Paulatic wrote: ↑21 Sep 2022, 6:29pm
Sorry I’d missed that scanning through posts to catch up.
Having read it I’d argue you’ve not increased efficiency but had adapted it to meet your needs. Creating a heat store and assisting convection. It must have taken a long time to heat up from cold.
My reason to have a steel wood burner is, after lighting, the room is cosy within 20 minutes.
Heat pumps are cheap until the government gets hold of them and their schemes then the double glazing salesmen jump in. I put my ASHP in 12 years ago. It’s paid for itself because I put it in on the cheap only needing a refrigeration engineer to install. I’ve serviced it myself since installation there is nothing to them.
Too right about government grants bumping the costs up, I watched this happen with the RHI. These clumsy schemes need serious re-thinking - there has to be a better way of stimulating uptake of something new.
I take your point about the use of the word 'efficiency', the stove itself wasn't burning wood more efficiently but better use of the heat it produced was being made, so
something was more efficient. When we were about to move, I temporarily replaced the 4.5kW stove with an 8kW one I'd bought for the next house and run at its best (without the surrounding bricks or aluminium foil layers) over a week, it heated the house only marginally better, while consuming a good bit more fuel. Mornings were a lot cooler, temperatures fluctuated more.
The stove sat in a stone chimney which was built partially outside of the property's walls, on cold days or nights after the stove had been running for four hours or more, you could warm your hands on the warm, exterior stones at the chimney base.
I had expected that a couple of hundred bricks would somehow sap a lot of heat for the first hour or two of running but if there was a slight difference, it wasn't felt. Spaced a little away from the stove so air was warmed and convected into the room as soon as the steel heated, the bricks soaked up radiation previously sent into the massive stones of the chimney and through the register plate. Several sheets of aluminium foil were sandwiched between the bricks and the exterior wall to reduce radiation losses of the bricks to the chimney.
The chimney stones would take many hours to warm then would lose a lot to the outside, whereas after 90 minutes the bricks were radiating and convecting a lot of extra heat, temperatures were much more stable as the stove cycled and on icy mornings the sitting room was typically 13-16C rather than 8-11C. Heat otherwise lost was being captured and released to the room more steadily than the rapidly heating (and cooling) stove, significantly adding to the overall output while the stove was running and gently warming the room for many hours after the last embers had died.