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Discussion Starter · #1 ·
I have an insulated 20x30 workshop with 8 ft ceiling. I'm wanting to heat it to around 40-50 degrees all the time, and maybe 60 when I'm in there working. Located in Northern Michigan. What should I use? Pellet stove, coal stove, propane ventless wall heater, find an old house furnace somewhere ,etc. What do y'all think? How big? I'm thinking 60-75k
 

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Depends on the cost of electricity.

80% gas fired warehouse/unit heater is likely the way to go if the headroom is there. Size depends on how the shop is insulated, exterior surface area and more. You shouldn't need a very large unit for that space. 60-70k likely too big, but great for very fast warmups. With decent insulation i would guess the smallest available -> 40-50k or so. try an online load calc.

Furnaces are dust sensitive, unit heaters not so much because they have axial fans.

With furnaces the minimum return air temp to prevent damage is around 16c/60f. Run a fuel burning furnace too cold and the heat exchanger will rust out.

Ventless appliances should never be used long term. They may be okay for temporary heat in a well ventilated area.
 

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Cheapest 80+ furnace you can get your hands on i suppose. If you set the temp around 50-55, and hang the unit, the return "should" be warm enough. The manual is key though. A fairly short plenum with a grill on the end is usually all you will need. Even the warehouse style unit heaters will condensate if you're not careful. Condensing (90% or better) will be easier to vent the exhaust. I say cheapest, because if you keep it too cold, and not careful, you'll be hanging another sooner rather then later. (most people i know with garages away from the city don't heat at all while they're away. Obviously, no freezables can be left there)

If you can't get either of those cheaply, a ductless heat pump is the next step, but they can be more expensive. (you have Lansing in your profile, not the most north of Michigan. If you're actually closer to the northern tip of Michigan, the heat pump will struggle in the coldest few nights.)


It also highly depends on your NG/LPG/Electricity/Wood/Etc rates available to you. eg. If you get free wood, clearly that'll be the way to go, with backup heat.

Sent from my SM-G870W using Tapatalk
 

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if you go for a resi furnace get one with a stainless steel primary heat exchanger. they're few and far between now but i think amana is still using stainless.

i actually think that the 90%+ units may be better for low temp operation with the secondary heat exchanger pre-heating the air a bit before it hits the primary.

You'll also want to take combustion air from outside so any glue/finish fumes don't cause damage.

you would have to have a good filter setup as well especially if you're dealing with saw-dust.
 

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If you don't want to spend at least 50 percent of your time maintaining your heat source you'll go with gas. I would never consider a non-vented heat source. A vented wall heater with a thermopile would be my choice. No electric to operate and very little to no maintenance required.

I've been associated with hanging shop heaters and have never found one of those very handy to back up to warm the buns or dry the wet gloves.
 

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I have a 20 x 30 insulated garage with 8' walls and vaulted ceiling.
My gas furnace is 40,000 BTU's, separated combustion Reznor.
Very nice unit and runs on gas or propane.

My gas is currently disconnected and I have a small box type 240 volt heater with a built in fan. I have it set to the lowest setting and it keeps the garage approx 8* C. The funny thing is, it is rarely running when I go into the garage.

I'm sure if I need to do some work in there, it will maintain 17* C.
I had it up to 19*C when I was cutting bricks on a 5* outside air temp day but had to turn it down as it was too hot for working.

Gas in the best and most efficient, but in a pinch, a 240 volt outlet on your wall and you're good to go.
 

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pellet/wood stoves are a pain. You'll spend more time cleaning and stocking it than you will on your projects. I would go propane electric or gas depending on which is cheaper in your area.

60 to 75K is far too big. 40 will give you enough to keep it warm and a little bit extra to goose it up for a fast warming if you need.

Electric is probably more resistive to dust and a little more maintenance free but then electricity is far more expensive than gas in most places. You could go with a heat pump but you would not be able to drop the temp down more than about 62. It's worth considering though IF you don't already have gas.... you'll be paying a monthly service fee for the gas connection. If you already have gas.... then it's all probably a no brainer.... go with gas
 

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This question comes up every winter. Here's my answer. Direct vent furnace with a sealed combustion chamber so you don't have to worry about blowing yourself up. Draws air from outside for combustion. They have both natural gas and propane models. Two speed blower, very quiet, efficient, and quick recovery. I have three of these in three separate areas. One in my 24 X 24 garage attached to house. One in my 26 X 28 wood shop. And the other in my 28 X 36 auto shop with 15' high cathedral ceilings. Located in northeast Ohio. In the coldest days of winter, heats the largest shop up in about a half hour, then cycles on and off.
http://www.consumersplumbing.com/si...gn=Consumers&gclid=CLPboOurhsoCFQ-RaQodqqkL7Q
Mike Hawkins
 

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Thanks everyone, I think I'll go with a propane set up. Will a 100lb tank have enough pressure for a 40-60k BTUs?
Wikipedia: The vapor pressure in the cylinder is a function of temperature.

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Basically, at an equal temperature, the pressure in a 100 lb. bottle, a 250 gallon tank, a 500 gallon tank or a 1,000 gallon tank will be equal if the contents is equal chemically.
 

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Before deciding on the 100 lb. vertical bottle, if that's what you are considering, I might suggest more research to determine if the limited area in the bottle will maintain enough pressure in cold weather for your btu requirement. I haven't been able to locate any charts on the topic.
 

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Tank capacity has little to do with outlet pressure. You'll want to properly size the gas line, and have the proper regular set for the inlet pressure the equipment requires. For propane that's usually around 12" W.C.
My propane supplier sized the line and installed everything initially.
He may not need to size anything which would be great.
 

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In theory propane pressure is proportional to temperature, not so much the amount of propane until you run out of liquid.

The regulator drops the pressure below what's at the tank, then the regulator in the furnace's gas valve drops it further. Furnace has a input range on the nameplate.
 

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Discussion Starter · #16 ·
I already have a 100 lb bottle that's why I ask. It would be more handy with a 100 lb tank because I won't have to keep a road clear of snow going back to the shop, I can just load it in the tractor bucket and put it in the truck. I would be fine with doing this once a month if a tank would last that long
 

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It would depend on how well the garage is insulated and how cold outside actually gets. One year, you may only need 100lbs for the year, the next night be 300lbs. It's all relative. The good news however, is that the line or heater doesn't need to be changed if you decide to up/down size. Just the tank, connector, and maybe the regulator if it's a larger tank. (that's where the pros come in. I wouldn't worry about that)

Cheers!
 

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I already have a 100 lb bottle that's why I ask. It would be more handy with a 100 lb tank because I won't have to keep a road clear of snow going back to the shop, I can just load it in the tractor bucket and put it in the truck. I would be fine with doing this once a month if a tank would last that long
Before determining a heater and filling the bottle, visit with the folks that would be filling your bottle about the square inches available to off gas in your 100 lb. bottle and supplying enough pressure for the BTU requirements for your heater at given temperatures. Suppliers that's been in business for the long haul have more than like experienced this.
 

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I've fixed many of those. The brand around here is gasmac. Very reliable and does the job well. I've seen them used everywhere from small shops to large concrete block plants. Tubes will split after their life span of done, but they are easily replaceable a section at a time. The burner control side is simple as pie so not much to fail and easily fixed. (keep spares on hand if freezing is critical, as ordering can be a bit delayed)

Cheers!
 
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