Electric Boiler

[naylz82]

Hi all,
After some advice on electric boilers.

My predicament is this:
Live rural and currently have an ageing worcester combi set up with an external plastic oil tank that has developed a tear right at the top (ie doesnt cause a leak)
Anyway to prevent this tearing further I got my hands on some gas pipe repair glue, worked a treat, but now the company that delivers my oil has refused to top it up incase they damage it.

To complicate matters the tank was originally installed to close to the house and would apparently need moving, to a very unatractive position in the garden.

Bearing in mind the boilers approx 20 years old and probably hasnt got a great deal of life left in it, I am faced with having to replace a tank and possibly a boiler and have the tank smack bang in the middle of my garden .

I then thought if I am going to be forced to do this would it not be easier to have a combi electric boiler installed?
The house isnt that big and we had a log burner installed therefore the downstairs rads are never on, we only use approx 600litres of oil per annum as its only doing the hot water on demand (mixer shower, occasional bath, sink etc) and the occasional heating for upstairs (3 rads and 2 towel rails) - cavity walls insulated and loft well insulated so the house is very warm for a 20s semi.

I know the first comment is going to be 'they are lot more expensive to run' but bearing in mind our small use of oil and the savings in up front cost, and not ruining my garden I think this is a very good compromise.

Any comments greatly received.
thanks
stewart

 

[flameport]

Electric boilers are the worst possible choice, both in terms of performance and the cost of the electricity to operate them.
An electric combi is the worst type of electric boiler, and that's assuming you can actually have one, as your electricity supply may not be suitable for it.

Electricity will be about 3x more expensive than oil, so take whatever you pay now for oil and multiply by 3 - that's how much you will be paying every year on electric.
Oil is usually about 50p per litre, so your current £300 per year will be more like £900, an extra £600 a year or £50 per month.

Electric boilers are similar cost to gas and oil ones, so the only saving is not buying a new oil tank - a saving which is blown away in the first year by the massively extra cost of the electricity.
There is also the option of gas, LPG tanks can be put underground.

 

[ericmark]

The wood burner I assume some thing like this?

As to how efficient I don't know,

the unit shown is super efficient however most people use the cheaper types,

however today the units are rather complex even with simple types to stop particulate emissions, no longer do we have open fires, in most places they are not allowed, and the new units have a fixed burn rate to keep the temperature in the flue to 150°C the top one has horizontal plastic flue as gases so cool, but it needs the store shown in top picture as the fire does not vary much in output, in fact oil fired boiler have the same problem, where a gas boiler can deliver 6 kW to 28 kW oil is more like 18 kW to 24 kW at best, many are fixed output. As is the wood burner, however unlike oil you can't switch wood burner off/on 20 times a day, so a burn say 6 pm to 10 pm heats the water which then keeps house warm when wood burner not running.

So the electric systems is very much a part of the wood burning system, and as diagram shows maybe even solar panels, although to be frank in North Wales water solar panels don't work, great in Turkey, not so good in UK. So often solar panels are electric and excess is used to heat the water store.

Even possible to add heat pumps, however the problem is cost, all very good on paper, until you cost it.

There are home made wood burners that are very efficient, however as to if you could get insurance is another question. With last picture it is a mass of stones and concrete which stores the heat, not water. But you need to look at is as a whole, not individual parts. So much depends on what you have.

You can likely get away with a non compliant wood burner using it at Christmas day, but all year around is another story.

 

[EFLImpudence]

Yes, I was just thinking that.

 

[Echo the husky]

Stick with the oil, get a new tank properly fitted and a new oil line installed. Then save up for a new boiler when the time comes. Continuing to use a damaged tank is total madness, if it was to split open you would be saying goodbye to your entire garden, and possibly your neighbours garden and even the ground floor of your house when it is entirely excavated to clean up the oil that has soaked into the ground. The cost of installing a new compliant system is insignificant when compared with the cost of an oil cleanup.

We do a lot of temporary electrical work for a company that carries out pollution control from leaking oil pipes and tanks, the work is extreme, very disruptive and hugely expensive. Make sure you home insurance policy covers oil leaks.

Look on the bright side, the problems didn't occur during winter!

