Waste Heat Reclamation?

[mayhem]

Hi all, I usually post in the wood forums, but have a oil fired boiler question. I did a quick search and came up empty in the boiler area.

I have a 5 year old log cabin, install a 180k btu Weil-McLain with 5 zones in the basement. Due to the heihgt of the house and the extreme costs of putting in a draft chimney for the boiler we opted to use a powervent and ran it right through the wall. Other than having to clean and lube it periodocally its worked well for us thus far. It occurs to me though that I'm blowing tons and tons of heat right out the side of my house for no good reason, so how best to try and capitalize on this resource? Since its a powervent, the exhaust is going to go out the side of the house no matter the temperature, so from my perspective, it really shouldn't matter how much of the heat I pull out of the exhaust stream, is that a correct assumption or is my reasoning flawed?

I saw these things called "magic heat" online (Amazon, Nothern Tool , etc) and they do make an 8" model (the size of my exhaust pipe) and for $150 it sems like a reasonable cost to pick one up and try it out. Very likely you guys already know what I'm talking about, but I've provided a link below to an Amazon.com page.

http://www.amazon.com/Magic-Heat-Reclaimer-Wood-Stove/dp/B0000AXEXE

So, good idea? Bad? Indifferent? My basement floor is a heated zone, but because it uses so much oil I don't leave it on unless I really have to, thus my basement is on the chilly side these days. A good shot of hot air into that room every time we use the shower, tub or dishwasher could make a significant difference for not much money in running costs.

So what am I missing here? Whats the downside? Big soot collector thats likely to cause me problems down the road or maybe restrict my exhaust enough to throw my boiler out of whack?

Lastly, is this a DIY install or hsould I get my boiler guy to come in for it? I'm pretty handy, but not overly experienced with the boiler. Looks pretty straightforward...make an opening, splice it in, seal the edges with some goo and plug it into an outlet.

 

[j00fek]

we had this type of setup in my fathers garage for many years, it was great at pushing out the heat. i would investigate the noise output on this if you are going to put it in your living space.

 

[mayhem]

It would be in the basement which is not a living space for us, so the white noise of a fan wouldn't bother us...I'm assuming its not much more annoying than the powervent.

 

[mayhem]

powervent has to be adjusted via barometric damper tunig. to compensate for airloss from barometric sucking out cellar air, TJERNLUND makes a unit called INFORCER which blows in outdoor air as the powervent works. well tuned furnace + MAGIC HEAT = soot in magic heat + possible inefficient burn of furnace.

I'm not following you 100% here, but the impression I'm getting is a magic heat is liekly to cause me problems, yes?

I do not have an OAK for my boiler, but I've been considering one. The exhaust has a T in it and there is a large inlet flap on there. The flap opens inward and sucks air into the exhaust stream...I'm guessing this is the barometric damper? The flap is counterweighted so it only opens under significant pressure flowing outdoors.

It occurs to me that between the boiler combustiona dn this device on the exhaust, that I'm using an awful lot of air up from the inside of my house and in order to compensate for it, I'm sucking in a fair bit of cold air throught the little cracks and crevices all over the house, but probably mainly in the basement...contributing to my heat loss.

Is it possible to retun the powervent to accomodate the magic heat device? It just looks like asimple fan forced heat exchanger, so the exhaust gases are just passing through exchanger tubes and getting some heat sucked out of them. Would it be of benefit to install something like this either before or after the damper?

Sorry for the noob questions.

Thanks for the replies guys, keep em coming!

 

[SE Iowa]

I have a Weil-McLain boiler that runs on natural gas and is direct vented out of my house. It is supposed to be 92% or 94% efficient (yeah right). I can hold my hand over the schedule 40 vent pipe and not get burnt though. I thought that to be direct vented the boiler had to be something like 85% or better? maybe the experts no the official number. Either way, if it is direct vent, I wonder how much more heat you really could extract?

 

[mayhem]

The EPA sticker on my boiler says its around 85-87% efficient, but I cna tell you if I put my hand on the exhaust its way hotter than I can stand to touch. I should put a thermometer on it when it runs...I'd guess its proabbly well over 125 degrees on the outside of the pipe

I'm not sure if a powervent is the same thing as direct vent. Powervent is fan forced, is direct vent fan forced too or is it passive convection/draft?

Maybe this is the wrong formula, but I'm thinking if its 90% efficient and can produce uwards of 180,000btu, then I've got as much as 20,000btu going out the exhaust pipe. My powervent is about 6' off the ground and I can see grass under it year round because the vent melts enough snow to keep the ground exposed.