USSC OAK Air Flow

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Jeremy6500

Member
Jan 22, 2021
241
Indiana
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Hello.
I am looking at making an OAK for my USSC 6500. I have been looking online and couldn’t find a kit pre-made for it. Before I start, I wanted to make sure I am understanding the air flow path since it does not have a combustion air intake in the back that I can see. I believe the air intake is through the vent/opening on the front of the ash pan. Pulls air through there, then up through the dampener, through the burn pot and heat exchanger, then back down the cavity behind the burn chamber and out through the exhaust.
Here are pics of the front vent I am talking about and also the back of the stove (in case I am missing the combustion air intake)
 

SidecarFlip

Minister of Fire
Feb 7, 2010
5,273
S.E. Michigan
You don't so the air intake must be in the front like you state. Glad mine isn't like yours. Don't care for that design as you cannot add an OAK and can only use already heated inside air. I don't like the way the combustion fan is located either with that long header to the back of the unit. Looks to me like at one time there was a draft shutter than is missing but the screw holes for it are there. Not sure how to address that as there is NO inside cabinet access to the combustion are path.

She could use a paint job as well, pretty scruffy looking.
 

SidecarFlip

Minister of Fire
Feb 7, 2010
5,273
S.E. Michigan
In this before I refurbished the 6039 picture, you can clearly see the outside combustion air inlet to the firebox as well as the nipple where the flex hose attaches to access the OAK kit... The nipple on the firebox bottom, passes completely through the heat exchange area and into the fire pot pedestal and has a cover (freeze plug) that you drill holes in to allow outside air into the burn pot pedestal.

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Yours is entirely different than mine are (both the inside unit and this one are identical).
 
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Jeremy6500

Member
Jan 22, 2021
241
Indiana
I am thinking about attaching small box to the front of the ash pan over the vent. Then use some rigid pipe that can pull apart fairly easily when I need to dump the pan. I will have to check out the screw holes you pointed out. There is a shutter on the inside of the vent that opens and closes with the draft fan pulsing.

Doesn’t appear to really be designed for an OAK, but might be able to make it happen.
 

johneh

Minister of Fire
Dec 19, 2009
4,100
Eastern Ontario
Maybe it is just me but I don't understand how air that is drawn in the ash pan is sent to the burn pot?
Is the ash pan not open to the firebox so ash can fall into it?
 

SidecarFlip

Minister of Fire
Feb 7, 2010
5,273
S.E. Michigan
I don't care for the design of yours. Building a box and having to remove the pipe every time you empty the ash pan seems to be a tedious operation to me.

If it was mine, I believe I'd modify it by cutting a 1.5" hole through the backside of the firebox/heat exchanger and the front wall where it intersects the burn pot pedestal and close off the front intake entirely but that would take some tools like a Blu-Mol hole saw and some careful extrapolation is to where exactly the burn pot pedestal is in relationship to the backside of the heat exchanger and it would have to be welded in and sealed with RTV so as not to allow any combustion gases / smoke to enter the heat exchanger area and make it rigid and of course a length of 1.5" schedule 40 steel pipe.

Your slide damper is the same as mine. I never open mine at all. My outside air provides all the combustion air my units require. In fact the only time I open mine is to dump accumulated ash into the ash pan.

I'd like to see what your burn pot pedestal looks like inside the unit. I presume it's the same as mine is (a 3 sided metal pedestal, welded to the inner wall of the heat exchanger. On mine there are 2 walls. The inner baffle wall and then the actual wall of the heat exchanger. If you did that, that would eliminate a box and piping that you'd have to remove and replace every time you emptied the ash drawer.
 

