Fusebox - loose connection on busbar and mcb

24 Mar 2007
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West Midlands
United Kingdom
Hi could somebody please advise me?
The other day, I found that one of the mcbs had been tripped and would not reset. I called an electrician and he said that this was caused by a loose connection between something called the busbar and one of the mcbs. This in turn had triggered a small electrical fire which went out on its own because the mcb had been tripped (at least I think so).
The mcbs have now been replaced and everything is working fine. The electrician said that he advised that the consumer unit be replaced. My question is this? While I am looking into getting the replacement consumer unit, what are the safety aspects of the fusebox? What I am concerned about is another fire occurring which could spread to my flat. If the worst thing that could go wrong is that the circuits get tripped and I lose electricity, then this I could deal with. What scares me is the risk of fire spreading to the flat. Could somebody please tell me if there is anything in a fusebox to prevent spread of electrical fire? Is this what mcbs are for? I know the question sounds stupid but please help as it would put my mind at ease. many thanks, mogthefrog
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Is there any chance of a picture of your fusebox?

I'm assuming the MCBs are plug in and the electrician is worried that the clips on the busbar have slacked off a littl bit over the years, rather than a modern unit with a screwed busbar?

I beleieve CUs are relativly flame retardant they'll usually smoke a lot before catching on fire and if you catch it before it gets the surroundings warmed up, you can just switch it off, make sure its stopped and not need to call the big red thing with blue lights...

Also if a bad connection occurs near a mcb, what quite often happens is the heat is connected into the breaker and trips the thermal overload part, this isn't really by design, its just what usually happens, of all things a mcb is probably the sfaest electrical thing to have a poor connection on (if it was on a jucntion box, it'd just get hotter and hotter) You can't garentee it though.

What size MCB and what circuit? this boards (assuming wylex standard plug in board) quite often don't take anything bigger than a 30A but brute force and ignorance often sees 45A devices jammed in!
All electrical items that comply to the relevant BS are designed to contain fire. Obviously they will not survive a raging fire....

I don't think you had a 'small fire' - I think one of your MCB's overheated, and the surrounding plastic was damaged due to heat - I wouldn't say it was ever on fire.

If the enclosure is not damaged, and the MCB's and dinrail was replaced, I am not sure what the point in changing it is?

As said - post some pics of the CU now.
Howdy all,
Am trying to post pictures of my fusebox and the old knackered circuit breakers to show you what happened to them. Im not sure how to upload photos from my computer. HOw do I do this please?
With regards to there being a fire, it seems to me that this did happen as a couple fo the old mcbs have burnt through.
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Hi please ignore the last post regards photo uploading. Im rading something on the FAQs about it. Sorry! I'll try and work it out and post the photos somehow
Thanks for the tip John D

Let's try again. hopefully, here are the pictures of my fusebox and old mcbs



I'm not sure if I've done this correctly, so please forgive me if I havent!

best regards, mgothefrog
If you have had a new busbar fitted, and new MCBs, then I think you have had the damaged parts replaced with new, and there is no need to change the casing as well.

Verify that the electrician used genuine parts that are a perfect fit, not odds and ends from his toolbox. If the parts are correct it will be OK.

Changing a CU usually costs some hundreds of pounds due to the amount of testing and paperwork that is required. I would hope that your electrician is a member of a self-certification scheme (not an odd-job man ;) ) so he can be expected to have done the repair to a proper standard.

I suppose, if you wanted to badly enough, you could buy a new CU, swap the front panels over, and throw the rest away (or sell on EBay). Changing the front cover does not require much work and I doubt it would be notifiable.

the new mcbs were bought from a wholesalers which he did after seeing what the problem was. They were not simply out of his toolbox, and the electrician himself was part of a proper company which dealt with electrical repairs for emergency and routine situations. I got them from the yellow pages. They seemed v professional.
In terms of what he replaces, he got all new mcbs and a new RCD I think. In terms of busbars, are they part of the mcbs? I dont think he bought separate ones. he wrote on the receipt: "Consumer Unit needs replacing after an electrical fire on the shower mcb and RCD protected. Live busbar damage also to the outer case". I now nothing about electrical stuff so dont understand all of it, but this is word for word what he wrote.
Basically, Im wondering if the unit is at least safe with brand new mcbs and RCD, while I look into whether to replace the CU.
MAny thanks for all advice, best regards, mogthefrog
sounds like he didn't replace the busbar. This is a thick piece of copper with prongs that are gripped by the screw on the MCB.

Once copper has been damaged by excess heat is is likely to come loose again over time and give a poor contact.... which will lead to overheating again (this is very common on Shower switches, which carry a large current and get quite warm).

If you are happy with the company, ask if they will give you a quote to replace the busbar or the CU complete... explain that you have had new MCBs fitted as you don't want to pay for another set. It is not an emergency job so you do not need to pay a call-out charge.

If they seem expensive or unwilling, ask round friends and neighbours for recommendations of a local electrician. Ask if he is a member of a self-certification scheme, and which one. Describe the problem and ask if he would be willing toi fit a new busbar or if he would only change the CU. Ask if he will give you a certificate on completion (this is important).

If it was in my own house I would probably just fit a new busbar, but if you are paying an electrician to do the work, you (and he) will want to be confident it is a first-class job, and the cost of parts will be less than the labour cost.

It's the piece of copper that connects to every MCB. He should have replaced this too because copper that is damaged by heat has a high resistance, and this could lead to future overheating. The electrician should also have cut back the damaged parts of the cable for the same reason.

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