Harman SF-250 Firebox Reducer

Harman SF-250 Firebox Reducer

PostBy: Cap On: Wed Mar 15, 2006 9:06 pm

I purchased the factory firebox reducer about 1 month ago. It's simply a 13" wide x 8" steel plate with an angle welded to the bottom of it. The angle is designed to fit between the grates to hold it in place. The kit also came with 6 large firebricks. Bricks the size of an ordinary building brick. It did not come with any instruction sheet what so ever.

The dealer told me to install the plate with the angle facing down and toward the door between the 3rd & 4th grate. And I was to stand the bricks up on end with the spare lying behind to hold the others in place. ( What a joke! ) ':!:

The problem:
This will allow about 4" of air ( or draft ) to move right on under the coal bed, thru the blank grates and into the flue. The firebox is 15" wide but the plate is only 13" wide. So I am not only losing draft behind the firebox reducing wall, but along both sides. And when I would shake down, the entire unit would rock. This is the poorest design with little or no thought provided by the engineers/designers at Harman. I mounted the unit oppsite the way the dealer suggested which blocked the draft in the rear from escaping but still lost draft on the sides. VERY FRUSTRATING ':x'
Mad I returned it with a drawing I created to show the flaws. The dealer's son agreed it could not work & refunded $80. The boss was in Salt Lake and I am glad he was, he's not very good after the sale and in an earlier conversation the previous week, swore it should work. ( Maybe he needs some training at the Harman factory ). ':twisted:'

I designed my own reducer. :idea:
Cut a 1/4" steel plate the exact width of the box. 15 3/8" wide x 8 1/2" deep or two of five grates. It rests on the back & side edges. I used the heavy bricks and stood them up, I used some standard bricks for filler behind the heavy bricks. This simple design works GREAT! The shakers do not even bump the plate. I loose no draft and can maintain an excellent coal fire. I plan on welding strips of angle which will hold the bricks in place later next week.

It's hard to believe Harman would even sell this reducer kit. There is no way it will work. But the owner/dealer claimed it will. I told his son to send the unit and my DRAWING back to Harman so *Stu the welder* can design a better reducer plate., one which will work. I wasted gas, & time with this piece of scrap metal. But my design works perfectly. And it was FREE. ':)'
Hand Fed Coal Boiler: Harman SF 250, domestic hot water loop, heat accumulator

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PostBy: MILLERTIME On: Thu Mar 16, 2006 7:33 pm

Stove/Furnace Make: Harmon
Stove/Furnace Model: Harmon sf250

PostBy: Cap On: Thu Mar 16, 2006 9:14 pm

Pictures of my homemade unit? Not this week, I have been burning. Maybe next week. Do you have the 250?
Hand Fed Coal Boiler: Harman SF 250, domestic hot water loop, heat accumulator

PostBy: Cap On: Sat Dec 02, 2006 1:31 pm

I built two different firebox reducers this season using some used & very heavy 5/8" 304 ss plate for one reducer and 3/8" c-channel for the other.

The plate measures the exact width of the SF-250 firebox 15 3/8" x 13".
15 3/8" being the width of the firebox. This reduces my stove box by 50%. I used it this year till now as the weather in the NE has been somewhat mild. I simply stack firebrick on top of the plate on it's side 2 layers high. Otherwords, I jam as much brick as tightly as possible! See 1st image below of the larger reducer. The grates when rotated do not hit the plate.

In the 2nd & 3rd image is a slightly smaller version using SS C-channel. It measures 15 3/8" x 7 1/2". This reduces the firebox by about 30%. Both modifications I am using much heavier metal than what would be required. I aquired the ss from an old air seperation plant being dismantled & scrapped.
Firebox Reducer 010.jpg
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5/8 " SS plate fitted tightly along ledge. I stack firebicks on top.
Firebox Reducer 011.jpg
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Scrap SS C-channel works well as a reducer when fitted properly
Firebox Reducer 005.jpg
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SS C-Channel fitted into firebrick loaded with firebrick.
Hand Fed Coal Boiler: Harman SF 250, domestic hot water loop, heat accumulator

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