Removing storage heaters for oil central heating

misskiti

Hi all,

I'm looking at buying a three bed detached house which currently has storage heaters. I know how inefficient these are so would want to convert it to oil fired central heating (there is no gas in the area). Would anyone be able to give me a roughy cost to do this please?

Many thanks,

K

Cardew

£5,000 to £6,000 ???

Oil tanks are very expensive and they have to be sited and oil pipes laid etc. Boiler, flue, radiators etc.

Assuming you have a combi, removal? of hot water tank.

rogerblack

Storage heaters - properly dimensioned and used - may not be inefficient, and may be cheaper than oil.

A quick google says that heating oil is about 6p/kWh - assuming a condensing boiler - that's 8p/kWh or so.

Economy 7 here is 5.2p on the cheapest tariff.

Then you have the additional costs of gas - heating tank, bunding, periodic boiler maintenance, convenience - the heating is much less likely to fail randomly.

It's almost certain that there are better places to spend this money.
For example, spending 6K on upgrading the insulation (not windows!) will likely save quite a lot.

Note that you need _enough_ storage heaters - skimping leads to running out of stored heat during the evening, and using expensive rate electricity.

Dunroamin

Give yourself a winter with them to see how you get on. They may not suit you but you could be pleasantly surprised and save yourself a lot of money.

HappyMJ

misskiti wrote: »

Hi all,

I'm looking at buying a three bed detached house which currently has storage heaters. I know how inefficient these are so would want to convert it to oil fired central heating (there is no gas in the area). Would anyone be able to give me a roughy cost to do this please?

Many thanks,

K

Storage heaters are 100% efficient and are cheaper to run than an oil fired central heating boiler. All of the heat generated by a storage heater goes into the room. Maybe not at the right time but it will all go into the room at some point during the day.

rogerblack

HappyMJ wrote: »

Storage heaters are 100% efficient and are cheaper to run than an oil fired central heating boiler. All of the heat generated by a storage heater goes into the room. Maybe not at the right time but it will all go into the room at some point during the day.

This is only effectively true if you want the heat.

Heat leaks out of the storage, meaning that you can't turn them 'off'.

If you require heat all day - this is ideal.
If however, you'd be quite happy to have the heat off most days till 4PM - a considerable amount of the energy is wasted.

Unfortunately, no heaters I've found seem to publish this.

Doing some rough numbers.
http://www.dimplex.co.uk/products/domestic_heating/installed_heating/storage_heaters/fan_assisted_fxl_range/technical_specification.htm

Taking the largest model - which has 120kg of bricks.
The quoted energy storage is 3.4kWh.
Brick has a heat capacity of 840 joules/C/kg, so for 120kG of brick - 100kJ/C of storage, or 27 watt-hours/C.
This implies the bricks are heated by 125C, which seems quite reasonable.

Assuming that the bricks are arranged as four blocks of four single bricks, this would give a dimension of 80cm*10cm*30cm or so, which seems reasonable.
This leaves space for 4cm of insulation easily all round.
This is about .75m^2 of insulation.
Assuming you can get .06W/m^2/K - that comes out to around (.06*.75)/4cm = 1.1W/K heat loss, or at operating temperature - 150Wish.

Taking as an example if you don't need heat for 8 hours in the middle of the day, you will lose around a kilowatt-hour, for an effective efficiency of a bit over 70%.

Please note - these are rough numbers - and could feasibly be out by a factor of two either way.

HappyMJ

rogerblack wrote: »

This is only effectively true if you want the heat.

Heat leaks out of the storage, meaning that you can't turn them 'off'.

If you require heat all day - this is ideal.
If however, you'd be quite happy to have the heat off most days till 4PM - a considerable amount of the energy is wasted.

Unfortunately, no heaters I've found seem to publish this.

Doing some rough numbers.
http://www.dimplex.co.uk/products/domestic_heating/installed_heating/storage_heaters/fan_assisted_fxl_range/technical_specification.htm

Taking the largest model - which has 120kg of bricks.
The quoted energy storage is 3.4kWh.
Brick has a heat capacity of 840 joules/C/kg, so for 120kG of brick - 100kJ/C of storage, or 27 watt-hours/C.
This implies the bricks are heated by 125C, which seems quite reasonable.

