PostBy: davebehrens On: Wed Dec 21, 2005 2:02 pm

I bought a Harman Mark II with brass trim in October 2005 for $1673. I purchased this stove because I wanted a stove that did not require any electricity to operate. The dealer advised me not to purchase the larger Mark III because 'it would blow me out of the house.' He was right. The Mark II heats my 1700 square foot ranch style home very well, keeping my living room (where the stove is located) approximately 80F to 85F.

This stove drove me nuts for the first month of cold weather during which I tried to use it (Just as the very honest dealer in Port Jervis, from whom I purchased the stove, told me it would).

I use bagged nut coal purchased from Agel Coal in Scranton, PA for $170 a ton in 50 pound bags. I purchased and transported three tons for use this year, based on my burning approximately 3 to 4 cords of wood in previous years with a DutchWest Extra Large woodstove

The stove has a six inch vent outlet into which I inserted a 22 gauge welded tee outlet with tee runs to a bottom cap (to catch ash) and a 12" length of 22 gauge 6" stovepipe to a 6" x 8" increaser to an existing eight inch single walled stovepipe 4' long to a SS insulated Metalbestos flue approximately sixteen feet high. With the exception of the tee, the flue is straight up (the safest way to install a flue, and the way to insure the best draft possible). There is no barometric or flue damper because I choose to control the draft with the amount of air I let into the stove. I have learned through the years that if the flue temp is kept above 250F, there is no back puffing. The existing flue was used with wood stoves for many years.

It's now around Christmas, and I think I have learned enough about this set up to make it work reliably, albeit I still have much to learn. Initially, the fire would go out prematurely, because I was running it much too hot by allowing too much air into it. My set up works reliably with the draft control about 3/4 to 1-1/4 turns out (flue temp approximately 250 F.), depending on the amount of heat I need.

I was not building a deep enough bed of coal, although when I filled it to the top of the firebrick, there was a build up of ash in the center of the bed that put the fire out. I now don't fill it to the top of the firebrick. And I shake hell out of it in the morning and at night. I shake it vigorously for approximately two to three minutes in one minute increments (my arm gets tired), with fresh coal and an open ash door to allow full draft. I leave the draft door open until I see it burning hot, with a flue temp approaching 500 F.

Next year, I will burn wood in this unit in cool weather. It has a firebox of sufficient size to burn small loads of 18" logs.

Email me with any suggestions for operation.

PostBy: Richard-deactivated On: Wed Dec 21, 2005 6:05 pm

I bought mine [Harman Mark II] last January. The first load of coal that I used was junk. I had a hard time keeping a fire unless I ran it extremely hot. I went through 1/2 ton in about 10 days. The next load was purchased from a different coal supplier and the difference was amazing. I load the stove twice a day and shake the grates each time. I usually only need to shake the grates a few times, maybe 10 to 15 strokes, just till some red ash falls through. This is the first time I burned anthracite coal so I really didn't know what to expect. The coal that I am using now burns very easily. I doubt that the flue temp runs much more that 220 degrees usually much less. I don't think that I have ever, even with wood, had the stack more than 500 degrees. I have never had a back draft, even in very windy conditions. I am using 14' of 8" triple wall dura-vent flue and 4' of 6" just off the stove. with only 1 elbow at the stove. I am heating close to 2500 sq ft. So far this year, I have burned about 1 1/2 cords of wood and not quite 1 ton of coal.

PostBy: Cap On: Wed Dec 21, 2005 9:33 pm

I do have the Mark III. I am trying to heat 2500 square ft plus a large basement. The 2nd floor bedrooms barely reach 62F on a 15 F night. The stove is in my basement with 2 large vents with fans pulling warm air up into 1st floor living area.

I made a modification which I believe works well. Based on the fact that I too was burning hot in the center and finding the edges of the firebox going dead even though I had some coal left, I drilled one 1/2" hole on either side of the bottom ash door. This allows better draft along the edges of the firebox. I only need to leave the brass dampner open 1/3 -1/2 turn once I get a good fire going. If I ever find the holes don't work out, I can simply install 1/2" bolts to plug up the holes.

My flue temps are anywhere from 110-140F. I do not understand why you are seeing such high flue temps. The top of the stove measures a toasty 400F when I have a nice slow steady burn going. See my images in the *pictures* thread.

I am looking to sell the Mark III for the larger SF-250.
Hand Fed Coal Boiler: Harman SF 250, domestic hot water loop, heat accumulator

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PostBy: MILLERTIME On: Wed Dec 21, 2005 10:43 pm


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

PostBy: Richard-deactivated On: Wed Dec 21, 2005 11:09 pm

I must have some exceptional coal or a very good draft. I almost never have the edges go dead. I have a register directly above the stove, which is in the basement, and have extended a piece of flex. ducting from the front vents on the stove directly up to the register. It looks funny, but does the job. I also have registers in the far bedrooms upstairs that blow air down to the basement. This seems to circulate the air very well. My electric baseboards haven't been used so far this year. [I just hope the price of hard coal doesn't go much higher] :cry:

PostBy: davebehrens On: Wed Dec 21, 2005 11:52 pm

To Cap...

The flue temp ran around 250F with my wood stove also. It drops to around 200F when I use the heat exchange blower supplied with the Harman Mark II.

You have two blowers helping the hot air rise into the second floor of your home. How are you permitting the colder air near the floor on your second floor to return to the basement to complete the air circulation?? A return path is required to provide approximate equalization of air pressure on both floors. See Richard's post.

PostBy: Cap On: Thu Dec 22, 2005 7:10 am


I do have a good return draft. The basement actually stays cool on the oppisite end of the stove. ( 40' ) I have 6 registers cut thru the floor. ( This was actually overkill on my part. ) The far registers actully release cool air back into the basement returning draft to the stove. I've tested many times with same results each. The design of my house doesn't make it easy for warm air to make it into the bedrooms. The fans I refer to are in the ceiling of the 1st foor. I have no fans pulling air to the 2nd. Not practical with my layout.

I'm asking $725. It's a Mark III. The largest of the 3 Harmon Mark series.
Hand Fed Coal Boiler: Harman SF 250, domestic hot water loop, heat accumulator

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