Downstairs light circuit fuses - freezer's fault?

[UselessFatBloke]

Hi

Since having an extension put in, which adds an extra 12 mains voltage downlighters to the downstairs light circuit, the consumer unit fuse thingummyjig for the circuit keeps tripping.

We've since found out that the electrics in our garage (including a fridge freezer) are linked to the downstairs light circuit. Is that why it's tripping? Should we have a higher amp fuse gubbins in the box to cope with the fridge freezer? Is the right (probably expensive) answer that a fride freezer has no business being on a lighting circuit, and we need some rewiring done?

 

[ban-all-sheds]

Hi

Since having an extension put in, which adds an extra 12 mains voltage downlighters to the downstairs light circuit, the consumer unit fuse thingummyjig for the circuit keeps tripping.

That could be an extra 600W. Since lighting circuits are only 1380W in the first place, I'm not surprised to hear about the trips.

We've since found out that the electrics in our garage (including a fridge freezer) are linked to the downstairs light circuit. Is that why it's tripping?

I'd be surprised, quite honestly, if the F/F is on the lighting circuit - the surge when the compressor(s) start up would have been tripping the lighting MCB all the bl**dy time.

Should we have a higher amp fuse gubbins in the box to cope with the fridge freezer?

Never, ever, put a higher rated MCB on a circuit to cure tripping problems unless you are sure that the circuit cable can cope with the higher load. See here //www.diynot.com/forums/viewtopic.php?p=81696#81696 for an explanation of the relationship between design current, cable capacity and MCB rating.

Is the right (probably expensive) answer that a fride freezer has no business being on a lighting circuit, and we need some rewiring done?

As I say, I doubt that a lighting circuit could ever have sustained a F/F, but if somehow this is the case then you need to get it fixed asap. Which may mean some rewiring.

Sounds like you should get an electrician in to check it all over for you, but not the one who did the electrics for the extension. Who was that, BTW, what sort of person was he? When was it all done, and what did he do about Building Regulations approval for the work?

 

[UselessFatBloke]

The builder was competent, although we had our doubts about the electrician (although new light switches were earthed, existing switches which formed part of the extension were left unearthed). Building regs inspections were cursory, frankly.

Perhaps we've been guilty of buying too many fancy light fittings from B&Q, and are overloading the circuit. Hall has 4*50W, living room 5*60W, kitchen diner extension has 12*50w, exterior light is 100W, new fitting for study has 4*40W.

If a lighting circuit is only meant to be for 1380W then watt should we do?

 

[ban-all-sheds]

Well that lot doesn't actually add up to what a 6A lighting circuit can supply, so given that you would not be likely to have them all on at the same time, you should be OK.

Can you trip the circuit at will by turning them all on at once? If you unplug the F/F, does the problem stop?

 

[UselessFatBloke]

I'll give that a go tonight. Many thanks.

 

[mapj1]

Please run the F/F from an extension lead from a circuit known not to trip for the duration of the test !

As a rule of thumb any lighting circuit with more than 1000watts total should be split into smaller circuits, each of 6A, unless you wish to rewire in fatter cable (1.5mm) and have 10A breaker.
Many small circuits has advantages for servicing, but needs a larger consumer unit.
Large loads like 1KW flood lights, and outside lights that might get water ingress are better spurred of the socket ringmain with individual local switch fuses.

 

[securespark]

The electrician probably left the existing switches unearthed because that's how they were before he arrived.

Doesn't mean necessarily he's a cowboy.

Whenever I visit a house, there's at least one thing wrong that I could point out to the customer, but I can't go round rectifying everything - even if the customer wanted me to!

As long as the work he did complies, then that's OK.

 

[keyplayer]

Building regs inspections were cursory, frankly.

Indeed I bet they were. I bet your cheque went through nice and efficiently though.

 

[UselessFatBloke]

Just to update - the FF was definitely on the lighting circuit. Now disconnected, and all the downstairs lights can blaze away quite happily.

Dunno how a FF and 1200 watts of lighting ever managed to fit on the circuit, or whether we were at risk of an imminent fire, but cheers for all the info.

 

[UselessFatBloke]

Building regs inspections were cursory, frankly.

Indeed I bet they were. I bet your cheque went through nice and efficiently though.

Actually, they forgot to ask us for money . . . I checked with the council and they've said that the certificate will be held indefinitely until we decide to pay for it. That puts it rather low in the priority list for me.

 

[securespark]

Until you sell up.