Adapting old window a/c unit for shop use?

[crazybrit]

I'd like to add A/C to my detached shop (460 sq ft).

I already have a portable Cadet "The Hot One" (http://cadetheat.info/RCP) I use for heat.

The shop is packed. I don't really have room for a floor standing unit as floor space is at a premium. At least it's an option I'd like to avoid.

I have the pictured window mount ac unit (16"x12") that is surplus since we added full house ac to the main house. It's designed for a sash window.

Whatever I do, I'd like it to be a permanent install (winter and summer). I don't have the space to be removing and storing the a/c in winter.,

The options I've been considering:

- modify the window somehow (red arrow - 26"x26") to allow the surplus window mount ac to be fitted.

- modify the wall adjacent to the window (blue arrow; may have to relocate 120v wiring) to allow window unit to be installed -- I don't think this is viable due to wall thickness, not the right kind of ac.

- Buy a new thru-wall mounted heater/ac (at blue arrow) and sell the current Cadet heater.

Disadvantage of the window install is that:

a) it reduces the available natural light
b) the surplus unit is old and was cheap $150. Not sure how much life it has left but then they are easily replaced.

What would you do?

Thanks

 

[nadogail]

When I was tasked with cooling a Security Shack (comparable to a small garage) I used a Sawzall and made an opening in a wall. I re-enforced things so that the repurposed window unit could only be remove from the inside. My boss said that I had hardened the Guard Shack wile adding the AC unit.

 

[Bert_]

I would never put a window unit through the wall. It's impossible to flash correctly and most end up leaking. Next issue is when it quits you won't find one exactly the same size. if you want to put it through the wall buy a sleeve unit. I think they have a flange around the outside.

Those look like old windows so the the sash should come out pretty easily. It's hard to see on the inside but there should be a stop that holds the sash in.Usually held in with a few screws or small nails.

If you plan to leave it in during the winter be prepared to wrap plastic around the whole thing inside and out. They leak air like a sieve.

 

[510ebl]

Not really what you are asking, but research the 120v mini splits. You should save electric, wall space, window area, and it will run more quietly inside. The trade off of course it the one-time cost, but the benefits are worthy of note.

Also, all the stuff Bert said.

 

[a_whale]

<deleted>

 

[crazybrit]

Crazybrit, another idea to add to the pile, have you seen these portable roll-around air conditioners? I have one that I keep in the corner just in case, it's called a pinguino or something like that. The one I have sits around 30" tall and a 15"x15" footprint or so, I think it is rated to cool upwards of 2500 square feet in that size. They make them smaller. I have seen them for around your $150 price range on craigslist and facebook marketplace. They have a flexible hose (mine is around 6" in diameter) that goes to a window for the hot air from the condenser side of the unit. You could easily adapt that hose to a dryer type vent in the wall. Would be a lot easier to seal than trying to keep a big wall unit hole from leaking.

If you reread I don't have the floorspace.

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[a_whale]

<deleted>

 

[crazybrit]

I would never put a window unit through the wall. It's impossible to flash correctly and most end up leaking. Next issue is when it quits you won't find one exactly the same size.

I was also concerned that the window unit isnt designed for the wall (stud) gap.

Not really what you are asking, but research the 120v mini splits. You should save electric, wall space, window area, and it will run more quietly inside.

Intriguing idea. We have a Mitsubishi dual zone heat pump in the house.

I assume you're talking about something like this?
https://www.pioneerminisplit.com/co...-mini-split-air-conditioner-heat-pump-115-vac




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[Bert_]

The portable window units aren't great anyway. The single hose units exhaust room air. Supposedly there are 2 hose units that use outside air.

Overall a window unit is better.

 

[yeldogt]

I have seen some rather lame installs where people put the window units through a wall ..... you need to make sure no side vents would be blocked. Or make the opening bigger ...

I would not mess up the current windows -- less light and interesting windows. If you go the wall way -- what's on the side. You could always replace with a window to make it nice again.

the solution would be a minisplit --t he one you liked to would require someone to do the evac of the lineset. Have you looked at the Mr Cool DIY .. google DIY.

If you have expensive electric .... the mini will save you in the winter as well ... about 1/3 less

 

[65ranchero]

I agree, mini split is the way to go

 

[crazybrit]

Oregon 11c kW/h approx. Much cheaper than East coast.

