electric boilers

[refurb man]

hi all need a little advice,,got a landlord with a number of homes wishing to change all of them to electric wet central heating
will be using 12kw fusion boilers needing a 63A rcd,, old cu on house i checked also had 2 electric showers(32A each) and was a bit of a mess,,my question is can we get this boiler fitted by installing its own cu and tails and leave the rest alone for sorting out later if he wants? do you think this is a lot for the main fuse (100A) etc to be handling? thanks to all who reply

 

[JACKC]

Your landlord will need to use a Part P registered electrician. It will be possible to split the incoming supply and fit another consumer unit for the boiler, personally I wouldn't want electric boilers in my house, very expensive to run. Could be that gas or oil is no option. It does sound like that the consumer unit that exists needs attention, I would suggest a Periodic Inspection Report be carried out on the property for piece of mind. The electrician will be able to assess that the 100 amp fuse is sufficient, I think that 100 is the largest the DNO fit for domestic use but will be corrected if wrong. Two showers and a 12Kw boiler is one hell of a load.

 

[electronicsuk]

With the boiler and one shower going you've already pretty much maxxed out your supply, and that's before we mention other large loads such as the second shower, electric hob/oven, portable fan heaters... You would almost certainly need a supply larger than 100A, and that would amost certainly require the DNO to lay a new supply cable, and that would almost certainly cost more than the installation of the CH system.

To be quite honest, it's a silly idea, and is bound to lead to trouble in the future. Storage heating would be a much better alternative to electric wet heating. Yes, storage heaters are the offspring of the devil and will never (in my opinion) even come close to matching gas fired wet heating, but they will be a LOT cheaper to run and only consume electricity at night, thus circumventing any need to upgrade the supply.

If the landlord really must have 'wet' heating for whatever reason, an air or ground source to water heat pump will be a lot more efficient than an electric boiler. Failing that, you could install air-air heat pumps (i.e. heat pump air conditioning), which would again be a lot more (around 300% more) efficient than an electric boiler.

 

[Taylortwocities]

Don't Fusion systems heat the water too?
If its like the ElectroMax systems you'll get mains pressure water hot and cold so can rip out the electric showers and just put in standard mixer showers.

 

[Chri5]

I thought that after initial heat up electric boilers use much less than the max rating to keep the system topped up.

So a 12kw might use 12kw for the 1st 30 minutes and then a more modest 4-6kw to keep the heat constant. A bit like a kettle using less power to reheat water than it would to heat cold to drink temp.

Has billy BS been at me? I was also informed that current gen electric boliers have very decent eco cred as in the cost v gas being marginal rather than excessive due to no wasted heat via flue.

 

[electronicsuk]

I thought that after initial heat up electric boilers use much less than the max rating to keep the system topped up.

So a 12kw might use 12kw for the 1st 30 minutes and then a more modest 4-6kw to keep the heat constant. A bit like a kettle using less power to reheat water than it would to heat cold to drink temp.

Once the building fabric is up to temperature then the boiler will spend less time turned on, although unless it has the ability to modulate it will still draw the full load current during operation. The load might average out at, say, 2kW over 24 hours - but that's still 48 units of electricity on heating alone, and that's probably a conservative estimate.

In any case, electric heaters in each room would be more efficient, as you're using electricity to heat air rather than electricity to heat water to heat air. It would also be a lot easier to install. If you're going down that route then the landlord would still get the best economy from storage heating.

Has billy BS been at me? I was also informed that current gen electric boliers have very decent eco cred as in the cost v gas being marginal rather than excessive due to no wasted heat via flue.

Modern condensing combi boilers waste very little heat through the flue, as they have a secondary heat exchanger that transfers what would be otherwise wasted heat back into the water in the CH loop. Not only that, they will also modulate their power output to meet heat load. Given that gas is around 4p per kWh and electricity about 13p/kWh, you do the math.

 

[Chri5]

Ta- now where's my calculator

 

[Steve]

And every time the boiler kicks in, your lights will dim.

Someone above mentioned heat pumps - these are great. Up to 400% efficient (I'm told), so a 2kw compressor would put out 8kw of heat into the house. Its proven technology, but the companies making them have yet to make a name for themselves with regards to reliability. Small scale versions are available in the form of single room air conditioners.

 

[ban-all-sheds]

If you're going down that route then the landlord would still get the best economy from storage heating.

It's a pretty safe bet that the landlord isn't the one paying the electricity bills...

 

[electronicsuk]

If you're going down that route then the landlord would still get the best economy from storage heating.

It's a pretty safe bet that the landlord isn't the one paying the electricity bills...

Probably not, but if he's got an ounce of sense then he might realise that the turnaround on his tenants will be pretty high if the house is too expensive to run.

 

[rebuke]

I think some landlords aim for high turnaround (in areas with busy rental markets anyway), as it allows them to charge a nice reference checking fee and admin fee for each new tenant, over and above the rent...

 

[Stoday]

On-peak electric heating, wet or dry, is a good solution for small recently-built flats. The current building regulations require such a high level of insulation that only one kW or so of electric heating is required once the flat is up to temperature.

Probably not applicable to this example of course, because the building's old.

 

[nozspark]

I did a 12kW electric boiler a couple of years ago.. they had a 9.5kW shower aswell.

Basically you have to ensure that the shower and boiler cannot beswitched on at the same time, so a supply via a fused spur at the shower isolator goes to a relay at the boiler which gives a "at temp" signal to the boiler when the shower is being used and shuts down the boiler heating command.. this is all on the low current side of the boiler!!