Outside Air Kit - Oak - My research after investigating

Zebby said:

... <Breckwell> omitted a tube connecting the back panel of my stove to the firebox inlet.
<snip>
I also installed an inexpensive automotive manifold heat hose inside the stove to make the connection that Breckwell left out.

Click to expand...

I was told the "gap in the OAK path" you describe was a safety decision in case the OAK became clogged. Many trailer home installs are done with the OAK "drilled & dropped" down thru the trailer floor boards without proper critter guard. Great place to store supplies & make a nest.

Also, someone mentioned frost on the outside of the OAK tube. This is from the warm moist room air, and I solved that by wrapping foil coated pipe wrap around the flex tube. Also solved the small water puddle that would form when the frost melted. I've never heard of an OAK frosting over and blocking airflow.

It's a fact that colder air promotes combustion as it contains more o2 per unit due to density. Us hot-rodding guys know that well- we spend all sorts of money trying to cool the intake air going into our engines. With cooler, denser air, you can add more fuel (which is the important point for this argument) as well as better control detonation (which is the more important argument in the engine performance application). The ~70*F difference of intake air nor the slightly more enriched O2 content of the colder air probably have much of an impact on the firebox output temp, but a 70*F difference of air turning over in your house 10+ times a day is gonna be noticeable.

A few years ago I was installing a Harman Advance pellet stove to replace a wood stove. I got some help from my son the Mechanical Engineer. At the time we were debating the benefits of Installing an OAK. This Is what we came up with. All Measurements are rounded and approximate

House Is a 1400 Square foot 2 story cape X 8 foot ceilings = 12,000 cubic foot
Combustion blower Is 80 CFM X 60 Min. =4800 cubic feet of air moved per hour
So every 2 1/2 hours without an OAK you will be sucking all the air inside your house that you just spent big bucks to heat up and replacing It with outside air be It 20 Deg. or -20 deg. that will find all the nooks an crannies In your house.

With an OAK all the combustion air will come from the outside
Since the reason for putting In the stove was to make us roast toasty and save a few bucks the OAK was installed and the pipe wrapped with 3 In.X1/2 In. neoprene boiler pipe wrap I got at home depot.

It was also pointed out to me that all the new cars have OAKs that are ducted to bring in the cold air In front of the radiators as this air Is denser and makes more Horse Power
Jim

New Hampshire Jim said:

A few years ago I was installing a Harman Advance pellet stove to replace a wood stove. I got some help from my son the Mechanical Engineer. At the time we were debating the benefits of Installing an OAK. This Is what we came up with. All Measurements are rounded and approximate

House Is a 1400 Square foot 2 story cape X 8 foot ceilings = 12,000 cubic foot
Combustion blower Is 80 CFM X 60 Min. =4800 cubic feet of air moved per hour
So every 2 1/2 hours without an OAK you will be sucking all the air inside your house that you just spent big bucks to heat up and replacing It with outside air be It 20 Deg. or -20 deg. that will find all the nooks an crannies In your house.

With an OAK all the combustion air will come from the outside
Since the reason for putting In the stove was to make us roast toasty and save a few bucks the OAK was installed and the pipe wrapped with 3 In.X1/2 In. neoprene boiler pipe wrap I got at home depot.

It was also pointed out to me that all the new cars have OAKs that are ducted to bring in the cold air In front of the radiators as this air Is denser and makes more Horse Power
Jim

Click to expand...

As do the cold air intakes installed on my high performance '90 Stillen 300ZX Twin Turbo and '69 Vette LT 1. Unfortunately you will find that, at times in this thread, physics takes a back seat to "I found it on the internet so it must be true."

I can't wait to get an OAK installed, because cold air comes in through the bath vent like it never did before and everyone hates it. It'll have to wait until summer, because I need to drill through a brick hearth to do it properly.

