Outside Air or Inside Air

[Lordtimothy200]

Over the years I have had both a Outside air intake for the stove and used inside air. So I thought, which one is really better? Still no answer but here is some interesting data points in the attached image. The middle up and down was when I switched from outside to inside air. It overloaded the burn pot pretty quickly when I went to inside air. Restarted it and was back to burning like it should.

No changes to any settings just capped the outside air and opened the inside vent. When things warm up next weekend I plan on redoing the test to see if temps in the 20's/30's make any difference.

Does a average increase in the temp of the stove (theoretically providing more heat) trump the amount of warm air pulled from the inside and exhausted from the stove? Interested in your thoughts.

Internal Temp is taken in the combustion chamber and the Intake air is taken 4" away from the stove on the intake air pipe.

Outside air 2 F -5 F
High 368 F
Low 348 F

Inside air 69 F - 72 F
High 389 F
Low 372 F

 

[tlc1976]

I can see how the intake air and firebox would be a little warmer with inside air, because you’re sucking warm air from the room that you’ve already paid to heat and sending it up the chimney. You might even have a bit warmer air coming off the room blower. But some of that is going right back up the chimney. And it gets replaced with cold air that gets sucked in through drafts elsewhere in the house.

Outside air doesn’t pull anything from the room.

So I would try it with the thermostat far enough from the stove so you’re not reading that warmer air circulating back to the intake, and see what the overall room temperature is both ways. It would be interesting.

I have to have the outside air. My stove just chokes and dies without it, I have a tightly sealed house.

 

[Lordtimothy200]

After playing with the numbers a bit, it is as I expected. Better to have a OAK, it is just jarring to know the combustion chamber is lower temp. The blower on my stove is a 210 cfm blower. That is a lot of air removed from the house. 70 plus degree air verse loosing 20 degrees in the combustion chamber, I will take the 20 degree's.

After looking at the numbers and how my stove location, going to leave it so I can switch from outside air to inside air. If I get a straight North wind it triggers the vacuum switch and causes the stove to go out. Nice to have options.

 

[SidecarFlip]

My philosophy has always been, why use heated room air for combustion when outside air os less that 2 feet away and... mine 'seems' to run better, the colder the intake air is. Just a visual thing, Never documented it one way or another. Not a stat geek, just seat of the pants observation.

 

[tlc1976]

Another way to think of it is, your stove is going to get outside air regardless. Would you rather have that cold air coming through drafts in the house, or coming through a contained pipe behind the stove? You wouldn’t punch a hole in the wall or open a window when you’re trying to get the house warm. But that’s essentially what’s happening without the outside air kit.

It would be ideal if my clothes dryer had outside air capability. So I keep the laundry room closed. I had to cut an access hole right in front of the dryer to fix pipes behind the shower. So I just put a vent cover over it and now the dryer pulls air from the unfinished basement. Which pulls air from the unused masonry chimney nearby.

 

[Washed-Up]

if you’re really interested in pulling warmer air into your stove to burn, have a look at direct temp, stole this from Dons post

 

[Lordtimothy200]

I have been considering something like what was in Don's post but to pipe the air into my bin of corn above the stove just to help dry out the corn a bit before it hits the stove. This seems only an issue at these sub zero temps. From another persons math the cut off point is 14 degree's, anything lower than that does not add anything to the density of the air. Going to keep an eye on that as the temp increases towards the end of the week.

Ahhh future projects.

 

[SidecarFlip]

If I have frost on my fresh air intake pip, all is good with me...

 

[tlc1976]

If I have frost on my fresh air intake pip, all is good with me...

No frost on mine yet this season but no subzero temps yet either.

 

[SidecarFlip]

Been on the other side of zero almost every night for the last week. Dang cold in SE Michigan lately.

Toasty inside though, at the expense of a lot of corn, glad it's free.

 

[Washed-Up]

Cold broke here today in western Alberta, 20-30f
WOOHOO

 

[SidecarFlip]

Cold broke here today in western Alberta, 20-30f
WOOHOO

Thong time.................

