Mini Split System AC for garage shop

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Forum topic by Kelby posted 09-26-2012 03:12 AM 12248 views 0 times favorited 10 replies Add to Favorites Watch
View Kelby's profile


134 posts in 2378 days

09-26-2012 03:12 AM

I have a contractor coming by tomorrow morning to give me a quote on installing a mini-split system heat pump for my garage workshop. I would love to hear opinions and feedback from those who have put such a system in their shop. In addition to any other thoughts you care to share, I would particularly be interested in:

1) What size system did you get, and how big is your shop? My shop is roughly 550 square feet, and is a three-car garage. I have installed foam insulation on the doors. I have one very energy-inefficient window. There is no insulation in the flat roof or in the two exterior walls. I will put insulation in the roof and walls, but there’s none there yet.

2) How cool does it keep your shop, and how much cooler than the outside temp?

3) How do you handle the dust issue? I have a decent dust collection system, but nothing is perfect. I have heard that replacement filters on the split system are expensive. Can you clean them? How many filters do you go through in a year, and how much do they run?

4) If you don’t mind sharing, what did the system cost you, and how much of it was done by a contractor?

Thanks for these and any other insights you can offer.

-- Kelby

10 replies so far

View AandCstyle's profile


3027 posts in 2224 days

#1 posted 09-26-2012 03:12 PM

I can’t answer your questions, but I think fellow LJ, “Sandhill” went through a similar exercise recently. You might contact him.

-- Art

View Brickman's profile


51 posts in 2338 days

#2 posted 09-26-2012 03:49 PM

We use a Mitsubishi Mr. Slim split system to cool our servers at work. It has held up very well for the 24/7 use it gets. It has a washable filter but we still have to vacuum and blow out the interior unit every 6 months (the room is relatively clean but I work at a brick plant).

The system was not cheap but the installation costs made up for putting in a ducted system. I wold look at an actual air conditioning system over a heat pump as I believe they are more efficient.


-- Mark - Pueblo, Colorado

View JollyGreen67's profile


1663 posts in 2730 days

#3 posted 09-26-2012 04:08 PM

I have a YMGI mini-split system with heat pump – I LOVE IT ! Had it installed this last spring, so haven’t operated the heat pump yet but, the AC part works really good, set it at 78, which keeps my shop – 1/3 of a 3 car garage – at @ 15 degrees cooler than outside. I removed the stock interior filter to allow more air flow, as I built an airtight box around the unit with a 12×24 for a filter opening in front to filter out the dust. Works excellent as an air cleaner. I change the filter once a month, in between I use the shop vac to suck out the dust on the filter. I have partially disassembled the box twice to check for dust inside the unit – very little, just blow it out. Wish I had did this years ago. Well worth it.

Bought it through the internet > YMGI $1100 including shipping, certified HVAC contractor $350

-- When I was a kid I wanted to be older . . . . . this CRAP is not what I expected !

View MT_Stringer's profile


3160 posts in 3198 days

#4 posted 09-26-2012 04:54 PM

I just recently completed installation of a Fedders split system. This is working great for me. No worries from the homeowners assoc about the unit sticking out through the wall. We ran a protective shroud along the wall to the condenser, which is located behind our wooden privacy fence…about 35 feet of refrigerant line. My son works for a hvac company. I installed the unit and ran the lineset, he made the hook up and got it running.

I have a one car garage…under 350 sq ft. I bought the 12K heat pump model from Delivery took three days. :-) We made up our own line set from 1/4 and 3/8 inch copper tubing and ran power from the condenser to the inside unit. That is concealed inside the shroud.

I also insulated the ceiling with blown insulation to R38. The overhead door was replaced several years ago with an energy eff door. The outside wall is also insulated. we had our siding replaced 2 years ago and I had the contractor insulate the wall while he had the siding off. Good move on my part for sure.

The unit maintains a constant 77 deg. F when operated n Auto. I have the timer set on my remote to turn the system on at noon. Being retired, I normally sleep late most days. :-)

-- Handcrafted by Mike Henderson - Channelview, Texas

View JesseTutt's profile


854 posts in 2077 days

#5 posted 09-26-2012 05:00 PM

besides cost for installation, you should ask about operating cost.

