New consumer unit

Christ0 · Aug 7, 2015

Hi all,

I'm new here and hope one of you can help me.

Recently, while I was away from home, I had a new 6 way CU fitted by a qualified electrician and he did a like for like change for the old box and fitted new MCBs/RCDs which all seems fine.

My house is supplied from a 100A box outside.

I have an electric shower, an oven, a 32A ring main, a 6A light cct and a 16A cct, the latter labelled as water heater on the CU but "rail" on the test certificate.

Q1 - The chap inspected what he could of my house wiring and assumed that the shower and the cooker were on the same radial, with a junction box between them, which I believe is not acceptable. He noted this on the test sheet but I am unsure as how to remedy this. If it needs a new 32A radial to feed solely the shower from one of the spare CU slots, will this not exceed the maximum rating of the main input supply? i.e. (32x3)+16+6 = 118A. I presume that diversity rules mitigate against any overload as not every single circuit is going to be running to max at the same time. If this is all the case all I need to do is get him to run a new 32A feed to wither the shower or cooker?

Q2 - I don't know what the 16A "water heater" feeds as I have a combi-boiler. Did this used to feed a hot water heater when the house was built maybe? The house is about 30 years old.

Thanks in advance for any replies and apologies for the long winded question but hopefully it will save any ping-ponging of answers!

Richard Burns · Aug 7, 2015

The shower and cooker on the same circuit is not acceptable and the circuits do need to be split up so that each item has its own circuit breaker.
There is not likely to be an overload as you say with diversity and also that fact that it will be using the same amount of power as it always was.

16A water heater would have been an immersion heater before the combi boiler was put in, if the combi boiler is in the same place as the immersion used to be the circuit is probably powering the boiler now.