I want to have a back boiler on my new wood-burning stove but have read that the heat taken away from the stove by the water in the boiler will reduce the efficiency of the burn and cause problems such as tarring of the flue. Aarow (amongst others) produce boiler stoves that, I assume, are specifically designed to burn efficiently and heat a back boiler, but is this true? Anyone have any direct experience? Sometimes you hear about these 'theoretical' problems that, in practice, aren't encountered.

I would support Katymac's comments, it does seem that its better to have a boiler on the bigger side rather than too small.

My father and I had to take out the boiler in my parents wood burner, as it was too small and a box shape. The one that replaced it was the same size but with tudes running from top to bottom. Maybe I would have been better saying surface area rather than size.

Anyone seen a wood burning stove that can heat water and has a cooking top on it? I've seen stoves with one or the other but not both.

Yeah, I've been reading that. I was thinking more along the lines of something to put in the living room, that was basically a normal multifuel stove with back boiler but had a top (or a small oven) you could boil a kettle on or put a casserole on for back up rather than an everyday cooker.

Ideally, what I'm thinking about is a masonary stove/Finn oven type affair you could build between the living room and the kitchen up through the centre of the house. You would fuel it from the living room side through a glass door to get the real fire feel and there would be a cooking top and oven on the kitchen side. The massive heat store would provide back-up heating for the whole (well insulated) house, a back boiler would heat the water in winter (solar panel in summer), and some of the cooking could be done on the stove in winter (with an electric cooker for summer).

Seems to me that such a construction would be a good way to future proof your home against interuptions to energy supplies which threatened the grid or gas/oil supplies. Can't seem to find anything on the internet that does everything in the way I have described. Maybe, you would just have to try and design something yourself and get a mason to build it? Alternatively, I wonder if you could have an Esse and a normal stove sited back to back with the flues going into the typical chimney arrangement of a Finn oven (i.e. snaking around to extract the heat from the flue gases into the brickwork)?

Anyone got any ideas?

Spike,
All stoves (including best conventional gas boilers) when started from cold exhibit the warm up process inefficiencies. For wood burning stoves when the thermal mass of the stove and flue are hot they become highly efficient especially as the fuel is free and the flame soporific. The back boiler does have an initial cooling effect but as it is before the flue any tarring or condensates just get burnt away. Having an insulated flue (double skinned) helps as does keeping it going as continuously as possible in the heating season whether on low or high. Another aspect is using wood stoves in a thermosyphon system which does not require any pump.

On the negative side you will have to plan for ash removal so try to get an ash pan with a lid. It is good for the garden though.

There are some excellent modern and nostalgic stoves available able to take a wide variety of fuel types. They do work very well and I for one can vouch that when combined with solar thermal heating and any other conventional sources via a twin coil calorifier all heating and hot water requirements can be provided.

Add in the fact that you can now have the double whammy of reducing your waste and turning it into hot water!


I have the following tuppence worth for any installation to last over ten years.
The main aspects are how long are you expecting it to last without intervention?
There are specific regulations regarding flues and fire places which are well worth referring to covering the health and safety side.
Due to the temperatures it is well worth planning out the flue installation first. Use the largest double insulated flue you can,Limit bends, use propietary materials, allow for condensate trap , fit top cowl.

Obtain your intake (combustion) air external to the heated space and specify a butterfly valve on it.

Have a top and bottom air control mechanism to cater for different wood types and moisture levels

Plan the back boiler connections to central heating /hot water to be in the largest pipe size you can.
Purchase a stove with freely available spare parts

There will be minor lifestyle changes required to include a wood stove in your house but these are better than the frustration of relying on Corgi Plumbers.
Oh I could go on but perhaps my closet pyromania is coming out.

regards
www.thamesrenewables.com

Terry
If you are likely to burn green and dry and different wood fuels the varying moisture levels can play havoc with the flue.
If your flue is straight / vertical with no sets the condensates will just be burnt eventually but if you have a set (bend) you should put a little hatch/door at the lowest point or even a fitting with a simple valve/tap. There are a number of these on the market. It can be fairly concealed but not too much.
regards.