SidecarFlip

Minister of Fire
Feb 7, 2010
5,273
S.E. Michigan
Maybe it is just me but I don't understand how air that is drawn in the ash pan is sent to the burn pot?
Is the ash pan not open to the firebox so ash can fall into it?
Kind of wondering that myself. My ash pan is completely open to the bottom side of the burn chamber and my ash pan has NO securing clamps on it. Just slides into the lower compartment and sits there. My combustion air is coming from the OAK but if there is no OAK installed, the combustion air is controlled by the center slide and comes from the base of the unit, which, of course I don't allow. On mine, the base is screwed together and there are open spaces in it (which I have closed off with blue glue as I don't use room air anymore, Only outside air for combustion air.
 

SidecarFlip

Minister of Fire
Feb 7, 2010
5,273
S.E. Michigan
In this picture, you appear to have unobstructed access to the backside of the heat exchanger but you need to determine the exact location of the burn pot pedestal in relationship to the back wall of the HX before modifying anything. I see you also have a 'sister' board. I don't have that at all. My control board is a single printed circuit board. I also take it that there is no motorized 'stirrer-rouser' in the burn pot which is necessary for burning corn if that is your end game. Mine have a side mounted to the heat exchanger / firebox motor driven stirrer controlled by the brain box.

Sounds to me like a warm weather project instead of a now project.

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Jeremy6500

Member
Jan 22, 2021
241
Indiana
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Next time I shut it down to clean it I will get some pics of the burn pedestal. I do have an agitator to burn corn if I want. It is accessed through a side panel on the stove (see pics).

My ash pan has a gasket around it to help seal it.

The back wall of the burn area is double walled with about an inch between the 2 walls. It has an opening at the bottom of the 1” gap area that leads to the exhaust fan. So it appears that the combustion air flows in a big upside down U.

There is also a small plate with a few small holes in it behind the ash pan that leads to the exhaust fan blower area as well.

The 2 sides next to the burn pot have sliding doors on the bottom (you can see the handles next to the dampener handle in the front). Pull them open and the ash falls into the pan. I do the same with the dampener.

There are also sliding doors on the back bottom of the burn area wall that you can open to access the 1” gap area and clean out ash.
 

Jeremy6500

Member
Jan 22, 2021
241
Indiana
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Here is part of the exploded view of the setup. You can see where it calls for the gasket around the ash pan the the clean out door behind it.
 

Mt Bob

Minister of Fire
Oct 31, 2013
3,953
park county montana
it is an old style discontinued multi-fuel furnace, I recommend do not modify it. You might even disrupt the return air flow.
""The use of outside air is not required for this unit but
is highly recommended. If installed into a tightly
constructed home, (Mobile Home) a fresh air
opening of at least 2” diameter (150mm) into the
room where the unit is installed is required. However,
return air make-up is required for maximum heat
distribution throughout your home.""
 

SidecarFlip

Minister of Fire
Feb 7, 2010
5,273
S.E. Michigan
In reality you should have the agitator in there whether running pellets or not as the agitator helps 'push' the ash through the burn pot holes into the big slide damper area and then you pull the damper to drop them into the ash pan.

One thing I do with my burn pots is, I enlarge the burn pot holes to allow the agitator to move the ash more efficiently into the damper area and that also allows in more combustion air. All mine are enlarged nd I countersink the holes so the interior of the pot is smooth because you have to drill them from the backside.

The interior of the unit is the same as mine is with the false wall and cleanout plates but your burnpot is different than mine are.

I have 2 pots for each unit. When I clean it, the pot and agitator go in a pail of water to soak and just before I clean the stove, the pot and agitator come out, I scrape them inside with a putty knife and Scotchbrite them inside and do the agitator as well. That removes all the hard carbon. Modding it for an OAK would be quite an undertaking. Not sure if it's worth doing actually.
 

SidecarFlip

Minister of Fire
Feb 7, 2010
5,273
S.E. Michigan
I also reversed the rotation of the agitator motor so the agitator moves the burning fuel towards the front of the burnpot not the backside because when moving the burning pellets towards the back of the pot, that causes hard carbon to build up on the backside. I don't want that.
 

