Wood pellet boilers

[Bayliss]

I would be very interested in your views, comments and experiences in respect of the wood pellet central heating boilers for domestic dwellings. We currently use oil and the boiler is now about 13 years old. We live in our 2 bed detached thatched cottage in Suffolk, you can imagine the heat goes straight out the walls and windows.

 

[AMc]

I did some research into a system from Winhanger (sp?) back in 2006 speaking to Anglia Woodburners just off the A47 to the East of Norwich.

First problem was that there were no good supplies of pellets from the UK so it was all trucked from Germany. The price varied with the cost of diesel and had the associated environmental impact. At the time we were told there were plants coming soon in the UK so that may not be a problem now. The quality of the pellets was very important.

The second problem was storage - shipping the pellets being a substantial part of the cost we were advised to have a store large enough for an annual supply delivered in one go. Our house is bigger than yours (5 beds, 5 receptions) but the store was in the order of 4m x 4m x 3m (again if memory serves). So either a large hole in the garden (with tanker lorry access) or a lost room. That would use a double worm pipe to feed the boiler automagically - reversing itself automagically if it jammed which sounded very clever and also potentially prone to failure to my skeptical luddite ears. Alternatively filling a hopper by hand weekly - which sounded like hard work and would put many people off.

The third problem was cost - the installed cost (at the time) was in the same order as Ground Source Heat Pumps using bore holes (not enough space for slinkies here) as a result it was going to be very expensive - circa £20-30K IIRC (but it was a while back and we discounted it quite fast).

You could also consider log boilers with thermal stores if you have the space.

You may get more thorough advice over at the Green Building Forum but they (as I) will probably recommend reducing heat loss as much as possible before going along another heating route.
http://www.greenbuildingforum.co.uk/newforum/

Your most cost effective choice is probably to continue with the oil at least until the details of the Renewable Heat Incentive are cleared up and you can work out if a govt subsidy tips the scales in favour of something less fossil dependant. I doubt you will save much if any money compared with oil if that is your motivation. Sorry if that sounds negative but that was the conclusion we came to.

 

[Penners]

Bayliss - forgive a very obvious question, but instead of spending a considerable amount of money on a pellet boiler, have you considered the possibility of substantially improving the insulation and glazing provision in your cottage? There are various financial subsidies available under the Government's Warm Front scheme (subject to qualification).

http://www.warmfront.co.uk/

 

[middi]

To add to AMc post.
In Italy, especially in the rural area's, wood and crushed olive nuts pellets are quite popular. The installation of the boilers is not cheap and the bulk storage of fuel has to be substantial.
Also the cost of these fuels is not cheap any more. ( this proves the point that sheap fuel energy days are dwindling quite fast)

I am not absolutely sure that if you have one of these fuel burners fitted is going to be the best choise in this Country

Middi

 

[skier-hughes]

I looked at all sorts of boilers;
Pellet, expensive to feed, lots of space needed for fuel, but could be run automatically.
Log, cheaper if could source good quality equally sized logs, not as much space for storage as logs may be sourced locally, could also be automatic to a degree, more like weekly or twice weekly feeds.
Log, quite a lot cheaper if loaded manually, twice a day burn to heat a thermal store, odd sized logs easily available for free, more work involved.
Our boiler would be in an outhouse as it where, so that entailed going outside to feed a boiler for 1/2 hour or so twice each day. We had easy access to a chimney here, so installation was ok on any of these.

In the end we went for, solar panels to give us spring, summer, autumn hot water. No work, no fuel, no storage.
900 litre thermal store.
Wood burner in the lounge with back/side/top boiler, takes any wood, so far all free, we cut our own logs and get free offcuts from outr local shed/fence maker who drops it all down for us. Ok, has to be filled on a more regular basis, but I do it from inside, having to fill my internal log store every 3 days with logs or 2 days with offcuts from my outhouse, but we work from home so getting to the fire isn't a problem.
The rayburn is also connected to the thermal store.

So far it's all worked brilliantly and it's nice having a warm house to walk around it.

 

[worms]

In the end we went for, solar panels to give us spring, summer, autumn hot water. No work, no fuel, no storage.
900 litre thermal store.

Do the panels feed into the thermal store or do you still have a domestic HW tank?

 

[FamilyWiggs]

( this proves the point that sheap fuel energy days are dwindling quite fast)

Cue Penners!

 

[Flyfisher]

Based on the enquiries I made a couple of years ago, AMc and Skier have given a good summary. I got the strong impression that such wood pellet or wood chip boilers were more suitable to large installations - farms or small industrial estates. They have the advantage of being able to operate automatically but storage was the big issue for me. Because wood pellets/chips are fundamentally a fairly low density fuel source, they need to be delivered in bulk to make them economical, which means large lorries and the requirement for large storage hoppers. And if you don't have a local depot, delivery costs could become very expensive.

Personally, I'm moving towards Skier's system. In particular, the flexibility of the thermal store.

 

[Penners]

( this proves the point that sheap fuel energy days are dwindling quite fast)

Cue Penners!

Well, it's perhaps a further idea for Bayliss to consider. It just depends on whether he has a reliable source of combustible sheap.




