Greetings all...I am looking for a fireplace heat exchanger that I could use to capture heat, from the fire, to use in the radiant floor system. The ideal plan is to have a heat exchanger concealed to the rear of the fire place or possible up the chimney. The intention is to use this heat for the underfloor heating or to boost the hot water storage tank. If anybody knows a good web site, or has information they could e-mail or maybe a few interesting ideas they could jot down they would all be most appreciated. Many thanks MR

Is this an open wood fire? Or stove? Either way, the usual wisdom seems to be that you want to keep the combustion area as hot as possible to ensure complete combustion and minimise smoke, therefore best to have any heat extraction downstream, ie up the flue.
Tony - why won't it work?
Cheers
Mike7

It will work a bit but it will be very inefficient. If you must burn wood then how about buying a wood burning stove with a water heating boiler in it? Then you will need a thermal store and some controls and mixing valves to run the system.

Why not design the job so you dont need heating if it is possible up here it must be able to be done where you are -- also it will be cooler in summer too.

Try reading up on Passivhaus -- they do it in northern Europe where it gets even colder. -- yes mega good insulation, passive design, heat recovery ventilation etc

wood burning stove with back boiler with give you massive savings in firewood volume (4 fold at least) will restrict drafts due to the controlled flue rather than a gaping hole, allows for temperature moderation by controlling air flow, and will provide a far more efficient hot water supply.

incidentally, if you spec the right fire, you wont need UFH.

Posted By: Terryyup, open fires lose something like 80-90% of the heat straight up the chimney. .

Open fires get a very bad press here, and usually for good reason, but I suspect it need not be anything like so bad as Terry's figure of 80 - 90% loss. Most open fireplaces appear to lack any design at all from the energy efficiency point of view. Some basic guidelines I suggest:-

1. Make the hearth as low as you can, below floor level if possible.This allows you to ....
2. Make a hood as low as possible above the hearth. This means only the coolest air in the room will supply the chimney draught, leaving higher warmer air in the room.
3. Make the hood as small as possible to ensure gathering smoke from the fire, but no bigger.
4. Place firewood upright, leaning back at about 60 degrees and light about 15cm below top. It burns much cleaner this way, and allows a smaller hood.
5. Incorporate a baffle in the flue or hood to restrict the draught to the minimum necessary plus a bit. Make it easy to adjust - it has amazed me just how small a vent is needed for an open fire well alight.
6. Have a fireclay or some such non-metallic fire-back to help maintain a high temperature in the combustion zone. Make it V-shaped rather than flat against the wall so that the logs tend to lean in together.
7. Don't bother with supplying outside air direct to the fire - it is difficult to do this without generating turbulence which makes gathering all the smoke/exhaust more difficult, and if you attend to the above items, the draught flow will be no more than you would want for airchange anyway.

It works for me. Having declared my vice, I wonder how many other closet open fire burners there are on this forum. My excuse is that the fire is occasional and would not justify the cost of a stove where it is.