-- Jesse, Saint Louis, Missouri

View lazyoakfarm's profile


144 posts in 2764 days

#6 posted 09-26-2012 05:30 PM

I have a Daikin, it’s fantastic. Its quiet, cost almost nothing to run in a well insulated area. you really need to control the dust or you will be cleaning out the coils on a regular basis. Mine is in a 550SQFT apartment attached to my shop and I still have to clean the coils regularly. This is my 2nd unit, my first unit was oversized and was too efficient. it would not run long enough to take the moisture out of the air and I was having a mold problem. Bigger is not better in South Ga. The Daikin is DC, it has a built in inverter and is variable capacity. The only problem I have is keeping it clean. The permanent filters are not very good so I keep a spray bottle of coil cleaner and spray was it down every week. I paid around $1,600 for it and installed it myself. 220V runs to the outside unit and the outside unit powers the inside unit. I used flex conduit that you would use for outside wiring for the drain. All you do is flair the ends copper for the refrigerant and tighten it down before opening up the release valve.

View Kelby's profile


134 posts in 2378 days

#7 posted 10-02-2012 11:13 PM

Thank you all for your input!

I met with several contractors, one of whom clearly stood out from the rest in terms of both price and competence. He’ll be installing a Mitsubishi 24,000 BTU mini-split heat pump, 19 SEER, installed next week. He’ll also upgrade our house’s HVAC.

For anyone who might be interested in something like this in the future, I’ll post updates and reviews as the shop portion of the project gets completed.

-- Kelby

View Ed's profile


28 posts in 2042 days

#8 posted 10-04-2012 06:05 PM

I have a tiny shop, 8×20= 160 sq ft with a 10,000 BTU air conditioner for cooling. My walls and ceiling are insulated and my shop runs at 73 F and 45% RH (I have de-humidifier for summer and humidifer for winter.) with an outside temp of 100F and RH of 90%. My wood stays stable.

I took dust collection very seriously and installed a ClearVue cyclone which is 5 HP and spent hours designing and implementing point source dust and chip collection. Reading Bill Pentz’s site helped a lot with this. A 3 HP system would be border line for any home shop when you run the engineering numbers for air flow needed Vs HP. As a result, my shop stays clean with healthy breathing air as verified by an air quality meter. The filters can fo go for a year or more and then be blown clean continued to be used with no replacement costs.

When running a 5 HP dust collector and a 2.5 HP band saw my shop starts heating up. Depending on how long I run them it may get to, say 78F. Then is takes a few hours for my AC to bring it back down to 73F. I wish I had a bigger unit.

Your shop is 3 1/2 times bigger than mine and your insulation is currrently poor (sometimes future insulation projects take years to get done) If you ever plan to REALLY take care of chip and DUST and run other llarge machines, I believe your 24,000 BTU is undersized if you want a very comfortable tiemperature like mine in very hot weather.

The comment you said about dust collection, namely “nothing is perfect” is true. But what most people truely mean by a comment like this is “I let myself of the hook and 1) have not gottern a system with enough point source air flow and 2) have not gotten a system with enough final particle size filtration and 3) have not spent qualtiy time and effort figuring out effective point source collection methods.” Only you know if you fit this bill. But if you can ever see any dust in the air OR a pile on the floor then you know the answer.

-- Ed

View Kelby's profile


134 posts in 2378 days

#9 posted 10-04-2012 06:18 PM

Ed, thanks, those are excellent points.

On the DC issue, I would like to improve it. My ductwork is 6” mains throughout the shop. Some of the tools have 6” ports, but some do not. And those that do not would be difficult to adapt to 6”. The weak link in the change is my cyclone. I have a Laguna 2HP portable cyclone with .5 micron filters. This is an enormous improvement from the 1-1/2 HP Jet bagger that I had before. Leaps and bounds. But someday I would really like to move up to a 5HP Clearvue. Right now, unfortunately, I don’t have a way to fit that into my shop.

As for sizing the AC, you make excellent points. The one caveat I would offer is that I don’t enjoy having the temperature as low as 73. I prefer it around 77 or 78. Outside temps here in the summer are typically in the low 80s, occasionally getting into the 90s, and we might have 1 or 2 100+ days per year. Humidity rarely gets above 55 here. But with the poor insulation and large shop, you may be right that an even larger unit would be better.

Thank you for your insights and experience!

-- Kelby

View Ed's profile


28 posts in 2042 days

#10 posted 10-04-2012 06:38 PM

Sounds like you are in much better shape than most folks with dust collection.

Must be nice living in a cool environment. ... I hope again some day. :)

If I can fit a ClearVue in a 160 sq ft shop, I KNOW you can fit one in a 550 sq ft shop! (smiling) Mine takes up 3×4=12 sq ft. That is 7.5% of my shop space and only 2% of your shop space. Your shop is huge. ;)

Modifictions to increase port sizes on machines is just one modification for imporoving the point source dust collection. There are lots of others modifications too. Consider your most difficut/challenging woodworking project and apply that same quality and amount of thinking for your point source collection challenges.

Best wishes on your project.

-- Ed

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