To OAK or not to Oak

wsar10 said:

So the theory is hot air rises, which will keep the exhaust (gases) above the OAK ?

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Yes. And keeping OAK & vent on the same side of the house will effectively cancel any wind that might blow into the exhaust.

rwreuter said:

the wall is below grade and is 8" thick of concrete......

i don't think it can be any worse than the vent or the exhaust going out the rim joist.

i am just wondering it will be safe?

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If the OAK is exiting the rim joist, you will have to bring it above the high snow level. Otherwise it should work. Just watch the equivalent length. Excessive length adds resistance to air flow.
When I installed my PDVC in the basement I went out through the concrete wall because I couldn't figure out how to clear the first joist. That necessitated an exterior rise. The exterior rise meant having two elbows outside. I used a 4" flexible aluminum duct inside so that I wouldn't have to worry about air restriction.

Just out of curiosity, what has everyone been doing when using there dryer with these air tight homes (opening a window maybe)? Why is there no way for an OAK on a dryer (a dryer pulls a lot of air)?

Reading this post I well understand the frustration of that "madcodger" .

But then I can't cook either.

If you want to be a pellet master, you must put in an OAK.

dave2112 said:

If you want to be a pellet master, you must put in an OAK.

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That would be Pellet Meister, wouldn't it?
Your idea, you choose.

We have an air vent in the main air handler that brings fresh air in from the roof.

I have not used the Oaks on any of the three stoves.

We don't get any stale odors in the house from cooking or ???? that I have seen with many homes that are tight.

Fresh air is healthy, this said, if it was -30F outside, I might want to limit the amount of it though.

I would say this, if your house is sealed up tight, by all means install the Oak, as the stove will perform better.

Working the stove against a slight negative pressure inside is bound to have undesirable effects.

Snowy

The equations and calculator on here basically do no good because we don't know the number to put in. Take my stove for example. The cfm that it can move is when it is sitting on a bench. The rating is at the end of the assembly. My stove has a manual adjustment and my fan is running at about half. Then the air it is sucking has to come through a tube then through the inside of the stove and out the vent. Now add to that I have my damper open about a half inch if that. What is my cfm? It is unknown but I would lean more towards the 8 someone mentioned then the 25, 40, or 80 that has been brought up so far. Like I said I am not for or against an oak. I am new to pellet stoves and have a lot of questions before I pop a hole in my wall. Does moisture cause issues? If I am bringing air in that is -10 instead of the room temp air it is using now does that have an effect? Does the stove cool down using air that is 80 degrees cooler?

Even at 8 cfm you're talking close to 12,000 cf per day. That's about 1/3 the volume of the house I used in my crude calculations. I think the problem is that we are talking about air infiltration that isnt noticesble because its so spread out. Imagine a hole in the wall of your house bringing in air at the rate of 8cfm.

bondo said:

If I am bringing air in that is -10 instead of the room temp air it is using now does that have an effect? Does the stove cool down using air that is 80 degrees cooler?

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If you do not want to put that cold air into the stove,,,just lay it on the floor instead of hooking to the stove. Let the stove pull room temp air in. The object is to not create a vacuum ,,,does not have to feed directly into the stove

Realtor said:

Even at 8 cfm you're talking close to 12,000 cf per day. That's about 1/3 the volume of the house I used in my crude calculations. I think the problem is that we are talking about air infiltration that isnt noticesble because its so spread out. Imagine a hole in the wall of your house bringing in air at the rate of 8cfm.

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True but there are natural air leaks in every house. I am not saying that air is not pulled in and needs to be replenished in some way. I am just curious about the other questions also to see the whole picture. Everyone wants to show me equations which is fine but what about the other questions also. If I put a 2" hole in my wall that will also allow new air to come in.

razerface said:

If you do not want to put that cold air into the stove,,,just lay it on the floor instead of hooking to the stove. Let the stove pull room temp air in. The object is to not create a vacuum ,,,does not have to feed directly into the stove

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Hmmmmm never really thought about that method. Is that something you are doing?

bondo said:

Hmmmmm never really thought about that method. Is that something you are doing?

