HVAC in a Garage

[600SL]

OK I'm getting ready to select a heating and AC system for the garage. Her in NC the most popular units are heat pumps.

But I'm wondering if the beast unit for intermittent use in a garage might be something different and I would think larger.

Using most of the online HVAC sizing tool, I'm coming up with about 3 ton unit for my 48x30x10 garage. But this is a garage and it will have the need to bring the temperature up or down ~ 30° as quickly as possible because it will be off most of the time. So that being said I'm considering 5 ton as a minimum.

Also under these types of conditions I'm wondering if the heat pump is the most ideal over a conventional HVAC system like I had in CT.

Your thoughts.

 

[Bsj04]

I have 4 ton heat pump in my 26x40, I think it works great as it is usually off and only turned on when needed. I chose a heat pump because I don't have any other option available like gas and I didn't want to use electric heat because I didn't think there was enough electricity available. I didn't want to have to turn something off the run a/c or heat. In Texas the heap pump works perfectly fine since my garage is insulated well.

 

[Ohmthis]

FYI, making a lot of cold air doesn't fix the whole issue. It only makes cold damp air. Part of sizing is for the cool air, the other is to dehumidify. Dry air feels cooler, thus makes it more comfortable. Just quickly looking at your shops specs, I'd say a 3.5 ton would be good. This of course is ball park and the only right way would be a load calculation. As always, spend money up front on insulation and sealing the building. Good luck!

 

[600SL]

FYI, making a lot of cold air doesn't fix the whole issue. It only makes cold damp air. Part of sizing is for the cool air, the other is to dehumidify. Dry air feels cooler, thus makes it more comfortable. Just quickly looking at your shops specs, I'd say a 3.5 ton would be good. This of course is ball park and the only right way would be a load calculation. As always, spend money up front on insulation and sealing the building. Good luck!

I do run a Santa Fee Dehumidifier at all times. That would never be turned off as it would be needed most of the time when no one there. The building has no windows but it does have two insulated 9 x 10 doors.

 

[amocoharley]

Oversizing your ac actually will cause trouble. Ac needs to run to dehumidify the air. Short run cycles because it's oversized won't allow that to happen. Heat pump is fine if electricity is cheap in your area. In Wisconsin gas is very inexpensive compared to electric so we heat with that.


Sent from my iPhone using Tapatalk

 

[jloehlein]

What temp do you want the garage? I live outside Richmond VA and just went through the same decision process for my 32x80x16 steel building. Insulated, with 5 roll-up doors. My friend was working for the local Trane distributor so I had him talk to a bunch of folks. The consensus was that a 4 ton ducted heat pump would be best for my needs. I keep the building at 52 degrees in the winter and plan on keeping it at 78 in the summer, bumping it up or down a couple degrees when I'm in there. Last summer, without the HVAC system, the building was never over 85 degrees (even on 100+ degree days), so I'm hoping it won't have to run much when I'm not there. To me, 3.5 tons sounds large for your size building, depending on where you are in NC.

 

[Falcon67]

Our house is 200 sq/ft larger than your shop and a 3.5T Ruud heat pump can cool it down pretty quick. The shop is 960 sq/ft and if I turn on both AC units, that's 18K BTU and it'll be low 80s in under a hour with it 100F+ outside.

 

[HAP]

I installed my old 3.5T 12 SEER HP in my 40x60 commercial steel building. I did not even run any ducting, just a custom register over the air handler outlet. It primarily knocks the humidity down. I feel that it is a bit undersized, but it was a no-cost deal. I only have 3" insulation and insulated commercial doors. I also have a 10" Big *** Fan that I use to move the air around. When I know I want the shop cool, I will turn it on from early in the morning and let it get a head start on the day. I'm really glad I have it...
The heat pump in the winter is the best part though. Nice clean warm air, unless its really cold, then I turn on the overhead IR propane heaters to help out.

R,
HAP

 

[bzinsky]

OK I'm getting ready to select a heating and AC system for the garage. Her in NC the most popular units are heat pumps.

But I'm wondering if the beast unit for intermittent use in a garage might be something different and I would think larger.

Using most of the online HVAC sizing tool, I'm coming up with about 3 ton unit for my 48x30x10 garage. But this is a garage and it will have the need to bring the temperature up or down ~ 30° as quickly as possible because it will be off most of the time. So that being said I'm considering 5 ton as a minimum.

Also under these types of conditions I'm wondering if the heat pump is the most ideal over a conventional HVAC system like I had in CT.

Your thoughts.

I have an 80k btu heater gas heater in my 2 car garage. It heats the air up about 30-40 degrees in about 20 minutes.

The downside is, the car, tools, floor, everything is still ice cold. You need a boatload of btu's to get that place up to temp quickly.

If I were to start from scratch, I'd seperate the two systems, one to get it up to temp quickly, and one to maintain.

Last winter I used a 175k btu keroseen hotdog. Got the place up to 90 degrees in 10 minutes, then switch it off and let the stuff in the garage absorb the eat, turn on regular system to maintain. Worked out well.

You need a massive amount of heat to make a place comfortable to work in quickly.

 

[thymer]

I have a 5 Ton heatpump (no heatstrips) for a new 60x40 insulated shop. Ran a 18" airsock down the length, heats and cools perfectly. I don't use the shop everyday but find that it's so well insulated the temp stays pretty stable. 5 ton for that size may be too much. Short-cycle and wont get rid of the humidity.

 

[Citation]

Depending on the interior layout of the garage you might consider getting one or two mini-split systems. Many have variable output so you can get a lot of cooling quickly as well as having an efficient, lower setting. I took the chance on a Pioneer brand mini-split. Though listed on Amazon I bought from the company. A 2 ton unit is $1500. Installation is easy. I did most of the install myself and paid someone to leak check and charge. You could simply buy two to get 4 tons total or buy a multi-head unit. Anyway, for a single open room I really like the mini-split option. I've been happy with my Pioneer unit but I've only had it a year. I would search a bit with respect to brands before committing.

