Ductless HVAC Systems

[stokester]

I'm considering adding a heat and air system to my shop.

It's about 2.5 bays downstairs and a workshop upstairs with the only insulation in the upstairs ceiling and walls.  Currently the 220v window unit upstairs keeps it comfortable upstairs in the summer and a couple of kerosene heaters keep it tolerable in the winter.  Downstairs stays relatively cool in the summer but cold in the winter.

The Mitsubishi split system air pumps may be a solution to keep the garage temperature tolerable and cut down on humidity during the early spring and fall days when the outside moist air warms up only to condense on the floor and my tool boxes because of the night cold soak.

So does anyone have experience with these systems and can I use it to stabilize the temperature without breaking the bank?  I know they are pretty efficient but I don't want it to be so expensive to operate that I can't use it often enough to be worth the expense.  Secondly is there a better solution?

[bonneyman]

OK, you're looking to use a mini-split the way they were originally designed to be used: not as the primary source of heat/cool. (i.e. if the thing quits it's not going to be critical)
Lots of brands out there with different features and gimmicks, some work better than others as I hear. No direct experience, although I did install one on a computer room like 16 years ago. Did a decent job of keeping the computer servers running cool, don't know what the running costs were.
Some of the new ones are inverter (i.e. variable speed compressor) technology, which promises ultra-high efficiency and low energy costs. Can't speak to any operating characteristics on those though.

You might want to consider "portable" A/C units. They're about the size of a standard luggage bag with wheels, and all they need is access to a window or hole for in and out airflow and a 115 volt plug. Added bonus is you can wheel them into the house if you're having an issue with a hot room or want something just to cool the bedroom at night without running the house A/C.
Like these:
https://www.popularmechanics.com/home/g3066/best-portable-air-conditioners/

Hope this helps!

[Matt_T]

So does anyone have experience with these systems and can I use it to stabilize the temperature without breaking the bank?  I know they are pretty efficient but I don't want it to be so expensive to operate that I can't use it often enough to be worth the expense.

They're definitely going to be your cheapest running cost for cooling. For heat they're generally cheaper than everything but wood and natural gas. Though that can vary a bit depending on local energy prices. So it's among the cheapest options. Whether that's cheap enough depends on the building..........................

I'm running two cheap 12K 15 SEER inverter units in my 1,400 SF house for primary heat and air. Place was built in the early '50's so no insulation in the walls and crap insulation in the attic. But the place is pretty tight. T&G everything including the roof deck. North Miss so summers probably hotter/longer/humider and winters shorter/milder than yours. IIRC you're somewhere in VA?

Anyways best as I can figure last summer cooling used 2,000 kWh and this winter heat was 2,100 kWh plus about 50 gallons of propane for backup heat. That's under $500 for the year at my local energy prices

Secondly is there a better solution?

First off it sounds like you've got a serious air leakage problem since everything is getting wet when the temp swings. Do what you can to seal up the building or you're going to be fighting humidity leaking in and energy/money leaking out.

Second insulate the downstairs if you can do it for reasonable money and time. My place I will insulate the attic once I get done with rewiring. The walls maybe, at some point, because it'd require ripping the siding off. And I'd likely never see a return on investment from insulating the walls. If I do it it'll be to kick the mean radiant temperature up in the winter.

Once you get as much of the above done as you reasonably can then start looking at climate control. Based on your description of the shop a minisplit downstairs and keeping the window shaker upstairs would be a good starting point.

And if you do go with mini splits consider tooling up to install them yourself. You can buy everything for what a lot of HVAC pros charge for one install. And some of it crosses over to automotive A/C so you can get more use out of it.

[stokester]

Secondly is there a better solution?

First off it sounds like you've got a serious air leakage problem since everything is getting wet when the temp swings. Do what you can to seal up the building or you're going to be fighting humidity leaking in and energy/money leaking out.
[/quote]
Thanks Matt, good info.

