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One for the sparks?

IANB

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#1
My bro in law has just been on to me about a problem with his shower. He said that the breaker in the consumer box is burnt out and that the thing had been tripping. He asked if putting a new shower switch in as a replacement to the breaker was the answer.
I told him no not really and it should be checked out as to why the breaker burnt out.
I asked him what rating the shower was and the cable type.
It is 9.5 kw and on 6mm cable and a long run of it at that.
It was on a 50 amp breaker in a dorman smith unit so the breaker rating seems ok. I told him that the cable was a bit light and i thought it should be 10mm. So am i correct in assuming that if the cable is under rated this could cause heating at the breaker esp if the connection was not as tight as it should be.
Any advice welcomed.
P.S. i have told him that a qualified spark should be consulted to sort it out.
 

carlos

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#2
The 50 amp breaker is way too much for that cable m8, max current for 6mm cable clipped direct is about 45 amps, about 35 when buried in a wall. i have a 9.5 kw shower running off a 32 amp MCB on 6mm with no probs and have installed same in others.
defo sounds like a loose connection with the mcb for it to burn out. just tell him to get a 32 amp MCB installed.
 
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#3
Loose connection will of more than likely caused it im a spark and use to work for a leading shower company most burn outs where loose connections either switch terminal block or back at d.b.Any shower over 8.5kw should be wired in 10mm t&e cable as a rule.Recheck all connections make sure they are tight you can get a spark to check installation over though better to be safe :Clap:
 

Mick

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#4
9500 / 240 = 39.5A

you would not use a 32amp MCB :)

it should be a 40amp (and should also be protected(RCD)) but must be lower than the rating of the cable which is about 45amps and as said before you must also use diversity because if it goes through any kind of insulation it will drop that by almost half if not more and also length is important but without going to the van and getting me on site guide i could not tell you the length vs drop ratio on that.

But also saying that cable is allot tougher than thought of and can withstand allot but those are the values.

Anyway i would check all connections as the guys said because more than likely its a lose connection in the NEON FS (if used) or shower unit!

But now you might need to check the cable it could be burnt out... 10mm should of been run for this because with 9.5KW your not leaving allot of room for play And look for discolouration on the cables where its being connected (where you can see the cable red/brown blue/black and earth).

I fixed a shower just the other week with the exact same fault and it was the connection in the FS before the shower.

Good luck and if in doubt get a proper sparky out m8
 
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