I fought the OAK and the....

Corie said:

Yes, I'm aware of air density varying with temperature and how density affects mass flow rates.

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All you need to do is adjust the flame with the damper to account for the difference in the increased mass flow rate from both the colder air and the increased flow rate of the combustion air fan. It's true this is offset slightly by choking down the damper. Still, it's like putting on a extremely large air filter on your car vs a small dirty one (a smaller restriction vs a big restriction on the intake). The car will run more put out more power with the larger filter and even more with the colder air. In my opinion, once a good enough adjustment is made to the damper after the OAK is installed, that will probably be good enough irrespective of typical outside air temperature changes mainly because you've maximized the combustion air fan efficiency - you have maximized the flow to the burn pot.

The outside air kit that I bought from Quadrafire for $ 120.00 came with a thin aluminum flex hose. It ripped while I was installing it. I managed to rap some of the ripped pipe around itself to double the thickness. I used pvc to extend it into the basement and out the side of the house sill. I couldn't find any metal 1 1/2 flex pipe to replace the junk from Quadrafire.
Any suggestions?

gobuck said:

The outside air kit that I bought from Quadrafire for $ 120.00 came with a thin aluminum flex hose. It ripped while I was installing it. I managed to rap some of the ripped pipe around itself to double the thickness. I used pvc to extend it into the basement and out the side of the house sill. I couldn't find any metal 1 1/2 flex pipe to replace the junk from Quadrafire.
Any suggestions?

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Try getting some scrap exhaust pipe (new pipe) from a local muffler shop. Or, pay them a small price to have them make what you need if the lengths are longer than typical scrap.

Corie said:

Yes, I'm aware of air density varying with temperature and how density affects mass flow rates. But if the control board of a stove isn't able to adjust fuel feed rate based on incoming air density, what difference should that additional oxygen make to the heat output of the unit? Certainly a slightly more complete combustion process, but 40 or 50 degrees difference in output temperature? I'm not saying I disagree, just that while I'm in the process of emissions testing on the new pellet unit I'm working on, I'm going to run some tests connected to outside air and disconnected and measure incoming air temperature, as well as actual output air temperature.

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Actually I`m kinda surprised that this issue isn`t a concern or consideration by a stove manufacturer and even more so that there aren`t any canned answers or conclusions already drawn based on past tests that I think should have been performed?

Since outside combustion is not used for EPA emissions testing, I find it hard to find a scenario where I'd be running a full blown efficiency/emissions test with outside combustion air connected. Why go through the trouble to run a full scale 5G emissions test with a combustion air hookup that makes the results invalid.

Also, ENOUGH with the automotive comparisons. An internal combustion engine compresses air 9 or more times it's original volume. Of course the density of the intake charge is profoundly affected by temperature. This is a pellet stove. Atmospheric pressure. Settle down.

Corie said:

Since outside combustion is not used for EPA emissions testing, I find it hard to find a scenario where I'd be running a full blown efficiency/emissions test with outside combustion air connected. Why go through the trouble to run a full scale 5G emissions test with a combustion air hookup that makes the results invalid.

Also, ENOUGH with the automotive comparisons. An internal combustion engine compresses air 9 or more times it's original volume. Of course the density of the intake charge is profoundly affected by temperature. This is a pellet stove. Atmospheric pressure. Settle down.

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I`m still surprised and would have thought any and all stove makers would have at least tested the effects of the burn with and without an OAK on their particular stove regardless of whether the results have anything to do with EPA emissions or not.
I mean if it`s negligeable , thats fine but even if it proved a 1-2% increase in efficiency at a given temperature it would be nice to know.
Seems like this wouldn`t be rocket science either.

Corie said:

...This is a pellet stove. Atmospheric pressure. Settle down.

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Settle down? As if there's a conflict??

Look at it from the big picture and forget about the details. Both pump air (how and why and the details are irrelevant). If you increase the efficiency of the stove's fan by removing a restriction, it helps. The only reason why I used an automotive analogy is because it might make the concept of the OAK easier to understand. Would it have helped if I only provided theory and equations? Probably not.

BTW, the instant you turn on the combustion air fan, you're no longer dealing with just atmospheric pressure. Maybe in a regular wood stove, but not a pellet stove with a combustion air fan.