I myself look at it this way, in most cases the oak is a super easy install and doesn't cost alot to put in. And what are the negative effects of having a oak, i don't for see any. I mean no chance for negative pressure inside the house, there isn't air from outside being pulled in through cracks and cool dense oxygen rich air is really good for combustion ( hence why your car pulls air from outside the engine compartment). Will the stove cause negative pressure? who knows it depends on how tight your house is and what other machines are exhausting air. I just feel the oak is a no brainier if its not to hard to install and may have positive effects with no negatives. My stove has had a oak from day one so i have no experiance without one, so to each his own i just think in my opinion its a good idea.

I also doubt that the stove not using a oak is "stealing" tons of heat from your house, but i bet the cold air being drawn in from all the cracks is affecting temperature.

Hmm With all the gear heads on this forum I was just wondering when we will see someone try to hook up a NOS fogger to there OAK for faster starts and some REAL HOT temperatures. And the bragging. My stove puts out 600 H.P. what will yours do.
Tongue In cheek

I just can't understand how people can argue against an OAK. Take heated air from the house and push it outside only to let new COLDER air in through any and every leak in the house, or take outside air and have a max of what 20* difference come out of your stove to heat your pressure equalized house? Is this really still a serious debate? HONESTLY?

What ever happened to common sense?

Lets quantify this a little bit more. If a non-OAK'd stove has a 100CFM combustion blower, that's 144,000 cubic feet of air that has to be pulled inside and heated. Let's say it's 70*F inside, and 0*F outside. 1 cubic foot of air requires 1.274 BTU to heat from 0*F to 70*F (specific heat of .0182BTU per cubic foot per degree). 1.274BTU x 144,000 cubic feet a day is 183,456 BTUs of additional heating a day, 22lbs of pellet fuel (8,250BTU/lbs), $2.78 ($5/40lb bag of pellets).

So on a cold day, a non-OAK'd stove could cost you a few extra bucks a day. Even if you go conservative and figure a 4 month heating season with half that loss ($1.50/day x 120 days) you've paid $180 extra to heat that outside air, almost an extra ton of pellets! For those of us in cold climates with longer heating seasons it's even more. That's not insignificant at all, there is really money to be saved there.

New Hampshire Jim said:

Hmm With all the gear heads on this forum I was just wondering when we will see someone try to hook up a NOS fogger to there OAK for faster starts and some REAL HOT temperatures. And the bragging. My stove puts out 600 H.P. what will yours do.
Tongue In cheek

Click to expand...

Well. . . .I DID install High Speed Bumper Bolts on mine. . . .

f4jock, Don't forget about that cheesy inline electric supercharger fan in your OAK!!

New Hampshire Jim said:

Hmm With all the gear heads on this forum I was just wondering when we will see someone try to hook up a NOS fogger to there OAK for faster starts and some REAL HOT temperatures. And the bragging. My stove puts out 600 H.P. what will yours do.
Tongue In cheek

Click to expand...

I love tuning and tweaking the pellet stove, I look at it like tuning a carburetor (or EFI now that I have a stove with digital fuel/air trims instead of damper) in slow motion, with a window into the combustion chamber. I don't have any nitrous on my stove, but once it's out of warranty I might do a little burn-plate/air flow modification - I guess that's cylinder head work in my other hobby!

SteveG518 said:

I just can't understand how people can argue against an OAK. Take heated air from the house and push it outside only to let new COLDER air in through any and every leak in the house, or take outside air and have a max of what 20* difference come out of your stove to heat your pressure equalized house? Is this really still a serious debate? HONESTLY?

What ever happened to common sense?

Click to expand...

we have a 90 yr old barely insulated 2 story house and without an Oak it would almost be pointless to have a pellet stove with no OAK.
Be glad you have one and don't fret much about those that don't... they will argue till the cows come home cause change is easier said than done. but if someone we're to put one in for free and do all the work,
many would go for it in a heartbeat.

SteveG518 said:

f4jock, Don't forget about that cheesy inline electric supercharger fan in your OAK!!

Click to expand...