 

[semipro]

Cold air is denser and contains more oxygen per unit volume.
Since the combustion fan is only going to pass a certain volume of air, cooler air should provide a net increase in the supply of O2 to the fire. Whether that affects fuel use rate or efficiency I'm not sure.

 

[bubble]

if you’re really interested in pulling warmer air into your stove to burn, have a look at direct temp, stole this from Dons post
View attachment 274632

I have this: https://www.walmart.com/ip/4-quot-PelletVent-Pro-Combustion-Air-Wall-Thimble-Kit/37920036
Works great, but may have been discontinued by DuraVent.
It's a coaxial intake/exhaust. The intake air is preheated by the exhaust, & the exhaust is surrounded by cool air.

 

[railfanron]

Here's a thought for you. I believe most stoves combustion blowers put out somewhere between 80 and 110 cfm's. If your home is 2,000 sq. ft. and has 8ft ceilings it has 16,000 cubic ft of air in it. The 80cfm combustion fan draws 4,800 cubic feet an hour. So for every hour the stove is burning your house is TOTALLY EMPTIED of it's heated air every 3 hours and 20 minutes. Can't see how running using inside air can be cheaper.
Ron

 

[SidecarFlip]

Figures don't lie, thanks Ron..... Always had outside are intake right from the beginning...and Duravvent still makes the axial thimble but personally, I prefer COLD intake air.

Getting some 'frost on the pumpkin' tonight or should I say frost on the intake pipe... it's snowing to beat the band here, just spent an hour putting the rear mount blower in the tractor and about froze my butt off. Supposed to get 10-12 by morning with a stiff southwesterly to north east wind so I suspect it will be 'all stop' around here tomorrow.

Stove is eating corn like it's starving and it's barely holding 68 in here but considering it's 17 outside, I'm not complaining at all.

Think I'll snap a picture of the snow beast tomorrow and post it. 'Able to beat down a 6 foot drift and not break a sweat'... Hardest part for me is keeping track of where the edge of the plow is. it's a 10 foot wide plow and hard to manage sometimes.

 

[SidecarFlip]

Cold air is denser and contains more oxygen per unit volume.
Since the combustion fan is only going to pass a certain volume of air, cooler air should provide a net increase in the supply of O2 to the fire. Whether that affects fuel use rate or efficiency I'm not sure.

I guess it's mostly conjecture, other than sucking the heated air out of your living space and then ambient outside air replaces it through cracks and such in the house. I do know (from observation over the years) that when it's cold out like it is right now (+10F) my unit 'seems to run better than when it's warmer out. Could be my imagination too.

All I know is, I'll have the electric blanket maxed out in the bedroom tonight. The wind is blowing on the south wall where the bedroom is at and it has no heat in it except for the central furnace and we keep the door closed (no cats allowed) so it's a might frigid in there as in you can see your breath. Good for cuddling....lol

 

[tlc1976]

Mine is on heat range 3 of 5 and it’s 68f at the center of the house, 7f outside. Burn 1.5 bags a day at this rate, but by the weekend it will be back to 20-30 where I burn 1 bag a day.

Cold air being denser and more oxygen rich. Cold air intakes are a big thing in the engine performance crowd for that reason.

 

[Washed-Up]

Someone HAS to do an experiment...I’m not convinced either way

 

[Don2222]

Hello
The Selkirk DT makes the ash light
& fluffy so easier to clean too.

 

[SidecarFlip]

My ash is always fluffy and light, corn ash is.....

 

[Lordtimothy200]

I forgot to get a screen shot of it but yesterday the intake temp was between 15-20 degree's and the combustion chamber temp averaged about 380 degree's. I am sure there is more variables in there like humidity ect, to make this more scientific but it is good enough for me.

This is what makes sense to me ,there is no benefit and a little less efficiency below 10 degree intake air temp and diminishing returns from 20 degree's and up. It is really a moot point as it is not worth the extra effort to keep the intake temps right between the 10-20 degree range.
Just made me feel a bit better to do some research and have some hard numbers. Too often you are told something is a fact (or read it on the internet) just to find out it was someone opinion but no actual numbers to back it up.