I'm looking at a system to heat mu 30x40 shop and I want to use wood as a fuel source since I live in the woods and have plenty. I don't want a wood burner inside due to space and insurance reasons. That has led me to an outdoor burner. I know there are boilers and forced air systems. I don't plan to heat all the time, just when I'll be out there a while working. I like the boiler idea because I don't have to have large duct holes through the wall but I have been wondering how long it generally takes to get the water hot and producing decent heat. It seems like a forced air system would heat up much faster. Can anyone tell me if that is the case and about how long it takes to get a boiler up to temp? I understand the amount of water makes a difference but I'm looking a rough estimates for a system to heat 1200 sf.
Boiler heat up time
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It depends on the volume of water the boiler holds. The bigger question is how are you planning to keep it from freezing if you are not there often?
Bad LP
Minister of Fire
I understand it is water volume dependent and I figure air to air will be faster for sure. I was just thinking someone here has a smaller boiler and could tell me about how long it takes to heat up from cold. I know it will have to have an antifreeze in the water, propylene glycol I assume.
brenndatomu
Minister of Fire
Hot air furnace will respond much faster than a boiler...but even that will be painfully slow to actually heat the building up...and modern wood furnaces do not like heating real cold air...you can expect a 40-50 temp rise through the furnace...so if the shop is 30*, you will have 70-80* air coming out (peak temp) of the furnace, sounds OK right? Well 80* air will take a long time to heat up that cold space and its contents!
Now, say if you had a boiler system already running to heat the house, and the shop had a line to it also, where you could go out and turn up a tstat and chuck extra wood in the boiler a few hours before you are planning to work out in the shop...that would work better.
Another issue is the heat cycling, of going from ambient outside air temps, up to 1000*+, and then back down again, its really hard on things! And doing frequent cold starts on any firebox sitting outside is a real pain!
Now, say if you had a boiler system already running to heat the house, and the shop had a line to it also, where you could go out and turn up a tstat and chuck extra wood in the boiler a few hours before you are planning to work out in the shop...that would work better.
Another issue is the heat cycling, of going from ambient outside air temps, up to 1000*+, and then back down again, its really hard on things! And doing frequent cold starts on any firebox sitting outside is a real pain!
I have a 45kw (~150Kbtu) indoor gasifier installed in an outbuilding. It charges 1000 gallons of thermal storage. Once storage temps drop to about 120f I fire the boiler to recharge to 180-185f. Boiler output feeds the top of the upper storage tank, and feed to the heat load is pulled from the same location from a separate fitting about 12" away on the top of the tank. I would say that with in 30 minutes of firing the boiler, the feed to the house has gone from 120F to 160F plus. The boiler itself probably only holds 20 gallons. The boiler water temperature at the start of a typical burn is usually around 90F (one firing per day)
maple1
Minister of Fire
Agree, half hour is a good estimate. That's what I always figure here with mine.
I'm not sure a boiler outdoors is the best fit for this. Or how they would take all those cycles from stone cold outdoor ambient to pumping heat - as opposed to how they were intended to be used, which is kept warm & heating all winter (and eating a lot of wood in the process).
Are there no other buildings close you could also heat with it? How much do you use this building?
How cold is your climate? A ductless heat pump might be a good choice, to hold a steady warmth all winter.
I'm not sure a boiler outdoors is the best fit for this. Or how they would take all those cycles from stone cold outdoor ambient to pumping heat - as opposed to how they were intended to be used, which is kept warm & heating all winter (and eating a lot of wood in the process).
Are there no other buildings close you could also heat with it? How much do you use this building?
How cold is your climate? A ductless heat pump might be a good choice, to hold a steady warmth all winter.
From my experience with Heatmaster units:
(Cold to 180) larger units take longer, smaller less time.
Grated models 30-60 minutes
G series (gasser) 1-2 hours.
Very much would depend on the brand and water volume of the individual model. As was mentioned it works best when it's heating your house, then load it up and turn on a big blower in the shop giving instant heat.
(Cold to 180) larger units take longer, smaller less time.
Grated models 30-60 minutes
G series (gasser) 1-2 hours.
Very much would depend on the brand and water volume of the individual model. As was mentioned it works best when it's heating your house, then load it up and turn on a big blower in the shop giving instant heat.
BoiledOver
Minister of Fire
The idea that you are considering, an outdoor wood boiler used occasionally, is pretty much the worst case scenario for a boiler. As others have stated for an indoor unit it will be a minimum of 30 minutes from a cold start to the boiler reaching a performance temperature. That is an indoor unit that has residual heat from the previous day.
Starting cold at 15 Fahrenheit, or lower, could possibly triple that warm up time. The fuel, water, steel, insulation and any refractory components will all need to be brought up to temp. This will take googobs of wood. And then at shutdown, there will be a huge amount of btus dissipating back to a miserable low temp as abandoned btus. Crazy expansion and contraction issue will come quickly. And enough creosote to treat railroad ties.
If you will be in the shop 5-7 days a week, ya might get a boiler to work if you cooperate with it and keep a fire 24/7. Not a full out burn but enough to keep 40 degrees indoors over night and a boost for daytime hours. For occasional times, forget it.
The ideal thing for what your described would a freestanding wood stove inside. You can find some very small units (or make your own) that take just a small footprint. Using the proper material on the walls will get you almost zero clearance. Before going with a boiler in my shop to heat the home too, I used a stove in the shop. Doesn't take much of a fire to take the chill out. Here is a link as an idea, I wouldn't buy but make my own. Maybe I would spend $400 on something similar. Or maybe a pellet stove.
www.tinywoodstove.com
Starting cold at 15 Fahrenheit, or lower, could possibly triple that warm up time. The fuel, water, steel, insulation and any refractory components will all need to be brought up to temp. This will take googobs of wood. And then at shutdown, there will be a huge amount of btus dissipating back to a miserable low temp as abandoned btus. Crazy expansion and contraction issue will come quickly. And enough creosote to treat railroad ties.
If you will be in the shop 5-7 days a week, ya might get a boiler to work if you cooperate with it and keep a fire 24/7. Not a full out burn but enough to keep 40 degrees indoors over night and a boost for daytime hours. For occasional times, forget it.
The ideal thing for what your described would a freestanding wood stove inside. You can find some very small units (or make your own) that take just a small footprint. Using the proper material on the walls will get you almost zero clearance. Before going with a boiler in my shop to heat the home too, I used a stove in the shop. Doesn't take much of a fire to take the chill out. Here is a link as an idea, I wouldn't buy but make my own. Maybe I would spend $400 on something similar. Or maybe a pellet stove.
The Dwarf 5kw Small Wood Stove - Tiny Wood Stove
The Dwarf 5kw is an efficient, compact, fully featured wood burning stove that is a perfect addition to small, non-residential, spaces less than 500sq’.
www.tinywoodstove.com
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