I am thinking about heating/cooling my 300 sq. foot shop with a split unit heat pump . I have asked one HVAC tech what he though. His response was that it would probably work, may need to clean the inside air handler filter once a week. I am wondering if anyone has a unit in their shop and how it has worked out for them.
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Any experience with heat pumps in the shop?
- Thread starter John Chalikian
- Start date
I have one, it works great. Woodstove for backup/supplemental heat. You do need to clean the prefilter regularly, get the coils professionally cleaned periodically and control the dust level in the air as well as possible
I had a heat pump installed when I built my shop maybe 9-10 years ago. My shop is about 1400 sq ft so my HVAC guy sized a 1.5 ton system with outside and inside components. I built the walls with 2x6s for extra insulation; the heat pump keeps the building as warm or as cool as I want with ducts to the different rooms. The climate here in TN is a somewhat warmer in the winter that when I lived in PA, if that makes a difference. I keep it fairly warm in the summer and somewhat cool in the winter to save energy costs but it's always comfortable. Since I process green wood into blanks, dry, and store wood I really like that it keeps the humidity fairly constant.
I do have to keep the filters clean but have to for the big heat pump at the house too. I use a central dust collector in the shop so the filters don't get clogged with wood dust floating around.
JKJ
I also have a heat pump. I turn it off when doing something that makes a lot of sawdust to cut down on the frequency of cleaning the filter. Make sure you install a surge protector. I did my own installation and didn’t think about that. Cost me a bundle when we had a brown out!
I was tired of hauling/stacking pellets, so I installed my own a couple years ago. My shop is similar size and a local HVAC guy came out to give me a quote and said it would never work and tried to talk me into a radiant ceiling propane heater instead. He said it would be about $4k. 
I got one on Amazon for about $500 and also ordered a vacuum pump for about $100. It runs on 110v so install was a piece of cake. I installed an outdoor outlet next to it and plugged it in. I extended the porch of my shop with a few pavers and set the outdoor unit on them. It drains a lot in winter, so I had to put some bricks under the feet. I should've hung it on the wall, but didn't because i thought it would be noisy. It's not at all; whisper quiet. I do wish it could be set lower than 60° in winter, but it's really nice to not be messing with ashes and pellets or a cold shop. I also gained enough floor space that I added another lathe.
I got one on Amazon for about $500 and also ordered a vacuum pump for about $100. It runs on 110v so install was a piece of cake. I installed an outdoor outlet next to it and plugged it in. I extended the porch of my shop with a few pavers and set the outdoor unit on them. It drains a lot in winter, so I had to put some bricks under the feet. I should've hung it on the wall, but didn't because i thought it would be noisy. It's not at all; whisper quiet. I do wish it could be set lower than 60° in winter, but it's really nice to not be messing with ashes and pellets or a cold shop. I also gained enough floor space that I added another lathe.
My shop is heated with a gas furnace (ceiling hung) and cooled with a window AC when needed. But I still have on my list getting a mini split installed. There are lots of examples of folks who have done this in a woodworking shop and had no problem. The occasional cleaning mentioned above is the only downside, the lower cost of conditioning the air is a bonus.
One thing about central heat and air - the HVAC companies typically don't let you install or even help install, probably since they want to make sure it's right since they'll be responsible for it. But to save money, it doesn't hurt to ask.
When contracting for my shop, I asked the guy who came out to size and bid the job if I could save some money by doing some of it myself. He went back and asked the owner, who said no.
Then when the owner came to measure and do the actual deign, including the ducts and plenum, he started looking around and asked if I built the shop myself. Told me if I installed the inside components, ran insulated ducts to diffusers, did the wiring, etc, it could save some money! I guess without seeing all that he had imagined future problems and conflict if someone installed and botched things. After seeing what I'd built he offered me $1100 discount - sure, might be fun!
The supplied all the pre-formed plenum, return filter housings, ducting, diffusers, rivets, sealant, insulation, tape, and even loaned a crimping tool. It took me a week or so but I cut and framed as needed, ran all the electrical, installed the plenum and inside unit, cut the holes in the ceiling, insulated and hung ducts, mounted diffusers in various rooms, mounted the outside unit on a concrete base, the inside controller, did all the electrical. Nothing was difficult. Their guy came back and soldered the copper, charged with coolant, connected the wiring, and tested the system.
This was a company I and friends had used before so they knew me - another company might not have done the same. Other bids I got (for the same Trane heat pump) were twice the cost. Pays to shop around. I found the most popular HVAC company in this area for residential were the most expensive. If you want to find a reliable and reasonable HVAC company, maybe do what I did and ask a good architect friend who designs and gets things built - they know all the contractors, structural engineers, material suppliers, regulations.
One thing I discovered about outdoor breakers - the big outside unit at the house unit at the house uses three. Even in a quality outside box gradual corrosion on the terminals can increase resistance, increase current draw, and evenutally destroy the breaker. I learned to I coat every terminal, inside and out, with dielectric grease to keep the moisture and air away. (available at any electrical supply house)
I do call the HVAC company every few years to inspect and test pressures and function both at the shop and and the unit at the house.
Of course, a window unit is trivial to install and a mini-split not that much more. The thing most of us can't do is the refrigerant charging and leak testing. A good friend installed his central heat/air system for house and garage completely by himself - bought the charging and test tools and everything. But he was a lot smarter than me.
JKJ
I have a 12k BTU Mitsubishi minisplit for my 24x24 garage. Costs around a dollar a day to heat in the coldest parts of the winter, and half that to cool in the summer. Probably $150 annually to keep it between 68F-58F. Garage and door is old but insulated, and I installed extra weatherstripping around the door to reduce drafts. I still need to blow a bit of extra insulation in the attic space. Single-head units are very easy to install DIY, just rent a vac pump from an autoparts store and let it go for a good couple hours, and check that it holds for a good while. The unit itself comes pre-charged, so it just needs vac'd lines.
