OAK use = Higher Fuel Consumption?

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Evan_J

Member
Dec 23, 2010
54
Southern NH
Over the last few weeks I have been reading all the various posts regarding outside air intakes. The pros & cons and different experiences, and various set-ups.

I was in a local Harman dealer a little over a week ago and asked them their take on outside air. The employee I was speaking with was very convinced that a stove would burn more fuel to achieve the same temperature using cold outside air. His logic was that by sucking cold air in for combustion, you would lower the temp of your stove, and as a result need to burn more fuel. He admitted that by using inside air for combustion it would ultimately get replaced by outside air pulled in somewhere in your house. However he felt that it was minimal, and since it was already warm it would use less fuel. He even threw the "I've been doing this for over twenty years" line at me as part of the conversation as if that was going to convince me that he was absolutely right.

Since I already had my mind made up to try OAK on my insert (installed without OAK) before talking to him, I thanked him for his time and moved on. Have any of the OAK users here, or perhaps the OAK converts seen any evidence to support his claim that using outside air cools the stove and as a result burns more pellets?
 
I burned many samples for my testing without an OAK. And then went back to using an OAK once I was done testing. I used more fuel without the OAK than when I had it connected. 2 ways I saw that the OAK helped me save fuel. 1.) was house air leaks. I didn't need to heat that air. 2.) was the damper. I was able to get a nice clean burn with less damper. I didn't send as much heat out the vent IMHO.

And the OAK debate continues!
 
Evan_J said:
Over the last few weeks I have been reading all the various posts regarding outside air intakes. The pros & cons and different experiences, and various set-ups.

I was in a local Harman dealer a little over a week ago and asked them their take on outside air. The employee I was speaking with was very convinced that a stove would burn more fuel to achieve the same temperature using cold outside air. His logic was that by sucking cold air in for combustion, you would lower the temp of your stove, and as a result need to burn more fuel. He admitted that by using inside air for combustion it would ultimately get replaced by outside air pulled in somewhere in your house. However he felt that it was minimal, and since it was already warm it would use less fuel. He even threw the "I've been doing this for over twenty years" line at me as part of the conversation as if that was going to convince me that he was absolutely right.

Since I already had my mind made up to try OAK on my insert (installed without OAK) before talking to him, I thanked him for his time and moved on. Have any of the OAK users here, or perhaps the OAK converts seen any evidence to support his claim that using outside air cools the stove and as a result burns more pellets?

I'll call BS on that BS...

Ask him how that damn air got warmed up. This is SUCH BS. Hell he has been doing it wrong for 20 years I wonder what else he is doing wrong....
 
Sounds like more of the same nonsense that many others here post about in regards to dealers and the whole OAK situation.

What a bunch of bunk...

Excuse my strong language.
 
My house is much warmer with the OAK because it is not pulling in outside cold drafts through windows etc. I am burning no more pellets with the oak than without in fact probably less. I really think some of these dealers, not all, need to learn more about these stoves.
 
Hello

Well if you really must have the best, then you can buy the pellet venting with the OAK on the outer wall. Then the air will get preheated by the pellet exhaust. That is exactly how my Direct Vent Gas Fireplace works so there maybe something to it!!

See SelKirk DT Pellet Venting

http://www.selkirkcorp.com/WorkArea/showcontent.aspx?id=8420

see pic below. Click to Enlarge
 

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In years past, people also thought the world to be flat. I've been told that debate also went on for a long time. At least this time no one is going to kill you for you beliefs! I stumbled around for a while, but now that I have out side air installed, I can't help but wonder how those without it can continue to not recognize why it is important.
 
The benefit I see that a preheated OAK gives is lack of condensation. No sweating or frosty OAK. But in reality the cooler air doesn't seem to bother my stove one bit.
 
I highly doubt that the OAK will cause you to burn more fuel but even if it did I would rather burn a bit extra than have a drafty house.
 
His logic was that by sucking cold air in for combustion, you would lower the temp of your stove, and as a result need to burn more fuel. He admitted that by using inside air for combustion it would ultimately get replaced by outside air pulled in somewhere in your house. However he felt that it was minimal, and since it was already warm it would use less fuel. He even threw the "I've been doing this for over twenty years" line at me as part of the conversation as if that was going to convince me that he was absolutely right.

