Older Harmon Magnum ST8-VF8 water coil

Last year I purchased a used Harmon Magnum, well I thought it was a Magnum. The model number listed on the back is a ST8-VF8, for the most part it looks just like a Magnum, except there are some differences. The stoker grate is one piece, the front door is 3 pieces of glass instead of one, and the inside of the stove is double walled, it doesn’t have the little peaked roof over the fire. Plus I noticed in the manual that I received with it that it is only 75,000 BTU instead of the new ones being 85,000 BTU.

Now with that all out of the way! Has anyone installed a hot water coil in the stove? I am not sure how they mount but I am going to assume they have a nut on the inside and outside to hold it in place and create a seal. If I were to drill thru both layers I am not sure how I would get a nut on the inside of the outer layer, if this makes any sense.

In the picture that I am attaching from the manual (showing how to clean) you can get an idea of what I am talking about.

If you do a search on here for Hot Water Coils, You can see how many are mounted.

Coal stove as hot water heater

http://www.hilkoil.com/

http://www.therma-coil.com/

Normally, they are a kit with all the hardware to hook into the stove. They are just a loop or two and you have to drill (2) approx. 3/4-1" holes thru the side of the stove and insert the coil from the inside and then tighten up the nuts/washers to make it air tight seal where it comes thru the side of the stove and then run your plumbing to your hot water tank/pump, safety releif valves (VERY important!), etc..... spending on how far away your tank is, you may need a pump and aquastat to control it.

I kind of understand how all that works.

I tried to draw a little picture. Will it be ok to put the nuts where I have them in the picture? Will there be enough threads? I guess I could drill the inner holes large enough to let the nuts slide thru.

I would purchase a coil along the lines of the Hilkoil 18TL and drill the holes in the back of the stove if there is enough room. That way you have the unit installed in a single wall part of the stove.

If that one won't fit then try and find one that will, IMO it will be more efficient to keep the coil right over the fire and in the high heat area.

The back is no good either, the convection air comes up the back and across the top and out the front.

Having the double wall makes it much more difficult. That would probably work, since you can't get in between the air channels.

However, You just have to make sure you have a GOOD high temp seal on the nuts/Gaskets between the air flow and fire box (Inside). You don't want to leak any CO from the fire box into the air flow path.!! The stove should be under a vacuum anyway with the way draft pulls the exhaust from the stove.

reicharb wrote:The back is no good either, the convection air comes up the back and across the top and out the front.

Yeah forgot about the air plenum, but at least at that point it's only about an extra inch of distance. As WNY said if you seal it should work fine.

Yeah I don't like the idea in the back, if it would leak CO, I wouldn't want it getting pulled into the air stream. With it going thur the sides it would only leak into the exaust going to the stack.

Oh, I thought the sides were the convection air into the room.....

Here are a couple of pictures.