Englander 30NC OAK fabrication -- 2 inlets?

CenterTree

Minister of Fire
Sep 15, 2008
1,045
SouthWest-Central PA
Going to install a homemade Outside Air Kit on the basement 30NC. At first glance I thought it would be an easy straight forward job. But upon closer inspection, I noticed that besides the typical 3 inch circular inlet hole at the back of this stove, there is an additional small rectangular hole directly above the 3" hole.

I understand the one hole is for primary and the other for secondary air?? Or something like that.:confused:

My question is : While fabricating an OAK, should I include BOTH holes in the external piping or just the 3" hole. I figured out a way to make a connector that would feed the square hole down into the round pipe and then to the outside. Is all that necessary though?

I am trying to avoid the air handler from drawing combustion gases out of the stove at the low end of the burn cycle when the flue draft becomes less. Also, the stove is in the same room as the clothes dryer.

Basically , looking to stop the affect of negative pressure caused by room fans.

So, whats the deal with those TWO holes in the Englander?
 

begreen

Mooderator
Staff member
Nov 18, 2005
81,852
South Puget Sound, WA
Got a picture of the area where the OAK connects? On some stoves outside air is introduced to a plenum or in the vicinity of both intakes and not a sealed connection. The factory kit looks like it just connects to the 3" hole.
https://heatredefined.com/products/ac-oak3
 

CenterTree

Minister of Fire
Sep 15, 2008
1,045
SouthWest-Central PA
Got a picture of the area where the OAK connects? On some stoves outside air is introduced to a plenum or in the vicinity of both intakes and not a sealed connection. The factory kit looks like it just connects to the 3" hole.
https://heatredefined.com/products/ac-oak3
47574331_1997856686959798_6688070335427772416_n.jpg?_nc_cat=105&_nc_ht=scontent-iad3-1.jpg

PIC is a bit deceiving, but the round is 3 inches. The rectangular is 1"x 1.75"
 

begreen

Mooderator
Staff member
Nov 18, 2005
81,852
South Puget Sound, WA
I think I'd just connect the 3" primary air hole. Has negative pressure been an issue for this installation?
 

CenterTree

Minister of Fire
Sep 15, 2008
1,045
SouthWest-Central PA

begreen

Mooderator
Staff member
Nov 18, 2005
81,852
South Puget Sound, WA
Thanks for the link. I thought this sounded familiar. Was the return issue fixed?
 

CenterTree

Minister of Fire
Sep 15, 2008
1,045
SouthWest-Central PA
Thanks for the link. I thought this sounded familiar. Was the return issue fixed?
The HVAC company is scheduled to come this week. I told then about the issue and they seemed to doubt me. (though I am CERTAIN the new vent is bad).

I did, however, block off the vent temporarily with some magnetic vent covers one night and built another fire out of curiosity. The covers did not seal the hole 100%, but fairly good. The CO detectors did not go off audibly, but the ones with PPM readouts DID INDEED SHOW INCREASED LEVELS that night. (28-34PPM). The first night the reading were much higher ( 87). So, the proof is there.

I still have the clothes dryer to deal with, though THAT is much lesser of an issue.
 

begreen

Mooderator
Staff member
Nov 18, 2005
81,852
South Puget Sound, WA
Sounds like a plan. Basement installs can be tricky. They are commonly a negative pressure zone. In addition to these steps examine any possible air leaks upstairs.
 

CenterTree

Minister of Fire
Sep 15, 2008
1,045
SouthWest-Central PA
Thanks begreen.

Anyone else familiar with this stove and care to shed light on the OAK in regards particularly to the 2 sets of inlets (ie the rectangular hole)??
Should both holes be included in an OAK;?. From the link provided I see the factory OAK does NOT include the 2nd hole, but can it be made better or more profitable by venting BOTH inlets?
https://heatredefined.com/products/ac-oak3
 

begreen

Mooderator
Staff member
Nov 18, 2005
81,852
South Puget Sound, WA
Will the OAK intake be well above the stove? One thing to watch out for with a basement install with an OAK is a draft reversal turning the OAK pipe into a chimney.
 

blades

Minister of Fire
Nov 23, 2008
3,424
WI, Leroy
I asked the question of combining the outside intake to both the main(3" dia) and the secondary intakes. did not get a clear answer just "well it could be done type". that was about 8 years ago.
Besides these two intakes there are 2 more by where the front legs bolt on not sure what they feed - somewhere someone once said they supply the glass air wash- do not know if this is true.
 

Ludlow

Minister of Fire
Jun 4, 2018
1,374
PA
Burn a fire and block off the 3" hole. Watch for effect. Then block off the rectangular as well. See if fire will burn with just the rectangular open. Etc.
 