The building is really pretty tight.  The condensation I was referring to is when I open up the overhead door in the morning after a cool night which leaves the concrete slab and all inside cool, a warm/moist day will cause sweating on these surfaces.  My thought is that a system to keep the inside temp at least 50deg or so would prevent this.  I've worked downstairs on very hot/humid days without much discomfort using just a shop fan so I don't need to keep it house-comfort cool and upstairs I have the "window shaker" when I work on the electronics bench.

Long-term plan is to insulate but I'd like to get the HVAC in first.

[bonneyman]

"And if you do go with mini splits consider tooling up to install them yourself. You can buy everything for what a lot of HVAC pros charge for one install...."

IDK. You could probably get by without a torch setup but a good vacuum pump ain't cheap. Plus, if you're just an average DIY, there's alot of HVAC stuff that you'll have to guess at. And - if you have any problems - many companies hassle you with the warranty if you didn't have a licensed guy do it. Get a reputable dealer to install it and you'll be miles ahead.

[stokester]

I've got an HVAC company that has taken care of my house for over 20 years and the Trane system installed over five years ago has been fault-free.  I have a maintenance contract with them for twice a year checkups and will use them for any new system I purchase.  For me it is worth any amount I would save.

[slip knot]

When I was looking at this I found most of the warranties are void if a DIY installed it. 

[Matt_T]

The building is really pretty tight.  The condensation I was referring to is when I open up the overhead door in the morning after a cool night which leaves the concrete slab and all inside cool, a warm/moist day will cause sweating on these surfaces.  My thought is that a system to keep the inside temp at least 50deg or so would prevent this.  I've worked downstairs on very hot/humid days without much discomfort using just a shop fan so I don't need to keep it house-comfort cool and upstairs I have the "window shaker" when I work on the electronics bench.

Long-term plan is to insulate but I'd like to get the HVAC in first.

OK if the condensation is only happening with the door open you should be alright. Downside of doing HVAC before insulation is you're either going to be living with undersized equipment until you insulate or oversized afterwards. Inverter minisplits handle oversizing better than most systems but the closer you can size them to the cooling load the better the humidity control. Another thing regards sizing is you'll probably need to go with a "hyper heat" mini to get the heating you need without oversizing for AC.

Regards whether heating to 50* will be enough for your condensation problem try plugging in the outdoor temperature and RH you're having problems with at the following link. What it calculates for dew point is the temperature you need inside the shop to prevent condensation. Also a lot of minis don't really have a good way of handling low indoor temperature heating. A lot of them jump from a frost protection mode to normal heat starting in the 60*+ range with nothing in between.

http://bmcnoldy.rsmas.miami.edu/Humidity.html

[Matt_T]

IDK. You could probably get by without a torch setup but a good vacuum pump ain't cheap. Plus, if you're just an average DIY, there's alot of HVAC stuff that you'll have to guess at. And - if you have any problems - many companies hassle you with the warranty if you didn't have a licensed guy do it. Get a reputable dealer to install it and you'll be miles ahead.

No torch needed. Just bending the lineset and 45* SAE flares for the ends. I did my first two installs hand bending but I do have a lot of experience hand bending tube so it might be best for a DIYer to buy a tubing bender. The flares I use a Ridgid flaring tool which wasn't expensive. And you're supposed to torque the flares so figure in a few bucks for a couple 3/8" drive crowsfeet if you want. Under $200 for all of this.

The vacuum pump I just googled my Yellow Jacket SuperEvac and I don't remember how much I paid for mine but it wasn't close to what they're selling for now. But poking around on Amazon it appears a 2 stage Robinair can be had for well under $200 and you could go much cheaper.

Gauges under a $100 including the 1/4">5/16" adapter you'll probably need.

So what you've got to have comes in under $500 and a good chunk of the tools are going to have other uses for most folks on this forum.

To do the job 100% by the book you should also have a micron gauge and high pressure inert gas but that's only another couple hundred dollars for the gauge and high pressure regulator, plus whatever the gas costs you. Personally I use the argon cylinder from my TIG for an inert gas source. And FWIW some pros will skip these parts.