If you do go down the electric boiler route, you will need to inform your local DNO to obtain permission to connect such a heavy load to their network. It is very likely they will at least have to upgrade your cutout, as many are only rated for 60-80A maximum.

 

[DetlefSchmitz]

So people understand the problems though... We needed a new oil tank. We had to show that at the existing position any spill could not go down any drain into the sewer (we were lucky there). Unfortunately next door had been given planning permission to build an extension about a meter from our tank. We were not allowed to simply replace the tank as it was too close to next door's extension. So we had to erect a fire shield to be allowed to put the replacement in the same place as the existing tank. It was only the third tank installer we approached who was prepared to do what was necessary to make this possible.
Some joined-up planning would have been nice.

 

[fluorescence]

We're on LPG and as already mentioned above this may be worth considering. I think Calor do some deals on a tank installation if you sign a supply contract with them for a few years. Gas combi boilers being very common are also cheap and usually don't cost much (if anything?) to convert to run on LPG.

Again, as already mentioned above, I would advise against an electric boiler or indeed any form of electric heating if it can be avoided!

 

[SimonH2]

Generally converting a gas boiler to LPG is just a nozzle change and some setting up - though they also sell them already setup, at a significantly higher price
As Ericmark says, if you don't already have one, fit a thermal store heated by the wood burner - that will do all your hot water and heating while you have the burner going. You can have electric backup (to an extent) with immersion heater(s), and your existing boiler can provide any heat that the burner doesn't meet - such as during summer when you don't want to light it every day.
Thermal stores are great as a "neutral point" for connecting multiple heat sources to multiple heat loads.

 

[Deleted member 18243]

The wood burner I assume some thing like this?
…….

So the electric systems is very much a part of the wood burning system, and as diagram shows maybe even solar panels, although to be frank in North Wales water solar panels don't work, great in Turkey, not so good in UK. So often solar panels are electric and excess is used to heat the water store.

Even possible to add heat pumps, however the problem is cost, all very good on paper, until you cost it.View attachment 162691There are home made wood burners that are very efficient, however as to if you could get insurance is another question. With last picture it is a mass of stones and concrete which stores the heat, not water. But you need to look at is as a whole, not individual parts. So much depends on what you have.

You can likely get away with a non compliant wood burner using it at Christmas day, but all year around is another story.

Digressing slightly, the National Trust property Gibsons Mill at Hardcastle Crags, near Hedben Bridge in Yorkshire has all its electricity and heating provided by solar, biomass and other "sustainable" means. You can visit the power room and see how it's all done. It's a good day out, that and the surrounding woodland.

 

[JohnW2]

As Ericmark says, if you don't already have one, fit a thermal store heated by the wood burner - that will do all your hot water and heating while you have the burner going. You can have electric backup (to an extent) with immersion heater(s), and your existing boiler can provide any heat that the burner doesn't meet - such as during summer when you don't want to light it every day.

I think that an important general point about wood burners (which may not be so relevant to the OP) is that much depends upon where/how one gets one's logs. Assuming that one has to buy them, I think that it would not be difficult to find oneself paying as much (if not more) per kWh of heat production with log burning as with heating by electricity.

Kind Regards, John

 

[SimonH2]

Yes indeed - wood is expensive to buy.
But some have a burner for the aesthetics as much as the thermal - and such a burner could provide a useful input even if it's not providing all the heat. And don't forget that both oil and LPG are themselves rather expensive compared to mains gas.
A lot depends on the OPs circumstances - each person/location will have their own priorities etc.

 

[JohnW2]

Yes indeed - wood is expensive to buy. ... But some have a burner for the aesthetics as much as the thermal - and such a burner could provide a useful input even if it's not providing all the heat. ... A lot depends on the OPs circumstances - each person/location will have their own priorities etc.

Indeed - as I said, my comments may not have been all that relevant to the OP's situation/wishes.

And don't forget that both oil and LPG are themselves rather expensive compared to mains gas.

Again, very true - but my point was that wood (particularly logs) can be more expensive that either oil or LPG, and possibly similar (or higher) in cost in comparison with even electricity.