If you want to heat in a colder climate, you should choose a unit that has reasonable cold-weather performance. HSPF will indicate that.
As for dust, I assumed I would need to build some kind of pre-filter for it, but put that off at first. I found that the unit simply doesn't accumulate dust as I thought it would, even when my shop is very dusty. The little mesh filter is easy to clean and will load up periodically, but the coils themselves remain clean. If you're in a warmer or moister climate, this might not be the case, but at this point I don't plan to do anything but blow the filter out every few months.
If you want to heat in a colder climate, you should choose a unit that has reasonable cold-weather performance. HSPF will indicate that.
As for dust, I assumed I would need to build some kind of pre-filter for it, but put that off at first. I found that the unit simply doesn't accumulate dust as I thought it would, even when my shop is very dusty. The little mesh filter is easy to clean and will load up periodically, but the coils themselves remain clean. If you're in a warmer or moister climate, this might not be the case, but at this point I don't plan to do anything but blow the filter out every few months.
All of what Kevin said. My shop is setup for excellent dust collection, but not every process is going to be amenable to that. Most relevant to this forum, I don't really have DC setup for sanding at the lathe yet (the ducting is in, but I still need to solve the "last yard problem" via a collection hood and hose). No problems at all with the prefilters or coils getting gunked up, and I do get it serviced. It probably helps that the head is in a corner of the shop near the door, which is outside the immediate blast radius of the messiest operations (sanding, sanding, and sanding).
I have one mini-split head inside the shop, with the compressor right outside – it's a Mitsubishi system. When all this was being planned, I realized that we could also add a couple of extra heads on that system for the main house. That resulted in some wonderful improvements to this weird old house's overall HVAC setup. (There was a daylight basement expansion done decades ago by prior owners, but all of that was outside the original ducted system's reach.) Related, when the shop space was being rebuilt during our remodel I made sure the walls were insulated. There are two garage doors which were replaced during that work, also now insulated.
It's amazing to come into the shop whatever time of year and find comfortable working conditions, more stable humidity levels for wood, and very little maintenance required for rust-sensitive things like machined cast iron surfaces and tools.
Thank you to everyone who has shared their experiences. I will be going ahead and install a heat pump. I will be doing the work myself. Will now go ahead with the research to find the correct unit for me. So far it seems like 7 to 8000 BTU would work but smallest unit I can find is 9000 BTU. I think that will be fine but I want to talk with some tech people.
I found on-line calculators that take input like square-footage, floors, windows, R-value in walls and ceiling, and climate and estimate the BTU requirements. Might also contact a small, local HVAC shop and see if they will calculate and maybe provide consultation for a small fee.
JKJ
John,
I put in a 24k 18 months ago and it has been flawless. No problem with the filters clogging. As someone else said, I do wish I could set it lower than 60 degrees.
I put in a 24k 18 months ago and it has been flawless. No problem with the filters clogging. As someone else said, I do wish I could set it lower than 60 degrees.
I'll give you another option: PTAC (Packaged Terminal Air Conditioner) PTAC's are found in hotel rooms everywhere. you have to cut a hole in the wall to install a PTAC "sleeve" but once done any PTAC will slide right in. My 24X24 shop has a 15k BTU unit that heats and cools. I'm in Hot Springs AR. Mine's 12 years old and still works great but if it ever fails there are numerous manufacturers and all PTAC's fit into the same sleeve 
Dave, is the PTAC self contained with the condenser and air handler all in that one unit. Is it as energy efficient as a split heat pump? Something new to look up. I will check it out, thanks.
I have a Mitsubishi mini-split for my 24’ x 30’ shop with 16’ ceiling (at the peak). It heats and cools well. Do keep your filter clean, it keeps it efficient.
Like John I built with 2x6 walls**, and the non-ventilated, cathedral ceiling** is 2x10s, with blown-in-batt, and two layers of 1.5” R-Max between two layers of sheathing under the roofing material.
**(I sealed every stud bay and ceiling bay before insulating so there is no air movement - making the insulation more effective)
The shop I built seven and a half years ago is separate from our home (which was built in 1959). I don’t need to start cooling the shop for at least a month after the house AC gets turned on, and likewise don’t start heating till a good month and an half after the house needs heat.
Pete,
I thought mine only went down to 61*F, until I read the manual!! There is a vacation mode so I can leave it at 50*F when I am away in the winter.
Like John I built with 2x6 walls**, and the non-ventilated, cathedral ceiling** is 2x10s, with blown-in-batt, and two layers of 1.5” R-Max between two layers of sheathing under the roofing material.
**(I sealed every stud bay and ceiling bay before insulating so there is no air movement - making the insulation more effective)
The shop I built seven and a half years ago is separate from our home (which was built in 1959). I don’t need to start cooling the shop for at least a month after the house AC gets turned on, and likewise don’t start heating till a good month and an half after the house needs heat.
Pete,
I thought mine only went down to 61*F, until I read the manual!! There is a vacation mode so I can leave it at 50*F when I am away in the winter.
I was curious and looked up what I bought. It's a 12000BTU, 115V, 20 SEER2
Pat, not seeing any vacation mode setting, but that would be ideal. I go thru spells that I'm not in the shop and a lower temp would be really nice. It's not that bas bad cost-wise to just keep it at 60 though.
Pat, not seeing any vacation mode setting, but that would be ideal. I go thru spells that I'm not in the shop and a lower temp would be really nice. It's not that bas bad cost-wise to just keep it at 60 though.