Greetings All,
I need your help understanding a topic that is new to me. I am planning to install a coal burning forced hot air furnace in a seperate furnace room attached to my garage/workshop. The furnace I am considering has a 20″ x 20″ plenum on top. In an effort to minimize the amount and cost of duct work and its intrusion into my shop space, I would like to route the duct from the furnace then split it into two outlets (still in the furnace room) that then discharge into the shop space above a man door on one side and above my tool box on the other side. (The shop is partitioned into two seperate rooms. One outlet would discharge into each room with the outlets being about 10 feet apart and both fed by the single 20 x 20 duct coming off of the furnace.)
With a coal furnace, I know the duct work needs to be all metal. I understand the required clearances etc. If it is relevant to the discussion, the furnace I’m considering has a 3-speed circulating fan that operates at 1400, 1600 and 1850 c.f.m.
The part I have no experience with is this…is all duct work custom made? Can I transition from the 20″ x 20″ at the furnace to a duct with a lower profile to better fit above the door and tool chest? Must I maintain the 400 sq. in. cross section in the duct work that exists on the furnace plenum? Is there a “common” rectangular duct dimension that is more cost effective than another?
Thanks in advance for your help.
Bill B.
Replies
Not to put you on the spot but you can still buy a residential coal furnace? Wow! just curious
why? What about propane or oil or NG even electric for that matter? Pellet stove? Why coal?
I know that is not what you are after defending yourself and you don't have to, I am just curious.
Wallyo
Hello Wallyo,
The fact is, my shop is a hobby enterprise. It doesn't generate any income. I live in Pennsylvania, only 30 minutes from the anthracite region. In my area, using current prices, one ton of coal produces 86,400,000 btu of heat for $205.00. The same amount of heat using propane would cost me about $2273.00 and $1185.00 for No. 2 fuel oil. I do not like being cold in my shop, so I would typically have the shop at 65 degrees or better. With the oil or propane option the goal would have to be conservation of fuel, not an acceptable level of comfort for way I like to work.
Prior to this winter, I had a nice wood stove on a brick hearth in my shop. Insulated pipe, masonry chimney, the whole nine yards. It was not a cobbled together install. I had ocassion to have my entire property evaluated to be sure I had sufficient insurance coverage. After the insurance guy left, I received a letter telling me I had seven days to get rid of the wood stove or they would cancel my homeowners policy. Period. No appeal, no explanation.
I figured they were jerking me around so I investigated changing insurance companies. Five different insurance companies refused to take me as a client as long as I had the wood stove in place.
Although the installation of a propane unit heater or wall furnace would be the least expensive in terms of equipment, I would spend far more for fuel over the long term. The propane option is only appealing in terms of its convenience. True, the coal furnace must be tended twice a day, but to me thats a small issue compared to the fuel costs. Plus, I can buy coal when the price is down during the off season.
As far as my shop goes, it is 36' x 55' with 9 ft ceilings. Well insulated and well built. I had a heat loss/cooling load calculation done by a local HVAC supply company. The results said I need 40,000 btu per hour to maintain the comfort level I prefer.
Regards, Bill B
Thanks for the education I did not realize coal was that cheap or available. Every coal unit I have ever seen has been converted to oil. And we ripped those out and went to gas. I wish I could be of help but I usually post my own heating questions.By the BY had kind of the same thing happen to a rental I manage, Insurance came did an on site review said bad roof bad concrete walks gave us three months to remedy or they would drop, they dropped us. We had better results, got another company to write it happened 5 years ago and we just did the roof and concrete work last year with no prompting.Oh the roof did not leak just looked bad even after the five years.Just another question, insurance has no problem with coal?Wallyo
Hi Wallyo,
From what I've been able to determine, the insurance company has a problem with the fact that my shop has overhead doors...they see it as a garage...that could have cars in it...that could have gas tanks...that might leak...that make fumes that might find the wood stove. You get the picture. A standing pilot light in a propane furnace apparantly doesn't bother them. Go figure.
My new plan is to build a small, seperate room on my shop with an outside entrance. That way, the furnace is not in the shop, hence my desire to understand installing duct work. I'm a pretty accomplished do-it-yourselfer but I know where my limits are.
If you would like to know more about heating with coal go to the Anthracite Forum at http://www.nepacrossroads.com There are thousands of postings there about using coal heat for the novice and experienced user alike. They're friendly folks, alot like here and at Fine Woodworking.
If for no other reason, I'd rather buy coal from hard working Pennsylvania miners than oil and gas from a middle eastern anti-USA oil cartel. And by the way...my house is geothermal. No oil or gas there either.
Take Care
Bill B
Bill you heat the house with a geothermal heat pump? If so how does that work out for you. We are thinking of that for our next house.Here in some parts of town we have hydro geothermal my sisters house is heated that way. They pay a flat fee of about 400 a year to the district to heat 2800 sf.Wallyo
Bill You may want to wander over here or repost with coal in the tile at breaktime.http://heatinghelp.com/Wallyo
Some ducts are custom ... some are 'stock sizes'. It varies ... even w/in a job. Your main 20x20 may be custom made. Your transition will likely require custom fab ... transition to standard raound duct sizes and then buy standard round duct ... either spiral or straight sheet metal. Your 20 x 20 translates into two aprox. 16" diam ducts, if my calcs are right. If you have a long run down each side ... exposed spiral ducts would be sweet.
Or you can have a custom made round duct exactly the diam. you need ... which few people would do ... just round up to the nearest diameter (assuming it's w/in reason). A sheet metal bender will do just about anything you want. Cost is reasonable and you get a good result. Don't let them talk you into radical transitions if you would like to keep air flow smooth. That is ... no square boxes w/ two 16" holes in it ... ideally a smooth 'Y' would maintain good air flow and eliminate turbulance (although the box will cost you a lot less). Pay your money, take your choice ... ain't no free lunch. Good commercial jobs generally wouldn't allow the 'box' style transition.