Just Bought Used Harmon Mark II

Thanks so much for everyone's good input! @uglysquirrel: I appreciate the technical breakdown, and will look more into the mortgage / "unconventional" heating system situation. How ridiculous, but not unexpected! If America is to kick the foreign oil habit, then some attitudes have got to change. I have a small propane stove upstairs with a thermostat I can set to 60 for a backup. It chews up some $$$ when it runs, but I'm guessing we'd have a 4-5 day window before any damage if the house was unattended in the winter. Not that I'm planning to test that theory!

When we were talking to the seller about reload times, we decided it would probably work well for us for me to load the stove in the morning and after I get home from work (long commute, sometimes long days), and she would stoke it up at noontime. They had loaded the coal in flat to just under the door with a 8-10 hour burn time -- I would think mounding it up in the middle higher would be helpful. Thanks for that!

I didn't think that adding a bigger blower to the inlet woud be much of an option, the guys who design these things (if they're good) must know the optimum CFM that can pass through it. I figure if I were to encase the top as well as the output holes, then the best thing would be to draw the heat from a point closest to the use; therefore, the duct boosters to replace the "register" covers. I'm hoping to avoid an inline blower unless I'm not getting the distribution I want.

One nice thing about the stove is the wide, thick lip of the top, which I plan to clamp the ductwork to. I haven't worked out the design, but I can see what I end up with might not be too pretty (I'm not much of a sheet metal worker). What the heck, it's in a cellar that doesn't get any visitors. I guess the biggest challenge for me here is to curve the ducting in front of the stove output holes so it blows upwards without restricting the flow too much. I don't want to be singeing the little bit of hair left on my head when I load the sucker!

I'll look more on this forum about filters, it's a very good idea. I noticed a lot of dust in the blower squirrel cage from the previous owner.

There is a guy that just did what you are talking about, It is in the venting, ducting forum, he did it with a hitzer 50-93. Also if the basement gets to warm, you could try putting a bathroom type exhaust fan in the basement and blow it up through a vent, also remember to move heat, you have to have a cold air return back to the basement to match what air blows up, this acts as a vacuum to draw the heat into a room. I am a bit skeptical of a 72k BTU stove heating a house in MAINE. I use an 80-90k BTU stove in pa. . Now I do get good burn times, I would wonder on how bad your going to get klinker issues running a stove as hot as you plan.

There is no doubt the Harman is a good stove, but I am not sure of the installation and size being enough to have the confidence to rip out the oil. If you don't have to rip out the oil, I wouldn't this season and see how the stove works before going to that extreme.

Thanks sharkman8810. My lady read this thread and says I forgot to mention, or didn't make clear enough, a few things. Maybe this will explain why I'm being extreme.

We're replacing the brick chimney with a metalbestos one that we inherited. We're not allowed to share it between two appliances. Her brother has oil and wood, unplugs one and plugs the other in at different points during the winter. That sounds like no fun for me!

We heated the house last year primarily with the pellet stove, but she'd kick on the furnace manually early morning sometimes because the floors were cold in the dining room, though no problem with the air temp. The coal stove being placed directly under her computer chair should help a lot with that.

On the coldest days we ran our Athens pellets (not the best quality) on 4 out of 5, so I think we were pumping out 30,000 BTU from that. I'd try in on 5 once in a while, but I didn't like how hard the combustion fan sounded like it was working or how fast the ash would pile up.

We're installing a box woodstove in the living room where the pellet stove is now. We also have a propane stove in the dining room, which we don't want to have to use.

She's nervous about having the oil storage tank so near the coal stove. We have a very small part of the cellar that has a floor and 6.5' clearance. The oil furnace itself is right where we want to put the coal stove anyway.

Sharkman, I'm not sure but I think I found the thread you were talking about
Modified Stove With Ducting

That's great! I'll probably use that setup, since it looks like stock parts, but add a bit more metal to enclose the entire top as well. This whole thing will be sitting right under the existing ductwork so we're not talking a lot more metal anyway.

