use window unit inside

[edl]

if you wanted to use a window unit inside (that is, no part of it through the wall or a window, the unit completely inside) how would you

1. exhaust it - build a wood box around the rear and side exhausts and reduce to a vent tube? other?

2. what about the water - are these designed to drip water? it seems as if they have a tray that catches the water - is it supposed to overflow from there? - could you cut a hole in tray and draing into tube on bottom? - does it need any of this water for cooling purposes?

the reason I am asking all this stuff is because Sam's club sells a ge window unit that is a whopping 24,000 BTUs for 372 bucks - if a minisplit alternative is something like 6K installed (at least according to another post) - 24K btus for under 400 bucks???? pls help me out so i can use this thing!!! - here are a couple of pictures, but they don't exactly give me the answers - thanks!! ed

 

[edl]

so here is what i am thinking:

the unit has 3 exhaust vents - 2 grill types on the sides, just near the back before it rounds the corners to the back, and the whole back of the unit - i went back to sam's and felt the exhaust (on a smaller unit) - noticed that it is not blown out very hard - this makes sense - the back of the unit is supposed to be outside, so it just needs to drop out the back - it is not meant to blow through ducting - so...

duct tape the 2 side exhaust vents - not pretty, but it will work - then, screw a piece of plywood across the rear with a few sheet metal screws - cut a 4" hole in the middle of the plywood and install an inline 4" exhaust fan ($24 at HD) - connect that to some flexible 4" vinyl ducting (10') so it has slack for the door to open and close - then, some clear vinyl tubing (1/4") to drain the water - i'll take pictures...and pls let me know if you think this won't work - thanks!! ed

p.s. if this works...just think about it...2 tons of ac for about 400 dollars...beat that! and if it works for you...i am very happy to have shared...let us know!

 

[kenfath]

Why would you want to do this?

 

[edl]

Why would you want to do this?

money - the unit costs $372 and puts out 24K btu's of cooling - the next closest thing i have seen on this forum for a 2 ton unit is anywhere from 2 to 6 thousand - are you trying to say it wouldn't work? - that is what I am trying to find out - if it would, at that cost, why wouldn't I?? - thanks, ed

 

[kenfath]

I fully recognize that room air conditioners are priced right! My 640 sq/ft garage has an 18000 BTU unit installed through the wall. I've installed three of them that way and know from experience it is a fairly simple job. Also I helped a friend install one in a rental garage. The owner gave permission with the understanding the unit and wiring would remain. My friend got three years of use before moving and he had no reservations about walking away from the investment.

About ten years ago we had a similar brain storm and spent some time thinking about. Our conclusion was we'd never be satisfied. The negatives we came up with included: lots of floor space lost by AC unit and hoses; the unit we considered would have required two 16 inch diameter flex vents to provide sufficient exhaust capacity; exhausted air will be replaced with outside heated air; and, the greatest concern was the heat which is transferred through the air conditioner's cabinet.

There was another recent thread where the AC unit was on a dolly and positioned in the garage door opening so the unit is outside. The door is lowered so it rests on the cabinet. Forgot how, the open space was blocked off with some kind of panels. IMHO that is the simplest way to go and will provide for a far more efficient operating unit.

 

[edl]

many thanks Kenfath - appreciate these comments - pls let me tell you my thoughts on them:

1. floor space is clearly an issue - I have build a wooden platform, about seven feet up that will house the unit - so that particular concern is dealt with

2. I don't follow on the exhaust or replaced with heated air - my thought was that the unit does not have much exhaust output primarily because it has such a large exhaust surface - that is, the whole back of the unit and a couple of side exhaust vents - so i was planning to reduce that to a 4 inch space to provide a bit more force, and to avoid overheating the unit, put an inline 4" exhaust fan (80cfm) to **** the hot air out - that will hook to a 4" duct to exhaust the hot air outside - as for the replacement air, as the unit is inside, it will be sucking air in from the inside of the garage - so this should be like the "recirulcate" button on the car - right?? - so it should actually cool faster as it will be taking already conditioned air - and even it were taking outside hot air, if it were through the wall or a window that is exactly what it is designed to do - so aren't I better off with the unit inside??? - finally, a very small vinyl tube to drain water from the pan to outside the garage door - so, why did you need 2 vent hoses? - were you just going to let it passively exhaust with the current exhaust output? - do you agree that with an active, motorized exhaust the 4" solves the problem??

