Wood burning stove.

[Kate600]

I currently have a 24kW oil fired Rayburn running my heating and hot water, and I am looking at replacing it with a wood burning stove with back boiler.

My house is a traditional 1 1/2 story croft house that has been renovated, so it has 600mm thick rubble Walls, with 75mm insulation inside Walls, under the floor and 100-150mm in the roof.

I have done the online calculators to see what size of boiler I need, if I count radiators it says approx 20kW (so it would be a 24KW stove) if I do it based on my house insulation and size, I get 8.6kW.

I find that the house is way too warm when the Rayburn is running even on half output so don't want to oversize the wood burner...

Wha I would like to know is does any one have any experience of how realistic the figures given for stoves are? I have seen one that is 18kW.....

 

[Burnerman]

Absolutely no business of mine really, but do your radiators have TRV's and is there a room thermostat somewhere?
After all, your Rayburn will shut itself down if the heat isn't needed.
You'll have to burn a huge amount of timber to get the output you seem to need!
John

 

[Kate600]

Lol, yes the radiators have trv's, and there is a room thermostat in the hall way. However, even if I turn that right down, the Rayburn still fires, which makes me think there is something not right with it, I have the boiler output turned down to about 1/3 which gives me a reasonable temp in the house.
But I have stopped using it for cooking as even with it turned down, and limited running times it is still costing me a fortune.
I am refitting the kitchen anyway, so am looking at replacing it with an electric cooker, and will need some form of new boiler.
I would like to move away from oil (being a bit of an Eco person) and have looked at the wood pellet boilers, but they are just out of my price range, hence why I am looking at the wood burner.

 

[Burnerman]

The thermostat in your hall should control the Rayburn completely - are you saying that the rads still heat up when its clicked to off?
I can certainly respect green issues, but when you consider the calorific value of wood compared to oil it doesn't make so much sense these days as everyone seems to be wanting logs to burn.
I think I could go down that way too - but only if I had my own personal forest!
Good luck with whichever route you choose.
John

 

[Kate600]

Yep, it heats the rads up, the thermostat clicks, but the Rayburn still fires (you can hear it burning) and the rads stay hot, pump is still going. In the rooms that the children remember to close the doors of, the trv's help moderate the temp, but downstairs where the doors are generally left open it gets roasting. I put a room thermometer next to the thermostat, it read 25 when the thermostat was set at 18, and the Rayburn was still firing. The only way I have found to regulate it is to turn the boiler output down on the Rayburn itself.
So, as I don't use it for cooking, I figured the best thing would be to change it for something else. I have considered putting in a different oil boiler, but don't want one in my kitchen, and putting pipes through the 3' thick Walls to connect an external one does't appeal. Hence why I looking at wood burning stuff, it will go in the same place, use the same flue, pipes are there already... Just don't know which estimate for size requirement is more accurate, the one based on my house size and insulation, or the one based on the number of radiators....
Guess. Should speak to a heating engineer and then start saving.

 

[Burnerman]

Kate, there are definite issues with your room thermostat here.....once it clicks off, the Rayburn should shut down....if it doesn't, then there's something not right. Its costing you an unnecessary fortune, the water circulating pump keeps running and the burner stays lit.
Talk to a heating engineer, will you? I appreciate Rayburns aren't the most cooperative of domestic appliances but it just isn't working correctly.
I look after a double burner one, with Nu Way oil system - it drives the central heating / hot water and has a cooker side too. Once the room temperature reaches what the thermostat says, it shuts right down.
John

 

[Agile]

I do hope that Kate has remembered that wood needs to be regularly topped up to keep the stove burning.

My friend in France has one of perhaps 7-8 kW and a load of wood burns in about 1-2 hours so needs three topups each evening.

With his electric saw it would take me about 45 min to cut up an evening's supply starting from 1.2m logs!

Tony

 

[Burnerman]

I'm assuming (maybe wrongly) that Kate's Rayburn has a pressure jet burner, as she can hear the thing burning....this wouldn't be the case with a vapourising system.
To produce 20kW or so with wood has to be one hell of a task.
John

 

[Norcon]

To produce 20kW or so with wood has to be one hell of a task

Its pretty easy with one of these....
From the brochure....

In action.....

 

[Kate600]

Lmao, that is one huge burner! It is a pressure jet Rayburn, with twin burner, one for oven the other for heating/hot water. I had suggested to my ex and his (plumber/electrician) friend who installed said appliance that I didn't think it was working right, because it should switch off when the stat clicks, to be told there is nothing wrong with it....

I also think that the 20kW is too high, my house isn't that big, there are 3 rooms down stairs and 4 in the loft space upstairs, it is well insulated, not to current specs but not far off, has low ceilings, small windows all of which are double glazed.... But it does have lots of radiators!

I have a small wood burner in the living room (2-3kW I think) which I use to avoid putting the heating on in the whole house, if I leave the door open it heats half the house comfortably. I used to have an old solid fuel Rayburn which ran the heating and water, before it was all insulated and it did fine until the barn was added to the load, and it wasn't quite enough when it got cold, and the kitchen was ROASTING when it was running.... Made some lovely roast potatoes though .... Then we 'upgraded' to the current oil model.

I agree that the Rayburn isn't working right, and I will get it looked at, but I have decided I want to change it, deciding what I am changing it too is the tricky matter!

 

[Agile]

Kate, at the moment you can turn a few knobs and get heating.

Do you really want to go back to a senario where you need to be loading loads of wood ( or pellets ) every few hours?

My friend in France and another in Devon burn wood because they own about 12 acres of mostly woodland each and they are happy to do the cutting because the wood comes free to them. But it is a significant chore as I saw when I was helping during my stays.

Tony

 

[Corgigrouch]

Of course Biomass doesn't have to be so industrial looking and this pellet boiler can modulate between 3.4kW and 12kW http://www.baxi.co.uk/products/baxi-bioflo.htm

But don't ask Baxi about them as they don't know a great deal about them...

 

[Kate600]

What I really want is an efficient boiler that runs with a room stat linked to a stove with a back boiler, and an efficient means of cooking, oh and some pv cells would be nice too.

What I have is an extremely Inefficient boiler that is also ridiculously expensive to cook on, a calor gas cooker, which only has two working burners, an open fire and a small wood burning stove without a back boiler.

What I am looking at is the first step on the way to what I really want. If I put the stove and back boiler in first, then I can sell the (hopefully fixed) Rayburn so that I can buy an efficient cooker. Then I will have heating and cooking for minimum initial outlay and hassle, and I can save up for a boiler to link into the system as althogh I will be paying for wood (as I do now anyway) I will not be paying the £700 a quarter for oil.

I cannot afford to do it all in one go, and it will be cheaper for me to put the stove in than it would be to put a new boiler in in the first instance.

 

[Burnerman]

Kate, your twin pressure jet burner can be regulated by the room thermostat - thats why its there!
When the stat clicks off, the burner should go out, but the pump keeps running for a while to prevent the boiler overheat stat tripping.
I would have the wiring checked out, personally!
John

 

[Tibbot]

What I really want is an efficient boiler that runs with a room stat linked to a stove with a back boiler

No stove can do what you've asked. They are more useful as dry versions for space heating or small wet backs for serving an additional hot water cylinder. If you want wood-fired whole house central heating it has to be a boiler of the type described earlier. Personally I prefer the batch-fed log models over pellet ones.