Have two large cold air returns from the main part of the house, but the living room is a recent addition that doesn't have one. I'm unsure that adding one from that area would do much good, though, as we're not talking about a lot of air flow that's needed by the little blower on the Harmon. I might have to add a duct with an inline fan under the addition to blow cold air back towards the main house. Experimentation is what keeps these projects fun!

The previous owner ran this stove without a damper, nor is there any mention of it in the manual. My planned layout is a short horizontal pipe going to a tee (for easy cleanout), then straight up the chimney.

Would this ever make sense to have a barometric or manual damper in this setup?

jimcooncat wrote: I'll look more on this forum about filters, it's a very good idea. I noticed a lot of dust in the blower squirrel cage from the

Hi,
You are right on about the flyash being drawn into the air pump, blown through the heat collection chamber and out the front of the stove. The Mark II has virtually no air filter at these points so whatever flyash is in the air is drawn in and blown back out. I didn’t realize this until this past winter. I was willing to put up with the flyash in exchange for the heat and energy savings; not anymore, I know enough about burning coal now that I know I can do something about it.

So I have been thinking about it a lot. I don’t have the expertise or facilities available to me to build or attach a filter box so I intend to cut some pieces of furnace filter to fit and attach them over the pump and air vents with magnets. I am a little concerned about the heat the stove generates and its impact on the filter material so I’ll be particularly mindful of that when I finally buy something. My bottom line is that I have nothing there now so anything I do will be an improvement. Lisa

jimcooncat wrote:The previous owner ran this stove without a damper, nor is there any mention of it in the manual. My planned layout is a short horizontal pipe going to a tee (for easy cleanout), then straight up the chimney.

Would this ever make sense to have a barometric or manual damper in this setup?

I think it always makes sense to put a barometric damper on a coal stove. After I added one in my third season, I noticed a huge increase in my burn times. My personal best burn time is 37 hours with burn time left on the fire when I returned from a weekend trip. I also experienced a decrease in the amount of coal I was using - going from an average of 40lbs a day to 30. I ended up with left over coal at the end of the season instead of having to run out and get more as I did the previous years. The fire burned better and I was able to not open my door as much which impacted the amount of flyash in the air. I vote yes to the barometric damper. Lisa

Would this ever make sense to have a barometric or manual damper in this setup?

A baro damper is essential for this stove, the owner's manual requires one. Good luck with your purchase!

I am a little concerned about the heat the stove generates and its impact on the filter material so I’ll be particularly mindful of that when I finally buy something.

Air Conditioner "cut to fit" foam filter
Cut to size of screened inlet with scissors...
Suction of fan holds it on...
Wash or replace as needed...
Cheap and effective!
No design skills needed.
Fan stays cool enough back there no problem!

jimcooncat wrote: ... air returns ... the living room ... doesn't have one ... we're not talking about a lot of air flow that's needed by the little blower on the Harmon. I might have to add a duct with an inline fan under the addition to blow cold air back towards the main house.

That "little blower on the Harman" is a weak link in the system. The stove will produce way more heat than that blower can deliver. It's very likely you WILL need inline fans in your ducts; I think you said there already is one or more than one? I wonder what the CFM rating is for your current furnace fan compared to the sum of the inline fans?

"Air Conditioner "cut to fit" foam filter
Cut to size of screened inlet with scissors...
Suction of fan holds it on...
Wash or replace as needed...
Cheap and effective!
No design skills needed.
Fan stays cool enough back there no problem! "

Thanks for the information. I'll be sure to get some of that before I fire up the stove again. Thanks, Lisa

Get a few sheets now while it is 'in season' it heads south when the cold returns!

CapeCoaler wrote:Get a few sheets now while it is 'in season' it heads south when the cold returns!

Good suggestion! I'll head over to HD in the morning. Lisa

baro is a must, really a help especially on windy nights.

I'm starting to miss coal burning !!!!!!!!!!

b

They also sell vent filters in the winter at HD, they are 4 x 12, each is 1/8" thick, come 10 in a pack for 2-3 bucks per pack. The fiber density content seems a little more close than the air cond filter stuff suggesting this stuff may have a little more delta p drop which may restrict air more than the air cond stuff.

Good idea on the prefilter. I'll put those on the Pocono.