB trips out, CU gets removed & original wiring reconnected no tripping. To cut down fault finding time go to CU & shut off, if MCB stops tripping then fault is on CU or internal wiring, if MCB still trips then fault is on supply side or connections & you've narrowed things down without even opening your meter.

 

[Dunx]

Yes I agree....assuming you believe what a customer tells you! I rarel find thema reliable source of information!