Harman 300i

Harman92

New Member
Oct 21, 2018
3
Pennsylvania
Could anyone tell me how to remove the firedome on the Harman 300i insert? I know the stand out models like the Harman TL300 come out through the back, but there are no bolts on the back of the 300i. Any help is greatly appreciated!
 

branchburner

Minister of Fire
Sep 27, 2008
2,755
southern NH
Welcome to the forums! Have you talked to a Harman dealer, or a tech from Harman? Not too many owners of the 300i on these forums, I don't think.
How old is the insert, and are you trying to access the firedome because the stove stopped performing well?
 

bholler

Chimney sweep
Staff member
Jan 14, 2014
20,973
central pa
Could anyone tell me how to remove the firedome on the Harman 300i insert? I know the stand out models like the Harman TL300 come out through the back, but there are no bolts on the back of the 300i. Any help is greatly appreciated!
There are bolts holding the side brick retainers in pull them and the side bricks. The the retainers for the back bricks pull them and the bricks. Then the shoe brick. Now you will see 2 metal plates on either side of the back with 2 bolts each. This is the fun part. Pull the insert out and remove the shroud so you can get to the loose nuts on the back side of those bolts so you can service the stove. It is quite honestly the stupidest design i have seen in a long time. I always bring a welder and weld those nuts fast when i do it so the stove can be serviced properly. Try the bolts first in case they changed things but the new one i installed last year was still that way.
 

Harman92

New Member
Oct 21, 2018
3
Pennsylvania
Bholler, thanks so much! That does seem like a real weird way to get to it!

Branchburner, I thought it was but I learned that I need to get a thick hot coal bed before the afterburner kicked in. My burn times however are still very low, although clean burning. I get about 5 hours till the stove is cold again if I do not reload it. That's with the air slide on the middle notch. My house will just start to warm up then it gets cold. My wife and I both work daylight so I cannot keep up with the wood while I'm working.
 

branchburner

Minister of Fire
Sep 27, 2008
2,755
southern NH
Once you are sure the AB has kicked in, you can probably lower the air supply more than you have been. Paradoxically, you might be getting less useful heat by introducing too much air into the firebox, which serves to generate a lot of heat but also might push more of that heat up the chimney.

I am not sure how to measure temps on the insert, but my cast iron Oakwood could get pretty hot even with the air control almost fully closed. Stove top temps might be 500-600f but the rear of the stove (which houses the AB) could easily push 800f. Internal flue temps can also run very high with this type of burn technology, so there is already the intrinsic potential to send more heat up the flue than with other types of stoves. If you can run the stove at lower air settings that should extend your burn times (but having well-seasoned wood is ESSENTIAL for this, and burning too-green wood is a common reason for lower heat output).

With an insert, there are other factors, too, that will determine how much of your heat production is effectively transferred into the living space (such as the efficiency of the blower, the potential for heat loss to exterior masonry, etc.). Is your insert in a fireplace that is on an exterior wall, and does it have any insulation or block-off plate to prevent heat loss into the chimney area?
 

Harman92

New Member
Oct 21, 2018
3
Pennsylvania
Branchburner,
My pipe is heavily insulated around it and blocks off anyway for heat to escape up around the pipe. I have a 6 inch liner inside of the old terracotta flue, which insulates the pipe more. The stove actually sits inside of an old heatilator (old metal box used for old fires) inside of the masonry chimney that is half inside and outside. The old heatilator is insulated around and holds in heat itself. I have tried to set the air down to the second notch and woke up with a charred log and soot covering my window. Do you think the afterburner may be going bad? The draft down the pipe is excellent. The fire roars with the damper open. It seems to run alright when I first close the damper and set the air back, but the charred log and soot threw me off. What do you think is wrong or what am I doing wrong? I have ash that sat split for a year and a half and locust wood that is seasoned 1 and a half years.
 

branchburner

Minister of Fire
Sep 27, 2008
2,755
southern NH
How old is the insert? The AB should last at least several years. Pulling it should be a last resort.

The stove will run its best when fully loaded in very cold conditions (giving stronger draft). Perhaps your experience with sooted glass was an exception, so I wouldn't let that be too decisive unless it repeats itself over and over. There is definitely a learning curve in the timing of stepping back the air supply in increments. It is trial and error, and will depend on your particular flue set up, wood supply, and individual technique with loading, etc.

From a cold start, I found that I could get a quicker coal bed by using a fair amount of smaller-diameter branch wood (2-3"). When reloading a stove that's still pretty hot, full size splits worked fine and the air could be stepped back more quickly. Its been a few years, but I think I would usually set the air back from full, to 3/4 open, to 1/2, and then to 1/4 or even fully closed. If stepped back too quickly (or wood not quite dry enough, or coal bed not deep enough) the AB would stall out. So it required some babysitting of the stove until I got a good system in place.

Has the wood been covered but still with good air flow through the stack? I found that even if I had wood cut and split over a year, some of it would not perform well depending on species and storage/weather. Red oak was especially a problem, needing at least two years. The performance of the stove was night and day when using 1-year old vs 3-year old. Like cat stoves, these with the downdraft firedome are picky about what you feed them!