 

[hippie2cams]

I have a 3.5t heat pump in my 30x40 with r 19 in the walls and ceiling and you couldn't ask for anything to work better. I still haven't run any duct work it just blows out of the end right down the middle of the shop but Man does it cool down and in the Winter its nice and comfy also. I LOVE IT

 

[dshop]

I am in NC, near Raleigh. I have a 40x60x12 shop I run with a 3.5T 11 SEER heat pump. This building is stick built on a 6" slab, and is spray foam insulated from the floor all the way around the top...total enclosure. 2x4 sidewalls covered with OSB after the foam was sprayed.
I had some insulated ducts run to spread the air out...maybe 12 vents total in the whole shop.
The spray foam insulation is the key...the temp has never been below 50 or above 85 no matter the outside temp. which has ranged from the 20's to 100.
I basically run the heat pump probably 30 times a year, otherwise the insulation keeps things OK, no heat pump needed. If it gets uncomfortable, I kick on the heat pump and all is good within 2-3 hours.
This has worked for me for 9 years now.

 

[600SL]

Some good information here. My cousin is a REHM dealer. hes looking into this for me. My challenge is getting the area up to or down to temperature in a short period of time since I have limited time to work in the garage. The unit would be off most of the time with a Santa Fe dehumidifier running 24/7. A typical day might be open a garage door to bring in 1 car close the door and work for 2 or 3 hours. I would like to work comfortably in those 2 to 3 hours so getting to temp as fast as possible is a concern.

He will be looking into this further this week but he does feel at least 4 tones is sounding appropriate based on the type of use.

 

[600SL]

I am in NC, near Raleigh. I have a 40x60x12 shop I run with a 3.5T 11 SEER heat pump. This building is stick built on a 6" slab, and is spray foam insulated from the floor all the way around the top...total enclosure. 2x4 sidewalls covered with OSB after the foam was sprayed.
I had some insulated ducts run to spread the air out...maybe 12 vents total in the whole shop.
The spray foam insulation is the key...the temp has never been below 50 or above 85 no matter the outside temp. which has ranged from the 20's to 100.
I basically run the heat pump probably 30 times a year, otherwise the insulation keeps things OK, no heat pump needed. If it gets uncomfortable, I kick on the heat pump and all is good within 2-3 hours.
This has worked for me for 9 years now.

I found the same thing the temp in my building never gets to the outside extremes. I am also well insulated and have a 6" slab. I believe the slab being un-insulated in my case keeps the garage temperature somewhat uniform by acting as a earth temperature heat mass. This would work against me if I were to keep the garage temp conditioned at all times.

 

[HAP]

Just get a smart thermostat that you can control via a smart phone and turn it on ahead of whenever you plan to be in there...

 

[600SL]

Depending on the interior layout of the garage you might consider getting one or two mini-split systems. Many have variable output so you can get a lot of cooling quickly as well as having an efficient, lower setting. I took the chance on a Pioneer brand mini-split. Though listed on Amazon I bought from the company. A 2 ton unit is $1500. Installation is easy. I did most of the install myself and paid someone to leak check and charge. You could simply buy two to get 4 tons total or buy a multi-head unit. Anyway, for a single open room I really like the mini-split option. I've been happy with my Pioneer unit but I've only had it a year. I would search a bit with respect to brands before committing.

I have been considering those. I cant use the wall mount units but the ceiling units would do the job.

 

[600SL]

I have a 5 Ton heatpump (no heatstrips) for a new 60x40 insulated shop. Ran a 18" airsock down the length, heats and cools perfectly. I don't use the shop everyday but find that it's so well insulated the temp stays pretty stable. 5 ton for that size may be too much. Short-cycle and wont get rid of the humidity.

Humidity is not an issue since I have a Santa-Fe dehumidifier running 24/7. Interesting that 5 tones does a 40 x 60.

 

[LS6 Tommy]

5 tons is WAY too big for the OP's garage. There is no good fix for "rapid cool down". Comfort cooling systems are designed to bring a space down to set temp and then maintain it. They're not blast chillers. Run your Sante Fe 24/7 & use a setback thermostat to maintain a reasonable unoccupied temp, then bring the space down to your occupied temp whe you use the garage. Ecobee makes a smart stat I really like. It will adjust setpoints based on activity or you can adjust from your smartphone. Also, opening the roll up door is gonna kill it no matter how big of a unit you have. Install warehouse door curtain strips to help keep some of the heat out.

Tommy

 

[600SL]

5 tons is WAY too big for the OP's garage. There is no good fix for "rapid cool down". Comfort cooling systems are designed to bring a space down to set temp and then maintain it. They're not blast chillers. Run your Sante Fe 24/7 & use a setback thermostat to maintain a reasonable unoccupied temp, then bring the space down to your occupied temp whe you use the garage. Ecobee makes a smart stat I really like. It will adjust setpoints based on activity or you can adjust from your smartphone. Also, opening the roll up door is gonna kill it no matter how big of a unit you have. Install warehouse door curtain strips to help keep some of the heat out.

Tommy

Is that true for heat up as well can I do rapid heat up. That's usually the bigger problem.

 

[turbowoodworker]

I am not posting as an HVAC expert, in fact I know jack squat about the technicals. I did have two minisplits installed in my shop (partitioned units) for year round comfort and humidity control. Humidity is our biggest problem in NC and with good minsplits, you won't need your dehumidifier.
I've been in my shop for two winters now and right now (87F and very humid), I can work anytime comfortably and not be concerned about the rust stuff.