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Posted by: bondo Dec 9 2006, 10:51 PM

Our house has electric heat, which gets expensive to actually use. We have a fireplace, but it doesn't have an outside source for combustion air. The result is that whenever we have a fire, the living room gets warm, but the bedroom actually gets COLDER because cold outside air is being drawn in by the fire.

The solution to this problem was to build a heat exchanger to sit at the back of the fireplace. Air gets bown through it and then plumbed to our bedroom via PVC pipe. The air comes out of the exchanger at about 140 degrees, and by the time it gets to our bedroom it's about 85 degrees (bigger drop than I expected, but whatever).

In case you're wondering, the PVC pipe is rated at 90 degC and we have a CO alarm in our bedroom in case something goes wrong.


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Posted by: biosurfer1 Dec 9 2006, 11:05 PM

I'm a HVAC engineer and this is a first for me. We use heat exchangers all the time, but its usually for running through pipes to which air is then blown across and heated up. In a round-about way, I guess it's sort of the same concept. Why didnt you just run spiral ducting?

quite out of the box thinking , thats for sure:)

Posted by: firstknight13 Dec 9 2006, 11:05 PM

good idea BUT co alarm won't save you from the dangerous plastic fumes if a fire arises....

Posted by: Aaron Cox Dec 10 2006, 12:53 AM

wrong on soo many levels.....

Posted by: Britain Smith Dec 10 2006, 02:00 AM

If you are married, I can't believe the wife let you do such a thing.

-Britain

Posted by: SirAndy Dec 10 2006, 03:07 AM

a few things ...

get some hitemp paint and paint the metal part inside the fireplace black. that should be good for a few more degrees starting temp.
you can also increase the surface area by adding fins to it, if possible. actually, the same goes for the inside of the heat-exchanger (fins, not paint) ...
then insulate your ducting to the bedroom.

does your fireplace have a flow-restrictor? if not, buy one ... it'll help reducing the air flow out of the chimney and increase the temperature inside the fireplace.
alternatively, you can get the same effect by adding a airtight glass door to the front of the fireplace and some kind of air-regulator on the intake side ...


i like it!
Andy

Posted by: highways Dec 10 2006, 03:13 AM

Wowsers! You guys are tough. Ok that setup is butt ugly, but beautiful in the eye of the heat blower.

I would think it could be concieved to work independantly from the fan, by using induction or something. And could be plummed out of sight like the under the floor... hopefully with copper and to code or something. Energy transfer is cool. PVC, not.

One thumb up for "get off your butt imagineering". One thumb down for "Ow!! my Eyes!"

Posted by: Nick Dec 10 2006, 04:36 AM

The only thing I have seen like this circulated water through the fireplace then out to radiators in other rooms. It had the advantage of looking like a fire grate and I think it would lower your chances of transferring fire gasses to other rooms of the house.

Nick

Posted by: kwales Dec 10 2006, 10:04 AM

Here is what we did....

In North Carolina, they use those heat pumps that stop producing heat at 32 degrees. When the temp got that low, the electric heat strips turned on and your power meter could be heard spinning and banging on the wall...

A fireplace insert with a fan and glass doors was the trick. Had a sheetmetal flue. Throw in a coupla logs, turn on the insert fan and a plume of hot air came shooting out. Go to the heat/ac thermostat, turn on the FAN only, pump the heat through the house.

Ken

Posted by: rhodyguy Dec 10 2006, 03:04 PM

do the down pipes from the manifold extend into the fire? if the firebox is masonry i don't think i would paint it. don't dampen the flue unless you restrict the firebox opening. the fireplace will not draw correctly and will it *smoke*. how often do you burn in the fireplace?

Posted by: bondo Dec 10 2006, 03:04 PM

Hehe, my wife loves it... I guess I'm just lucky. I agree it isn't much to look at but it's temporary and we're cold. When the weather warms up it can all come out. None of it is glued together. Unfortunately there is nowhere else to run the ducts... we ave a slab on grade and a flat roof. The electric heat is radiant, so we have no air circulation at all except for this contraption.

I like the idea of glass doors to keep the exiting air to a minimum. I'll also add some black paint next time I clean out the fireplace, it it hasn't naturally turned black by then.

As for burning plastic fumes, I'm pretty sure burning plastic would release CO and set off the alarm. We also have a smoke detector (of course).

Posted by: rhodyguy Dec 10 2006, 03:14 PM

what does a cord of firewood run in los osos? i heated with wood for years. i can't imagine doing it again.

k

Posted by: bondo Dec 10 2006, 03:31 PM

We use the fireplace almost daily in the winter. I work at a shop and burn a lot of scrap wood from the trash. I've seen ads for half cords of wood for around $100 to $150. We may buy a bunch now that we have this setup.

If we use the electric heat our bill for one month goes up about that much.

Posted by: rhodyguy Dec 10 2006, 03:44 PM

get some doors. you won't pull as much heated combustion air. slows down the house air loss as the fire goes down at night also.

Posted by: TROJANMAN Dec 10 2006, 03:51 PM

have you consider a fireplace insert with a blower on it?

We had one, and they are pretty awesome

Posted by: Vacca Rabite Dec 10 2006, 04:13 PM

Or a fire place insert pellet stove.

Any fireplace insert is going to really heat up more then a regualr fire place.

Zach

Posted by: Air_Cooled_Nut Dec 10 2006, 05:20 PM

Bingo! My parents did this and DAMN that thing pumped out the heat! The pellets were more cost effective than dear ol' Dad buying wood, chopping it, stacking it, hauling it, etc. His back thanked him, too

Posted by: Air_Cooled_Nut Dec 10 2006, 05:23 PM

Correct. There is a good amount of engineering in the design of a proper fireplace. Unfortunately, the majority aren't done properly. For example, mine is located outside of the house and the opening was too big. I say "was" because I created a small steel lip to reduce the size of the opening and thus keep smoke from 'spilling' into the house. Yeah, I've done a good amount of reading on fireplaces in the library & on-line...