Institutional Boiler Project - advice needed

Let's say you have been asked to design an infloor radiant heat system for an institutional building new construction (in this case a church) built with concrete slab floors on grade. Seating capacity is say 200, with a wing for Sunday School rooms, and a kitchen and Hall. These would be zoned so temps could be set differently. Much of the time during the week, the thermostats would be turned down to the low 60's, and only really cranked for the weekend.

What brand and size of coal fired boiler would you recommend for this application? It would have to be an automatic stoker, capable of running up to 2 days unattended if possible. I'm in Canada, and availability of parts and service is vital also. It would also be super neat to be able to use the same floor pipes to pump ice water through to air condition the building in the summer...Perhaps a boiler and airconditioner unit side by side utilising the same piping system? This project may happen this summer. Any company reps feel free to pm me, or just post on here. Thanks in advance!

I would do a heating loss calculation using the ACCA Manual J method. Use the full edition, not the abridged edition. See: http://www.acca.org/store/product.php?pid=172
This will give you the heating BTU's needed. Then you can start looking for boilers of the appropriate size. Be sure to understand the building permit agencie's requirements. Since it will be a public building the design will likely require a licensed engineers stamp. You are a long way from selecting any boiler. My recommendation would be to hire a registered profession engineer. One mistake or an overlooked requirement will be costly.

With regard to engineer's stamps, anything we build will be done by a contractor experienced in large public buildings, and I would assume they would look after the total design/build with all permits etc. I was hoping to get some actual concrete advice as to boilers you might recommend or ones to stay clear of. There is not likely an engineer in this part of the world who has even seen a shovelful of coal...let alone a coal fired furnace or boiler. It would be the guy with the coveralls and the pipe wrench who would know about boilers and piping etc.

For size, let's pretend it is a square building 100' X 100' with an average ceiling height of 20', 10000 sq ft or 200000 cu ft. There are numerous windows and doors. What approx btu rating would be required minimum to heat this size of building if it is well insulated, assuming it was one big room? I'm not looking for specifics, just ballpark numbers, as I really know little about this type of thing. I'd rather be over sized than always chilly...

There will likely be some sort of backup, oil or natural gas. But I'm the coal guy, so there is no worry about supply, if that is what the building inspector might balk at. Who are they to say that coal is not allowable as a primary heat source? Geez...half or more of our electricity here is generated in coal fired plants...pretty reliable if you ask me.

I'd contact AHS, Axeman Anderson, EFM, for a start. I'm guessing in the ball park of 200K btu. I used 80K to heat an insulated concrete slab in my shop, but not to toasty warm temps.. I think at least 120K is needed to keep the slab warm enough to have a congregation warm... unless the sermon is a real fire and brimstone scorcher !! [sorry, I couldn't help myself ].

There is a lot to take into account, what is the underlying ground??? High, dry and well drained, like sand/gravel?? or is it low and damp, ocassionally soggy? Ground water will draw heat from a slab like a sponge soaks up water.. You need to put down a plastic water barrier as well as a layer of insulation under the slab, AND insulate the perimeter down to the frost line [deep in your area I bet]. This will keep the slab from loosing heat to the surrounding land.

Any of the three boiler makers above can provide 200-250 BTU boiler, most can run at lower heat settings for 2 days untended if the instalation is designed for this, a large hopper and large ashpan/ashpit. My AA260M can go 7 days on one full coal hopper, more if I wanted to raise the sides of the hopper.. the limiting factor is the ashpan... It is full after 48 hours, and will overflow if left any longer... but is doesn't cause any operational problems, I just have to sweep and vacuum up the ashes, And the full ashpan is HEAVY... I usually shovel out about 1/3 of the ash , then pick it up to dump it... Saves the back.

Once you have the heat loss/demand calculations done, and know the BTU load, then you can figure out the best boiler for the job... I'm thinking the AA260 and the EFM can have a coal hopper just as big as you want to build and load, They re both auger fed boilers. The AHS will require some special hopper setup or loading device, 'cause the hopper is gravity feed on top of the boiler.. Maybe a set of steps beside the boiler to still allow hand filling of the Hopper??

I don't know if Harman, or Keystoker make a big enough boiler for this application, the gravity feed hopper in both will requird some thought and preplanning, as well as the ashpan size. I think they are both smallish ashpans.