SidecarFlip

Minister of Fire
Feb 7, 2010
5,273
S.E. Michigan
If it was mine, I's be putting it on Facebook Marketplace or CL and selling it and getting a newer unit. The other thing I don't like is where the heated air comes out of it. I don't care for the low louvers. Mine are all high up and the room air passes over the HX from the bottom, over the top and exits high up.

Like I said (contrary to Bob's comment), you can modify just about anything but you have to decide if it's really worth the aggravation and it would take some serious fab work.
 

SidecarFlip

Minister of Fire
Feb 7, 2010
5,273
S.E. Michigan
Think I'd relocate it to a new owner myself. If I can buy a run hard and put away wet 6039 for 500 clams and get the venting too and put about150 bucks in it total, you can find one too. In fact there are 2 on Facebook Marketplace and one is in Indiana. Asking what I feel is too much money so I made an offer on both and haven't heard squat so I'll give them time to stew, I have nothing but time.

The one in Indiana is a 2 button and that board is obsolete and unobtanium but I happen to have a 4 button corn / pellet board on the shelf so no big deal.

Check out the one in Indiana and buy it if you want and you can have the 4 button board I have. Needs some work, but all of them used do.
 
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Jeremy6500

Member
Jan 22, 2021
241
Indiana
Think I'd relocate it to a new owner myself. If I can buy a run hard and put away wet 6039 for 500 clams and get the venting too and put about150 bucks in it total, you can find one too. In fact there are 2 on Facebook Marketplace and one is in Indiana. Asking what I feel is too much money so I made an offer on both and haven't heard squat so I'll give them time to stew, I have nothing but time.

The one in Indiana is a 2 button and that board is obsolete and unobtanium but I happen to have a 4 button corn / pellet board on the shelf so no big deal.

Check out the one in Indiana and buy it if you want and you can have the 4 button board I have. Needs some work, but all of them used do.

Thanks for the offer. I saw your other thread about the one you re-did. Looked kinda fun.

I’m gonna see how this one goes for the winter and then decided prior to next winter what route I want to take.
 

SidecarFlip

Minister of Fire
Feb 7, 2010
5,273
S.E. Michigan
It wasn't fun it was filthy but I modded it with everything I know from 20 years of experience with the intent of selling it, but with the way propane prices are going and free corn, I decided to keep it and put in in the shop. I'll still use propane to heat the floor but it will be turned way down with the stove in there. Of course I'm on the prowl for another cheap one but I'll refurb and mod it and sell it. New ones are retailing for 2700 bucks if you can even find one. I have a 500 buck limit and it has to be close enough to go fetch too. Now, I might pay more for a Harman if one bubbles up. I kind of like a challenge and never refurbed a Harman. Like I said, the one in Indiana is a 2 button obsolete board but I have a 4 button board that is fully functional ever though I adjusted the algorithm's to run field corn. Easy to change back.

If I can find a 'junker' with Cal Rod ignition, I put it in the shop and sell the one I just did. I'd like to have auto ignition with a WiFi t'stat so I can fire it from in the house.

Just cleaned the house one and the clean out Tee was full of ash. That happens with corn, corn is 2 times as filthy as pellets.
 

Paul197

New Member
Jan 7, 2022
6
West Michigan
I also reversed the rotation of the agitator motor so the agitator moves the burning fuel towards the front of the burnpot not the backside because when moving the burning pellets towards the back of the pot, that causes hard carbon to build up on the backside. I don't want that.
Great idea. To reverse, just switch the wires? Right?
 

Jeremy6500

Member
Jan 22, 2021
241
Indiana
I shut the stove down today to clean it and while it was off I reversed the rotation of the agitator motor. I can verify that it is done just like the auger motor that is shown in the video.

My hope is that it will help reduce the buildup of ash under the burn pot since the original rotation pushed the ash to the back of the burn pot and there is a shelf under the burn pot at the back that it lands on. With pushing the ash to the front of the burn pot the ash should drop easily into the ash pan when I slide the dampener all the way open.

The real test will be the results the next time I shut it down for a cleaning.
 
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