Heater Sizing

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I have a room in my pole barn that I am building for my man cave. It is 14 x 20. I have R19 insulation in the walls and R38 in the floor and ceilings. It is on the second floor and the ceiling is about 7' tall. I am located in central Ohio. How would I figure out what size heater I need to make it relatively comfortable to work in when it is cold out. Near as I can figure I need about 14,000 BTU, do you think this is correct? Thanks,
R
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Roanin wrote:

I think you take (square feet of surface X deltaT inF )/R-value = btu/hr
http://www.pexuniverse.com/content/calculate-heat-loss
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Thanks Mike I will check that site out.
R
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wrote:

Sounds a bit light to me. How did you come up with that number? Thee are some calculators on line that will help you. You have to include window area also for a really accurate number.
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wrote:

'work in'? Man cave or workshop? To me, 'Man cave' implies' warm enough to lounge around-- workshop would want to be cool enough so you don't sweat all over your work.
You need to figure in windows, doors, and 'infiltration'.
Then decide whether you're going to keep it warm all the time, or if you're going to go out there when it is -20F & hope to have a party in an hour.
Jim
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Actually it is just a room that I want to make comfortable when I go out there to do whatever. Probably will not be out there when it is -20F. Who knows what I will use it for. Plans are always changing.
R
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-snip-

In that case- throw out all the BTU factors and whatnot, and put a torpedo heater there to bring you up to comfort level. [100k wouldn't be overkill]
Or look into infra-red heating. Then you need to pay more attention to the surfaces in the room-- color and material.
You don't say what kind of fuel you'd prefer. That might affect how much it pays to just over-build to capacity.
Jim
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I don't know about 100K BTU, which is enough for a whole house. But I would factor in that you most likely want it to be able to raise the temp quickly. Scenario being you keep it off or at a low temp and turn the temp up on the random times you decide to use it. That's a different usage than what the standard calculations are based on. For example, if you size a whole house system, you should wind up with BTUs that are slightly more than required to maintain the temp on the coldest day. However, with that sizing, if you let the house get down to 40, it would take a very long time to heat it back up, even when it's only 30 outside. So, I think you need to be large enough to heat the place quickly. On the other hand, you don't want it so large that there are short cycles, wide swings, etc.
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On 12/8/2011 8:37 AM, snipped-for-privacy@optonline.net wrote:

Trader4 has a very good point. I have a pretty large basement that is divided into 3 rooms, insulated from the house above. I use one room, 25' x 16' with 9' ceiling, as a workshop. In the winter it only gets to about 60 degrees no mater what the outside temperature is. So, I run a 2 electric heaters. It takes about 3 hours of run time, plus my body heat, plus the added lighting heat, to raise the temperature about 5 or 6 degrees. As the furnace/heat pump is in that room, I plan on adding a zone for that room. BTW, all the ducts and the furnace itself are pretty well insulated. Adding the zone only requires a thermostat and a 24VAC damper and maybe a little duct work, as the zone controller is there and it has 2 spare ports. But, I would have the whole 100K + BTUs available for quicker heating. The furnace is propane, so I suspect when there is a large difference between the room temperature and the set point, it would kick in the propane.
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-snip-
You made me look. I don't know where 200K came from, but that's what I thought I had in my un-insulated 2 car garage. It is a 50K. So I'd cut *that* in half and come up with 25K. [or leave it the same if there is a window the OP can open- and he might ever want to use it in a bigger/draftier space]
-snip-

It all depends on how you're using the space. I heat mine up for 15-20 minutes, then go to work. When it gets too warm, I take off my jacket. Then if it gets warm, I turn off the heater. If I get cool I either put the jacket back on or turn the heater on again.
$5-600 worth of infrared would make life easier, but it wouldn't be portable.
Jim
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On Thu, 8 Dec 2011 05:37:09 -0800 (PST), " snipped-for-privacy@optonline.net"

The SMART way to do it is with multiple units. If you need to come up to temp quickly, you pull out all the stops - and if you just want to "keep" it warm you use only a fraction of the total capacity. Easy to do with electrics, and not hard to do with gas, oil, or propane if you install a minimum of 2 units. One relativly small unit to maintain temp, and one "big muthu" to warm up quickly.
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On Dec 8, 4:45pm, snipped-for-privacy@snyder.on.ca wrote:

Maybe I'm missing something, but I don't see multiple gas or oil units being smart. It's one 280 sqft room. Just get one that's sized to heat the room from being cold when unoccupied to 65F in a reasonable time, say 30 mins to an hour? With electric, being easier to install, no service, cheap, etc, then I could see using multiple units, primarily if it's desirable to heat the whole space more evenly. But for a shop, maybe all he really cares about, at least for quick heat up, is one area around a workbench, etc. In which case one electric could be fine.
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Need to know if you're maintaing temp all the time, or just a quick warm up for occasional use. For quick warm up, an over size heater may be needed, for rapid temp rise.
Of course, you could do the practical trying out method. Try one plug in space heater, typically 5,200 BTU. If that isn't enough, try a second. Three is fairly close to your 14k. Once you get a rough idea how much BTU you need, then look at natural gas heaters, how to vent the flue, etc.
Just from a wild guess, 14k sounds about right. You can also combine techniques. Have a gas heater of 14k, and use a plug in space heater for rapid warm up.
--

Christopher A. Young
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I will use electric as I do not have gas or the desire to cut a hole in the wall/ceiling for a flue. That being said, what I am looking for is something that I can go out and turn on and have it heat it up so it is not freezing. It will not be on all the time only when I am out there putzing around. Don't want a kerosene heater as they stink.
R
R
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wrote:

If it's electric, first consider the circuit amps you have there. Common and cheap 120V 1500 watt heaters need a 15 amp circuit. About 5000 btu/hr each. After you figure that out, just add them until it suits you.
--Vic
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And, eventually figure how many BTU are actually needed.
This one looks expensive, but should work http://www.ebay.com/itm/NEW-G-70-Electric-13-000-BTU-Garage-Shop-Utility-Heater-Portable-Shed-Unit-4k-W-/160695525141?pt=LH_DefaultDomain_0&hash=item256a331f15
This kind of thing from the store should be inexpensive, and helpful. Put it on the floor, heat rises. http://www.ebay.com/itm/Portable-Electric-Space-Heater-w-Fan-Unit-1500W-89-/310319603644?pt=LH_DefaultDomain_0&hash=item48407d5fbc
These ceramic heaters, supposed to be safer. No glowing filament, just heat. Same watts and BTU as the other heaters. http://www.ebay.com/itm/Pelonis-1500-Watts-5200-BTUs-100-Ceramic-Disc-Furnace-Heater-Model-B6A1-/300621526846?pt=LH_DefaultDomain_0&hash=item45fe70773e
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On 12/8/2011 9:26 AM, Roanin wrote:

I built a 12' x 20' shed to live in while I was building my house. The shed is standard 2 x 4 frame construction, R-12 in the walls and R20 in the ceiling. It was heated with a 240V 4800W construction heater like this.
http://www.homedepot.ca/product/4800w-240v-construction-heater-almond/954396
I slept comfortably in that shed when outside temps were down to -45 Deg.
The heater is now over ten years old and I still use it to heat my 22' x 28' garage/workshop.
LdB
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Roanin wrote:

Remember that temperature is not your only problem. You also gotta consider dew point. If you have electronics or machinery that can rust, or furniture that can mildew, you need to worry a LOT about relative humidity. That's the reason an unvented combustion heater is a bad choice. But your body puts out a LOT of moisture that will condense everywhere that's below the dew point. You may find you need to add ventilation, and heating that air as it enters might make the place feel less drafty.
For electric resistance heat, the incremental cost of overkill is pretty low...as is the cost of adding more if you undershoot.
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In that case, how much power do you have? If you've got two eaches 15 amp circuits, you can buy a couple "ceramic" heaters at the hardware, and set them on the floor. Heat rises, y'know and all. That plus a box fan should be good for a test. If that's not enough, you can also consider an over head electric heater with a fan, and wire it for 230 volts. More watts, with the same wire size.
If you're comfortable with propane, these are effective, and less stinky. http://www.ebay.com/itm/NEW-DH-Propane-TankTop-Heater-Double-/170667110738?pt=LH_DefaultDomain_0&hash=item27bc8d7152
Variations available, single burner typically 14,000 BTU. http://www.ebay.com/itm/REDDY-ALL-PRO-HEATER-PROPANE-10-15K-SINGLE-TANK-TOP-/160695377542?pt=LH_DefaultDomain_0&hash=item256a30de86
I've got a single burner heater, and have used it for friends when their heat was out. A lot better than freezing. I have much smaller heater (3,500 BTU in the back of my service van, I have used it while doing work in the van. Again, much better than freezing. Really makes a difference.
--

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On 12/7/2011 9:54 PM, Roanin wrote:

Too bad you don't want to go with gas. Sounds like a perfect place for a Rinnai heater. Quiet, efficient, Very unobtrusive, and very reliable. I've been installing them for over 15 years, and after we install them, we usually tell the customer that it's more than likely that they won't be seeing us again for the heater. Only takes a 3" hole for the vent and a small hole for the gas line. Check them out at Rinnaiusa.com, or do a search for Rinnai heaters.
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