3. heat transferred through the cabinet - well, truth be told I hadn't thought of that - the first 2/3's of the unit should be ok as that is where cool air is drawn in and cold air is sent out - the back third where the exhaust is will be hot - but with the fan sucking all the exhaust out that should help - and given the entire back will need no air outlet other than the 4" in the plywood screwed into the back (side vents will be duct taped), I could rap the back third in insulation - thoughts??

thanks!! - ed

 

[walt111]

Not being an a/c man I think the unit will over heat and not cool properly if you block the back and sides. There doesn't seem to be much air from there because of the large area. Think of your car see what happens if you block the front of the condenser with a piece of cardboard with only a four inch hole in the center. Tha a/c in the car will not cool very well. Just my thoughts.
walt111

 

[thrytis]

You'll need two 4" ducts, one for the air coming in and one with the air blowing out, and a fan on one. I don't know what speed of a fan would be needed, but i would think at some level it would provide enough air movement to cool the unit. Isn't this what some of the portable AC units do?

 

[67fairlaner]

Two more things:

1. That unit is 240 so you will need a dedicated circuit & a 240 volt extension cord.
2. Why not just cut a hole in the wall & install it the correct way?

 

[edl]

walt - thanks - if you just covered the exhaust vents and left a 4 inch hole for it to go out under the blower in the unit, i think you would absoluteley be right - it would overheat - the idea is to have an exhaust fan to **** out hot air faster than it would exhaust under its own steam in order to avoid overheathing - at least this is my theory - not sure if it would work.

thrytis - i am curious about this, saw this in the pictures at the top too - i would think this is true if you put the whole unit in a box where you are covering both the exhaust vents and the intake vents - in this case, the exhaust is getting channeled to a 4" duct, but the intake vents are all open - so that should be ok - right? - as for a portable unit, that is where I started - I bought one of those at sam's - but the highest rated one i can find is around 12,000btus and it just didn't cut it for my space - but that is exactly the way they work - open intakes, 4" exhaust with a blower inside exhausting it with force and a duct out - and a drip line for the water.

67 - correct on the 240 - had space for a breaker and can wire the outlet - as for doing it "correctly" I think you are right that the best way is to cut a whole - but that is work - already have a shelf for it - was thinking that if my idea works, it would be easier - but maybe you are right - maybe cutting a whole is easier - either way i need to plug into a 220 outlet

 

[thrytis]

If you don't cover the intake vents, then you'll be blowing your cooled inside air out your exhaust vent. To make up for that, warm outside air will be drawn into your garage through any cracks around doors and windows. I'm sure you would get some cooling effect from it, but it won't be very efficient. If you have a gas water heater in the same space, you'll be pulling the exhaust from that back into the room.

 

[edl]

"If you don't cover the intake vents, then you'll be blowing your cooled inside air out your exhaust vent."

-- right...this is one of the main concerns - my thinking here is that if the cfm's on the exhaust fan installed in line in the exhaust duct isn't too high, that should be minimized - but I do understand that what goes across the condensor will be coming from inside the garage and out - but this now explains why there a two duct hoses in the pictures at the beginning of the post.


"To make up for that, warm outside air will be drawn into your garage through any cracks around doors and windows. I'm sure you would get some cooling effect from it, but it won't be very efficient. If you have a gas water heater in the same space, you'll be pulling the exhaust from that back into the room."

-- good point...all the more reason for the intake line...i am starting to see...the hurdles are mounting...

 

[thrytis]

I wouldn't consider this stuff hurdles, just something to account for in your design. From this, it sounds like one hose portable ACs do exactly what you had originally suggested. For the cost of an extra hose and a slightly different cabinet design, you'll get better cooling. Using a window AC in this manner had crossed my mind too because i figured i could probably pick up a used AC for cheap. It is good to see that it has actually been done before.

 

[edl]

Thrytis - thanks for the word's of encouragement - I'll keep plugging away - I wasn't thinking of a "box" initially, i was going to tape the side exhaust vents and board up the back with plywood (so same size as back of unit, screwed in) - cut a hole and exhaust - if I need to do an intake as well, i suppose i could do the same - that is, duct tape the sides and then plywood the top (where most of the intake vent is) and cut a hole, run 4" ducting and get another in line fan in the opposite direction (so 80cfm in; 80 cfm out) - i'll let you know where I get...thanks, ed

 

[PoorOwner]

along the lines of this topic, do you think I can put a small window A/C on wooden dolly, with some plywood sized to fit my door, I can just block the whole door for a temporary cooling device just for the extra hot days?

I mean now we are talking about a fraction of the cost of portable and mini split systems.

 

[jm1fd]

A 4" inlet and outlet duct and an 80 cfm fan will not be sufficient for a 2 ton unit. That would be sufficient for a small refrigerator.

