Just bought used Harmon Mark II

$900, and the guy helped me load it! Included was all the pipe I need to get it to my stainless chimney (Metalbestos), plus 7 bags of pea coal. I'm phsyched, and actually be looking forward to seeing how it will do in a Maine winter. We're going to blow a hole in the foundation to make a bulkhead, and drag the oil tank and furnace out, then hook this new baby to the ductwork. Pellet stove we used last year (Napoleon NPS40) is going to our rental property to keep our tenant warm and able to pay us.

Any links; advice on the stove, the chimney, coal availability, ducting; testimonials welcome!

-- just doing my part to ensure America's freedom. Nice to be here -- jimcooncat

Jim, nice catch! Here is the Owner's Manual, just in case you didn't get one with the stove....
http://www.harmanstoves.com/doc/MarkSer ... l%20R2.pdf

DVC500 at last wrote:Jim, nice catch! Here is the Owner's Manual, just in case you didn't get one with the stove....
http://www.harmanstoves.com/doc/MarkSer ... l%20R2.pdf

Thanks! The seller had printed it out for me, but I couldn't find it online when I looked at that site. It was late, though.

Got any pictures of the new stove???

Sweet Deal! We've been burning a Harman Mark II for 3 seasons now and are extremely happy. We are burning 2 and 1/2 tons of nut/pea coal (range coal) yearly to a heat 1900 square feet house to an average temp of 75* here in Northern VA. Our average daily winter temperature is only 27* but last January we got down to 4*s and the stove just kept pumping out the heat; easily maintaining the 75*s inside temperature. Our natural gas back up never came on.

I think you’ll find the Harman Mark II to be an easy stove to learn to burn coal in – it’s very forgiving - but there will be a learning curve. The experience on the forum is truly amazing; check the archives and I bet all your questions will be answered there. Welcome to the forum! Lisa

jimcooncat wrote:advice on the stove

Advice? I don't know your setup or layout or size of your house, so take the following for what it's worth.

The Mark II is not really designed to go into ductwork. A lot of radiant heat comes off the sides, so presumably you would want to encase those within the ducting. If you remove your furnace, will you leave its blower in place? The Mark II blower doesn't move much air compared to the big blower in a furnace; and the air it does move is only along the back and top of the stove. Could you put the Mark II in series with the furnace -- that is, return air from the house circulates past the Mark II and then on to the oil furnace? That way you'd still have the big furnace blower to move lots of air, and the furnace burner could come on to supplement the coal if necessary, or if you go away for a few days and the coal fire dies.

Where was your pellet stove? Have you considered leaving the oil furnace in place, unchanged, and just put the Mark II in where the pellet stove sat?

lowfog01 wrote:Sweet Deal! We've been burning a Harman Mark II for 3 seasons now and are extremely happy. ... Welcome to the forum! Lisa

Thanks, Lisa! I knew there's be a learning curve, which is why I joined the forum as soon as I got it. Hearth.com's forums helped us immensely last season with our pellet stove, I'm not sure we would have survived from our dealer's "support" alone.

coalkirk wrote:Got any pictures of the new stove???

It's got a little surface rust on top and side, but that's what they make steel wool and high-temp paint for! No rust on inside or bottom, thankfully. Window's just dusty, no staining. And the firebrick didn't survive the bumpy road back home. Oh well.

rberq wrote:The Mark II is not really designed to go into ductwork. A lot of radiant heat comes off the sides, so presumably you would want to encase those within the ducting... Where was your pellet stove? Have you considered leaving the oil furnace in place, unchanged, and just put the Mark II in where the pellet stove sat?

I plan to encase the top and air outlets in the ductwork. I know there will be a bunch of radiant heat I won't capture, but I think that will be OK. We lined the cellar walls with double-bubble-foil-foil, so hopefully it will bounce around until it heats something that I want to heat (except for the floor). I imagine they sized the blower fan to the output of the stove, so I'm thinking a bigger fan would be overkill. I will be putting booster fans on the farthest outlets though. I bought a nice one (actually for my passive solar panel) that has a thermostatic control and three speeds -- works like a champ.

The situation with the pellet stove was that the floors remained cool and cellar stayed moist through part of the heating season, which I'm hoping this setup will fix. We're not scared to get rid of the furnace, but I do need to insulate all the pipework for the very unlikely occurrence that the stove goes out for a couple of days without anyone to feed it. Last year the cellar stayed at 45 degrees without the furnace on for weeks during the cold season, and we had two good snaps of -10 temps outside.