Hope this helps, Greg L

Coal Jockey,

I did a heat loss calculation on your pretend building using Manual J abridged edition. Not exactly what should be used, but it's free.

My assumptions:

1. Location International Falls, Minn. Winter 99% Dry Bulb temperature -23 F.
2. Square building, each wall 100 ft. wide x 20 ft. high. Block construction with R-19 cavity insulation plus R-5 board insulation.
3. Each wall has 100 sq. ft. of double pane fixed sash wood windows.
4. Roof is plywood decking on wood joists, R-38 insulation, dark asphalt shingles.
5. Floor is over enclosed craw space with R-19 insulation and a 62.8 deg difference between the inside floor and the craw space earth.
6. Doors are Metal, Polyurethane Core, 128 sq ft.

For such a building the Total Sensible Heat Loss = 214,892 BTU

See attached spread sheet output for details. ABSOLUTELY NO WARRANTY ON THE NUMBERS. No calculation was made for summer heat gain, i.e. A/C load.

wow, now if only I knew what it all meant...!

Thanks yanche. I would be guessing that windows would be aluminum frame thermal pane w/stained glass for the main nave. floor is slab on grade. But still I think it was neat the way you figured it out. So how big a boiler unit would we need??

I was looking at the Axeman Anderson Anthratube 260. and it looks like a durable outfit, I've emailed them re: Canadian sales and service or shipping. I guess they have it so you can hook up multiple units side by side if need be.

I appreciate all the input guys. Thanks.

Coal Jockey wrote:I was looking at the Axeman Anderson Anthratube 260. and it looks like a durable outfit, I've emailed them re: Canadian sales and service or shipping. I guess they have it so you can hook up multiple units side by side if need be.

I would run two A-A 130s (or whatever is needed). It may be a little pricier @ install, but it will make up for it in backup and efficiency. Most of the time you will only need one, a little one running hard will beat a big one loafing any day of the week in that regard.

Well, I'm not a licensed anything to do with heating or plumbing - so no sale there.

Does anyone know of any make of coil fired commercial boiler for this type of application who sells and services in Canada? Oil and gas fired boilers are a dime a dozen, every street has a heating place that sells and installs them, same with wood boilers.

No one is going to lay out twenty grand for a boiler and piping that cannot be serviced or repaired. No matter how economical the fuel.

Newmac sells a small coal boiler, but it is hand fired, so no deal.

Do any manufacturers or sales/service reps ever read these threads? if so I would welcome any contact.

coaledsweat, What is the cost of a single 130 model? What is the cost of a 260 ? If the difference is substantial, then perhaps another make, such as the ahs 500 mentioned would be better?

Hi CJ, compare your location, and assumptions Yanche made: Location, the coldest place in the USA. Where will your building be located??
How about the ceiling height?? the amount of insulation in the walls and ceiling? with your hot floor you don't need to heat the air as hot for creature-comfort, and the heat loss is less.

With the assumptions Yanche made which are about as heat-costly as possible, he came up with ~215K btu required.. So I'd say an AA 260 would do the job well.. Or two AA130's. the cost of two 130's is around $12K us dollars, an AA 260 is around $8500.

I wouldn't worry about servicing the boilers, if you can change a tire on a car, and know which end of a screwdriver to grab, and which end does the work, you could service the boilers.

Greg L

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Well, our dollar is pretty much par. So it would be the shipping and extra stuff that would double the cost. I know that I looked at a wood outdoor unit 7 or 8 years ago and all the extra stuff and circulating pumps just about doubled the price.

If I were buying this for myself I would certainly do the maintenance myself. If you've ever dealt with committees and so forth you will soon realise that they need three or four competing quotes on prices, extended warranties, options, service plans etc, etc ad nauseum. and then the middle aged women on the committee hem and haw about things they have no clue about and take a vote and the decision is made. That is how ess aitch eye tee happens on volunteer committees.

So 8500 and change for the 260 or 1200 or so for the two 130's. If one could purchase them. Axeman Anderson have not yet returned my email about Canadian availability. Hopefully they reply. There is a part of me that is ready to accept that in the end we'll have a thirsty Buderus thundering away pissing loonies down the drain and out the stack... While some Arab sheik sits counting his petro dollars to blow up more of our soldiers...