My new-found love of coal has progressed to the point where I'm trying to make a decision about a boiler to add to the home system. Stuck on selecting the right boiler. So, I have a few questions and hope I can get some guidance. Here's my situation:
I currently have a Weil McLean oil-fired boiler that I installed (hated the heat pumps) with basboard about 15 years ago. Works fine. I have three zones. House is 18 years old, about 2,400 sq ft. Open design, with big cathedral main room so lots of wasteful air space with three levels of pella windows. Insulation is pretty good. The boiler is a model 68. Tag says it is rated at 114,000 btu/hr. I use it to heat my domestic hot water, but I run this into an electric water heater. Actually have the water heater switched off. I figure I burn about 6 gal/day of oil. I also use a propane fireplace insert to get a little more heat in the main room during the evenings. All my utility gear (boiler, water heater, pump tanks and water conditoner) is in the crawl space. No room there for any more gear and it wouldn't be fun handling the coal and ashes if I had a new boiler down there.
My plan is to put a new wing on my barn, probably about 16 x 24. I'd put the boiler in there and coal storage. Run about 80 feet of insulated pipe underground and tie into the oil fired system so heat would switch to oil if we are away and the coal system is down. So, here's where I'm stuck and a few questions:
I like the AHS-130, but I got a pretty nice quote on a Harman VF3000. The AHS is probably more efficient, but I think they are both good boilers. And, the folks at AHS indicated they probably won't do much for "spring discounts" so I'm looking at a big enough price spread to tip things to the Harman. But, the BTU rating is 95,000. We did an audit when the oil system was installed, but that was long ago and I can't remember if we went with the boiler I have because it was about the smallest available at the time. So, I'm wondering--since coal is burning all the time (even at idle) do coal boilers work differently than oil, and should I be concerned that the Harman may be undersized? I know there will be some additional heat loss in the pipe between the barn and the house, but the specs indicate it won't be too bad.
The other question at this time is how much radiant heat should I expect the boiler to generate? Will it be enough to warm the boiler room? And, if so, will there be enough residual heat to provide some modest boost to the main barn area if I have a sizable opening into the barn? I have a standard garage door on the side of the barn where I would bump out for the addition. I have a stove in the main barn now. It would be real nice if the boiler added some heat when the garage door separating the main barn and addition is open. Of course, I could put another zone in the main barn area but then I think I definately would have to upsize the boiler (the barn is 30x40x12) and even the AHS 130 might be too small.
So, any thoughts?