Electric Combi Boiler

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Good Morning,

I have been asked to price a job where there is no gas available and no space for the storage of any fuel. The client has asked for electric combi boilers to be fitted. I’ve never fitted one before and wanted to see if anyone has any recommendations on make and/or model and if there is anything else I may need to consider.

Obviously there will be no gas, flue or condense to consider but is there anything else that I should be aware of?

Thank you
 
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An electric combi boiler would require an electrical supply of 12 kW plus. So, the properties electrical supply must be able to cope with that, as well as the existing demand. Also, 12kw is quite small for providing an instant hot water supply and only really any good for an average shower. It would take a long time to fill a bath. To put in perspective, most Gas combis start at twice that capacity.

Running cost is a big issue:
The cost of a kW of electricity at the normal rate is probably about 11p. There are no flue losses, so electricity is more or less 100% efficient.
The cost of a kW of gas is about 3p, but gas boilers aren't 100% efficient so between 10 to 20% is lost via the flue. Even taking this into account the running cost difference is still big.

Unless running cost is not a concern and as gas / oil is not a possibility, I would consider storage heaters running on an off peak tariff. They store up heat during the off peak times (night) when it is half price, and then release it during the day. A hot water cylinder can also be heated overnight in the same manner.
 
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Hi Stem,

Thank you very much for your detailed reply. These are new build flats so I would imagine that the electrical requirements have been considered. I will certainly raise the issue though before works commence.

Regarding running costs, I agree but this is what has been asked for. If we do go down the route of electric combis, do you know of a decent make that I should be looking to go with?
 
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Sorry I can't help with the detail. Only once have I installed a circuit for a Heatrae electric boiler, but it wasn't a combi and I wasn't there when it was commissioned or heard any feedback.
 
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These are new build flats so I would imagine that the electrical requirements have been considered.
Highly likely that they haven't been.

Find out in writing what the service capacity actually is before quoting anything.
As these are new build, that information will be readily available as it's required when ordering the electricity connections. If electric combis are going into every flat, that fact would also need to be stated on the application for the electricity connection.

Electric combi boilers are by far the worst option for heating in just about every way possible.
Typically only specified where there is zero space for other heating solutions, or the place is so tiny that they are desperate to save as much space as possible.
 
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I have only worked on a few brands of so called electric "combi" they are actually thermal stores with a plate heat exchanger and either zone valves or 2 x pumps, they take up a lot of room, they all require a Pressure releif valve so you will have to consider that.
 
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Thanks for the advice guys. Looks like I’ll be trying to talk them into alternative options if it all goes ahead.
 
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I've had a few tenants use the types of electric combi boilers that Ian mentioned, the thermal store types.

Haven't had any problems so far.
 
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