Window AC sizing
#11
Not sure which forum to put this but I’ll start here since it’s shop related.

Thinking about putting a window unit in my roughly 650’ shop. Thought about a mini split for a long time but for a few reasons I’ve decided against it. I’m torn between 12k and 15k units. 12k all says for 550’ and 15k is 750+.

I also know I’m not supposed to go over or under by too much so I’m undecided. Price isn’t a factor as it’s only the difference of $100 or so but size is a factor. I’d like to minimize the projection outside as I drive right by the shop window to pull in the garage. (Luckily it’s my garage bay and not my wife’s so that helps my odds of not tearing it out with a car!)

I’m thinking I might be okay with the smaller because:
Basement shop, below grade on two full sides.
Only one standard 30”x48” window
Temp rarely gets above 78 even unconditioned.

What say the braintrust? I’m leaning toward the smaller but I’d think it’s probably an easier to condition space than the average living space with windows and people constantly coming and going.
-Marc

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#12
What state are you in?
What temp do you want to maintain inside?
Is the shop insulated? How well?
Is the shop tight with little air leaks?
What particular excessive loads are there in the shop in the summer? (Lot of traffic, big power tools, lighting...)
Do you want heat? (You can get a heat pump or elect heat).

If you have fairly clean shop with a DC, a GE Zoneline might be a good choice- will stick out only a few inches and last longer than a typical window a/c. Come time to replace it, just slide another one in- no replacing the case and doing all that cutting and fitting. Initially it will require cutting a hole and framing a 42"x16" space anywhere on any wall and out of the way. Easy to pull and clean. I would choose this way over a mini-split. (Long term suggestion).
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#13
Daddo's questions are important, but I'll mention what has worked for me in west central Ohio. We don't get real hot, in fact we have had summers where we never reached 90. But my last shop was 24x32x8 , and R18 walls and R40 ceiling. I had a 10K unit in it, and it worked quite well...unless i ran the DC on a marathon session. The DC air comes out warmer than it goes in, and that heat could overwhelm the AC. We moved, and my current shop is 32x30x10 (R19 and R40), and I bought a 12K unit for it. I've pretty much the same results...it wrks well unless I run the DC for several hours (like a drum sander session), then it's not able to handle the load. In both cases those marathon DC session weren't all that often so the units I had were adequate.
I started with absolutely nothing. Now, thanks to years of hard work, careful planning, and perseverance, I find I still have most of it left.
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#14
Appreciate the input so far.

I'm in Alabama, just outside Birmingham so our summer are pretty hot but moreso than hot they're humid. I'm too lazy to google it but I'd say we have more days above 90 than not in the summer.

Shop is pretty tight. There's no HVAC in there at all. All the household mechanicals are in the garage. The longest wall is shared with the garage and is insulated, about 8-10' of wall extends out beyond the garages and that is where the window is and where the unit will go (also insulated). Ceiling is insulated from the space above too. The other walls are either completely below grade or mostly so.

There's no traffic in there unless I'm down there working or go in to grab a beer from the fridge. I have the usual complement of tools, tablesaw, jointer, bandsaw and DC are all 3hp 220. I have 8 8' fluorescent light fixtures and a mini fridge.

As I said it rarely gets above 78 even in August. I keep the house at 72 so I don't see trying to drop the shop much below that. No real need for heat. I've not seen it below 60 down there yet which is fine for me with a long sleeve shirt on...have to hold on to some of my Canadian roots down here.

House is brick so cutting a hole in the wall is a little beyond the scope of the project. Really shop isn't terribly uncomfortable even in the summer with a few fans going but just looking to make it a little nicer. I've certainly had hotter shops in other houses.
-Marc

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#15
Ceilings are 9.5' (don't ask me how they came up with that.
-Marc

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#16
see you added more info while I was typing so some of this is irrelevant.

how low do you want to make temp? 72?


still think smaller unit is better. a variable output or unit with dehumidifier even better. not sure if those are avaliable in window units.


---------------

I have a 1500btu Mitsubishi mini split with variable output in my just under 700sqft garage here in N georgia. Insulated garage door but otherwise uninsulated except for one shared wall with home. works great for AC and good for heat untill it gets into down to about 15 degrees.... insulation in the attic someday. At 15 or so it works but has to work continuously.

I would think below grade you will want the smaller one unless you are trying for heat. it your delta T(difference in temp between inside and out) is so low the bigger unit will probably short cycle meaning it wont dry the air as much.

are you looking for cooling, heating, moisture control?
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#17
Looks like there are inverter(variable output) window units

an example not an endorsement.

LG LW1517IVSM Window Air Conditioner, 14,000 BTU, White https://www.amazon.com/dp/B07D81476Q/ref...gDb01WS0D5
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#18
The humidity is most of the heat you'll have to remove (then there any liquids, metals and everything else in the shop). It will have to run a long time just to bring it down 4 degrees doing so. Then if it is left on to keep the humidity down, it will cool easier if you need it. If you want to walk in and cool it down quickly, you'll want the larger unit. If you leave it running most of the time, the smaller unit will work.
The run time is the only time it will be removing humidity, so if you were to set it at 76*, it won't run much, and it will be a little cooler but with high humidity and uncomfortable.
If the blower is left to run all the time, the humidity will be higher- best to set the blower to shut off and cycle with the cooling cycles.
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#19
I have a small 320 sf shop in Mobile, Alabama. It is fully insulated with 9' ceilings and lots of florescent lights. I had a 10k window unit mounted through the wall that was inadequate. The 12k unit I replaced it with is adequate most of the time. For your shop, I think I would strongly consider the 15k or larger unit. Remember, you are cooling a space to work in not sit and watch TV.
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#20
Willyou, appreciate the input. Is your shop inca basement also?
-Marc

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