Reznor Heater size?? UPDATE: Advice

[tod]

Hey Guys,

I an earlier thread, I asked about which size Reznor heater I would need (100,000btu vs. 125,000btu) for my polebarn in Michigan. The feedback was great, but I realize now I did not provide enough information. Most people said the 100,000 btu hanging unit would be fine. Today I have to confirm with contractor which unit (100 or 125), so I dug up my receipts with all info.

Contractor and on-line calculators say 100,000 btu's should work. I'm in Michigan and plan on keeping barn heated at about 40 degrees during the winter when not in use. Then, when I'm out there cranking the thermostat up to about 65 degrees when I go out to work. This barn is just for my pleasure and is not a business.

Specifications of barn:
Size: 30x60x12 ft ceiling
Poured Cement floor with vapor barrier
OSB on outside walls with vinyl siding exterior
OSB on all inside walls and ceiling
Insulated with: R-30 in all walls and ceiling
No windows
One large insulated garage door 16x11
One small insulated garage door 9x8
One steel entrance (service door)

So, calculators indicate between 86,400 btu's and 108,000 btu's dependent upon insulation factor.

Is 100,000 still sufficient for my application. I fear the heater will be too small and I'll regret it later. Thanks to those that responded before, but I added new information on insulation and garage door size that was lacking from a previous post.

Thanks
Tod

 

[bobbyjean]

hey.... didn't see the earlier post -is the 100 or 125k input btu rating? sounds like it
do you know the efficiency of the unit...many are 80%
if your looking for 40-65 degree's...either works....the 100k seems closer to the calculations as contractor say's....
my 2 cent's- i would go with the 100k...

 

[grinch365]

So ? Which one did you go with and is it working out ?
I'm in a similar boat, looking for real life experiences.

Thanks!

 

[finn]

A 75k heats my garage, which is similar in size, 32x54x13’, just fine.

Mine has three garage doors and five 5’ windows, and probably less insulation.

 

[Will S.]

85k Reznor, 36x48x16 ceiling P.B., well insulated. Quickly heats and hold any temp set, but typically 55-60 when I am working. Any warmer is just too hot for me. No business use, just projects & maintenance. Cold, but not Michigan cold.

 

[grinch365]

Are these 75k and 85k BEFORE taking into account most are 80% efficient ?

The reason I ask is that I think I need about 80k BTU, but a (rated) 80k is really about 64k, so I was thinking a 100-125k would be about right.

My pole building is 40 x 56 x13.5 H with one 18x10 insulated garage door, one 10x10 insulated garage door. two insulated man doors, (5) 3x3 windows. The walls are R19 with OSB and the metal ceiling is covered with R38 blown in fiber fill.

I'm still shopping for a heater.

Thanks for any input

 

[RB30]

Any links to units with a higher efficiency?

 

[finn]

Are these 75k and 85k BEFORE taking into account most are 80% efficient ?

The reason I ask is that I think I need about 80k BTU, but a (rated) 80k is really about 64k, so I was thinking a 100-125k would be about right.

My pole building is 40 x 56 x13.5 H with one 18x10 insulated garage door, one 10x10 insulated garage door. two insulated man doors, (5) 3x3 windows. The walls are R19 with OSB and the metal ceiling is covered with R38 blown in fiber fill.

I'm still shopping for a heater.

Thanks for any input

I traveled to Colorado Springs quite a bit.

Pretty mild climate, relatively speaking, with lots of sunshine, which helps a lot if you have windows.

My other building also has a 75k 80% heater, used to boost temperature from the mid forties to low sixties

Two large garage doors, 32x75x16’. Takes about an hour to stabilize at a little over sixty, which is comfortable. That’s when it’s zero to five or six degrees outside.

Radiant is set at mid forties

 

[grinch365]

Yeah, I'm only looking to raise temp to 50-60. It does get down to zero and single digits fairly often where I am. I'm also at 7500 ft , so not sure how that affects heaters ?

 

[WP9]

Are these 75k and 85k BEFORE taking into account most are 80% efficient ?

The reason I ask is that I think I need about 80k BTU, but a (rated) 80k is really about 64k, so I was thinking a 100-125k would be about right.

If my recollections serve me correctly, this is correct. At 80% efficiency a 100,000 BTU heater will deliver (100,000 X .80) 80,000 BTU's.

Also, if you are keeping it at a low temp ( some heaters require a minimum temp ( usually about 50 degrees) otherwise the life of the heat exchanger will be shortened.

In my case, I went with an oversized heater as I like to raise the temp up to 65 degrees quickly when I decide to work in the barn ( hobbyist , so sporadic use)
A larger heater will raise the temp more quickly. ( but will not be as efficient as a properly sized heater)

 

[finn]

Yeah, I'm only looking to raise temp to 50-60. It does get down to zero and single digits fairly often where I am. I'm also at 7500 ft , so not sure how that affects heaters ?

Forgot about the altitude there.

Rule of thumb for altitude derating for internal combustion engines is 2%/1000 feet.

That’s pure physics and chemistry, based on availability of oxygen to support combustion.

Logically, space heating devices burning hydrocarbon fuels should follow the same laws of physics.

 

[grinch365]

so, that would be another 15% derate, in addition to the initial 20%. I'm thinking the 125k btu unit is the way to go, then since that puts me at about 81 btu after derating. Otherwise I'd be at 52 btu, which is way under all estimates for me. Thanks for the input guys.

 

[Matti]

As far as I can tell there is about a $200 difference so I would go with the bigger unit based on the calculated size. If there is a substantial difference in installation cost that might change things. With such a big area I might consider installing 2 smaller heaters although that will definitely cost more. Its something to look into.

 

[grinch365]

I'm fairly certain I'll go with the 125k heater. Now I just gotta get the propane guy to call me back with some numbers for tank rental/purchase and install (of a 500 gallon tank). I'll do the heater install myself.

The heater is about $200 more than a 80k version. I thought about doing two smaller heaters, but that just adds to the complexity. I'm not living in there, so I'll deal with some uneven heating. I've been using a jet engine tube type (LOUD) heater (salamander?) and a patio heater for temp heat. I just want to get away from fumes and noise.