Outside Air ?

Hello everyone - please be patient as this is my first post & I am new to coal stoves.
I have been reading online about them for a couple of years & believe they would be a good fit for my house.
I live in south central PA & have access to coal.
My question is, why are there no stoker stoves with an outside air feed?
It would seem to be wasteful to be sucking in all that air to have it pulled from your drafty windows or doors, or in through your dryer vent.
Thank you.
Vance

Because they work well without-------Why wasteful?? Wasting what?? Welcome to the FORUM V--:)

Whether it's outside air or inside air you still going to raise the temperature X degrees. It's a wash because the outside air lowers the temperature of the hot air you are making. Perhaps an easier way to explain it is you are recycling the heat.

A work around for that would be a double or triple wall pipe that preheats outside combustion air with exhaust gases running along side it. Seems like my buddy has a Harmon free standing Stoker that does exactly that, if I'm not mistake.. I'll check with him about it.

If you can extract heat from the flue gases without affecting the draft then you are in business.

The new Anthramax has an air intake. It runs with DV Pellet Pipe so the air is preheated on the way in.

Striving for efficiency with almost no return for cost. I cut 2 4 inch holes in my boiler room door and installed dryer vents with screens in them....Cheap....My boiler room was always overheated by the boiler....this kept it from sucking air in from parts I didn't want cooled....maybe.....

Kevin

Simple but workable Kevin!! KISS!!!!!!!!!!!!!!!!!!!!!

Welcome, my Harman does that, preheat the combustion air ! The exhaust is in the middle of an outer pipe that sucks air in and warms it from the exhaust, I like that idea because it never gets hot anywhere near combustibles !

BostonBob wrote: ↑

Mon. Feb. 24, 2020 9:21 pm

Welcome, my Harman does that, preheat the combustion air ! The exhaust is in the middle of an outer pipe that sucks air in and warms it from the exhaust, I like that idea because it never gets hot anywhere near combustibles !

That’s Direct Vent pipe.

I think there might be some benefit to pulling outside air into a heating appliance, but I think that benefit diminishes as house size increases.

It would be easy to figure out.

Take the size of mechanical draft blower in cubic feet per hour, and divide it by house volume of air in cubic feet. That would tell you how much air is changed in a given hour.

When we lived in our Tiny House, yeah the pellet stove pulling in inside air for combustion probably had an impact, but in the bigger house of 2600 sq ft, I do not think it has much of an impact at all. I mean it would take 3 times longer to pump the air fully out.

But the real question is how drafty a home is.

Our Tiny House was very drafty, so the induction blower on the pellet stove probably was not amounting to any negative pressure in the house at all.

But in the bigger house, where it is super-insulated, to the point where shutting one door causes vacuum on another open door, the induction draft might have an impact.

I the case of the Tiny House, the impact was small, but in the case of the bigger house, it is probably more of a benefit then curse.

I noticed a difference in the draftiness of the basement when i put in the 4" pipe providing outside air to the combustion blower. The end of the basement where the crawlspace connects felt warmer and less cold air movement from the crawlspace area into the basement. The cold outside combustion air doesn't seem to impact the heat generation of the stoker as the sides can still easily reach 600+ when on full burn. A dryer vent with some screening to keep out the critters is on the pipe on the outside.

You will be creating a negative pressure inside your home either way with or without using outside air for combustion. Your source of the negative pressure will come from the barometric damper which i believe is required on all stoker stoves. Its always sucking air from the room to regulate your draft.

I think what many people don't understand or know about is the turn over of air that naturally occurs in a home during the cold months. The air in your home should turn over (be replaced) several times per day just to maintain a healthy atmosphere to live in. This turn over happens because of pressure differences caused by warm air wanting to rise, or put more correctly be pushed upward by cold air infiltration. As cold air infiltrates down at the first floor or basement, the same amount of warm air is finding it's way out at the ceiling/roof line. Somewhere in between is the neutral pressure plane where the air pressure in the house matches the pressure outside.

The EPA actually advises .35 air exchanges per hour which means completely replacing the air in your home with fresh air every 3 hours. No wonder we burn a lot of coal when it gets cold out lol.

A baro or used combustion air actually change the nutral pressure plane's location in the house forcing the plane upward (caused by negative pressure mentioned in the previous post). With the NPP closer to the roof less air is being forced out by incoming cold air infiltration. That volume difference between air coming in as cold air infiltration and air leaving at the roof line is what your stove and baro are using..

I'm personally not onboard with dedicating a cold air inlet for stove/baro use. In my mind it lowers the NPP creating more pressure at the roof line to force warm air out. Overall it would make turn over happen faster, but your mileage may vary..