Propane heater BTU output question...

[hvclassics]

What drawbacks if any are there to having a unit that is TOO large for your building?

I currently have a 26Wx32Lx10H garage with a Sterling hanging propane heater that has worked just fine for my needs for the past 8-10 years.

Looking forward, I am about to build a 36Wx48Lx16H (pole style) garage,, 6x12 pitched roof scissor trusses with a loft/second floor and 10' ceiling height downstairs.
The lower area will primarily be used to store vehicles, occasional work and a bit of a 'hangout area'.

Question on heat for the new garage:

To level set, in my existing garage (26x32) I purchased the heater used, and it it WAY oversized (150,000 BTU) for what would be needed, ...BUT it has worked perfectly for me. No complaints what so ever, and has been flawless.
With that said, as I look for a unit for the new garage, I DO realize if it were "spec'd out", I suspect a unit around 75,000 BTU would be recommended.

I've come across a great deal on a relatively new Modine 200,000 BTU unit, but is going TOO large not a good idea?
One detail I notice on the Modine units is that once you go over 175,000 BTU's, the inlet pipe goes from 1/2 to 3/4". This is to be expected since a large unit will need more volume of gas.

SO, ...since the space doesn't call for a large unit and I wouldn't be running the thing at 'full' capacity, am I better off purchasing a smaller unit (ie. one with 1/2" inlet) that might end up being more efficient?

For the record, ... I can purchase the 200,000 BTU unit for about 1/2 of a 150,000 BTU unit.


Thanks,

Kevin

 

[HoosierBuddy]

Downsides would include:

1. Your heater will tend to short cycle because it is putting out so much heat relative to the space.
2. The piping will have to be larger to carry that much gas. In fact, the meter will likely have to be larger if it also feeds your home. Most natural gas meters at homes are rated for 275,000 BTU's....meaning you'll be sapping yours just for the garage.
3. Your flue will be bigger.
4. It will likely be less efficient.
5. It will be louder.
6. It will likely be less comfortable as you'll have a bunch of hot air blowing at you for a short period of time.
7. It will take a larger physical space.

Other than that I think it will about the same.

Phil

 

[Bretny]

As far as i know those heaters have two settings. On (200kbtu needing 3/4in) and off (0btu needing no pipe)

 

[laser3kw]

For the record, ... I can purchase the 200,000 BTU unit for about 1/2 of a 150,000 BTU unit

Great find! Now - sell it on C-list and buy a proper size heater. Others ^^^ have outlined the reasons why. If in doubt, call your preferred HVAC guy and ask him.
I would say a 45k unit will suit you just fine. It is spending your money wisely from start to finish and heating bills in the future.

 

[Jackfre]

Great find! Now - sell it on C-list and buy a proper size heater. Others ^^^ have outlined the reasons why. If in doubt, call your preferred HVAC guy and ask him.
I would say a 45k unit will suit you just fine. It is spending your money wisely from start to finish and heating bills in the future.

We have a winner. You will have heat. You won't be comfortable. You will get blasted by heat and then it will shut off. 3/4" will supply 200k, but not more than 20' total. Add the connected loads of all the appliances on the system for sizing. Furnace, range, WH, etc

 

[hvclassics]

Thanks for the replies.