And I got that special in-hopper device that increases pellet burn temperature by 200 degrees. Just screw it into the hopper and let the pellets vaporize as they pass through it! Only $19.95! (Plus processing and handling.)

F4jock said:

And I got that special in-hopper device that increases pellet burn temperature by 200 degrees. Just screw it into the hopper and let the pellets vaporize as they pass through it! Only $19.95! (Plus processing and handling.)

Click to expand...

Like the old magnet on the fuel line to straighten the fuel molecules for enhanced economy!?

All im saying is that its crazy for people to even argue about that subject.

f4jock, PS I installed that hopper device and now my girls in her bikini all winter. Worth every penny in P&H


but honestly on a serious note; yes if you want one, install one and feel the benefits. If not, leave it be and continue to spend the extra $ to heat the house. Wish I was made of money too....

I have one last comment on this OAK thread. The average air exchange rate in a standard home with closed windows and doors in this country is about half the air in the house every hour. Look it up, that's a fact. The rate is determined by the difference of tempature between inside, outside and wind speed. So air exchange is happening anyway. It's not like you heat your air and it hangs around the place. How does that effect things? I guess you can say not having an OAK would increase the air exchange rate. Perhaps we are sitting in a breeze of cold air from outside anyway and stealing a little to run our space heaters that radiate heat off the stove and the contents of the room?
If the savings was so clear there would be a hard number out there. I'm sure there a heads exploding across North America at this point. The search for truth has casualties on occasion.

Bridgeman said:

I have one last comment on this OAK thread. The average air exchange rate in a standard home with closed windows and doors in this country is about half the air in the house every hour. Look it up, that's a fact. The rate is determined by the difference of tempature between inside, outside and wind speed. So air exchange is happening anyway. It's not like you heat your air and it hangs around the place. How does that effect things? I guess you can say not having an OAK would increase the air exchange rate. Perhaps we are sitting in a breeze of cold air from outside anyway and stealing a little to run our space heaters that radiate heat off the stove and the contents of the room?
If the savings was so clear there would be a hard number out there. I'm sure there a heads exploding across North America at this point. The search for truth has casualties on occasion.

Click to expand...

Sorry but "a little" can be quantified by the capacity of the combustion blower. (See post above.) and it's more than "a little." Also, I challenge the "fact" of that much passive hourly air exchange, especially in this day of tightly insulated homes. Blower capacity and temperature differential are provable, quantifiable facts. I can EXACTLY calculate the air turnover the combustion blower causes and thus, given the temperature differential between inside and outside air and the BTU of pellets, the EXACT amount of money your lack of an OAK costs YOU. All you can quote is some nebulous average that is based on what, exactly? My house? Your house? Whose house?

Average air turnover is something that, no offense meant, you believe to be true because you read it on the internet. I'm an Engineer x2; chemical and mechanical. I deal in facts. I can prove my case. Prove yours!

SteveG518 said:

All im saying is that its crazy for people to even argue about that subject.

f4jock, PS I installed that hopper device and now my girls in her bikini all winter. Worth every penny in P&H


but honestly on a serious note; yes if you want one, install one and feel the benefits. If not, leave it be and continue to spend the extra $ to heat the house. Wish I was made of money too....

Click to expand...

burning the US Hardwoods right now..

There are multiple govement funded studies by actual scientist that show the air exchange rate in all types of buildings. Residential buildings are not sealed space. Air flows in and out at a surprising rate. There are a few exceptions and newer is generally less leaky. Every two hours all the heated air is gone in most homes. If it didn't we would need air exchangers in our home to be healthy.(some new homes do)
How do you calculate the radiant heat component in your calculations? All that hot air is heating up objects too. I use very efficient radiant heaters at work that use massive amounts of interior air and the space is very comfortable.
I just don't think it's as simple as a calculation as it seems. It defies logic to think I would cut my pellet needs by a third. I think there is a small savings but it's not clear that it is. My opinion is that the savings is overstated.
The engineers that work with me often need guidance on what to calculate not how. It's big picture thing. No offense intended here either.

