stoker coal furnace and radiant?

J.Scott

I have a 130k btu stoker coal furnace that heats my house with forced hot air. I also have a hot water coil for my domestic hw. I am courious if I could add a seperate hot water coil to the fire box, tied to an indirect water tank and use this water for radiant floor heat.
The radiant would be for two smaller rooms and not the primary heat in those rooms, just to keep the floors warm.

Christian Egli

An idea for re-use of hot water coil

This sounds old fashionned. How do you make domestic hot water when you don't need heat?

I'm thinking it might be worth it to use a new and seperate hot water heater (and I am guessing you must have one for the summer anyway). That way, you'll have reliable domestic hot water.

Then, use the abandonned domestic coil in the coal fire for the radiant heat. You'll get some heat for the floor. You are looking at just supplemental heat anyway, aren't you?

For the work of installing something, at least you'll get good hot water and some radiant heat as a bonus. The other way, you might just be dissapointed with all the labor. Make sure you don't do a hook-up where you get to drink the radiant hot water.

How expensive is delivered coal in your area?

J.Scott

still building the system....

This is actually the first year with my leisure line stoker in the basement. I bought it as a supliment to my elec.baseboard and propane direct vent fireplace, I haven't had the elect. on since installing. I have not tied in the water to the stove yet,I just bought the water coil when I purchased the stove.I was planning to install a used elect.water heater before my existing electric water heater to be used as a tempering water tank,{not powered} in hopes the elect. would not need to run in the winter. In the summer the elect. would be used but the entering water would be warmer from sitting in the tempering tank. I plan to add radiant heat in two rooms and I was wondering if I could heat enough water to supply the radiant. This is where I was going to add a seperate water coil looped to an indirect water tank to supply the radiant. The coil that came with the stove is only about 5'total length therefore I was concerned it would not be sufficiant just to loop the radiant through without a holding tank. Any suggestions would be great, I pay around $130 per ton delivered...probably 3 ton per season should do it.

Christian Egli

Cost of coal

At about 12000 BTU / lb and 2200 lb / ton and 130 $ / ton comes out to 0.49 $ per 100000 BTU. Not a bad deal, it's half the cost of natural gas and it is dug right here in this country. Your coal furnace sounds like an interesting proposition. Is it easy to handle? Does it smoke or stink outside?

Old time boiler makers seemed to go by the guideline that one unit of surface in contact with fire would heat ten unit of surface on a radiator. So with a 5 ft long pipe coil you could heat a 50 ft long pipe radiator. That was for steam. You plan on using water which is way colder, say half as cold as steam, then you would stretch the 50 ft into a 100 ft length. Is your coil finned? if so you need to measure the surface of the fins in addition to the surface of the pipe. These are ballpark figure. Try getting something better from the manufacturer.

Thinking that ordinary (small) water heaters are around 30000 BTU/h, and if we assume whoever built the pipe coil to do the same, then it would be as if you were trying to heat your 2 rooms with those 30000 BTU/h. It does not sound unreasonable.


Don't invest too much or make the setup too complicated. If it is disappointing, you won't have wasted too much effort and if it works good you can always improve.

As far as using the coil to help the electric heater for drinking water. Domestic water heating is not where the bulk energy is used, so your savings won't be phenomenal. Worry about not loosing electric heat through the coil when the coal fire is not on. This reverse flow would be a big waste.

Do not drink the same water that goes around in the floor heat.

Have fun. Keep us posted.