Increasing a Stove’s thermal efficiency with external house bricks?

[CaneyJ]

I have a 23ft narrowboat which comes with a Villager Heron 5Kw Multi-Fuel stove.

 

I’m limited to mainly burning smokeless fuels to minimise the stove’s heat output since it only has lower airflow control, it tends to be a blast furnace when using wood.

 

I’m yet to master keeping the stove going until the morning and it starts getting a bit chilly waking up in the mornings.

 

If I bank the fire up before bed; even if I close it right down, the heat can get overwhelming.

 

I used to live in a flat fitted with storage heaters which got me looking at trying out a crude form of thermal mass storage using clay bricks or concrete paving slabs laid up against the stove’s sides and back wall.

 

Has anybody tried this method? I’ve heard of adding another thin layer of fire bricks inside the grate but I was more thinking the outside since the firebox is already quite small. Would insulating the stoves heat from the outside cause issues with the steel body?

 

I have about 10cm of clearance all around the stove but also have a concern that the weight of bricks quickly adds up to being the at least the same weight again as the stove and could cause issues with the supporting hearth?

 

I guess my main question is; would a dozen or so bricks on the stoves top and sides release the heat slower and store enough heat for a couple more hours of warmth in the mornings?

[Phil Ambrose]

Wow! no wonder you cook, we only have a 4.5kw stove on our 60 footer which heats the whole boat, and yes at times we have to open the doors.

Guess it would be silly of me to suggest putting fire bricks in the stove to reduce the size of the fire and experiment with banking the fire up with ash to hold it in over night.

Phil

[MoominPapa]

If I bank the fire up before bed; even if I close it right down, the heat can get overwhelming.

This suggests there's something wrong. It should be possible to put out a stove full of fuel by completely closing the air vent.

 

I'd check that the air vent is sealing correctly, the door seal is sealing correctly and that there are not gaps or cracks elsewhere in the stove.

 

Once you have control of the burn rate, all the other problems will go away.

 

MP.

[matty40s]

I go the other way. I have put reflective metal sheet behind the stove.

This means ALL the heat comes into the cabin rather than heat the hull side and canal. This means I can use less fuel to be warm.

Even when stove is blazing, I can put my hand behind the stove and sheet and it feels cool.

[cereal tiller]

I go the other way. I have put reflective metal sheet behind the stove.

This means ALL the heat comes into the cabin rather than heat the hull side and canal. This means I can use less fuel to be warm.

Even when stove is blazing, I can put my hand behind the stove and sheet and it feels cool.

Greenie for that

 

I have Perforated Metal Sheet around three sides of the Stove,as you say,keeps the Cabin lining cool.

 

CT

[blackrose]

I've got some storage heater bricks in my stove to reduce the size of the fire box. The downside is that it takes longer to heat the stove (and boat) due to the stove's increased thermal mass/ heatsink. The upside is that heat will continue to emanate from the stove long after the fuel has all burned out, although that could be a potential downside too.

[system 4-50]

This suggests there's something wrong. It should be possible to put out a stove full of fuel by completely closing the air vent.

 

I'd check that the air vent is sealing correctly, the door seal is sealing correctly and that there are not gaps or cracks elsewhere in the stove.

 

Once you have control of the burn rate, all the other problems will go away.

 

MP.

Absolutely right. Replace the rope seals. I've had trouble even with new rope not sealing correctly. Getting the doors to seal well is the key.

[Machpoint005]

Absolutely right. Replace the rope seals. I've had trouble even with new rope not sealing correctly. Getting the doors to seal well is the key.

 

Anyone know what the "high temperature rope adhesive" actually is? A minuscule bottle cost me about a fiver, but it doesn't half look like PVA!

[Mac of Cygnet]

 

Anyone know what the "high temperature rope adhesive" actually is? A minuscule bottle cost me about a fiver, but it doesn't half look like PVA!

