Some Help on Whether to Heat DHW Via Coal or Electricity

If you are running a coal boiler and trying to decide whether or not to shut down and clean out vs. burning coal to provide DHW all through the non heating months, here is 'roughly' how it breaks down for the wife and I.

Estimated BTU's to heat DHW daily for only the two of us = 40,000 BTU's.

For electricity based DHW:
40,000 / 3,412 = 11.7233 KWH per day, which = ~356.5 KWH per month for DHW
356.5 KWH x $0.132/KWH (delivered) = $47.06/Month

For coal based DHW:
~15 lbs per day "burn rate" required for both DHW and keeping the fire going during the non-heating months
This comes to about 456 lbs. coal per average month
Price of coal here = $243/ton delivered (including tax), or $0.1215/lb.
456 lbs./month x $0.125/lb. = $55.40/month

Bottom line:
We pay a penalty of roughly $8.34 per month when heating our DHW with coal vs. electricity. Over the 5 non-heating months this comes to a total of $41.70. I believe this is a small price to pay for keeping the boiler going instead of worrying about it (and the flue pipes) rotting internally over the warm months, plus it helps keep the basement dehumidified, and I'm willing to bet that I couldn't run a dehumidifier for 5 months on only $41.70.

I guess it would depend on the situation. For starters, I have a dry basement. So dry, I had to hang a chain off my shop Vac so that static electricity did not build up. I was getting some hefty jolts. I take the stove pipe off for summer., I clean the pipe, and chimney. Block the inlet/outlet of the boiler, and stick a small cubicle heater in the boiler. The cubicle heater actually maintains warm boiler water. Just enough heat that it's like never shutting off the boiler. This will be my third year with the cubicle heater. IT WORKS GREAT! I get a break from coal all summer. Electric hot water tank works out just fine for me. I'm all plumbed for an indirect hot water tank. Some day I may hook one up only to have a never ending supply (in my case) of very hot water. By adding ball valves, the hot water would travel a lot less to bathroom #1 during winter months. I'd still shut down in summer months. The indirect would then become a tempering tank for the cold well water headed for the electric hot water tank.

Larry, what about the extra wear and tear on the coal appliance. You don't think it has any impact?

Lightning wrote:Larry, what about the extra wear and tear on the coal appliance. You don't think it has any impact?

There would be extra wear and tear to all of the moving parts and electronic switches, but I can't quantify the degree of it. The boiler doesn't fire much during the summer months. Based on its rated 24 hour input BTU's I figure our boiler eats 0.1667 lbs. of coal for each minute it is firing. And if it eats only 11 lbs per day at pure idle fire (assuming no fan run time, and no DHW used for that day) it is burning about 0.008 lbs. per minute of idling.

If we are burning 15 lbs per day of coal in the summer (as we are) that would require about 4/.1667 = 24 minutes of total firing (fan running time), and the rest of the time merely loping along.

1,440 minutes = 1 day
24 minutes x 0.1667 lbs./minute when firing = 4 lbs of coal burned
1,416 minutes of idling x 0.008 lbs./minute of idle = ~11 lbs. of coal burned
Total = 15 lbs. burned per day

And where does 0.1667 lbs. of coal burned per minute of firing come from:

If the stove was at high fire (meaning the fan is running) for an entire hour: 60 minutes x 0.1667 lbs./minute = 10 lbs.
10 lbs. per hour burned x 13,000 gross BTU's/lb. = 130,000 gross BTU's per hour. And this is the gross BTU input rating of the S-130 Coal Gun

Thanks for the detailed reply ... Sounds like wear and tear on moving parts are pretty insignificant for summer use..

On the day in January when it hit -17 degrees here we burned a record 120 lbs. That means the Coal Gun was theoretically firing (fan running) for 30 minutes out of 60 minutes on average for that day, and that is about what it sounded like to me. Plenty of capacity remaining to take on more heat demand.

I figured it out once that electric was going to cost about $50/month for hot water. Coal cost more, estimated the poundage. But, our basement is cold, damp, and most every time it rains 1/2" or more, was have a stream flowing through. So I keep it burning 24/7/365. If I had shut it off during the summer, I can guarantee it would be rusting because of the dampness. Our water table is very high here, shallow well, lake behind us and creek in the back yard.