My only concern with a mini split is how fast it heats (and cools). I don't heat the shop all the time, I turn on the current 240v heater (Cadet RCP402S 4kw claimed 13648 btu) about 30 mins before I go inside for a few hours.

The unit I linked to before at 9000 btu may be a bit underpowered compared to the current Cadet but they have 12000 btu units for $40 more

120: https://www.pioneerminisplit.com/co...-mini-split-air-conditioner-heat-pump-115-vac

240: https://www.pioneerminisplit.com/co...-mini-split-air-conditioner-heat-pump-230-vac

Also I have several 240v circuits in shop and could repurpose the one that currently serves the Cadet for a mini split but at first glance specs of the Pioneer units didn't seem thst much different between the 120v and 240v units. Is there an advantage to the 240v units?

I was aware on the evac. I thought you could use a vaccum pump. The pioneers come pre installed with enough coolant for a 15' line, more than enough. Anyways, right now I'm just doimg 10,000ft thinking. The actual issues of install can come later. I'll for sure check out the Mr DIY you mentioned.

Thank you all!!!

 

[crazybrit]

Review of the Pioneer unit:

Linked from here: https://minisplitratings.com/complete-list-mini-split-manufacturers/#pioneer

It mentions they're sold on Amazon. I couldn't find them but did find this:

https://www.amazon.com/dp/B089N5Q745/?tag=atomicindus08-20

I looked at the Mr DIY and 12000 btu is around $1500 but they are supposedly actually DIY install. I guess it depends on how much of a Pioneer/Della install I could do myself, how much I'd need to farm out and how much that would cost.

Warranty on the Della would be an issue. Pioneer seems more established.

 

[510ebl]

I was also concerned that the window unit isnt designed for the wall (stud) gap.



Intriguing idea. We have a Mitsubishi dual zone heat pump in the house.

I assume you're talking about something like this?
https://www.pioneerminisplit.com/co...-mini-split-air-conditioner-heat-pump-115-vac




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Yes, that style. The DIY type would save the installation cost, beware of any differences in warranty. There are MANY threads here about members’ successes and challenges.

If you have 240 available, you might want to step up to more heat capacity. On the other hand, once you see how efficient these can be you might decide to maintain the shop at a more comfortable temp all the time.

How is your insulation?

 

[crazybrit]

Yes, that style. The DIY type would save the installation cost, beware of any differences in warranty. There are MANY threads here about members’ successes and challenges.

It's not just warranty, it's parts availability once the warranty is over. I went thru a similar thought process when buying a TIG welder.

The cheap unit I found on Amazon seems very iffy due to the above. I'll read some other threads here.

If you have 240 available, you might want to step up to more heat capacity. On the other hand, once you see how efficient these can be you might decide to maintain the shop at a more comfortable temp all the time.

The Cadet is already on it's own 20A 240 circuit. I rewired the whole shop when we moved in 5 years ago. If you look above you'll see I said I'd probably go with the 12000 btu as it's barely any more.

How is your insulation?

Walls and ceiling. Fiberglass batt. I forget the R value. I need to pull a new 240v circuit for my CNC mill so I'll check. The attic above (access via pull down ladder) is un-insulted.

 

[Syberia]

If you reread I don't have the floorspace.

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They don't work anyways. Sure they produce cold air, but for actually cooling a space and maintaining temperature, they're useless. They exhaust conditioned air across the condenser and out the hose, creating negative pressure and pulling in more hot air from outside.

That said, I have mounted multiple window air conditioners through 2x4 walls. Cut the hole a little bigger than you need to accommodate replacement with a different unit down the road, seal the gap with spray foam, and trim with 1x4 on the inside and fence pickets on the outside. Use silicone to seal between the frame of the unit itself and the trim boards. Leave the window bracket on the top and screw it to a 2x4 inside the wall. That plus the spray foam will keep it from going anywhere. Just make sure not to block the vents.

 

[Joe Reed]

Here's how I installed a window unit (cool & heat) through the wall of my garage while avoiding blocking the vents. Making the opening wider than the unit made space for the side vents. It's been in place since 2008 with no issues at all.

 

[subroc]

If that was mine, I would do that in the cheapest, effective way possible. I would tell myself, I have an air conditioner. I have a window. That air conditioner is going in that window. I would pull that glass panel and that would get put somewhere in the overhead in the shop saving it for reinstall at a later date. I would make a frame for the lower portion with two insulated panels on the outside with a rightsized opening in the center for the AC and a top plate to support the widow. The upper would be a glass panel that I would make. The 2 pieces would fit the window opening. Seal it. Trim it. Paint it. I wouldn't over think it.