Bridgeman said:

There are multiple govement funded studies by actual scientist that show the air exchange rate in all types of buildings. Residential buildings are not sealed space. Air flows in and out at a surprising rate. There are a few exceptions and newer is generally less leaky. Every two hours all the heated air is gone in most homes. If it didn't we would need air exchangers in our home to be healthy.(some new homes do)
How do you calculate the radiant heat component in your calculations? All that hot air is heating up objects too. I use very efficient radiant heaters at work that use massive amounts of interior air and the space is very comfortable.
I just don't think it's as simple as a calculation as it seems. It defies logic to think I would cut my pellet needs by a third. I think there is a small savings but it's not clear that it is. My opinion is that the savings is overstated.
The engineers that work with me often need guidance on what to calculate not how. It's big picture thing. No offense intended here either.

Click to expand...

I can factually refute every one of your arguments including the radiant heat question, which BTW, is extremely easy to rebut, but it's apparent that your mind is made up so rather than waste more of our collective time I'll just let you figure it out.

Curious about posters using the combustion blower cfm rating as the standard to calculate air exchange in a heated space.
Assuming the stove is running, the exhaust consists of products of combustion, excess air and a small amount of unburnables (ash).
All of this except the ash is expanded to a larger volume by being at a much higher temperature than the ~70 degree F indoor air used without an OAK.
I assume the air actually taken from the source to be of a smaller volume than that which the combustion blower sends out, therefore a calculation of air exchange via a hot stove should be based on intake air volume.

I know it is still a substantial amount being drawn into the firebox, and therefore taken out of the heated space, just not quite as much as the combustion fan cfm would suggest.
Anybody got thoughts on that? Is the difference between firebox intake volume and exhaust volume considered not significant? Or are people just using combustion blower cfm to simplify the discussion?

Using 20 degree cold air and 400 degree hot air, the latter seems to be greater in volume by 86% by Charles' law. V2/V1 = T2/T1 in degrees K at constant pressure. A pellet stove is not as simple as expansion of plain air, admittedly.

Zebby said:

Curious about posters using the combustion blower cfm rating as the standard to calculate air exchange in a heated space.
Assuming the stove is running, the exhaust consists of products of combustion, excess air and a small amount of unburnables (ash).
All of this except the ash is expanded to a larger volume by being at a much higher temperature than the ~70 degree F indoor air used without an OAK.
I assume the air actually taken from the source to be of a smaller volume than that which the combustion blower sends out, therefore a calculation of air exchange via a hot stove should be based on intake air volume.

I know it is still a substantial amount being drawn into the firebox, and therefore taken out of the heated space, just not quite as much as the combustion fan cfm would suggest.
Anybody got thoughts on that? Is the difference between firebox intake volume and exhaust volume considered not significant? Or are people just using combustion blower cfm to simplify the discussion?

Using 20 degree cold air and 400 degree hot air, the latter seems to be greater in volume by 86% by Charles' law. V2/V1 = T2/T1 in degrees K at constant pressure. A pellet stove is not as simple as expansion of plain air, admittedly.

Click to expand...

You have to calculate based on intake at ambient because that is the volume the blower is moving. Output = input plus a bit because as well as blower CFM you have stack draft due to heat thus you have a slight negative pressure in the firebox / stack. Volume difference us due to expansion of the same amount of air. Just takes up more space.

I second that F4jock, we're talking about intake air, at ambient, which would be the difference if you were pulling from inside vs. outside. Exhaust will be a much higher volume due to the heat. Everything was somewhat arbitrary in the air turnover calculation I laid out earlier, just food for thought, ball park figures to give a talking point and a better feel for how much of a difference we're talking about.

The argument still stands even in light of a residential structure turning it's air over every other hour without the negative pressure of an appliance on it - if you add that 100CFM pull on all those leaks you're increasing the turn-over rate by that much more.