For a 2 ton unit you'd need 14" ducts and you'd need to be able to move about 1400 cfm.

I understand wanting to save money, but you won't be saving anything if you bake the unit to death every year or two and have to replace it. Plus when the thing is running it is going to use a HUGE amount of electricity because the compressor will be working against an astronomically high head pressure because of all the heat in the box.....unless you ventilate it as stated above.

 

[paul29]

EDL : I think you will be much happier with a through the wall installation as it will be quieter ( the noisy parts are outside ) and more efficient. I just put a 15.1k btu unit in my garage , through the wall , not a difficult job at all ,the instructions are included with the units designed for it . Just make the wooden box sleeve as per inst to fit the case . I went through drywall , 2x6 stud , insulation , boards , building wrap , strapping and Hardie siding. The 15K btu units only req 120V . About a 4 hour job (at my speed ) not counting drywall touchup ,caulking , trim and paint

 

[V-10 Killer]

I don't think the point of an indoor enclosure revolves around how hard a normal installation is. For me, I'm concerned about giving someone that wants in and easy entrance point. If I were to put a window style AC unit in the wall, it would be in the back side of my garage where I could not keep an eye on it from the house.

 

[Fueler]

FWIW: I have a 1600 ft shop, 12 ft to the eaves, open ceiling.
I have 2 24000 btu window units in the wall on opposite sides.
1 unit does the deal just fine 95% of the time.
For those days that too many machines are running and the weather is really nasty the second one gets turned on.
If I dropped the ceiling and some more insulation 1 only would likely do the trick.


Tips:
1: Install so that there is a slight downward tip on the outside to ensure drainage.
Build a support tray on the outside wall. Failure to do this will make it a pain to do cleaning maintence later.
The big units are heavy and just screwing it to the wall won't work. The big units have an outer shell that stays
put if you desire and the inner guts slide out for maintenance.
A simple base made from Angle iron to grab the perimeter of the casing
with legs that extend angled back down to the wall will do the trick.

2: Be prepared to cover the outside and the inside during winter.
The wind will come right through those things. Nothing fancy on the inside. I use a doubled up garbage bag and duct tape.

3: Be prepared to clean the filters once a week in a working shop. They get dirtier a whole lot quicker than a house.

4: Get with an AC guy and find out what cleaner is best to clean the coils.
You want to pull the unit in the Fall, take it outside and clean, rinse it out.
If you ignore this cleaning schedule you will think, depending on air borne contaminents that the unit is junk within a year.
Nope, it's just clogged up with stuff that gets by the filter.
This is not hard to do. Just one of those maintenance deals.
Or just have the AC guy come by once a year to clean it and give a blessing.

5: installation height. While I am sure that there is a recommended height for these things I chose 8 foot at the top of the unit.
This got me out of the way for most cabinets and machines.

Only issue I have had in the last 7 years of AC other than cleaning is that the fan motor bearings went out.
It's a 150 buck replacement cost so other than the aggravation I was up and running again for less than half the cost of a new one.

6:Cost to run: 50-100 bucks a month running most every nasty day and worth every penny.

7: Regardless of your shop size get the biggest, baddest AC you can afford. You can always run it on the low setting.

Have fun

 

[PhantomEB]

Last year in my condo we were boiling and I was too lazy to fab up something I felt safe here, more so my bride and didnt want just the plastic screens on the side, so I put the AC on a cheap table, thing would run all day, with no good results, this year I fabbed up a wooden frame so I could install the AC thru the window and plywood off the excess gaps, something that an intruder would have to bust thru 2 sheets of 1/2" plywood and a bunch of 2x4s to get this AC out, way easier to bust a window IMHO. Been 32*C outside and a good 20* inside. I think all in all, I would cut a hole in the wall and install it properly for it to work properly.

 

[nickwarchol]

I think you will find that the simple fan inside the unit that blows air across the condensing coil to get the heat out of the unit was never designed for the backpressure that occurs when you attach ducts to the the unit. It may work, but not very efficiently.

Also, you need to make sure that there is some water in the pan, you don't want it all to drain out by putting a drain hole in the bottom. The evaporation of some of the water that gets kicked up onto the the condensing coil helps to get the heat out of the system.

Nick

 

[edl]

well here is how it ended - still stuck with the window unit - just couldn't see any better way to get 24,000BTU's of cooling for anything shy of 5 times the Sam's $289 price - but did give up on trying to use it indoors - so got the builder's framer out - cut through drywall, a couple of studs, cut through the strucco exterior (sawzall does it all) he built a header, i wired for 220 myself and there you go (his cost $250) - thanks for your patience with this one!! ed