Unit heater sizing - buying today, please help!

[bedn0009]

I need a final push... buying a Beacon Morris 45k or 60k BTU today for 11% rebate sale.

I am heating the following:

32x28x9 in Northern Wisconsin
R10 2" XPS under slab and perimeter 4'
R21 in walls
R 38 in ceiling
R 18 garage doors
5 windows (4'x5' each)
1 glass door (30")

I plan to heat to 45 degrees unless i go in the garage, then 55-60. Garage doors will rarely open in winter.

I'm leaning toward 45k to avoid short cycling it. Have to buy today for the rebate... any help appreciated!

 

[finn]

45 should be ok.

Be aware that Beacon Morris doesn't recommend their hanging unit heaters for maintaining temperatures below 50 degrees because the gasses condense within the unit and the resulting acidic liquid attacks the aluminized heat exchanger and voids the warranty.

The installation booklet has this disclaimer.

I assume the other manufacturers have similar disclaimers

Having said that.......

 

[Slowgsr]

If your building isn't drafty 45k will be fine

 

[Kevin54]

I have a 45,000 in my 28x36x8 and it does a great job. In my addition, I am putting a 75,000 and the addition is 28x36x10. With both on 65 degrees, they shouldn't run very much. My original garage has R13 in the walls and R32 in the ceiling. My addition has R19 in the walls and R32 in the ceilings. The original garage has 2x4 walls, and the addition has 2x6 walls.

 

[toyotadriver]

In my area (much warmer climate), the 45k would be fine. You live in a colder climate so might be worth considering the 60k. I have an 80k Mr. Heater in my 30x40 well insulated shop and it does fine. I think if I was in your shoes where you live, I'd go with the 60k and know that no matter what the outside temp is or how many times you need to open the garage doors, you'll still be able to easily heat your shop.

You also have more windows than me (I have 2 3x3 windows) and your windows are larger. In addition your glass door will **** a lot of heat out as well.

I'd go with the 60k.

 

[zmaxmotorsports]

Ive never actually been to wisconsin but Ive heard horror stories about your winters.
As long as you dont expect it raise the temp 15-20 degrees in 15 mins when its 25 outside and you have good doors Id think the 45,000 will be fine.

 

[volaredon]

so then a 100K Modine in a 30x36X10 with 6/12 roof above that in Chicago would be too much? I have run a 100K Salamander (kerosene) and some times that wasn't quite enough.