Assuming that the bricks are arranged as four blocks of four single bricks, this would give a dimension of 80cm*10cm*30cm or so, which seems reasonable.
This leaves space for 4cm of insulation easily all round.
This is about .75m^2 of insulation.
Assuming you can get .06W/m^2/K - that comes out to around (.06*.75)/4cm = 1.1W/K heat loss, or at operating temperature - 150Wish.

Taking as an example if you don't need heat for 8 hours in the middle of the day, you will lose around a kilowatt-hour, for an effective efficiency of a bit over 70%.

Please note - these are rough numbers - and could feasibly be out by a factor of two either way.

I agree with your assesment that over 8 hours that 1kWh of heat is lost when the user remembers to turn the output down at night and leave it down until the afternoon. That heat is lost to the room so instead of coming home to an absolutely freezing house it will be a little warmer. Then when the output is turned up the room will get up to room temperature quicker than it would have done otherwise. It could also be said that gas and oil central heating boilers have a frost protection setting to keep the house at or above a couple of degrees so they will also (on a freezing cold day) start to heat the house as well at inappropriate times. They also are timed to come on half an hour/an hour before the occupants return home and that heat could also be considered wasted heat.

However, I don't agree with efficiency figures of 70%. They load up with 3.4kW over 7 hours totalling 23.8kWh of energy. If 1kWh of energy is wasted over the first 8 hours then the efficiency by your method is 95.8%. A boilers output for central heating is usually 12kWh covering 6 radiators which is the same output as 3 E7 storage heaters (living areas) and 3 panel/electric heaters (3 bedrooms-where E7 storage heaters are not economically useful as heat isn't needed until 10PM and a cheap £10 convector heater can be timed to use E7 electric in the morning anyway before the end of the E7 hours).

An electric heater would also be needed in the bathroom and that is usually the most expensive heater to run when on E7 storage heating as it is either a electric bar radiator or fan heater and runs on the peak rate which is at a premium to standard rate electricity.

misskiti

Thank you very much for the information so far. I am not sure what means of hot water heating is in place yet (im in the very early stages of consideration of buying this house)

I have had storage heaters in the flat i just moved from, the bills werent too bad but that was mostly because our flatmate and I werent there very often! The main problem there was the old double glazing which let out all of the heat.

The property I am thinking of purchasing is relatively modern (i'd say 10-15 years old max) so i would hope the insulation and uPVC is more efficient. So using storage heaters may not be so bad and I would of course be willing to upgrade insulation if needed.

However there is going to be no-one in the house during the day as my boyfriend and I both work full time and have pretty busy lives, so it seems backwards to me having storage heaters releasing heat into the house during the day when its empty.

Cardew

misskiti wrote: »

However there is going to be no-one in the house during the day as my boyfriend and I both work full time and have pretty busy lives, so it seems backwards to me having storage heaters releasing heat into the house during the day when its empty.

That indeed is the biggest criticism of storage heating, they are a much better bet for people who are home all day.

GlynD

Oil fired costs about the same as gas fired heating to install. You can actually have the boiler sited outdoors though to save space. They make little metal houses for them which are filled with insulation. Oil tanks are a little expensive at (I think) around £300 for a 1300 litre tank. In a three bedroom house two full fills of oil should do a year as long as your insulation is up to scratch. Average cost of heating a three bedroom per year at the moment - about £600-£700. Always buy a fill of oil in the summer - it's much cheaper then!

We run oil and coal together btw - we're off the gas main too.

One tip - try to site your oil tank as close to the boiler as possible and make sure the pipe is well insulated. Oil can freeze in sustained temperatures of -10 ish. Easy to overcome by keeping the heating on low during long periods of freezing weather but I'd always recommend taking every precaution and the shorter the pipe - the less risk there is.

One more thing: get a condensing oil boiler (like us). At least 20% more efficient than the old fashioned ones.

Cardew

rogerblack wrote: »

Heat leaks out of the storage, meaning that you can't turn them 'off'.


Taking the largest model - which has 120kg of bricks.
The quoted energy storage is 3.4kWh.
.

A 3.4kW storage heater(not 3.4kWh) will consume 23.8kWh if left on for the 7 hours of off-peak.

It will lose heat during those 7 hours even with the output turned down and of course during the day as well(again with the output turned right down.)

Naturally the heat will 'leak' at a faster rate initially and the rate of leakage will slow as the bricks cool.

The amount of leakage depends on many factors, but it is way more than the 1kWh you suggest, even with modern storage heaters. I have seen it suggested that after 14 hours with output to zero there is little useful heat left.