 

I've tried in vain to find out what these contain (different brands have totally different appearances). But you can get a bottle and 2 metres of stove rope on Amazon for £4.99

[MoominPapa]

 

I've tried in vain to find out what these contain (different brands have totally different appearances). But you can get a bottle and 2 metres of stove rope on Amazon for £4.99

I'd guess it's probably sodium silicate, AKA waterglass.

 

Cheers.

 

MP.

[Mac of Cygnet]

I'd guess it's probably sodium silicate, AKA waterglass.

 

Cheers.

 

MP.

 

Really? The stuff we used to preserve eggs years ago?

 

I just looked it up. You may be right. It's very versatile stuff isn't it?

[Bee]

Funny stuff sodium silicate, I mix it with fine sand, then it makes an excellent material for sand casting in foundry work, reacts with CO2 and solidifies.

[CaneyJ]

OK; I came across wrong when I said about closing it down. When the ash door is screwed down tight the fire will indeed go out so I guess there are no air leaks on the rope seals. I replaced my ash door seal only last week but that won't help my current wood burning issue.

 

Maybe the ash door screw is just super sensitive. I'm mindful about adding too much fuel to the fire overnight but I guess this tends to not be enough as it is fully burnt down by the morning.

 

Anyhow; my focus is on latent heat retention and whether this method would allow a couple of hours extra radiant heat in the morning or should I just line out the stoves interior with another layer or fire brick?

Edited December 10, 2016 by CaneyJ

[Stilllearning]

When I had a Torgem stove, it was very difficult to control, either closed or a blast furnace and didn't stay in overnight either. In the end what I did was to drill a series of holes in the bottom ash tray flap of the stove, and put a bolt of a nice tight fit in each hole. Then as a fine control I would take one bolt out at a time till the draught was just right. I am not sure if your stove has a suitable plate at the front and low down that you could modify in this way, but if you have, it might work.

[Mac of Cygnet]

I see from the OP that the problems you are having are when burning wood. Are you burning it on a grate? Wood is much better burned on a solid base, so it can form a solid centre which keeps in much longer. I have no problems keeping my quite small stove burning wood all night (and sometimes well into the next day) since I removed the grate and burned the wood on the ashpan on the base of the stove, letting a good firm base of ash build up.

 

The air inlet is then at the level of the burning wood, not below it, which is how it should be in a true woodburner,

[Drayke]

OK; I came across wrong when I said about closing it down. When the ash door is screwed down tight the fire will indeed go out so I guess there are no air leaks on the rope seals. I replaced my ash door seal only last week but that won't help my current wood burning issue.

 

Maybe the ash door screw is just super sensitive. I'm mindful about adding too much fuel to the fire overnight but I guess this tends to not be enough as it is fully burnt down by the morning.

 

Anyhow; my focus is on latent heat retention and whether this method would allow a couple of hours extra radiant heat in the morning or should I just line out the stoves interior with another layer or fire brick?

Try it and see, but be aware of heat transference to any surrounding wood work.

I have sometimes put the odd brick on top of fire then used them as a bed wormer after wrapping in an old towel.

Edit to add. I used engineering bricks.

Edited December 10, 2016 by F DRAYKE

[Chertsey]

This suggests there's something wrong. It should be possible to put out a stove full of fuel by completely closing the air vent.

 

I'd check that the air vent is sealing correctly, the door seal is sealing correctly and that there are not gaps or cracks elsewhere in the stove.

 

Once you have control of the burn rate, all the other problems will go away.

 

MP.

This is no doubt true, but on some stoves (e.g. my Epping) the air vent (damper?) will never seal completely.

I find the secret is to be patient and put up with cooking for a day or two (and I'm in a back cabin!) while a layer of ash builds up in the bottom. This will do a great deal to reduce the air flow. After that, riddle only very judiciously and a tiny bit at a time. Once this is achieved, I can keep the fire in indefinitely, including overnight (eight hours plus) without overheating.