I'm also scratching my head at your "reputable dealer" comment. If you're in the trade and can't find a reputable employer to work for how is a customer gonna find one?

[Matt_T]

I've got an HVAC company that has taken care of my house for over 20 years and the Trane system installed over five years ago has been fault-free.  I have a maintenance contract with them for twice a year checkups and will use them for any new system I purchase.  For me it is worth any amount I would save.

If you do decide on a pro install talk to them and try to gauge how comfortable/familiar they are with minis. Our local Trane dealer is good on conventional systems but I wouldn't let them work on my minis. These things are a major technology leap compared to conventional air conditioners which intimidates/confuses a lot of hvac guys. If you go the pro route try to find someone who knows how to properly install and troubleshoot them.

[bonneyman]

I'm also scratching my head at your "reputable dealer" comment. If you're in the trade and can't find a reputable employer to work for how is a customer gonna find one?

Well, it's a prefaced statement so I don't come across as high and mighty. I know arrogant owners, I don't want to be one.

I don't say licensed contractor because I know alot of licensed companies that I wouldn't have work on my dog house. Besides, virtually all licensed companies have one guy (i.e. the boss) who holds the license - but the person doing the actual work can be anywhere on a wide spectrum of knowledge, ethics, and workmanship. And I can't guarantee that those techs are doing it right.
When I say "reputable dealer" I mean one that your friends have used and has a good reputation. People who's houses you can visit and see the work that the guy did. TV ads don't tell the story, suave radio ads don't, shiny billboards don't. The proof is in the pudding. If your friends like the work that's been done - and th follow-up maintenance - that would be the guys I would recommend you hire.

[slip knot]

I looked at these a year or so back as replacements for the window units in our rentals. I've got 6-8 window units running at one time and am replacing at least one per year. Heat/cool window units aren't cheap. Several people in the business recommended the Mitsubishi Mr slim units. they had really good luck with them and they came with a real good 5yr warranty IIRC. But the units were @$5000 for the size looked at. I looked at several other brands and they were a good bit cheaper but the warranty wasn't as good either. one thing I got from almost all of these was the warranty was void if you didn't have a factory trained installer put it in.

I had to put this project on hold for a while and will probably look at it agin when I have a vacant house again. I will go with a cheaper brand and do the install myself. I already have all the tools needed and it doesn't seem to complicated to install these things.

[Matt_T]

I looked at these a year or so back as replacements for the window units in our rentals. I've got 6-8 window units running at one time and am replacing at least one per year. Heat/cool window units aren't cheap. Several people in the business recommended the Mitsubishi Mr slim units. they had really good luck with them and they came with a real good 5yr warranty IIRC. But the units were @$5000 for the size looked at. I looked at several other brands and they were a good bit cheaper but the warranty wasn't as good either. one thing I got from almost all of these was the warranty was void if you didn't have a factory trained installer put it in.

I had to put this project on hold for a while and will probably look at it agin when I have a vacant house again. I will go with a cheaper brand and do the install myself. I already have all the tools needed and it doesn't seem to complicated to install these things.

I think we discussed this some before the old site crashed. Reliability might be better but I wouldn't bet on it with cheaper units. And when one does fail it'll be more aggravation, and possibly more cost, compared to switching out a window shaker.

The main benefits of minis are improved comfort, much lower noise, and lower running costs. They're not generally cheaper than window shakers when it comes to upfront or lifetime equipment costs. Which leaves you with the costs and your tenants getting the benefits so I'm not convinced they're the best solution for you. To drift the thread slightly maybe adding baseboard electric heaters and switching to AC only window shakers would be a better way to improve reliability/reduce your cost?

But yeah they're not difficult to install so long as you're a do it right electro-mechanically inclined type. And if you're really concerned about warranty take a look at the Mr Cool DIY minis. You'll pay a bit of a premium for them compared to an equivalent unit but nothing like the cost of a pro install. Main downside of them is you're stuck with a 25 foot lineset which you'll have to find a way to deal with.