Yup total bs I have looked into oak kits for a while and finally put one in a couple days ago and what a difference it makes. The air comes into my Harman wood stove on the back and circles the ash box to get warmed up before entering the firebox. I am getting much better heat and burn times because of the oak kit. We looked seriously at the Harman pellet stoves when we got our new stove and most of them had the same style intake going around the heated section a little in order to warm the air up first. I am drawing air from 3' away with a 4" wide pipe to the back of the stove and it defiantly runs smoother and way hotter.

Pete
 
Lets say your flame is 1,300 (give or take)... If you use an OAK you will pull in outside air. Lets say its 10* out tonight. That air is still preheated a little coming into stove. So now its 40* when it hits the pot.

Or you can use 70* inside air.. But bring that 10* into your bedroom through your leaky windows.

So the flame will see a 30* difference. (Even this is bad logic, but you catch the drift). A flame burning well over 1,000* wont notice a 30*-50- difference in air temp. Period. Cold air is denser and brings along more oxygen for the ride to the pot (better burn and you get to keep your warm air in your house). Without an OAK you are wasting money by sending BTU's out the vent.

Someone posted how many BTU's it was (average house, with outside temp @, and an 80 CFM blower) that you wasted by not having an OAK...

I call BS too....
 
He is right, if you are heating an open barn or have the stove out in the open air. But we use the stove to heat our homes. By not having an OAK you are pulling the same equivalent of outside temp air into the living space while removing the hot air that you just paid for that is near the open intake to your stove. You will also have burn issues as you build up a vacuum in your house the longer the stove is running without an open window or door. And this will waste your fuel.

My guess is those that speak against the need of an OAK in your house stove also sell pellets.
 
I wonder how that sales guy could ever sell high efficiency gas appliances that all rely on outside air from combustion?
 
So the real question I have in these threads is... Why does it seem that every dealer is opposed to OAKs? You'd think they'd be happy to mark up the kits (which are already priced too high for what they are) and charge some more for installation. Do they want to avoid the hassle of another hole in the house? Or the spacing usually needed between OAKs and exhausts? Or another reason to get called back? Think of how much $$$ this dealer has lost in the last 20 years. It's like McDonalds not asking if you want fries with that.
 
Just look at it from a heating point of view.

The stove is going to use 100 cubic feet of air per hour (I'm using 100 as an example) If it pulls in 10 degree air from the outside through an oak that air goes into the burn chamber where it is heated with 100% efficiency to say 1100 degrees.

If you pull the same volume in through your house and your stove is say 75% efficient, it takes more BTU to heat that air to that 70 degrees before it even gets to the stove. Then you heat it from 70 to 1100 degrees in the combustion chamber at 100% efficient.

Just getting your home supplied air up to 70 degrees takes more BTUs than doing it directly in the combustion chamber.

Now add to the fact that your house has more draft than if you do have the oak and you have to run the stove warmer to compensate for the draft and there you go.

Simple logic says BS on any person who says it is less efficient with an oak.

That being said, using waste heat (going out the pipe) to prewarm the air is going to be more efficient that a seprate oak. In my situation I couldn't set that up with a zero clearance kit. Just couldn't make it work within the space I had available

Thanks guys.
 
staplebox said:
So the real question I have in these threads is... Why does it seem that every dealer is opposed to OAKs? You'd think they'd be happy to mark up the kits (which are already priced too high for what they are) and charge some more for installation. Do they want to avoid the hassle of another hole in the house? Or the spacing usually needed between OAKs and exhausts? Or another reason to get called back? Think of how much $$$ this dealer has lost in the last 20 years. It's like McDonalds not asking if you want fries with that.

Lets see they have to chage another 300 or 400 to add the oak especially on insert installs and better to get the sale they have than loose it when the dealer down the street says "nahhh you do not need it"

It is just like the realestate broker tellign the seller that they should take the deal for 300K vs waiting for a deal at 330K to them they only make another $350 on that extra 30K but they might have to wait 6 months. They do get the $4500 on the lower sale today.

Which would you do. Remember this is about food on you table?
 
Good way for dealer not to have to mess with OAK.
 
Don2222 said:
Hello

Well if you really must have the best, then you can buy the pellet venting with the OAK on the outer wall. Then the air will get preheated by the pellet exhaust. That is exactly how my Direct Vent Gas Fireplace works so there maybe something to it!!