Kind Regards, John

 

[ericmark]

I was asked to write a web page stating how bad wood burning was. I felt uncomfortable with this, so first decided to do some research before writing the web page, and it seems the guy was right as to how bad burning wood is when done in a cheap and nasty wood burner as sold for DIY install by likes of B&Q and in the main the clean air act, and building regulations will not allow it. The heating in the house can be changed for one with a slightly lower efficiency rating that what is already fitted, I can't remember how much, but cheap wood burners are often down to 40% efficient which could not be used instead of oil central heating at around 80% or more.

I was surprised there was only one condensing commercial boiler running on wood, the picture says Hughes design, what seemed wrong was there seemed to be no safety cut out in the case of a power failure, so not sure it is really an option, the home made last picture is also condensing however again not likely to get insurance, so third picture or similar is about the best we can get, only around 80% efficient but it also complies with clean air act by taking the gases to such a high temperature, there are other methods including scrubbers in the flue, but one is looking at around starting price of £1000 for the fire not £150 B&Q special.

However the B&Q special is not illegal it is only burning wood and coal in it that breaks the law, burning charcoal or coke is likely OK as well as a whole host of other smokeless fuels. There is actually a problem ecologically with using charcoal as much is made without safely removing the nasties, however as to how you ensure any fuel is good or bad is not really up to the user, even electric may have been made burning coal.

Old pre used wood is also a problem, one because of the preservatives used, and also often we don't have a clue what wood it is, laburnum wood is quite nasty for example, the same of course removing wood from the woodland floor, as well as removing the wood which would normally rot and get bugs which in turn feed the badgers, you don't know if the wood is safe to burn, which is far more important.

Buying either wood or smokeless fuel can be expensive unless the burner is good quality, however I love to sit in front of a log fire as much as anyone else, and to light a fire a few times a month is not really going to break the bank or kill anyone with the smoke, it is no worse than going to a Steam rally and I love doing that. So not really worried about the ethics all I am considering is how to heat the home.

Any electric heater run as required 24/7 will work out expensive, but if only run using something like economy 7 then it becomes more reasonable, so in this case he already has the radiators etc, and may already have a storage cylinder of some type, and since using a wood burner it seems to make some sense to combine the two.

The question as always is compare running cost with installation cost, personally I would likely fit an new oil tank and try to hid it in some way, however at 67 looking at less than 25 years, if I was 27 then I may go for another option. My brother-in-law had a house with the solar panels, LPG, wood burner and he spent a lot of time away and actually found whole house would tick over with just solar panels. And when home used the wood burner maybe twice a week to top it up. However when I consider the system likely put £15,000 onto the cost of building the house, then I must question was it worth it, however it likely also boosted up the selling price so hard to tell.

 

[JohnW2]

Any electric heater run as required 24/7 will work out expensive, but if only run using something like economy 7 then it becomes more reasonable, so in this case he already has the radiators etc, and may already have a storage cylinder of some type, and since using a wood burner it seems to make some sense to combine the two.

Unless the 'thermal store' )'cylinder') were enoprmous and/or the house exceptionally well insulated, I would not have thought that one would be able to heat a house satisfactorily using E7 electricity and a (water) thermal store....

.... Thinking of my 140 litre DHW cylinder, it can, I think, store a bit over 7 kWh of energy. If that had to heat the house during the 17 non-cheap hours of a day, that would average at only about 400W heat output - which I imagine would be pitifully inadequate in most cases, such that a much larger thermal store would be necessary for that approach to be viable.

Also bear in mind that, as I have reported before, the cost advantage of cheap-rate E7 (or whatever) electricity is rapidly disappearing. For many years (maybe 'for ever') up until 2-3 years ago, cheap-rate electricity cost only about 40% of daytime electricity, but things then changed rapidly, and one is today lucky to find anything much less that 70%.

Kind Regards, John

 

[ericmark]

The thermal store seems to be around the 210 litres and I know in brother-in-laws house there were twin units so 420 litres, so at around 50°C temperature drop around 25 kW of power stored. As to if that is enough to bridge the gap is of course unknown, although my gas boiler can deliver more than that in an hour, that is mainly to run the shower the boiler cycles off/on and lowest output is 7 kWh not sure when economy 7 turns off, but the fire I would assume is lit when they get home so has to last until around 7 pm when the fire is up to heat, and with solar panels there is input for most of the day.

