Fuse for garden office keeps tripping

sparkieguy

With heaters...the longer they are on the more the element breaks down and can cause a trip.

Though..as its the mcb and not the rcd that trips I would say that you have a short somewhere

sparkieguy

What does the insulation resistants test say? Should be something like > 299

Crazy_Diamond

sparkieguy wrote: »

What does the insulation resistants test say? Should be something like > 299

It says > 200

Owain_Moneysaver

As far as I can make out the circuit breaker you are referring to is a MCB, i.e. there is NO RCD protection to the summer house cabling or sockets.

The electrician appears to have used a mix of manufacturers' devices in the consumer unit, which voids the type approval.

I suspect there may be a bad connection somewhere which overheats, expands, and shorts to earth, tripping the MCB. It may be as simple as a wire trapped by a socket faceplate fixing screw.

The electrician really needs to come back and thoroughly check and test the wiring - and redo the job to current Regulations incorporating RCD protection to wiring and sockets as required.

Crazy_Diamond

Owain_Moneysaver wrote: »

As far as I can make out the circuit breaker you are referring to is a MCB, i.e. there is NO RCD protection to the summer house cabling or sockets.

The electrician appears to have used a mix of manufacturers' devices in the consumer unit, which voids the type approval.

I suspect there may be a bad connection somewhere which overheats, expands, and shorts to earth, tripping the MCB. It may be as simple as a wire trapped by a socket faceplate fixing screw.

The electrician really needs to come back and thoroughly check and test the wiring - and redo the job to current Regulations incorporating RCD protection to wiring and sockets as required.

You are right it does say n/a in the rcd box on the certificate under summer house. However this has been signed off by building control. Do the regulations say an rcd should always be fitted in this instance?

Also sorry if this a stupid question but what do you mean by using a mix of manufactures devises voiding the type approval, should this work have not been signed off?

Crazy_Diamond

Another question, does the fact that the circuit board in the utility trips rather than the one in the garden room mean that the fault is in the wiring from the garden room to the utility rather than in the garden room itself?

muckybutt

Can you get a close up photo of the circuit that trips -to me that looks like an rcbo which is completely different to an mcb / rcd.

Which ever way you look at it though you really need a sparky to investigate the cause and rectify the problem, it's one thing giving you an online diagnosis but something else when you actually have the installation in front of you.

Owain_Moneysaver

Crazy_Diamond wrote: »

You are right it does say n/a in the rcd box on the certificate under summer house. However this has been signed off by building control. Do the regulations say an rcd should always be fitted in this instance?

All sockets for general use must be RCD protected.

All concealed wiring must be RCD protected unless run in steel conduit or a metal sheathed cable type.

Building Control will refer you back to the electrician who signed the certificate. Building Control generally know next to nothing about electrics.

Crazy_Diamond wrote: »

Also sorry if this a stupid question but what do you mean by using a mix of manufactures devises voiding the type approval, should this work have not been signed off?

The consumer unit manufacturer tests their units for standards compliance when fitted with their own devices. They can't test for compliance when a mix of manufacturers' devices are used. This includes electromagnetic compatibility and it's not impossible that the magnetic field from the coil in one device is contributing to false tripping in another device.

You need to get the electrician back to correct this work to current 17th Edition Wiring Regulations, resolve the faults, and issue a new certificate.

If you have problems with the electrician you can invoke NAPIT complaints procedure
http://www.napit.org.uk/consumerComplaints.asp

Crazy_Diamond

Just had another look at the certificate and under some of the tests it says it is rid protected.
http://s272.photobucket.com/user/Christinalusty/slideshow/

Owain_Moneysaver

The applicable line for RCD protection is on page DB3 Circuit 2 sockets. This should be the consumer unit in the summerhouse. If the one you linked to on TLC website is correct, the certificate is incorrect.

Hopefully what you actually have in the summerhouse is something like this

Note it has a main switch with a Test Button, i.e. it's an RCD. If that is so then the installation is correct.

However you are still getting MCB tripping - which one, the 40 Amp one on DB1 or the 40 Amp summerhouse one on DB2? There isn't necessarily discrimination between the MCBs, so if it's the DB1 tripping it doesn't rule out a fault downstream of DB2.

I suppose there's an outside chance the MCB itself is faulty. There's no way a 40 Amp MCB should trip on a 15 Amp load.