Urgent help with the mcb tripping on lights

[hunggaur]

hi folks i am hoping some one can point me in the right direction

i have just installed a wylex split load uint

http://www.electrium.co.uk/Wylex17th Edition.pdf

i have wired in the sockets on the rcd side to the left as you are looking at it on a 32 amp mcb and the lights to a 6amp mcb on the right of the unit on the none rcd side.

however when you turn on the mcb for lights they trip the rcd to the left of the mcb and i cannot understand why as they are on the none rcd side or have i done something wrong.

if i transfer the lights over to the left rcd side the work fine and do not trip

I think the problem may be down to a fault dimmer as when the lights are wired on the rcd side and you turn on the dimmer it trips the mcb


any advice welcomed

cheers

jon

 

[Taylortwocities]

Sorry to be rough on you but….

That link is just the Wylex catalogue. Whic is the EXACT consumer unit that you have installed?

There should not be a "non RCD side". Post a photo of the INSIDE of the consumer unit if you are not sure.

To comply with the Wiring regulations, for most domestic premises, all circuits must be RCD protected, except in some special circumstances. So your consumer unit should have TWO RCDs or all RCBOs or a mixture.

What were the results of the Insulation Resistance test that you carried out on teh circuits before changing the consumer unit?

Have you made sure that the neutrals are on the correct busbars?

And (a house keeping note) changing a consumer unit is notifiable. I hope that you have done the necessary with the Local Authority, before you did this work?
See //www.diynot.com/wiki/Electrics:part_p:DIY-Electrical-Work-and-the-Law for details.

 

[JohnW2]

i have just installed a wylex split load uint ....

Assuming that I understand you correctly, I'm a little surprised that you have installed a 'split load' unit rather than a 'dual RCD' one. Whatever....

i have wired in the sockets on the rcd side to the left as you are looking at it on a 32 amp mcb and the lights to a 6amp mcb on the right of the unit on the none rcd side. ... however when you turn on the mcb for lights they trip the rcd to the left of the mcb and i cannot understand why as they are on the none rcd side or have i done something wrong. ... if i transfer the lights over to the left rcd side the work fine and do not trip

You very probably have a 'cross-connection' between the wiring of the lighting circuit and that of one of the RCD-protected circuits - commonly known as a 'borrowed neutral'. In that situation, some of the neutral current from the lighting circuit will go through the RCD and cause it to trip. A competent electrician would always check for that before changing to a 'split load' or dual-RCD CU!

Such cross-connections are usually between two lighting circuits - do you have another lighting circuit on the RCD side of the CU? Rather than in the wiring itself, such a cross-connection could also arise if you put neutrals into the wrong busbars in the CU.

Kind Regards, John.

 

[Taylortwocities]

Ha! t o o s l o w

 

[JohnW2]

Ha! t o o s l o w

Indeed so - I must have typed particularly slowly (maybe I was distracted by something!), since your reply certainly wasn't there when I started typing, yet I didn't post mine until 6 mins after yours!

Kind Regards, John

 

[AndyPRK]

There are 2 neutral blocks

Put the sockets on the left one
And lights on the right one.

 

[hunggaur]

simple fix all sorted it was 2 neutral blocks for the split load and I had connected it on the wrong side as the spilt load and there was only 4 to 5 mm spacing between the 2 blocks and i had simply put in the wrong block and missed it.

amazing what you can see after a cup of tee and light bulb moment

I did not chose the the consumer unit i was just helping install it for a friend to give them a hand.

thanks for all your help and advice

happy bunny

 

[WabbitPoo]

happy bunny

Happy until a fault develops or he tries to sell the house. Did you get it certified?

Glad its working though

 

[hunggaur]

happy bunny

Happy until a fault develops or he tries to sell the house. Did you get it certified?

Glad its working though

No not got it certified yet and have told him he has to and he may have problems selling his house until he does. I made sure he was fully aware of this.

Just wanted to make sure it was done right and safe before he got someone in. If he chooses not to certify it then that's his call. I know everything is safe the way it was left for him.

Cheers Jon

 

[Taylortwocities]

As above, he and you cannot certify it because the certificate states that the work done conforms to BS7671 (2008) and it does not.

It does not because all circuits that have cables buried (in wall, eg) less than 50mm from the surface must be RCD protected. You have told us that this is a consumer unit with some circuits that are not RCD protected. So, it does not comply. (Not unless all wiring is clipped to the surface, or run in surface tyrunking, etc - which I doubt)

He also cannot certify it because you have implied that no tests were carried out on the circuits, or the board. I suspect that this is because you do not have the required calibrated test equipment? You need the test figures for each and every circuit, the incoming supply and the trip times for the RCD(s) to fill in the test schedule.

Also the work needs notifying to the Local Authority. (This is the LAW).
The person that has done the notifiable work has to be the member of a "Part P" scheme (neither of you are) or you have to demonstrate to the Local Authority that the work(DIY) has been carried out competently (it hasn't) and that it has been tested (it hasn't) and that it complies with building Regulations (it doesn't).
Oh yes and you have to pay a Building Notice fee.

So, the best of luck to him when he comes to sell the house and the buyers want to see the Installation Certiciate and the Building Regulations Completion paperwork.

PS Glad the light works. Such a basic error.

 

[JohnW2]

As above, he and you cannot certify it because the certificate states that the work done conforms to BS7671 (2008) and it does not. ... It does not because all circuits that have cables buried (in wall, eg) less than 50mm from the surface must be RCD protected. You have told us that this is a consumer unit with some circuits that are not RCD protected. So, it does not comply. (Not unless all wiring is clipped to the surface, or run in surface tyrunking, etc - which I doubt)

Although I certainly agree that there are probably a number of good reasons why the work could not be honestly certified, I'm interested in the above specific point you raise ...

... if the only work done is to replace the CU (with whatever), with nothing done to any of the final circuits (other than to connect them to the CU), do you feel that the requirements relating to the cabling of final circuits has to be brought into compliance with current regulations?

Pragmatically speaking, of the final circuits (the cabling of all of which was presumably compliant with earlier editions of the regs), some now enjoy more protection than they previously had and others are in no worse a position than they previously were (and could, legitimately, have remained, in the absence of any work being done.

Having said that, to install a 'split load' CU (without RCBOs) in 2014 is clearly just plain daft!

Kind Regards, John

 

[ericmark]

Using a mixture of RCD and RCBO would make some sense but the whole idea is dependent on factors like light from street lamps and emergency lamps and the risk assessment has to be installation to installation there is no one size fits all.

In the main tripping is caused by items plugged in and so having rings on RBCO and rest on RCD does make some sense.