I was unaware of the new rates for economy 7 internet says average pay 111% in day and 63% over night and clearly that 111% is the big thing, is it worth paying the extra during the day? However the big problem with economy 7 was not the cost, but the silly brick radiators which you can't turn off, it hardly matters what the cost is, if you can't stop the heat escaping on a warm day.

I have been living in mothers old house for a time, and I was amazed at the difference in running cost, theory both houses around same size, and same energy rating, however ours cost more to heat, when I sit back and try to work out why, it's simple, her house has a hall and landing and all rooms have doors, so bedrooms kept cooler than living room, and hall and landing heated but kept cool in comparison with rooms. Where my house was open plan.

So house in question they say average 18 kWh heat used per day, divided by 17 that 1 kW per hour since little used in summer domestic water only then assume around 2 kW per hour so the 25 kW will last around 12 hours and they want with wood burner running for 5 hours in the evening around 12 hours from the electric. If the heating is either supplemented with one or two storage radiators used in heart of winter, or the heating is turned down during the day, then yes it may well work with a 420 litre store.

The main reason for store in brother-in-laws house is the wood burner boiler needs cooling, or it will burn out, so there needs to be enough capacity in the tanks to take the heat from the wood burner, and while the fuel is wood, it has to run at a set rate, the flue needs to be maintained at around 150°C below that you get a tar build up, and above that your loosing too much heat, inside the fire the after burner is getting the gases above 1000°C to stop particular emissions, this is the problem with modern wood burner, until all fuel turned to charcoal you can't turn it down.

On the Falklands the fires were never put out, when they left the farm house they would "bank" the fires, and you could tell when banked as far more smoke from the flue, OK peat not wood, but smoke means unburnt fuel, they had enough peat not to worry, and not enough population to worry about the smoke, however in UK clean air act means visible smoke from chimney is a no no, no one is likely to report it once a week or so, but every day then specially if neighbours dry cloths outside, then one complaint and you end up being told to fix it, or hefty fine if not fixed. So nice roaring fire Christmas day great, unlikely anyone has washing out on Christmas day, and in the evening after dark again unlikely to be washing on the line, or anyone can see the smoke. So looking in the main how to keep house warm on Saturday and Sunday when at home during the day.

From the power they say they use, it will cost at 13.8p per unit about £900 a year on fuel, so around £600 a year extra on heating to move from oil to electric using their figures of 600 litres per year. Any saving by using better control would impact on both fuel types, so even with oil a heat store helps, not with gas as most gas boilers are modulating, but even when oil boilers do modulate it is 18 to 24 kW not the 6 to 28 kW typical with gas, every time a boiler turns off you lose heat from flue, and if you heat room to 22°C then let it cool to 19°C as with any off/on thermostat it will use more power than maintaining a room at 20°C however from reports on this forum it would seem most people still switch boiler off/on and have a hysteresis of temperature or repeat the off/on many times a day rather than allow the boiler to modulate. So all well and good saying boiler 6 to 28 kW but rarely used like that. Even though I know should use return water to modulated boiler I still have a wall thermostat which has anti-hysteresis software so switches off/on many times a day.

So even when we know what we should do, we still don't do it, and I would like to see a study of electric fires used to heat a house, in this house central heating heats all rooms, including two only used for storage, there must be losses from the pipework, non of it is lagged, so landing would get warm without a radiator as pipes under the floor, so in the old days of coke fires only the living room was heated, the heat from that room leaked into rest of house, but only that room was warm, could not do that if I wanted with central heating, so one electric fire in living room compared with whole house heated even if not used then likely electric would do quite well.

However I also remember my dad wiping lead pipes in great aunties house where they had frozen, even when not in the house we leave heating running although at low temperature as don't want frozen pipes or damp house. Not seen frost on inside of windows for years, grand kids have never seen it, OK on car in the morning maybe, but that's on outside too so not the same, even that with today's cars where you can start them from your phone to defrost before you leave house it is becoming less often seen.