air supply for pellet stove?

[MCPO]

I don`t see much in print (talk) regarding the necessity and benefit of combustion air being drawn from outdoors for pellet stoves.
Looking at my Harman P38 intake air flapper being 1/2 open and pulling in a considerable amount of indoor air I would think that a separate outdoor air supply would be a must do item since the stove would otherwise be contributing to indoor negative house pressure not to mention the heat loss somewhat akin to burning in a fireplace.
Comments and thoughts appreciated.
John

OK , I did a search and found some discussion on this. It seems it`s a trade off with the colder combustion air effecting the burn efficiency .

 

[stoveguy2esw]

i think its not an even trade off, looking at the loss of heated air pulled through the unit and out, as well as the tendancy to pull cold air in through leaks all through the house, and the miniscule loss if any from burning with direct cold outside air (whats 50 degrees gonna mean to a forced draft fire anyway?) im a firm believer in direct outside air intakes whenever feasible

 

[MCPO]

i think its not an even trade off, looking at the loss of heated air pulled through the unit and out, as well as the tendancy to pull cold air in through leaks all through the house, and the miniscule loss if any from burning with direct cold outside air (whats 50 degrees gonna mean to a forced draft fire anyway?) im a firm believer in direct outside air intakes whenever feasible

Thanks for the reply.
The Harman P61 literature reads "Efficiency can be further enhanced by using 100% outside air for combustion and keeping the glass clean." I would have to believe the same is true for the P38 so I`ve decided to bring in outside air to the stove.
John

 

[ugenetoo]

cooler air also holds more oxygen as i recall.

 

[MCPO]

I had to snake through 27 ft of sheetrock and suspended ceilings to get outside combustion air. It wasn`t the easiest job but it looks good and it`s done.
I used 4" flexible aluminum for all but for the last 8 ft drop to the stove where I used 3". I fired it up and it sounds to be drawing air freely and burning normally. I can hear and feel the suction / draft from outside with no whistling or any indication of 4" not being large enough. Since 4" is almost twice as large as 3" I figured it would make up for the length and sweeps.
John

 

[drizler]

I Cant say running with one made any noticeable difference after not having one for 3 seasons. If I had to put a pile of effort into one as well as lots of $$ or time I didn't have I wouldn't bother at least right away. On the other hand knocking a simple hole in the wall with a 3" hole saw and sticking in a $10 gas dryer exhaust cap into a piece of 3"aluminum dryer hose was about stone simple. Did I notice any big difference in heat output or the way it ran: not really but I suppose I feel better with it the way they say to do it. If you are cutting through drywall and exterior plastic siding beg borrow or steal a 3" circular cut off blade and get the plastic hot or do it on a nice warm day. If you come through the back just punch the center line up bit through then go outside and center it and come through carefully that way and you won't have any cracks running in your siding.. Using a hand jig saw is a lot harder, messier and just begs to break plastic siding. I did mine when it was about 10 F and the hair dryer kept it nice and soft to cut with no cracks.

 

[MCPO]

To be honest , I don`t see any difference in the burn aspect itself but the combustion air is certainly not taken from the house anymore. I spent 4 hrs and $55 for material myself but my mind is at ease now and I`m not gonna worry about it any more. It`s done .
John