This is my first post. I have been lurking for a few weeks an see many refer to outside air kits. I have a Harmon Accentra that I have heating my home with for 5 years with no OAK. My unit is located on a brick hearth that that is former location of a wood stove. The hearth is on an inside wall 8' from an outside wall. I burn 3.5 tons of pellets a season to heat the top floor of my split level. I have cathedral ceilings and ceiling fan. I'm currently burning Fireside Ultras with no issues. The Harmon seems to burn anything with no problems. I set the stove on 3.5 feed rate and run at room temp of 74 deg. five years ago and that's it. I scrape the burn pot every day and give her a minor cleaning on the week end. The question is, would I benefit drilling down through the brick and running a outside air intake to the outside? I understand I'm using heated air for combustion at a cost. What would I expect to save in pellet usage? The dealer indicated that the Hamon was on of the few units that would operate without an OAK. I'm not inclined to fix something that is not broken unless there is good reason.
To OAk or not to OAK?
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Now you did it! You raised the dead!
Only Kidding, you will receive as many opinions as there are members on these boards.
I run with an OAK because, to me, it only makes sense to draw air from outside the structure instead of from some crack or uninsulated area in another room, which would essentially create a draft.
As you stated, you are using heated air for combustion too.
Bill
P.S. Welcome to the forum. A great place to be when it is cold outside!
Only Kidding, you will receive as many opinions as there are members on these boards.
I run with an OAK because, to me, it only makes sense to draw air from outside the structure instead of from some crack or uninsulated area in another room, which would essentially create a draft.
As you stated, you are using heated air for combustion too.
Bill
P.S. Welcome to the forum. A great place to be when it is cold outside!
reallyte
Feeling the Heat
I think the OAK is a benefit. Without it you are using combustion air from within the house. That creates a negative pressure is the house, thus replacing that air via the path of least resistance. ie.cracks, leaky windows etc. This creats drafts and pulls cold air into the structure. Its amazing how much air the stove actually moves. If I cover my OAK outside while the stove is running...its like placing your hand on a vacuum cleaner hose. Just my $0.02
Tonyray
Minister of Fire
Correct me if I am wrong,?
but most pellet exhaust can go straight out a foot or so like a dryer vent..
to go up like this install, it helps to get rid of smoke that would fill up your stove if there was a sudden loss of power and stove stopped running.? sorry for multiple pixs..
![[Hearth.com] To OAk or not to OAK?](https://www.hearth.com/talk/data/attachments/120/120590-08f1563eb1d0a9ba0eae60aa8a51f670.jpg?hash=tHj5seXVH- "[Hearth.com] To OAk or not to OAK?")
P38X2
Minister of Fire
With the proper test equipment, there would HAVE to be a measurable difference, and likely a significant one.
reallyte
Feeling the Heat
Outside air is ALWAYS a good idea....never a good reason not to.
That largely answers it, frankly. You have already paid to heat that air. So essentially without an OAK you are saying "Let me just take that heated air and use a blower to push it outside so that I can bring in some cold air and pay to heat that."
That would depend on the CFM of your pellet stove combustion fan and the outside temperatures. Just figure that this is the volume of ALREADY HEATED air you are pumping back outside the house, every minute your stove is on, and that every molecule of it must be REHEATED. It will not take long for the OAK to pay for itself.
I am convinced that some dealers (not the ones on this board, of course - and that's actually true for the most part) will say anything they can to sell a stove. They are either morons or liars - it's hard to tell which. But essentially almost any stove CAN burn without an OAK. It's just that none SHOULD burn without an OAK. It's not different than paying the full price for a meal when you sit down to eat it, and then paying for it again as you leave. YOU'RE PAYING TWICE FOR THE SAME THING. It's not that it's "not broke". It's that you're paying twice for the same thing - a specific volume of air heated to a specific temperature. I can think of a million analogies, but people just have to get their head wrapped around this concept: You burn pellets to heat a specific volume of air to a specific temperature. If you pump some of that already heated air out of your house and simultaneously pump in cold air to replace it (that's exactly what you're doing), you have to burn many more pellets because you are doubling (or more) the volume of air you heat.
And for what it's worth, I have one stove with an OAK and another that I stupidly allowed the dealer to install without one while I was out of town (old stove without an OAK attachment). I am going bonkers trying to figure out a way to retrofit it with an OAK, including having one fabricated if necessary. It's that important...
the reason for a vertical rise is to increase the natural "draw" of the venting (chimney). This will help to remove smoke in case of a power failure, and in my opinion a minimum 3' rise (4' better) is always a good idea. What we CAN do and what we SHOULD do are so often different... Hope that answers your question.
I use to heat my house with an Englander 25-pdvc w/oak, on those stoves there is no flapper in the air intake tube so upon a power loss it will smoke into the house. My biggest issue with the oak is when it gets cold out the oak tube tends to ice up and drip on the floor. I now have a Harman Accentra and talked to my dealer about the oak, they said I could if I wanted to but it wasn't necessary. Stove been chugging along now for over a year and no problems. Guess its up to you. Don't miss the icy air intake tube or the soggy floor.
That would be called an improperly designed or installed OAK. I don't like half-cooked chicken, either. HOW counts.