Hi all im new on here anyway here goes, im after a log burner/back boiler to heat my above ground swimming/paddling pool i know you can get them of ebay but they are about 400 quid for a new one. Im only after anything that works as it will only be on the back lawn, so if any of you could suggest anywhere to go and find one i would be gratefull or if you know where there is one that would be even better.The reason is because last year it took me 12 hrs to heat the pool using a 3kw pool heater and two kettles so i don,t want to go through that this year so i thought about piping a log burner with back burner to it instead of using all the elctric and time for myself.Anyway if you could help let us know thanks.

Is it possible to fit a back boiler to an existing flue and if so can anyone point me in the direction of suppliers of such a wee beastie?
Peter

A stove with a backboiler will run just fine, but is generally a bit less efficient than one without a backboiler.
A stove with a backboiler has relatively cool flue gases and I'd also recommend lining and insulating your chimney with a 316 grade, not 904 grade liner. 904 grade is really for "heavy" use installations - 316 is cheaper and generally absolutely fine - 904 is more hardcore so better if you can afford it.
The Ironheart is OK as a cooker stove but it gets hot infront of it - they now supply a heat insulation mat to stop this happening though.
Wamsler cooker stoves are in a different league though and are worth looking at.

When making a chimney using twin wall double skin flue pipe do NOT use the biggest flue size possible try to match that of the stove Regs (Doc J) RECOMMEND a 150mm minimum flue size for multifuel stoves - having an oversize flue means that huge amounts of condensates can build up in the flue without effecting performance. These condensates then pose the risk of a chimney fire.
There is an arguement for using a 150mm flue on a 125 flue outlet stove if the stove is burning coal as coal fumes can kill you - the buildup of condensates in a 125mm flue can quickly block the flue resulting in fumes coming out through the stove. The idea of upsizing to 150mm in this case would be that the flue will function fine through the winter till it is next swept.
This compensates for improper sweeping of the flue - ie not really doing it enough.

The Villager Kitchener is a relatively small stove with cooking top that can come with a small backboiler attached.

Hunter make a practical range of stoves with backboilers as do Aarrow (the Stratford range). I have a hunter herald 14 with 45,000 BTU backboiler on a lined and insulated chimney. Produces little flue deposits and heats the house.

Stovax, Franco Belge and Morso also make central heating stoves but the backboilers are typically smaller -around 1-4 rads.
Of the modern stoves Firebelly and Hwam both make backboilered stoves.

Condensation traps - usually this would refer to a 90 degree tee on the back of the stove or a 135 degree tee if the flue goes diagonally out through a wall - the tee would be on the outside. You want a trap anywhere where condensates / deposits / rubbish would otherwise build up and block the flue.
In a lined chimney you would not normally have a condensation trap even on a bend in the chimney - but if you use the rear flue exit of your stove you would have a 90 degree tee - that way no condensates / deposits can block the flue.

To the guest stove installer - if you are interested in fitting more stoves / flue systems (without supplying materials) please email me sune AT stovesonline.co.uk - thanks (I have not written the @ in to try to minimise spam)

I am having a wood burning stove fitted in a garden room and thought it may be a good idea to have one with a back boiler, is it possible to connect this up to my central heating system, so in the winter when we have the stove on we can use the heat to heat up the radiators (and water if possible) instead of using our normal gas boiler which we would use at other times.

P.S, does this make sense ?

I have been looking at this option myself, have posted on another forum and the members there were less than enthusiastic, they did however come up with 3 options, 1) thermal store 2) Dunsley Baker Neutraliser 3) motorised valves (H2 control system).

After a lot of research I am now seriously considering the H2 control system manufactured by Heating Innovations, it is the only one that is fully automatic, once set up you can forget about it.

