Reclaiming woodburner lost heat

[Danjay]

Hi all,

 

Just looking for a little advice really before I get the professionals in to try and to resolve what I see as quite an inefficient woodburner/backboiler setup. I've had a couple ideas on how to improve it. Whether they're good ideas is a different story. This setup was already installed when I moved into the property so all I really know is what the previous owner told me and what I can physically look at/research.. I will just explain the whole situation incase any useful tips pop up from anyone.  Hope it's not to long!

 

Setup.

 

20kW fireglow stove. 

Stove is within a fireplace and flue runs straight up the original chimney, clearance between top of stove and register plate is not a great amount so a very large amount of heat from the flue goes straight up the chimney and outside. (Which I am thinking could be captured).

It's a very simple gravity system (no storage tank) just a top up/vent tank. Perhaps a storage tank would be the way to go?

Back boiler is piped to 6 radiators around the house, 4 medium 2 small.

 

The house is a 3 bed but it is a large house with big rooms 4x (6x4x3m) plus kitchen/bathroom/shower/hall and a box room. The original idea was to use the combi which is a separate circuit to heat the house and then the woodburner boiler to maintain temperature (to an extent) combi boiler will kick back in when woodburner needs help, I'm happy with that idea if it can be improved somewhat. It does actually work quite well as winter is setting in but when the temperature drops it's not the best. 

 

One thing I have looked at is heat exchanger products. Unfortunately I think this would be difficult due to space limitations between the stove and register plate, along with the space inside the chimney itself.

 

However, on a similar kind of principle I was wondering would it be possible to core 4-6" holes into the chimney breast in the loft and use a high temp extractor fan to basically pull that lost heat out of the chimney? Then it could be ducted to a key location in the house (the hall).. is this acceptable? Safe? Has anyone done it with success?

 

I'll stop there as it getting a bit long ha, Any advice or other ideas most welcome.

 

All the best,

 

Dan

 

 

Edited April 4, 2022 by Danjay

[openspaceman]

My first point is although the heat in the flue gas is wasted heat in that it doesn't get into the room it is necessary waste heat because it give the flue gas buoyancy to rise on up out of the chimney and it also prevents any condensation of the vapours on the chimney walls.

 

My take is the problem boiler stoves have in meeting pollution standards is that the water cools combustion and quenches flames before they are full burned out whereas chip stokers and advanced gasifier boilers heat the water after secondary combustion has fully completed.

[Alycidon]

11 hours ago, openspaceman said:

My first point is although the heat in the flue gas is wasted heat in that it doesn't get into the room it is necessary waste heat because it give the flue gas buoyancy to rise on up out of the chimney and it also prevents any condensation of the vapours on the chimney walls.

 

My take is the problem boiler stoves have in meeting pollution standards is that the water cools combustion and quenches flames before they are full burned out whereas chip stokers and advanced gasifier boilers heat the water after secondary combustion has fully completed.

Agreed,

 

There are currently very few boiler stoves that are now available due to the 2022 emissions requirements.    I did think none but someone corrected me on that last week.

 

The air inlets on a boiler stove are usually controlled by a thermostat,   once the water in the stove is up to temperature then the stove shuts itself down,  then the pollution issue can arise.

 

A