Consumer Unit Advice

Hi Everyone
I hope you can help me once more
For the last 12 months we have sometimes noticed what can best be described as a 'fishy' smell in the hallway of our house - nice !!! I removed furniture and we changed the carpet when we redecorated, but still we could sometimes smell it
On Saturday night the downstairs ring main tripped twice The led me to the consumer unit and I finally noticed the smell was coming from within
The mini circuit breaker for the downstairs ring main was slightly warm whereas the rest felt normal The washing machine and dishwasher were both on at the time
The MCB is rated at 32 amp and is a Hager type 2 M 3
I removed the cover to the consumer unit The two live feeds to this circuit have scorched insulation. There is some scorching to the MCB The wiring used is a thicker size for the downstairs ring than the upstairs ring (but not as thick as the cooker)
I've looked in the screwfix catalogue but can't see which part i need (happy to use screwfix as they are open today and just across the road !!)
What is my recommended course of action If the advice is to call a sparky, what work and price should be involved
Thank you in advance for taking the trouble to reply This n/g is SO useful
Regards
Hays
T610 Housings in stock now!! www.phonepro.go.to
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hays wrote on Sunday (08/02/2004) :

It sounds likely that the circuit is heavily loaded and that there might have been a poor job done in tightening the connections. The MCB will need to be replaced, the cable stripped back to where it is undamaged and put back together with properly tightened terminals.
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Regards,
Harry (M1BYT) (Lap)
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Offer to do the job for him. Don't bother switching off the power.
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Sore losers
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The Lord alerted my mind to the presence of this EVIL article by Harry Bloomfield, and I thusly replied:

it would seem that you have a number of terminals that aren't properly tightened, netKKKop.
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On Sun, 08 Feb 2004 15:16:39 GMT, Harry Bloomfield wrote:

Craig, what have I told you about sitting on that?!???????

Must've taken your advice on that one then.

This is too dull to comment on.
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Phil Kyle - Usenet Legend.

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You'll now recognise that smell as the smell of overheated electrical gear :-( Often it's the hard white plastic - urea formaldehyde - used in lampholders which gives off this smell, but here it may be the cable insulation.

So it shouldn't be overloaded if wired correctly in 2.5mmsq...

Then it's most likely that the screws holding the live conductors in the MCB weren't done up tightly enough, and have worked looser still as they hum and/or expand and contract as they heat up/cool down on load. Once it starts, it gets worse, as bits of sparking from poor contact erode away the wire at the point of contact, carbon deposits increase the resistance further, and the contact just keeps getting poorer.

(A bit odd, I'd expect both to be 2.5mmsq.)

W-e-ll, the diagnosis needs confirming (e.g. which conductors have scorched - live or neutral? was it the loose connection I've guessed at, or some other cause of overloading - maybe your immersion heater incorrectly shares the ring circuit, say?), and you need to work out what other damage the overheating's caused (e.g. other cables in the CU close to the scorched ones). Then you need to replace the affected cable ends - if you're really lucky the damage is localised to the last 6-9 inches of the cable and there's enough slack to cut off and make a new connection. Yeah right. Back in the land of Sod and Murphy you'll probably need to trace back and (for the nicest job) replace the first length of cable in both arms of the ring, or (a bit less nice) find a definitely good bit to cut back to and crimp or junction-box a fresh length back to the CU. And you'll want a new MCB.
If you're confident you can do the diagnosis and repair - go ahead. If not, call in that sparky: it's in the 50-100 quid region, I'd guess, and you can bias it towards the lower end (or below!) by doing the grunt work of pulling up floorboards and tracing the run of the scorched cable, which will make the sparky's job quicker, easier, and more pleasant (as well a cup of tea/coffee ;-). Oh, and you won't use this ring circuit until you've seen to it, will you - the cable insulation's damaged and you don't want to be using the circuit in this state (gloomy advice, I'm afraid).
HTH - Stefek
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