Harvey Schneider
Minister of Fire
This is from the MVAE users manual:
Outside Air
An outside air kit is recommended in all installations. The
Outside Air Kit must be ordered seperately.
Per national building codes, consideration must be given
to combustion air supply to all combustion appliances.
Failure to supply adequate combustion air for all appliance
demands may lead to backdrafting of those and other
appliances.
Outside Air
An outside air kit is recommended in all installations. The
Outside Air Kit must be ordered seperately.
Per national building codes, consideration must be given
to combustion air supply to all combustion appliances.
Failure to supply adequate combustion air for all appliance
demands may lead to backdrafting of those and other
appliances.
One thing that you may want to consider - Is your house at the proper humidity?
My thoughts are that with an OAK, you may not need to run a humidifier as much being that the cold dry air is being used for combustion and then vented back outside versus using your "conditioned" air and venting it outside and having to "condition" your air being brought in through your doors and windows. If you have excessive moisture in your home, you may want to leave your stove without the OAK as it is helping get rid of excess humidity.
My thoughts are that with an OAK, you may not need to run a humidifier as much being that the cold dry air is being used for combustion and then vented back outside versus using your "conditioned" air and venting it outside and having to "condition" your air being brought in through your doors and windows. If you have excessive moisture in your home, you may want to leave your stove without the OAK as it is helping get rid of excess humidity.
I'm having a GCi60 installed next week. The installer told me that being an insert it doesnt need an OAK. He theorized that the stove will draw air from the fire box and that the chimney cap will be sealed but not perfectly air tigh so it will serve as a source of air I'm prepared to install an oak if need be.
I don't have one on mine but I will likely get to it at some point. Keep in mind that an average house exchanges at least a third of its air every hour, and worst for older construction. This is to prevent mold and mildew, as a house needs to breathe. So with or without an oak, your paid heat is still escaping. Granted a little less.
Keep in mind there are plenty of other appliances in a house that throw inside air out. Such as your dryer and ventilation fans (bathrooms).
As others have mentioned an oak will generally have a positive impact. But I'm not sure you will be curbing your fuel consumption all that drastically.
Keep in mind there are plenty of other appliances in a house that throw inside air out. Such as your dryer and ventilation fans (bathrooms).
As others have mentioned an oak will generally have a positive impact. But I'm not sure you will be curbing your fuel consumption all that drastically.
I noticed a big difference in the temperature gradiant in the house. Stove seemed to burn the same with or without one.
Lets see metal air intake tube, outside air temp below zero at times, so what is your trick if you don't mind sharing?
heat seeker
Minister of Fire
When I see frost on mine, I just put a rag under it for when it thaws. Happens only once or twice a year, and it's only a few drops of water anyway. The rest evaporates off the tubing before it drips.
He theorizes like an idiot. Do not listen to him. And I would apologize for being so harsh, but installers and dealers should take the time to learn facts, not just "wing it". They do customers a disservice otherwise.
This is not a matter of theory. It's just physics... There is no reason to believe your insert will form a magic wall that will prevent household air from coming into your insert. Yes, some air will be pulled down the old chimney as it will not be airtight. But without an OAK, much will come from significantly larger volume of the rest of your house. The covers around the stove that fit over the fireplace opening are far from airtight and are largely decorative on many if not most inserts.
There should be required certification of installers and dealers, including this aspect of building science. Sadly, in many places there is not...
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I put a cheap disposable aluminum pan under it. Only happened once or twice that I thought it was going to drip. It gets frosty but the water evaporates at about the same rate it forms.
If it happens infrequently, heat seeker's and moey's ideas about just having something under the OAK tube to catch occasional drips works. In your climate, it would likely be useful to insulate the OAK intake duct itself (double wall pipe might be useful as well, but others from very cold climates can likely better comment on that). I believe there may be some new thimbles designed to help solve this as well, by using the heat of the exhaust to heat the incoming air a bit. For example, there are intakes that are above the exhaust pipe, which should help to some degree. I am not in a climate that cold, so have not seen them personally here.
Here is a thread from about three months ago. I believe post #4 references a Selkirk venting kit that addresses this issue via double walling, allowing the intake air to be warmed by the exhaust.
https://www.hearth.com/talk/threads/new-stove-owner-old-question.113161/
Ideally, you want two "loops" created: One that takes dry outside air, passes it through the combustion portion of the stove, and then vents it outside. No preheated (i.e., paid for) air with adequate moisture (~ 40 - 60% relative humidity) is used, and thus it is not pumped outside. The other loop takes preheated (paid for) indoor air, passes it through the side of the heat exchanger opposite the combustion area (thereby warming it), and passing it back into the room at a higher temperature, and with the same amount of moisture that it had before it was heated.
And for those who think their house is tight and that the venting of inside air via their stove "helps", IF you had a house that was so tight it needed an ERV / HRV (remember, most are not), then yes, theoretically you might be doing less damage with a pellet stove forcing this exchange. But it would still be an inefficient way to accomplish this, as it would be somewhat uncontrolled. An ERV / HRV with appropriate sensors is still likely better.
And on a side note, if Webbie is reading this: Your affiliate marketing is working GREAT! The banner ad above my reply box just changed to the Selkirk vent ad right after I used another window to find the thread above!
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