I have estimated to have a new Old style tried and tested Wylex 60 Amp. switch fuse installed with an H.R.C. fuse, next to the consumer unit. The electric boiler installers will run the supply cable from the new switchfuse to the electric boiler. I am not involved with that. I envisage a 10.0mm2 or 16mm2 circuit will be required. The run is about 15 metres in length. Personally I am not happy with the decision to have the new electric boiler installed in place of an existing oil boiler. At least with oil there is a back up in case of a mains failure, even if a small U.P.S. is needed for ignition and pump. Oh well, it's the customers' decision.

Z.

Are the DNO happy with the electric boiler load being added?

“Oh well, it's the customers' decision.”

Do not allow customers to make a decision Zoom lad.

That will be your downfall.

Craftily use tact & diplomacy to assist them to arrive at your decision

Whilst I see the comments, this is a very foolish idea. The running cost will be immense, and oil is much cheaper, roughly the same as gas. The electrical supply may well not really be available, and I suspect there will be flickering lights and other difficulties. This is probably the least “green” idea I have seen so far, the overall efficiency from gas in to heat out is about half or less than using a new oil boiler. Whoever sold this needs to be locked up. The alternative of LPG is another possibility, again greater overall efficiency than the “electric” solution, and only a bit more than town gas.

Edit added:

The idea that electricity is in any way green is completely untrue, as is the suggestion that it is somehow “free”. On a good windy day, the wind and solar output are still miles from being enough, despite having “invested” a huge amount of money. The idea that fossil fuel will not somehow be available is also ridiculous and despite the “Boris” ideas, we will use fossil fuel for a long time yet, if only to enable us to get petrochemicals, the by-product of refining. Imagine the world without nail varnish remover or any plastic items, including cable insulation. We truly would be back in the dark ages! There really could be no electrical industry at all, and all the turbine blades would cease to exist, as would solar cells. 

Having slept on it I would probably decline the job as there’s almost certainly going to be a lot of grief this time next year, I would have to let my concerns about the efficiency and running costs known to the clients.

If they really want it then a separate consumer unit with a 30 mA RCD main switch and a 63 amp circuit protective device is the way to go.

Note you are supposed to use heat resistant flex for the final connection, I was alright as it was the lowest rating boiler and I had some on the van.

Colin Haggett: 
 

Are the DNO happy with the electric boiler load being added?

I have advised the customers to contact U.K.P.N. and ask that very question.

Z.

The customers have already agreed to the 12kW electric boiler install and have signed on the dotted line. The installer said that the customers needed a new consumer unit. The existing one is an old Memera 3 with black M.C.B.s with push buttons and a bit like the old Wylex M.C.B.s with push buttons from the 70s. Probably obsolete nowadays.

Memera 3 M.C.B.s 

Z.

Then oversize the consumer unit to accommodate the flow boiler MCB and to allow for void ways to keep it cool or go down the two consumer units route.

The selection of the actual circuit cable is a minor matter, it’s the actual DNO intake and the customers consumer unit that need addressing first.

16 mm twin and earth is available as cut lengths from online suppliers, though I would try my usual wholesalers first.

Do not even consider rehashing the existing board.

Presumably the DNO supply is actually big enough to handle it?

If you put in a set of Henleys and a switch-fuse (which seems to be an excellent solution) the existing CU will be none of your business.

These electric “boilers” (calorifiers) appal me. There is enough fuel poverty without adding to it!

I can think of one or two houses that I visited in East Anglia in the 1980s that had one coal fire and that was it. No running hot water, or even running water of any sort indoors.

And shilling-in-the-slot meters.