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Yes, my oak lays on the floor beside the stove. It is easy to plug it when stove is not being used to keep cold air out too.

razerface said:

If you do not want to put that cold air into the stove,,,just lay it on the floor instead of hooking to the stove. Let the stove pull room temp air in. The object is to not create a vacuum ,,,does not have to feed directly into the stove

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My MVAE was originally done that way. It worked well except when the wind blew against that side of my house. Then a cold draft flowed across the floor. As a result I close coupled the OAK to the stove. It might work well in a less windy location, but didn't work for my location.

chickenman said:

On the multi-fuel stoves we sell we have a balanced air intake that runs in down the outer flue pipe with the exhaust running out through the inner flue. Pellets are an easy burn but other biomass need this warmed induction air to run effectively. In lab standard testing we achieved an efficiency increase from 88-95% so there is no question that a heat extracting Oak kit works. The trick is to not reduce the exhaust temp below condensing point but this is pretty easy to work out. In really cold climes, like all of you guys I guess, it can make the stove a bit harder to start but from there it is all upside. Below is a pic of a standard horizontal flue kit.
View attachment 128513

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Looks just like a standard direct vent gas heater setup.Selkirk makes a nifty setup for pellet stoves.I have wondered-yours and selkirks intake is very close together,but most stove mfg's specify a distance between them,usually 4 foot,except in vertical installs.Does this make yours and theirs illegal?Food for thought.Bob

chickenman said:

You need to remember Bob that many recommendations are made without much reference to reason. Our set ups are fully certified in Australia but I cannot speak for the US obviously. Selkirk is not a fly by night operator so I expect it is fine but don't take my word for it. We increase the intake - exhaust distances depending on the amount of air circulation and type of fuel if necessary as well.

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Will post a new thread about legallity.This ought to be good!Have a good day.

Beating a dead horse,here.Look at past threads,warmer air burns more effecient.Stop comparing stoves to auto engines esp. turbo or blower fed.Both are combustion,one slower and not contained.Stoves are not pressure fed air(they tried it,did not work well).Ever wonder why fire fighters pray for cool damp air?

Harvey Schneider said:

My MVAE was originally done that way. It worked well except when the wind blew against that side of my house. Then a cold draft flowed across the floor. As a result I close coupled the OAK to the stove. It might work well in a less windy location, but didn't work for my location.

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Do you think the amount of air going thru the OAK varies because of that wind?
I don't want to connect mine partially for that reason. I do not want the stove to get varied inputs of air due to changing conditions of wind outside. If it pulls from the room, it should be more constant. I do however, lay the end of the OAK close to the stove so that the circuit of air is close to the intake instead of drafting across the floor as yours did.

My OAK comes out on a walkout basement exit, shielded from wind, but wind can go anywhere. I have never felt any "puffing" or change in velocity thru the OAK,,, but I do not hold my hand over it 24/7 either. I just decided it makes sense to let the stove pull the air it wants instead of the OAK determining what air it receives. I think the OAK will naturally replace whatever the stove sucks in and sends up the chim.

Another thought,, my house is 2 yrs old. Code required the OAK with any chimney installation,,, so it was not my choice to put it in,,,but I am happy with it. My house is sprayed foam insulation with fiberglass over that,,, tight, tight, tight.

Also, i have wood stove, not pellet, but some things still apply.

bondo said:

The equations and calculator on here basically do no good because we don't know the number to put in. Take my stove for example. The cfm that it can move is when it is sitting on a bench. The rating is at the end of the assembly. My stove has a manual adjustment and my fan is running at about half. Then the air it is sucking has to come through a tube then through the inside of the stove and out the vent. Now add to that I have my damper open about a half inch if that. What is my cfm? It is unknown but I would lean more towards the 8 someone mentioned then the 25, 40, or 80 that has been brought up so far. Like I said I am not for or against an oak. I am new to pellet stoves and have a lot of questions before I pop a hole in my wall. Does moisture cause issues? If I am bringing air in that is -10 instead of the room temp air it is using now does that have an effect? Does the stove cool down using air that is 80 degrees cooler?

