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

 

[spark 68]

It must have a fairly low resistance short to knock the 20A MCB out, I suppose it is possible the garage DB is faulty in some way (is it new?).

or the OP has put the comb section across both RCD terminals.

 

[jase]

have i missed something?? when did shutting down boilers come into the original problem????

 

[GLENNSPARK]

so did you conduct dead testing to ensure that this circuit feeding the garage was good for continues service BEFORE undertaking any work here?......and what about both earthing and bonding n all?....check those BEFORE undertaking ANY WORK here?.....have you even got test equipment?...because i get the feeling you aint.....

 

[Specialist]

I allways believe what the customer tells me until I can prove otherwise, which i've gotta say has'nt been that often. But even if the customer has got it wrong, if you turn off the CU to start with & see what happens you can save yourself time. It's a common thing in Industry, you split the problem area into smaller chunks so you've got less testing to do & less downtime of equipment.

 

[Specialist]

It must have a fairly low resistance short to knock the 20A MCB out, I suppose it is possible the garage DB is faulty in some way (is it new?).

or the OP has put the comb section across both RCD terminals.

Yep System ok until he fitted a new DB & is ok again since he's removed the DB.

 

[Specialist]

have i missed something?? when did shutting down boilers come into the original problem????

I'll take a pass on that 1, it just came out of the Blue:lol:

 

[vernam616]

Proves that Part P will never eradicate these fools

Call an ELECTRICIAN pal

 

[Specialist]

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

Think he's a plumber who's just done his Part Pee, & is P****d off with Electricians for some reason lol.

 

[GLENNSPARK]

so...on the assumption that this "electrician"..lol.......electrician has got the relevent test equipment to verefy his work....would be interested to know if he has results such as a Zdb for this "install"?.....and he clearly doesn`t know how to fault find either as if he did then he would know that to break up a circuit into portions (point to point) and then dead test...is the way here.....will be something in that garage board or something disturbed in the circuit/s it is feeding as it was ok before....cant see it any other way....divide and test here....

 

[GLENNSPARK]

If tripping the 20A breaker (instantly presumably) with nothing connected to the new CU then there is a fault at the new CU that is connecting Line to either neutral or earth (or both). [If there is RCD protection at the house (shouldn't be, unless it is S type for discrimination) and that RCD is not tripping then the fault is Line to Neutral.)]
Make sure it is wired as in the right hand side of the diagram below (the first neutral terminal will not be there), and check that there is not a break in the SWA Line that maybe touching the case as it enters the CU (if it is metalclad).
View attachment 9787

yes but dont do it for him richard mate......if he cant get his head around stuff like this....then he`s got no business installing...period........makes me cross this kind of thing..(not you mate ...him)....taking money for work done that aint right....it aint on either......:nonod:

 

[Richard Burns]

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.

If tripping the 20A breaker (instantly presumably) with nothing connected to the new CU then there is a fault at the new CU that is connecting Line to either neutral or earth (or both). [If there is RCD protection at the house (shouldn't be, unless it is S type for discrimination) and that RCD is not tripping then the fault is Line to Neutral.)]
Make sure it is wired as in the right hand side of the diagram below, and check that there is not a break in the SWA Line that may be touching the case or the armour as it enters the CU (if it is metalclad).

 

[Richard]

Just another thought, what colours have you used for L, N & E? and do they correspond at the DB? Don't think this will be the prob but worth a look.

Rich