Heat capture from fireplace with heat exchangers

[86turbodsl]

Question for the veterans:

Has anyone here ever captured some heat using a coil over a firebox?

Let me elucidate my situation.

I have a BIS Ultima in a largish room in my house, which unfortunately is still
too small for the heat that thing can throw off. I can easily hit 90F in the dead of winter
while the rest of the house is a bit cold. I have hydronic heat in the house and keep
it dialed down because fuel costs are high.

Based on the amount of heat coming off the fireplace, and the fact that a BIS ultima is a
box inside a box and heat flows around the inner box, the thought occured to me to put a copper
coil above the firebox and circulate water through it when the fireplace is running. I'm aware I don't
want to create a steam bomb. I'd setup a heat sensor and a pump to circulate whenever the fireplace
was running. Seems like that could bleed off a good deal of heat to other rooms while making the room
more comfortable...

Any thoughts on this?

Thanks

Mark

 

[BrotherBart]

I am gonna leave the post here but suggest that you post in the Boiler Room. Those guys have a lot of experience with hot stoves heating water in pipes.

 

[86turbodsl]

Would it make sense to move the post to the boiler room then? Or should I just duplicate?

 

[begreen]

Before moving the thread, I'd like to know more about the layout of the house and the options for moving heat using fans. There are a lot more safety issues that would need to be covered with water heating. Especially if the power or a pump fails and the system is running full tilt.

 

[vvvv]

any alterations made to a UL approved system voids the UL listing, i think

 

[Jags]

As BG stated, the system will depend on power to run it, unless you make it an "open" system (and that probably has limited usefulness). You would need a backup for power unless of course you like mayhem and danger.

Your best bet may be to find a way to move the heated air. Fans, ducts, etc.

Note: please be aware that using duct work also has a list of "rules" to follow for safety reasons.

 

[firefighterjake]

No real experience with setting something like this up . . . but I have a few random thoughts.

I think if I wanted to move the heat around as you've described I would go with a wood fired boiler . . . and in fact I looked at wood fired boilers for some time before deciding on a woodstove. Rather than cobbling something together and hoping it would work and not violate any fire codes, void any manufacturer warrantees or risk the ire of my insurance company I would go all the way if I wanted to move the heat around in this way.

Have you tried using fans to move the heat out of the room with the stove and into cooler areas. I know without a fan blowing air towards my stove in the winter the living room with the stove can get mighty warm . . . and yet if I move a room or two over the temp difference is notable . . . but if I've had my fan going for a half hour or so the temp difference is barely noticeable as it tends to even out the heat in the house.

I also remember that my old Shenandoah had a piping system on the backside that you could apparently hook into a hot water baseboard system . . . never hooked it up . . . mainly because I didn't have a hot water system and my little camp was so small that it would have been over-kill. Seems to me that if such a low-key system worked well we would see a lot more of these types of systems these days . . . but other than dedicated wood-fired boilers you don't really see this in newer woodstoves which to me seems to indicate that they either have some issues.

 

[86turbodsl]

The house is mostly heated by geothermal water to water heat pump and in floor heat, we have a boiler for backup, but obviously this is expensive. The year I left the boiler going and didn't use the fireplace, I burned about 1800 dollars worth of propane in addition to the geo running. The geo is sized to the AC load, which leaves me to make up the difference with other means when it drops below about 30F. There' about 2-3 months a year when I'm trying to supplement.

The fireplace is enclosed in a wall in a 400 sq ft room with a 9 ft ceiling. There's a wall of windows in the room and even then I can hit 90+ easily in that room, with some spilling out into the hallway. Fans are a really clunky way to move heat between rooms. There's no chance in hell of putting holes in walls to add fans. This is an extremely nice house that I'm not going to cobble something together to fix. I"m somewhat funds limited due to the big mortgage, so anything I do will be done slowly.
I'm a mechanical engineer, so I understand the dangers of heated water/steam. What I'm more looking for is anyones' experiences or anecdotal evidence that this can work. Obviously this is not something that maintains the warranty on the stove. As far as power losses go, the house has a backup genset, so that is a relatively minor issue.

I am not interested in outdoor wood boilers for primary heat, I don't want to be married to stoking a woodstove for primary heat.

What I'm looking for is a way to harvest some of the massive heat that stove is capable of, and putting it somewhere I can use it, such as my floors, and keep my heat pump and boiler from running.

 

[begreen]

Short term, try a fan in the hallway, set low, blowing the cooler air into the hot room. I'll bet its temp drops 10+ degrees and the cooler areas warm up.

Will move this to the boiler room for assistance with hot water storage and circulation.

 

[Fred61]

I'm not endorsing a coil in the fireplace for the above reasons but a contractor friend of mine who built several contemporary homes at a local ski area back in the seventies installed a cast iron radiator in the exhaust of the masonry fireplaces of several homes.

 

[Wood Heat Stoves]

any alterations made to a UL approved system voids the UL listing, i think

prolly true, contact bis to see if they "approve" if you care

 

[86turbodsl]

Not going to bother. I know the answer...