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

 

[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