We've got a small cape with an addition (1500 square feet) and we've torn out whole walls to create an open feeling and air circulation throughout.

jimcooncat wrote:The situation with the pellet stove was that the floors remained cool and cellar stayed moist through part of the heating season, which I'm hoping this setup will fix.

When I installed my Harman DVC-500, the first thing my wife noticed (besides the heat) was how dry the basement was now. We even hung clothslines down there, in the same room as the stove. The cloths dried remarkably fast. The convection heat went straight up thru the uninsulated floors. How nice it was, to walk around the hardwood floors in winter, in bare feet! A luxury!

I would think you would want to build a hood or heat collection cabinet around the stove. Then put inline duct fans in. The stove you bought isnt the best model for this type of install though, it will help and save you money. A straight radiant stove with a heat collector cabinet, like the hitzer 82 or 55 F.A. models is what they make for this type of installation.

jimcooncat wrote:It's got a little surface rust on top and side, but that's what they make steel wool and high-temp paint for! No rust on inside or bottom, thankfully. Window's just dusty, no staining. And the firebrick didn't survive the bumpy road back home. Oh well.

You may want to think about putting a coat of "rust killer" on the stove before you paint it. It literally kills the rust so you never have to mess with that spot again. I use it on my RV and on my Harman Mark II. The nice thing is you don't have to sand the rusty spots to bare metal - just smooth it out and apply the Rust Killer. It dries black so it's a great undercoat. I found it on line but I'm sure auto shops would have it. Lisa

Good luck with it! (Harman builds solid stuff!)

I've had my Mk I for 5 or 6 years now. I know you'll be happy with your Mk II. As far as duct work is concerned, I had to install some at my old house. It was 1200 sq/ft on one level. Of course, the room with the stove was too hot and the bedrooms were too cold. I had a 14" x 14" sheet metal box made and installed it in the attic above the stove with just a standard HVAC vent open to the room. Then I used 6" insulated HVAC flexible ducting to a second box. In that line I had a small inline fan. Three more lines came from the second box to the bedrooms with just a 4" x 6" vent in the ceiling. As long as the doors were open(even slightly) the air would form a nice heat conveyor. The whole house was with in 5*-10* in every room.

It shouldn't take too much work to adapt your stove to your existing ducting. Just remember that air circulation is key. As long as the air has a way to get from the furthest point away from the stove back to it, then you'll be happy with the results.

I did a Harmon II in the basement for one season now and as some noted prior, I'd be pretty hard pressed to rip out my old furnace. First, if you sell your home the buyer will not be able to get a loan without a permanent "conventional" heating system. Second, you need to understand that you are married/committed to this stove pretty much every 12 hrs, shaking, ash out, coal in and if it is REALLY cold, with your basement install, you may have to really kick it into a high burn (~1.5 turns open). This suggests topping it off maybe sometimes more frequent than every 12 hrs to really keep the thing really cooking at 500-550 deg surface temp. My usual stove top temp by infrared reading was 375 to 425 to make the coal last 12-15 hrs before reload.

I'll say that with my basement stove (unfinished floor) near a stairwell and a register above the stove, the house stayed 74 deg when the weather was 20 but when it went into the single digits the house went down to 67 deg or so. This is with 1800 ft sq colonial , 6" walls with low e windows and storms.

The blower on the harman is 75 cfm and I tried blowers of higher capacity but the design of the Harman inlet (look at the back of the blower stove inlet, you'll see a plate) lends the flow of the inlet to be choked suggesting that no matter how big of a blower on the blower inlet you will not likely not get a lot more air flow out of the two front holes..more but not as much as you expect.

What I found was that the stove in the basement was a giant heat generator, even though I figure it was putting out 20k-25K BTU of heat per hour it was always on and the heat migrated up pretty nicely (with the basement door open 10-12" at night).

You may want to do some math regarding hw many lbs coal you need to burn each hour to get the rated 72K per hour with 13,200 btu per lb not considering efficiency losses. The stove holds 50-60 lbs of nut coal with teh coasl heaped into a nice mound which is what you really want. This is the ART of coal burning. :> You'll be feeding 20-30 lbs in each 12-15 hrs in the colder/coldest weather for that ~400 deg stove top temp.

Can't speak for your metal fab cover, you are likely smarter than me here, consider that any ash that is in the air from removing the ash pan, etc, may be sucked up into the house, u may need a filter. I have a hepa filter that catches the dust down stairs.

Hope this data dump helps!

Brucer