Custom Made Water Coil Going in Harman MKII

I am planning on make two changes to my of Harman MKII. Last year was my first year heating this old log farm house with coal. The house if fairly tight, good replacement windows, attic insulation, only the doors leak some, but pretty good over all. We had the chimney built in the fall of 09, and it did a fantastic job, sucks like a hoover. I put the baro in when I installed the stove and got the manometer to really tweek things out. However, no mater where I set the baro it just lets in tooooooooooo much air. It is the right kind for coal as I bought if from the local coal, masonry, and stove supplier. The baro would let in so much air the chimney would cool and I would loose the draw and fire unless I ran the stove pretty hot. Long slow cooler burns were just not possible with the baro unless if is foiled over. Half way through the season I started to put foil over the baro most of the time. I would leave it open when things got really windy though. The foil made a hug difference in heat out put but not coal consumption, so I will keep my foil handy again this year. Near the end of the season, I was burning evening wood fires just to take the chill off when I decided to put in the manual flue damper just to see how it worked. My heat out put was greatly increased and the burn time on the wood was almost tripled. Flue was running 200 going into the wall, but the stove was running 700-800! I intend to keep working with this flue damper to see how much difference it makes with the coal. Any advice on what to look out for?

Secondly I am having a water coil made and installed in the unit, but I will do the installation of all the plumbing in the house. It is the same basic design that the factor option is accept it is not stainless and it is a larger diamter. It is one inch black schedule 40, and the elbows ( two of them ) are the weld in type like you see on commercial steam systems. The holes will be cut in the side of the stove, and a plate will be welded to the pipe where they go through the wall of the stove and will be bolted in so I can remove if needed. If it works well enough I would consider getting a stainless one made later.

The intention is to feed a radiator in the northwest corner of the kitchen, the point furthest away from the stove, hence does not really get any heat from stove. Considering what would be best for radiator in this spot, old cast iron from scrap yard, copper finned baseboard, or small copper coils with a fan. The space to get the radiator into is just under 4 feet wide and about 18" tall, under open shelf under counter top. The intention is to install a spare well expansion tank (already have this part ) on the cold return side along with a circulator, relief valve, possible auto fill valve, and set up ball valves in such a fasion as to cut off coil in stove from loop and open to outside air if needed to blow off because too hot over fire. Circulator will run constantly when stove is fired up. Depending on how this works, I would also like to maybe tie in the domestic hot water for the winter. What options are there out there for the tubing other than copper once you get 5-10 feet away from the stove? The radiator will be about a 40-50 foot run away from the stove. Also planning on leaving a piece of the supply pipe uninsulated in the corner of the basement furthest away from stove for a little heat in that corner of the basement. (will insulate if too hot down there once it gets going.)

Any advice is greatly appreciated, and all advice will be considered in over all design.

Thanks in advance to all the gang helping with this little project.

I don't know much about the hot water coil but 40-50 feet seems like a long run? At any rate I'm glad the manual pipe damper is working well for you. That's all I have on both of my coal stoves. I too can also burn a little wood in either stove so it works out better for me than a baro. Once my stoves are up and running I cut the primary air back, flick the oven switch on the range or the backpipe damper on the Herald and then cut the MPD to a 45 degree angle or better. I installed the ones with an oblong hole in the middle so I can close them all the way and still vent. Saves heat and burn time are longer.

The project was completed in Mid-October.

I went with black iron pipe as that would be the safest in the long run should there ever be a seriously hot over fire, but it does not look like that is a real concern so far. Had a bunch of bad street 90's, so I had lots of fun replacing them after the system was together and started leak testing. Anyway that all got worked out and the system is humming along just fine. I expected to need a circulator to have this work properly, but for the most part so far that as not turned out to be the case. If I use the circulator, I have to close down one of the ball valves along the way to slow the flow so that there is actual heat coming out of the unit. However, the thermal siphon, or gravity flow works beautifully. I did not design this for gravity flow at all, in fact it has several ups and down as it goes across the basement ceiling to get to the radiator in the kitchen, but there is a straight up piece of pipe that rises 4 feet from the stove. The total rise to the kitchen radiator is about 6 feet, and the total distance away from the stove is about a 55 foot run. I guess that is enough to get the flow moving, and once started it keeps it moving and seems to do just fine at the lower temps. With a 400 stove the radiator is running around 115-120, and it is keep the COLD kitchen around 66 so far compared to 55-59 last year. The stove has not really been run much over 400 yet this year, so it may turn out that I need the pump when the stove it running in the 500-700 range when things are really cold outside.

But then again, maybe not as I have eliminated the baro and gone to a MPD, and the stove is much more efficient. It gives off much more heat (heated room air is not being sucked up the chimney, and the draw is much lower for a given temp compared to the baro operation) at lower stove temps and uses so afar 25-33% less coal. Only time will tell on this one how it works out, but I will update later in the season when I see how the numbers turn out.

One side thought, I had hoped to develop enough out of the stove to maybe handle domestic hot water and the radiator. I even put in a set of unions right over the water heater to tap into later. That clearly will not work as it just does not produce that much heat with this coil in the top of the fire box. It looks like it will do one or the other, but not both. Heating the kitchen, which is the furthest room away from the stove and there is no way for the heat air to move heat to that area of the house, is what I will be happy with.