See SelKirk DT Pellet Venting

http://www.selkirkcorp.com/WorkArea/showcontent.aspx?id=8420

see pic below. Click to Enlarge

With these combo kits, whats the chance that your stove will suck in exhaust gases through the OAK?
 
dtaylor said:
Don2222 said:
Hello

Well if you really must have the best, then you can buy the pellet venting with the OAK on the outer wall. Then the air will get preheated by the pellet exhaust. That is exactly how my Direct Vent Gas Fireplace works so there maybe something to it!!

See SelKirk DT Pellet Venting

http://www.selkirkcorp.com/WorkArea/showcontent.aspx?id=8420

see pic below. Click to Enlarge

With these combo kits, whats the chance that your stove will suck in exhaust gases through the OAK?

I was wondering the same thing. And since the exhaust gas contains less oxygen than fresh air, what effect would it have on the burn?
 
fyrfyter4 said:
dtaylor said:
Don2222 said:
Hello

Well if you really must have the best, then you can buy the pellet venting with the OAK on the outer wall. Then the air will get preheated by the pellet exhaust. That is exactly how my Direct Vent Gas Fireplace works so there maybe something to it!!

See SelKirk DT Pellet Venting

http://www.selkirkcorp.com/WorkArea/showcontent.aspx?id=8420

see pic below. Click to Enlarge

With these combo kits, whats the chance that your stove will suck in exhaust gases through the OAK?

I was wondering the same thing. And since the exhaust gas contains less oxygen than fresh air, what effect would it have on the burn?

If they are built correctly the exhaust is far enough from the fresh air intake that they will not suck the oxygen depleted other crap laden exhaust back in.

They are also likely to be resistant to penetration from the inside into the intake air jacket. But that is just a WAG on my part. Usually those folks know what they are doing and they do test that stuff.
 
Trickyrick said:
staplebox said:
So the real question I have in these threads is... Why does it seem that every dealer is opposed to OAKs? You'd think they'd be happy to mark up the kits (which are already priced too high for what they are) and charge some more for installation. Do they want to avoid the hassle of another hole in the house? Or the spacing usually needed between OAKs and exhausts? Or another reason to get called back? Think of how much $$$ this dealer has lost in the last 20 years. It's like McDonalds not asking if you want fries with that.

Lets see they have to chage another 300 or 400 to add the oak especially on insert installs and better to get the sale they have than loose it when the dealer down the street says "nahhh you do not need it"

It is just like the realestate broker tellign the seller that they should take the deal for 300K vs waiting for a deal at 330K to them they only make another $350 on that extra 30K but they might have to wait 6 months. They do get the $4500 on the lower sale today.

Which would you do. Remember this is about food on you table?

Yup - I guess I could see that. If they are competing against every other dealer not recommending them. But there are plenty of other examples of salespeople throwing in additional things at the end of a sale - extended warranty? undercoating? Sometimes the difference between a $4,000 stove installed and a $4,350 stove installed isn't so bad when your spending all that money anyway. And in this case the OP already has his stove installed. He's back looking to upgrade and they are still trying to talk him out of it. That would seem to be the best sales plan - leave it out initially to keep the cost down and then offer it down the road as a 'long-shot' to improve stove performance. I don't know, I just don't get it.
 
An OAK just makes sense. It was strongly recommended by the manufacturer, even though the dealer stated it wasn't really necessary. I can understand if the installation is a difficult one, like into a zero clearance, but most are easier than that. That Selkirk pipe makes the most sense, direct vent heaters have been doing it that way for YEARS. Their exhaust and intakes are much, much closer and they have no combustion issues, so why would it not work on a pellet stove. RT
 
Thanks all for the responses and feedback. I wasn't really expecting to find anyone here to support the dealers claim of increased fuel use, but was curious if anyone experienced anything that even remotely suggested it.

Since I didn't believe him, I continued on my way to install OAK last weekend. I used the Harman kit (so I can keep the easy docking of the insert) and then out through the ash dump all the way to outside with 3" metal. The dealer also stated it didn't use lot of air for combustion, but if I go outside I can certainly feel the air pulling in the OAK! I for one would much rather have that come from the outside.
 
I ran into the same thing when I asked the dealer about adding a OAK. My question was about all the fans blowing air out of my house (2 bath exhausts, kitchen exhaust, oil burner, pellet stove, cloths dryer). He was still against it. that seems like a lot of negative pressure.
 
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