Heat pump or mini split 40 x 30 detached garage

[Ultimabake]

Hello all, I'm sure this has been talked in the past but I have a 30 x 40 x 12 (ceiling) detached garage. Mainly used for work on cars, has a 2 post lift. The building has open cell spray foam in the ceiling rafters and fiberglass insulation R19 in walls. I have one window, 2 12Ft metal garage door, which will be insulated. I was thinking about a 5 ton heat pump but love the simplicity of a mini split. If I do go with mini split can a high seer one head unit keep up with the heating and cooling demands. It's in Columbus Ga, mild winter but high summer temps and humidity.

 

[pcmeiners]

Read through these threads first, 5 ton is over sized, a minisplit is a heat pump......

Insulation and mini-split for metal garage

I'm nearing the end of getting my concrete slab poured and trying to plan for how to configure the shop. I'm going to put a 24x35 ft metal building with 12 ft walls and I'm trying to figure out the best combo. I've looked at a bunch of different sites and Alans Factory Outlet or High Quality...

www.garagejournal.com

Mini split size

I have a 1000 sq.ft. carriage house (workshop) with 12 foot ceilings. It's very well insulated with 6" in the walls and 10" in the ceilings. I first thought 18,000 BTU"s but before ordering am thinking 24,000 BTU's. It would only be used when I'm out there for maybe 4-6 hours a day. Any suggestions?

www.garagejournal.com

 

[justinjoyal]

Read through these threads first, 5 ton is over sized, a minisplit is a heat pump......

Not all mini-splits are heatpumps.

5 ton indeed seems oversized. Start with a load calculation and go from there.

 

[Yankeefarmer]

Not all mini-splits are heatpumps.

5 ton indeed seems oversized. Start with a load calculation and go from there.

Technically, a cooling-only mini split is a heat pump, because an air conditioner pumps heat from the conditioned space to the outdoors. I think what you are pointing out is that many people use the term ”heat pump” to refer to machines that can provide heating or cooling.

 

[pcmeiners]

When was the last time an air conditioner was referred to as a heat pump at an HVAC supply counter?

 

[PoorUB]

Hello all, I'm sure this has been talked in the past but I have a 30 x 40 x 12 (ceiling) detached garage. Mainly used for work on cars, has a 2 post lift. The building has open cell spray foam in the ceiling rafters and fiberglass insulation R19 in walls. I have one window, 2 12Ft metal garage door, which will be insulated. I was thinking about a 5 ton heat pump but love the simplicity of a mini split. If I do go with mini split can a high seer one head unit keep up with the heating and cooling demands. It's in Columbus Ga, mild winter but high summer temps and humidity.

I would dare guess you are 2 times over on your size. I would bet 2-1/2 ton would cool the place nicely.

Not all mini-splits are heatpumps.

Which manufacturers build cooling only mini splits? I don't know of any.

 

[Jackfre]

There is little cost saving in buying a cooling only unit. From a value standpoint the HP is the correct choice. Air conditioners began to be called heat pumps in a bout ‘06 when we introduced the inverter units. Prior to that with the old single stage R22 units if one of my customers called and said he was going to buy a heat pump I’d ask him, “What are you nuts?” By ‘07 having seen the performance of the 410a inverters if I rec’d a call from the same guy saying he was not going to install a heat pump I’d call him back and say, “what are you nuts?” As far as the countermen at the HVAC supply house, it does take time for things to filter down but that should have happened by now.
Your 5 ton unit is grossly oversized. Fujitsu makes a 36k suspended unit that I had really good luck with. It is a beast.

 

[My Old Tools]

My shop is 30x40x12 with a 6/12 pitch, 22 feet tall. Conventional roll fiberglass insulation, 4" walls, 12" ceiling. A 3 ton MrCool single head cools and heats it just fine. Mine is mounted 9 feet high in the center of the long wall. I feel I'm 25% oversized. I have 7 large windows facing north and east and a 12x12 overhead insulated on the south wall, one walk door.

 

[justinjoyal]

I would dare guess you are 2 times over on your size. I would bet 2-1/2 ton would cool the place nicely.

Which manufacturers build cooling only mini splits? I don't know of any.

I know of a few. As a matter of fact, I just installed one today, Gree 18kbtu in a convenience store.

When was the last time an air conditioner was referred to as a heat pump at an HVAC supply counter?

This ^^. A heat pump is a heat pump. No one ever refers to a straight-cooling unit as a heat pump...

 

[dcg9381]

I was thinking about a 5 ton heat pump but love the simplicity of a mini split. If I do go with mini split can a high seer one head unit keep up with the heating and cooling demands. It's in Columbus Ga, mild winter but high summer temps and humidity.

I have more than 2x the shop in Texas. Spray foam, but huge doors and you have more foam. It cools pretty well on 2 x 24K BTU Daikins.
Oversize is a bit more OK with mini-spits as they can throttle back.

Heating the building in winter is a problem if it's below 25 degrees, but the units I bought were not well designed to be efficient in the cold.

 

[PoorUB]

I know of a few. As a matter of fact, I just installed one today, Gree 18kbtu in a convenience store.

I used to wholesale Gree and they didn't have a cooling only back a couple years. Was it a heat pump where the installer locks out the heat side, there was that option.

 

[PoorUB]

Technically, a cooling-only mini split is a heat pump, because an air conditioner pumps heat from the conditioned space to the outdoors. I think what you are pointing out is that many people use the term ”heat pump” to refer to machines that can provide heating or cooling.

Which is industry standard terminology. If you walk into any wholesaler and as for a heat pump they will sell you a heating and cooling unit. You you want AC only, you ask for AC. This applies to residential splits and mini splits equally.

If you walk in and as for a cooling only heat pump the counter guy will give you a confused look!

 

[Ultimabake]

Yes I want a unit that can handle both cooling and heating.

 

[road_king]

I installed a Mitsubishi mini split heat pump in my 30x40 garage. One air handler centrally mounted across the rear 40' span with 3 garage doors opposite. My garage is open..ie no interior walls, and it heats and cools the area very well. I live in a colder climate than Georgia so I'm thinking this would work well for you. I have radiant heat for the colder winter months. My garage is insulated similar to yours.