[bonneyman]

Yeah, the pre-made line sets seem to always be short unless it's on a spare bedroom where the cond unit is on the opposite side of the wall from the evap unit. Some installs I've seen had longer linesets - but didn't need them - but the installer(homeowner?) didn't mess with shortening and fittings and just left the excess lines coiled up out near the cond unit.

[skfarmer]

I find this topic interesting. My sons house is cooled with 2 window units. One big unit that is "supposed" to cool the kitchen, living room and bathroom and a smaller unit for the master bedroom. He wants to replace the large unit with a DIY minisplit.

Guess who he wants to install it?

[bonneyman]

I find this topic interesting. My sons house is cooled with 2 window units. One big unit that is "supposed" to cool the kitchen, living room and bathroom and a smaller unit for the master bedroom. He wants to replace the large unit with a DIY minisplit.

Guess who he wants to install it?

I learned a magic word many years ago - "NO!"   

[skfarmer]

Well he is about 80 acres ahead me doing tillage  and could have told me today so I suppose it will work out.thing is he is fully capable of running that tractor and i know very little about ac......

[Matt_T]

Yeah, the pre-made line sets seem to always be short unless it's on a spare bedroom where the cond unit is on the opposite side of the wall from the evap unit. Some installs I've seen had longer linesets - but didn't need them - but the installer(homeowner?) didn't mess with shortening and fittings and just left the excess lines coiled up out near the cond unit.

The "pre flared" linesets that are bundled in the packages being sold online are normally around 16 feet which isn't going to be enough for much more than straight out the back and down. But the flares aren't the greatest and the nuts they use are light. Best to cut the flares off and re-flare with the nuts furnished with the equipment. And you can buy longer linesets if you need them. Just have to read the installation manual because you'll have to weigh in additional refrigerant if you go over a certain length.

The actual DIY units are a fixed 25 feet which can't be shortened without opening the lineset and evaporator to atmosphere which defeats the whole DIY aspect. And using up 25 feet of lineset is going to take some planning to make it look good.

One other thing regards condenser placement. Do not hang one on a wall unless you absolutely have to. They will transmit low level noise/vibration into the building.

[Matt_T]

Well he is about 80 acres ahead me doing tillage  and could have told me today so I suppose it will work out.thing is he is fully capable of running that tractor and i know very little about ac......

You don't really need to know anything about AC to install a DIY unit. It's just pretty basic construction, mechanical and electrical. Buying the correct sized unit requires some knowledge but that's the kiddos problem

[bonneyman]

Well he is about 80 acres ahead me doing tillage  and could have told me today so I suppose it will work out.thing is he is fully capable of running that tractor and i know very little about ac......

You don't really need to know anything about AC to install a DIY unit. It's just pretty basic construction, mechanical and electrical. Buying the correct sized unit requires some knowledge but that's the kiddos problem

I respectfully disagree with you on this, Matt. I've been to far too many DIY mini split jobs where the guy was trying to save money and "all you AC guys screw people" and they installed the dang thing and it didn't work. Then they call me, and are in my face that a "repair" shouldn't cost all that much!
Sure, anybody with basic wrenching knowledge can do the mechanical install and hook up 220 volt leads but the evacuation and balance charge is not something the backyard mechanic can easily do. The refrigeration cycle is an experience as well as a finesse thing, and people are bound to get into trouble if they just wing it. I'd hate to say "anybody can do it" and then something goes south and they're left hanging with a fairly expensive paperweight that the dealer won't warranty.

[Matt_T]

I respectfully disagree with you on this, Matt. I've been to far too many DIY mini split jobs where the guy was trying to save money and "all you AC guys screw people" and they installed the dang thing and it didn't work. Then they call me, and are in my face that a "repair" shouldn't cost all that much!
Sure, anybody with basic wrenching knowledge can do the mechanical install and hook up 220 volt leads but the evacuation and balance charge is not something the backyard mechanic can easily do. The refrigeration cycle is an experience as well as a finesse thing, and people are bound to get into trouble if they just wing it. I'd hate to say "anybody can do it" and then something goes south and they're left hanging with a fairly expensive paperweight that the dealer won't warranty.