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The cfm moved by the blower can be fairly accurately estimated if the static pressure is known.
Below are some numbers for a 60cfm blower similar to that used by ESW:
60 CFM of air flow free air
47 CFM of air flow at 0.1" SP (H2O),
42 CFM at 0.2",
37 CFM at 0.3",
33 CFM at 0.4",
21 CFM at 0.5",
7 CFM at 0.6"

I believe most stoves run somewhere between 0.1 and 0.2" static pressure (somebody correct me if I am wrong on this). So for a typical stove running at full feed the volume is still fairly high, somewhere around 45 CFM. At reduced burn rates it will be somewhat lower. If you have access to some sort of manometer you can hook it to the vacuum switch port on the blower and get a reasonable idea of the throughput.
The SP measured may not represent the full backpressure the blower is seeing if you have an unusually restrictive vent system.

razerface said:

Do you think the amount of air going thru the OAK varies because of that wind?

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No, the problem with a vent into the house is that wind increases or decreases the outside pressure with respect to the house. That causes air to flow.
If the OAK and vent of the stove are on the same side of the house they see the same wind pressure and the wind can't, therefore, drive air flow.

Harvey Schneider said:

If the OAK and vent of the stove are on the same side of the house they see the same wind pressure and the wind can't, therefore, drive air flow.

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yea, I forgot again that this is a pellet stove thread, sorry.

Harvey Schneider said:

No, the problem with a vent into the house is that wind increases or decreases the outside pressure with respect to the house. That causes air to flow.
If the OAK and vent of the stove are on the same side of the house they see the same wind pressure and the wind can't, therefore, drive air flow.

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Hey harvey,figured you would know-last time had side of stove off,measured intake air speed,measured inside diameter of pipe,came up with 34 cfm,stove running at 1/2 setting(50%). Sounds about right,doesn't it?Bob

bob bare said:

Hey harvey,figured you would know-last time had side of stove off,measured intake air speed,measured inside diameter of pipe,came up with 34 cfm,stove running at 1/2 setting(50%). Sounds about right,doesn't it?Bob

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I don't really know your stove, but they don't differ all that much. The number sounds within the realm of believable. For a blower running at full speed, I would expect something on the order of 75% of it's label. Volume drops off pretty fast as speed is reduced, but there is no reason to believe that the 50% setting is anywhere near 50% of the speed. It may have been designed in an unquantified way. You know, "that seems fast enough". That approach works for most things until people start asking questions.
If you measured velocity at the center of the pipe, your number will be just a little bit high.That is because what is called the boundary layer effectively reduces the diameter of the pipe. Air at the boundary between the air and the pipe is standing still and as you move away from the wall of the pipe air velocity increases.
Measuring near the boundary layer gives results that are near impossible to do anything with.
Out of curiosity, what is the label plate rating of the blower?
I'm sure that I just added as much confusion as information. Engineers tend to do that. Ask what time it is and you'll get a dissertation on clock making.

Only have about a 1" gap between end of air pipe and back of stove where oak hose adapter is welded on,slid in my skymate,averaged out readings(I know better,ASE master)but was just looking for ball park.No blower markings on these old austrian stoves,just motor info(ebm papst).Next time I have side off I will try at full speed.Thanks.Bob

I have a thought or an addition for discussion.......
Let me draw you a mental picture, My house is essentially "L" shaped the bottom of the "L" has a basement under (concrete floors, stone wall UN-insulated ceiling or floor of "the first floor") under the latter part of the "L" which is under my kitchen is a crawl space. An opening roughly 3'X3' connects the two spaces.

This crawl space is 16'x16' stone walls no insulation with dirt floor, the center is a trench to crawl in that is probably 4ft deep (4ft from bottom of floor Joice to bottom of trench) and roughly 4ft wide, the remaining area in the crawl space is probably only 2ft from floor Joice to dirt. Most of my water lines are in this crawl space (go figure !) therefore when it is 0* outside I run my boiler once or twice a day to get some heat into the crawl space.

I am considering doing an OAK but pulling air from this space, its cold air and I think it would draw warm air from my basement into the space and maybe keep it a bit warmer....... than I do not have to worry about the thing sucking in my exhaust in the event of some type of wind situation or the wind taking from my OAK or excessive moisture from outside coming in .

any thoughts ??