You might want to look at this site that someone set up about their experience of installing the H2 panel in a Welsh farmhouse.

http://users.cs.cf.ac.uk/Antonia.J.Jones/CentralHeating/CH.htm

You can link a stove and back boiler up to your existing gas system providing its not a sealed system. You need a header tank. This is because of issues with boiling.

I personally always use 904 grade when linking to a stove that the customer has connected to a central heating system. 316 grade can corrode prematurely due to low temperatures and condensates. There is less than £100 difference in price between 904 and 316 so i'd always recommend 904 when linking upto to a back boiler stove.

Like said above. It sounds like you need the Villager Kitchener if you would like something with a hot plate on the top. The flue is off center and has room to cook on the other side if you wish.
Good for boiling the kettle during power cuts!

vanessa,

I'm no expert on this subject, but here goes with some advice picked up over the years...

There are a lot of variables involved in using a wood fired appliance to heat rads/hot water. You first need to work out how many radiators you require and what size they need to be to provide 'enough' heat to warm your house. You then have to get enough btu's out of your appliance. How big a boiler does the Wamsler model have? You will have to have access to a large supply of dry hardwood. To supply a full central heating system for a house will require a LOT of wood.

On to your specific questions.

1. I'm not familiar with the Wamsler range of cookers but we do have an ESSE W23 woodfired cooker/boiler. We have no trouble keeping it in overnight providing we use good dry hardwood. We currently are using 2 years seasoned oak. However the ESSE W23 only produces a total of 23,000btu/hr of which about 9,000btu goes to domestic hot water leaving around 14,000btu for heating. If you take a rough 'rule of thumb' that a typical radiator needs 5,000btu, that doesn't heat many radiators. We use ours for DHW and also have it linked up to an oil system (which we now hardly ever use, thank goodness) If your Wamsler CAN provide enough btu's to heat the whole house, the chances are that you will have to spend a lot of your time feeding wood into the fire unless you opted for some kind of thermal store (see below).

2. I'm not a plumber but other more knowledgeable contributors to this forum will probably INSIST you have an open vented system (including a header tank) for safety reasons. A sealed wood fired system is a potential bomb if things go wrong.

Most people in the know on this forum seem to be suggesting that the best way to provide heating and hot water from any wood burning appliance is to link them into a thermal store (which is effectively a large, well insulated hot water cylinder). This will act as a sort of thermal battery that can store the uneven heat production characteristics of a wood fired appliance so that you could still have plenty of hot water for heating/washing/whatever even if the fire did go out overnight. The larger, better (and more expensive) stores, can store enough hot water and keep it hot, so that you can still use it three or more days after the fire went out.

I'm sure that some of the serious 'plumber boys' will post soon and give you a more professional overview of your requirements, but in the meantime good luck and best wishes,

John.

No idea about French boilers but after much research we are looking at a Clearview 750 http://www.clearviewstoves.com/clearview750.htm comes with a boiler up tp 45,000 BTU. This seems strongly recomended on this web site no other reason for picking it.

As for French made thermal stores I can help you as my father has one running on solar in Portugal (dont know about fixing it up to a wood fired boiler as well you will have to check).

De Dietrich Thermique
57 rue de la Gare
F-67580 Mertzwiller
France

Tel : +33 3 88 80 27 00

www.dedietrich.com

Anne - Christine Boos is a english speaking contact email at Anne-Christine.BOOS@DeDietrichthermique.com for additional
information in English and she has been very helpful.

The system in Portugal is the Dietrisol Pro solar panels and the Dietrisol
Trio
DT250/3 storage tank.

Sounds like a great place you have in France - good luck

We had an Efel Kamina, where the back-boiler was an afterthought. The thin steel skin eventually rotted away due to moisture running down the back of the boiler. We now have a Yeoman with the boiler integrated in the whole. It works well.

i have been burning wood on different stoves for at least 30years and know wat the pitfalls can be . so if i can give anybody advice feel free to ask