Seems like we're talking about two different things. I'll mostly agree with you about a DIYer installing a flared lineset minisplit. It does require equipment, and probably skills, beyond what an average DIYer will possess. Their choice whether to invest in tools, and themselves, or pay a pro to either install it for them or fix their screw-up.

The DIY units I, and presumably SK, are referirng to are set up for a DIY install. Lineset and Evaporator are already assembled, and sealed,and attach to the Condenser with some coupling things which supposedly don't allow any atmosphere to enter the system. Then after the Condenser is connected to the lineset you open the valves to release the refrigerant like you would after evac, pressure test, evac on a conventional install. Below is a link to the the "manufacturer" for more info if you, or anyone else, is interested.

https://mrcool.com/mrcool-diy/

[stokester]

Well... I pulled the trigger and had a Trane/Mitsubishi split system installed in my garage/shop.

I'm amazed at how quiet the units are, especially the outside one, I can hardly hear it running even standing next to it.  These next few days will put it to a good test with the 90+ degree temperatures and coastal Virginia humidity.

[goodfellow]

You're livin' the life Nick! Great system and well worth it. I'm stuck with a wall mounted window unit -- it does a fair job, but yours is sooooo much better.

[muddy]

Would love to put a few if them in our house.

Sent from the twisted mind of the Mudman

[walrus]

I've been running a mini split for years, more for heat than for AC. An open floor plan house makes for a perfect fit for one of these. I use it for shoulder seasons, fall and spring. Shut it off in the dead of winter. Ran most of July this summer . Fujitsu is what I have

[fatfillup]

Walrus, reading your post I am reminded of how different your climate is then most here and radically different than Bman's in Arizona or any of our southern members.  Your need for ac is small but heat is huge and goes on and on and on

[stokester]

You're livin' the life Nick! Great system and well worth it. I'm stuck with a wall mounted window unit -- it does a fair job, but yours is sooooo much better.

Yes the garage stays cool and if I need to work upstairs I use the window AC too.  Best of all the humidity is under control.

But a word of warning! My wife commented with the cool shop she could now spend more time in there with me 

My response was for her to check the sign on the door.

Full disclosure here... she had that made for me when we built it.

[DeadNutz]

Good one Nick. Wouldn't work for me as most the machinery belongs to the wife and her art studio is upstairs and the stairs are inside. We could of put the stairs outside bet then the snow and ice would have made them dangerous.

[stokester]

This last week gave me a good test of the new AC - passed with flying colors.  It was nice to work in the shop at a nice 77deg when it was near 100 with 90+ humidity.

[Jamesyarbrough]

Good choice. Mitsubishi are about the best there is. They are more expensive tho.

I didnt wiegh in on this because i wasnt here but the flares are notorious for leaking on mini splits. I hope your installer was up to date.

[goodfellow]

It's a wonderful system. I must confess that this is THE way to go for ultimate convenience. Good job Nick!

Last week was very humid and hot, and I only have a window unit in my garage that I punched through the wall, and mounted very high. While doing oil changes on the family fleet I was able to maintain about 80-85F. My garage door isn't insulated and the driveway blacktop just radiates heat through those closed doors like an oven, but i was fairly impressed with what that little 8500 BTU unit could do given the circumstances.

[stokester]

It's a wonderful system. I must confess that this is THE way to go for ultimate convenience. Good job Nick!

Last week was very humid and hot, and I only have a window unit in my garage that I punched through the wall, and mounted very high. While doing oil changes on the family fleet I was able to maintain about 80-85F. My garage door isn't insulated and the driveway blacktop just radiates heat through those closed doors like an oven, but i was fairly impressed with what that little 8500 BTU unit could do given the circumstances.

At first glance I thought you were outside my garage 

I still use the upstairs window unit to keep the radio shop comfortable when needed.  It still remains to be seen when heat is required.