Is this a good mini-split for me?

[DWinTX]

Hi All,

I live in the Colorado Rockies at 8400' of elevation. I have a detached garage that is 24' x 40' and has an open ceiling. The walls are 10' tall with a center ceiling height of 16'. It is insulated with R19 insulation in the walls and R31 in the ceiling. The walls are finished in OSB and the ceiling with metal roof panels. I want to heat the garage with a mini-split system. I will never use the A/C side, only the heat. It frequently gets in the teens and twenties here during the winter, however it will sometimes get to single digits for the lows.

I was looking at this:

Pioneer® Quantum Ultra™ 22,200 BTU 20 SEER2 230V Floor/Ceiling/Low-Wal

Summary High Efficiency Quantum Ultra Floor/Ceiling/Low-Wall Ductless Split Heat Pump System Cooling capacity: 22,200 BTU/H with 20.0 SEER2 / 11.7 EER2 efficiency Heating capacity: 24,400 BTU/H with 9.5 HSPF2 / 3.44 COP2 efficiency Voltage: 208/230V, 60Hz, 1Ph Floor/Ceiling/Low-Wall Mounted...

www.pioneerminisplit.com

Do you think this will be sufficient for heating the shop? I will never use the A/C so I don't care about that. I'm not sure 24,000 BTUs is enough. I'm not particularly price-sensitive, but I don't want to throw away money either. ChatGTP recommended a Mitsubishi system that is $11,000. Not sure I want to spend THAT much.

 

[fitter30]

All heat pumps except brands that offer hyper heat down to -22° that advertise that they don't loose capacity. Most are designed heating temp at 47° and 17°is lower btu but the factory and distributor should have more design numbers.

 

[Yankeefarmer]

Not sure what you mean by “open ceiling.” Do you just mean there’s no dividing walls?
For comparison purposes, my 26 x 48 x 15 is heated with a heat pump that specs at about 40 k BTU/hr with outside temps in the teens, and only runs about 50% of the time to maintain 61 deg F inside temps under those conditions. My walls and ceiling are all R19. Based on that, I suspect the unit you propose could work for similar temperatures by running continuously, which mini splits do anyway. I find that a shop temperature above 61 is too warm for me when my body is accustomed to winter temperatures. My building is new and tight. If your building is older and has drafts, the infiltration losses might require more heat input.

 

[Mikes61]

I just put a Mr Cool 36,000 in my 23’ x 40’ attached garage. It’s attached to a 500 sq ft garage with a 9’ x 9’ walkthrough opening. It has a 9’ ceiling that’s insulated with R30 and R19 in the walls. I’m in So. Cal where it only gets down to 32*, maybe. It throws out a lot of heat.

Im thinking you need to go up to the 36,000 for your kind of low temps.

Id hate for you to get the 24,000 and it not be adequate, because most of the heat is up at your 16’ ceiling.

I paid $2300, delivered to my door, for my Advantage non DIY Mr. Cool. I had a HVAC buddy help me install it for free.

Are your garage doors insulated? Will you be opening them when it very cold outside?

 

[ericm]

Run a manual J and S at loadcalc.net. Then you'll have at least some idea. Otherwise you're just guessing.

In part the answer will be determined by the temperature you want to run the units at. I have mine set to 62 which seems warm enough to me when I'm active in the shop. Loadcalc lets you change that, and it also looks up the 98th percentile lowest temp (what you're supposed to use for Manual J) from a near by weather station.

 

[pembol]

Hi All,

I live in the Colorado Rockies at 8400' of elevation. I have a detached garage that is 24' x 40' and has an open ceiling. The walls are 10' tall with a center ceiling height of 16'. It is insulated with R19 insulation in the walls and R31 in the ceiling. The walls are finished in OSB and the ceiling with metal roof panels. I want to heat the garage with a mini-split system. I will never use the A/C side, only the heat. It frequently gets in the teens and twenties here during the winter, however it will sometimes get to single digits for the lows.

I was looking at this:

Pioneer® Quantum Ultra™ 22,200 BTU 20 SEER2 230V Floor/Ceiling/Low-Wal

Summary High Efficiency Quantum Ultra Floor/Ceiling/Low-Wall Ductless Split Heat Pump System Cooling capacity: 22,200 BTU/H with 20.0 SEER2 / 11.7 EER2 efficiency Heating capacity: 24,400 BTU/H with 9.5 HSPF2 / 3.44 COP2 efficiency Voltage: 208/230V, 60Hz, 1Ph Floor/Ceiling/Low-Wall Mounted...

www.pioneerminisplit.com

Do you think this will be sufficient for heating the shop? I will never use the A/C so I don't care about that. I'm not sure 24,000 BTUs is enough. I'm not particularly price-sensitive, but I don't want to throw away money either. ChatGTP recommended a Mitsubishi system that is $11,000. Not sure I want to spend THAT much.

No, that is not a good choice for a low ambient temperature location like Woodland Park.

Look at the spec sheet - with an ambient of 17F, the output of that unit has already dropped to 14kBTU, it is likely to struggle at low temperatures. I take that back, that is the rated output at 17F, the max output at 5F is still 19kBTU which may be OK.

 

[DWinTX]

Thanks for the responses guys. To answer a couple questions, by "open ceiling", I just mean there is no internal, dropped ceiling. It's open to the roof trusses. So there is a lot of area up there that has to get heated too. There are two single garage doors (8x8 each, I think), and they are insulated. On the opposite end, there is one man door and one sliding glass door (the previous owner had dividing walls inside and this opened to an exercise room. I have torn all those wall out and it is now completely open). I've attached some pics if it helps.

60-65 degrees would be fine with me. I ran the loadcalc.net calculation and came up with this. Does it look like I filled it out right? I can tear down a classic car and completely restore it, but when it comes to building construction, I'm an idiot. For the location, since they didn't have my town, I used Leadville, which is 1600' higher and generally colder. And I set the indoor temp to 70, which is a little more than I need. It only came up with 14k heating BTUs, which seems low. So maybe I didn't fill this out correctly.

 

[ericm]

You missed floor (linear if slab). Wall area east and west should be both east and west added together. They split off north and south for sun exposure but east and west can be considered identical. Yes this could be better explained on the page. You also need to add in the gable wall area above the 10' side wall height. Rather than calculate areas of two triangles I use a rectangle the average of the side wall height and the height at the ridge beam. So if the gables are on the 24' side it'd be 2 * 24 * 3 plus 2 * 24 * 10, or 2 * 24 * 13. I think you also did not account for the ceiling above the walls in the cubic foot volume entry.

I think I used "fair" for air tightness. My shop's got housewrap so it should be tight but I think even good garage doors leak a lot compared to doors and windows in normal houses.

A ceiling fan might help move the hot air around. Though I have found that mini splits do reasonably well at mixing the air up on their own, so I have not actually tried to use the fans in my shop for that yet.

 

[Yankeefarmer]

It looks like your calculation does not include heat loss through the ceiling. I see 0 sq ft of ceiling.