Highbeam

Minister of Fire
Dec 28, 2006
17,040
Mt. Rainier Foothills, WA
Blades is right. There are actually no less than four separate air inlets to this stove and the factory OAK only hooks to one of them. The other three are full throttle all the time. The holes up front are just inside the pedestal in the corners, about dime sized, and I was told they feed the doghouse air hole. Any of these four could possibly backdraft.

There are other stoves that are designed for 100% of air to be sucked through the OAK connection. My BK princess and my last stove, a hearthstone heritage, are that way.
 
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blades

Minister of Fire
Nov 23, 2008
3,424
WI, Leroy
IIRC the OAK is supposed to be lower than the intake posistion. So on a basement install to accomplish this you would need to create a supply source to satisfy that statement. From back in the 70's- Mother Earth News- supply line in connected to a sealed box located on floor. Line in should go to floor then back up and then down to box with a couple of baffles in it so it is not a direct line across to line from stove to box. This tempers the air entering the stove and breaks up moderate negative pressure that can occur from wind shear on the external to home intake. Tempering the air is the same thing those make up/ exchange air units do ( fed into the return line of conventional forced air heating system). In this case it is some what important so the stove does not have as large a differential in air temp to overcome. It is conceivable that with a large enough temperature differential that secondary combustion may not be achieved in a direct connection (say just above the stove out the sill area) as secondary air is preheated internally by the fire box - sorta like those water jacket owb where the jacket is sucking all the heat out of the fire box leading to a cold flame system. kind hard for me to explain but that is the drift of it.
 

CenterTree

Minister of Fire
Sep 15, 2008
1,045
SouthWest-Central PA
Blades is right. There are actually no less than four separate air inlets to this stove and the factory OAK only hooks to one of them. The other three are full throttle all the time. The holes up front are just inside the pedestal in the corners, about dime sized, and I was told they feed the doghouse air hole. Any of these four could possibly backdraft.

There are other stoves that are designed for 100% of air to be sucked through the OAK connection. My BK princess and my last stove, a hearthstone heritage, are that way.
OK, good info. So, if I can block off TWO of the four holes, I may be that much AHEAD of the game by at least REDUCING the amount of possible sources for back-draft?
;? I am wondering though, why does Englander sell an OAK for this particular stove when they should know that it is only fitted on ONE of FOUR air sources? Interesting design, but frustrating in my case.
 

Highbeam

Minister of Fire
Dec 28, 2006
17,040
Mt. Rainier Foothills, WA
OK, good info. So, if I can block off TWO of the four holes, I may be that much AHEAD of the game by at least REDUCING the amount of possible sources for back-draft?
;? I am wondering though, why does Englander sell an OAK for this particular stove when they should know that it is only fitted on ONE of FOUR air sources? Interesting design, but frustrating in my case.
To be legal in many states, countries, and I believe all mobile homes a stove must have an outside air hookup. It is apparently not important just how effective that hookup is.

Also marketing. Many people understand that it is always a good idea to burn outside air instead of your conditioned inside air.

Plugging holes is likely a violation of some federal emissions law so I don't think I would recommend it. I have heard that aluminum HVAC tape or magnets work well to temporarily block holes for testing purposes.

Here's my NC30 backdrafting smoke through the secondary system. It's pretty easy to do with the loading door open.
 

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CenterTree

Minister of Fire
Sep 15, 2008
1,045
SouthWest-Central PA
Will the OAK intake be well above the stove? One thing to watch out for with a basement install with an OAK is a draft reversal turning the OAK pipe into a chimney.
The OAK intake would be located through the rim joist of the house. So, it would be about 8 feet above the basement floor, or 7' from the inlet on the stove. I can leave it terminate at that level or even add some vertical outside to keep it off the snow level.

I read extensively on the AOK becoming a chimney theory. I honestly think it would be a stretch, but not impossible I guess. My thought is that if a draft reversal would ever cause heated combustion gas to come out of my air inlet hole, then I would much rather have that gas going into a long 4 inch pipe and to the outside than just being pumped out the back of the stove against the wall.
 

CenterTree

Minister of Fire
Sep 15, 2008
1,045
SouthWest-Central PA
...................


Plugging holes is likely a violation of some federal emissions law so I don't think I would recommend it. I have heard that aluminum HVAC tape or magnets work well to temporarily block holes for testing purposes.
.
No, I didn't mean I wanted to PLUG any holes in the stove. WHen I said "block off two of the four holes" I actually meant attaching those TWO holes (inlets) to the OAK. That's all I mean.

I gotta eliminate the backdraft issue from the fans (air handler and dryer) and an OAK just seemed like a way to do it. And that rectangular hole confused me.
 
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