PS: I'm always very hesitant about commenting on Middi's English, considering that I speak about seven words of Italian!

 

[Bayliss]

Thank you for such a good response of valuable hints and knowledge. Our main problem is the heat loss, straight out of the walls of the cottage. Walls are a mix of brick single skin, traditional plaster/lathe. We do not wish to insulate from the interior but may consider tackling the outside and then add secondary glazing which can be removed in the Summer months.
Unfortunately logs are just to expensive for us and we use house coal in an open stove (Franklin style) in the lounge to supplement the hopeless wet radiators. The oil boiler is sited in the dining room (previous owner :roll: ) and this is partly the motivation to replace into a more sensible position in the cottage.
Thanks for the links I will have a look and investigate the grants that may be available. We love our little cottage but find heating cost is becoming a real burden, like for many others I expect. The last thing we want to do is move to a highly insulated modern box

 

[skier-hughes]

In the end we went for, solar panels to give us spring, summer, autumn hot water. No work, no fuel, no storage.
900 litre thermal store.

Do the panels feed into the thermal store or do you still have a domestic HW tank?

The 900 litre thermal store consists of a 900 litre outer tank into which all heating is plumbed. Inside this is a 200 dhw tank, fed with clean water and heated by the 700 litres by conduction.

 

[AMc]

Thank you for such a good response of valuable hints and knowledge. Our main problem is the heat loss, straight out of the walls of the cottage. Walls are a mix of brick single skin, traditional plaster/lathe. We do not wish to insulate from the interior but may consider tackling the outside and then add secondary glazing which can be removed in the Summer months.
Unfortunately logs are just to expensive for us and we use house coal in an open stove (Franklin style) in the lounge to supplement the hopeless wet radiators. The oil boiler is sited in the dining room (previous owner :roll: ) and this is partly the motivation to replace into a more sensible position in the cottage.
Thanks for the links I will have a look and investigate the grants that may be available. We love our little cottage but find heating cost is becoming a real burden, like for many others I expect. The last thing we want to do is move to a highly insulated modern box

You don't talk about the roof - other than it's thatched - what's between the thatch and the ceilings?
If you don't have 300mm (a.k.a. a foot) of loft insulation over the ceiling and you have the space then get to B&Q and buy some of their subsidised insulation at £3 a roll (IIRC). This will make a noticeable difference for a very minimal outlay and you will feel the benefit almost immediately.
If you have unused chimneys then consider chimney balloons (or my lower tech bin bag full of scrunched up newspaper) to control the amount of heat going up an unlit flu.
If your radiators are wall hung on outside walls then reflectors beind them (or cardboard covered in turkey foil) will reflect radient heat back into the room which again is noticeable.

Wall heat loss is noticeable - but I have plenty of solid brick walls in the front of the house and it is possible to heat the place without too much trouble. Tackle draughts first, then secondary glazing as internal or external insulation of the walls are both complicated and change the appearance of the house.

 

[JohnB]

Has everyone seen the SPAB report that shows that the walls of old houses tend to have better u-values than the official figures used in SAP ratings etc? I don't know if it's on the SPAB web site, but it was sent to me, and you can download it here.

 

[worms]

In the end we went for, solar panels to give us spring, summer, autumn hot water. No work, no fuel, no storage.
900 litre thermal store.

Do the panels feed into the thermal store or do you still have a domestic HW tank?

The 900 litre thermal store consists of a 900 litre outer tank into which all heating is plumbed. Inside this is a 200 dhw tank, fed with clean water and heated by the 700 litres by conduction.

Thanks, that's interesting. With 900 litres to heat from solar through the summer months, does this still reach the advised daily 60C for Legionella control in the inner dhw tank?

 

[AMc]

You don't need to hit 60C every day - our Air Source Heat Pump system is manufacturer set to raise the tank to 65C once a week.

 

[worms]

You don't need to hit 60C every day - our Air Source Heat Pump system is manufacturer set to raise the tank to 65C once a week.

That makes sense!

 

[skier-hughes]

Thanks, that's interesting. With 900 litres to heat from solar through the summer months, does this still reach the advised daily 60C for Legionella control in the inner dhw tank?

Yes we were constantly hitting that figure and beyond. Bear in mind in the spring summer early autumn we have 900 litres of 6o'+ water and we have two showers a day, do some washing up, wash hands, wash the cars now and then, wash the floors sometimes.
Once the 900 litres is hot, it heats the 200 litres. The 900 litres stays pretty hot all the time, there is no heating on to take heat away, and we use very little DHW. For a family maybe the installers would have suggested more tubes, to ensure that the heating of dhw was maintained. I lit the fire once in september to ensure we had over 60' water.
We do have 50 tubes!

 

[Bayliss]

Thanks amc, I have done all the tricks that you have mentioned, except loft insulation. Our cottage is the typical one and half story with the bedrooms in the roof space, the ceilings still have mostly the old wattle daub plaster and so I don't think the loft space, such as it is , has been disturbed for many many decades, possibly longer. But the void in the loft is about 3' across only running the length of the cottage.
I am looking into insulating the exterior walls.