A temporarily permanent install with the ability to go back to original.

 

[PoorUB]

If you have no plans on moving, go with the mini split. Pay once, get something nice and be done with it. If you are concerned about warm up time, leave the electric heater in place, run both to bump up the heat, then use the mini split to maintain, or just start up the mini split earlier.

If you use your shop often, you might just leave it on, but bump the temp back a few degrees and turn the temp to where you want it when you spend time in the shop.

I have a Horizontal mounted gas furnace and AC in my shop, but I live in North Dakota so it gets cooold here. I don't use the AC much, but I wouldn't be without it either. I have a WiFi thermostat in the shop. I can change the temps from my phone and set it a couple hours earlier so the temps have stabilized when I go out there.

 

[Bert_]

If you have no plans on moving, go with the mini split. Pay once, get something nice and be done with it. If you are concerned about warm up time, leave the electric heater in place, run both to bump up the heat, then use the mini split to maintain, or just start up the mini split earlier.

If you use your shop often, you might just leave it on, but bump the temp back a few degrees and turn the temp to where you want it when you spend time in the shop.

I have a Horizontal mounted gas furnace and AC in my shop, but I live in North Dakota so it gets cooold here. I don't use the AC much, but I wouldn't be without it either. I have a WiFi thermostat in the shop. I can change the temps from my phone and set it a couple hours earlier so the temps have stabilized when I go out there.

One of the issues I have seen with using a mini split to maintain heat is that the lowest setting is often 62°. Most of the time I don't even want it 62° when I'm working out there.

 

[slodat]

It’s quite easy to maintain temperature below the 62F with a little automation. I use Cielo thermostats on my mini splits for this.

 

[crazybrit]

It’s quite easy to maintain temperature below the 62F with a little automation. I use Cielo thermostats on my mini splits for this.

@slodat I'm in Oregon so similar area of country to you.

Can you elaborate on your solution. Are you using a third party thermostat to cycle the unity between off and heat?

 

[slodat]

I use Cielo Breez thermostat controllers on my Pioneer mini-splits. The Cielo controllers have a phone app. I program them on and off to maintain temps I want. I tend to use the heat as a binary control on/off at the max temp. This is because my mini-splits only heat down to about 32F outside ambient temperature and I don’t have a thermally efficient building. I have several programs that I turn on and off based on when I plan on being in the shop. I have an off that runs the same time everyday that I always leave enabled. This prevents running overnight unnecessarily.





At some point I will replace these mini-splits with new models that heat down to negative F ambient temps.

This setup has allowed me to minimize my electrical usage and always walk into a comfortable shop. The splits are much more efficient source of heat that electrical resistive heat. We don’t have natural gas where I’m at and our electric rates are the lowest in the country. I do have resistive heat as well. It is all controlled by ecobee thermostats in a similar fashion. I have a thread about the heat control on here.

https://www.garagejournal.com/forum/showthread.php?t=381086

 

[crazybrit]

Ok. I ordered the 12K BTU 240V Pioneer Mini Split I've been very impressed with their customer support. They guys they have on their online chat are very knowledgeable. I hope it bodes well for the product itself.

I'll pour my own pad, so I also ordered the isolation mount.

They offer a line flushing kit but after talking to them they still recommend pulling vacuum if you can (plus you can pressure test) so I ordered their gauge and hose set which is setup specifically for their mini-splits.

For a vacuum pump they recommended this. Given the reviews I'm going to order it only once I've got everything in place as I may need the 30 day return I'll also check around to see if I can borrow one.

I'll pull a new 240v circuit. 12-2 will work fine with a 15A breaker. Local code doesn't require a fused disconnect (and the Pioneer label states "fuse/breaker") so I ordered this from Amazon.

Should be a fun project.

My only mild concern is whether I can run the coolant lines inside the wall. The condensor will be directly behind the interior wall unit but I'm fairly sure the wall is 2x4 construction and there is a min 4" radius bend requirement on the hoses, so I may end up having to run it externally and hide under a cover .... we shall see.

Anyways, time to offer up the A/C on Nextdoor for free. Should make someone happy.

So far I'm looking at: $791.34 shipped for the Pioneer. $40 with Amazon for the disconnect and 25' of 12/2 Romex.

Thank you for your help and suggestions!!!