Are MCB's standardised

[ed1000]

I recently upgraded my electric shower to a 10.5 kW model from an 8.5kW. After about 5 minutes it trips out the MCB.

Having investigated this further it appears that the old shower unit was connected to an MCB that was not suitable for the load placed on it. The old shower was connected to a 30Amp MCB which meant that the system was always running close to the MCB's upper tolerance.

I did some calculations (P=VI) to see what current each unit would draw and the old shower running at 8.5kW unit running at 240V would draw ~35.4 Amps and the new 10.5 Unit running at 240V will require about 43.8 Amps therefore I need at least a 45A MCB to take this current.

I have checked that the cable is 10mm2 to be safe and I have the following questions:

There seems to be no branding on the consumer unit but do MCB's come in a standardized fitting. I have seen numerous references to Type B so can I just buy a 45 or 50 Amp MCB and replace it in the consumer unit.

Can I just replace the MCB in the consumer unit with a 45A or a 50 Amp MCB. Which would you recommend.

Do the new building regulations in Jan 2005 affect me if I just want to uprate the MCB.

 

[andy]

you should have checked the MCB and cable size were adequate for the extra load before ou done anything. at worst, you could have started a fire.

all MCBs are different, altho most are similar size. take 1 with you when you go for the new 1


and the building regs will affect you changing the MCB. all you can do with a shower is change like for like. not change the rating

 

[ed1000]

Fair enough about checking before hand, at the time I thought that you could just replace it. The old shower looks like it was already installed by a DIY cowboy when I bought the place before the regs were put in place.

The shower is fitted now so once I get a new MCB what how do I get it past the regs. Can you self cert. Would a mate with a degree in electrical engineering count as a competant person.

 

[andy]

Fair enough about checking before hand, at the time I thought that you could just replace it. The old shower looks like it was already installed by a DIY cowboy when I bought the place before the regs were put in place.

The shower is fitted now so once I get a new MCB what how do I get it past the regs. Can you self cert. Would a mate with a degree in electrical engineering count as a competant person.

unless you registered to self-cert the work, which i doubt otherwise 1: you would know you were and 2: you would have known what you asked and you would have checked everything before replacing the shower

so youll have to either just do it, and ignore part P (which is just a money makin scheme...)

or get BC to come check it for you

 

[ban-all-sheds]

The old shower looks like it was already installed by a DIY cowboy

I don't think that doing the same with the new one is what is meant by "like for like"...

 

[ed1000]

Now that I have put my spurs away I have every intention of ensuring proper safety now that I know what is involved.

Obviously the reason I posted here is to try and get the correct info so that this is all done properly.

 

[andy]

Now that I have put my spurs away I have every intention of ensuring proper safety now that I know what is involved.

Obviously the reason I posted here is to try and get the correct info so that this is all done properly.

is the shower RCD protected?

 

[ed1000]

Yes, it is attached to a RCD protected part of the consumer unit.