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Old 12-04-2010, 08:11 PM   #1
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Convert portable AC to mini central AC. Any reason why this would not work?


Seems like a crazy time of year to think about AC, but this would involve going in the attic, and now would be the time to do it, not summer. I have a 12K BTU portable AC unit and it is very loud, so this summer while it helped keep me cool, I could hardly concentrate on anything I was doing while it was on. Was also a hassle to move it to the bedroom and back to the office all the time.

So I was thinking, why not put it downstairs, vent it out through the wall using a dryer vent, and also have an intake a couple joist spaces away (converted it to dual pipe so its more efficient) and then I'd run a 5 inch duct through the office closet, to the attic, then have have it go to the ceiling of my office and bedroom using a Y splitter. I'd use those round adjustable vents, so I could always adjust them so the flow is even across both rooms. I'd probably run one to the spare bedroom too. That way all 3 rooms would be cooled and that air would combine at the hall and essentially get to the lower part of the house.

I'd probably use a booster fan to push the air as the blower in the unit itself is not really designed for this. I'd also install a thermostat or/and timer in one of the rooms, probably the office. The unit is "auto restart" so this could just control a relay to turn the unit on/off at the plug. I'd use insulated duct once I get to the attic area. I'd probably go down to 4" duct, I'm sure they make Y's that go from 5 to two 4's, so I'd use that. Guess the tricky part is trying to push cold air up 8+ feet. Need a decent booster.

Pretty sure this would work fine, but from a code perspective, think this would be wrong? Any issues to watch for? The only thing I can think of that could maybe work against me is that the intake for the unit would be downstairs, but I'm sure air could circulate through the furnace ducts, crack under the door etc... so probably not that big of an issue. So I should not be creating a vacuum in the basement or anything.

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Old 12-04-2010, 11:24 PM   #2
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Convert portable AC to mini central AC. Any reason why this would not work?


I have one of those portable AC units, it's a DeLonghi. I use it when I want one room cooler. It has a 5 gal water tank that needs to be refilled every day or so. It's a freon/compressor based AC, not a swamp cooler, I understand it uses the water to prevent driping all over the floor.

Does your's use water? If so you'd have to get some kinda auto-fill thing.
Does it require a drain?

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Old 12-04-2010, 11:35 PM   #3
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Convert portable AC to mini central AC. Any reason why this would not work?


Mine is actually self evaporating, so from my understanding, the water goes into a temp container, and it is occasionally pumped over the condenser coils, helping to cool them off better, and causing the water to get hot and evaporate at the same time. There's a small plug and if I pull it, water comes out, but from a whole summer using it, I never had it stop on me where I have to remove any water. So I think I'd be ok in that sense. I don't have to actually add water to it, either.
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Old 12-05-2010, 11:48 AM   #4
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Convert portable AC to mini central AC. Any reason why this would not work?


never mind, in not even going to comment
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Old 03-29-2011, 08:00 PM   #5
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Convert portable AC to mini central AC. Any reason why this would not work?


I forgot about this thread, and I was thinking about this project again.

Any reason why it should not work, or any improvements I should do to ensure it does work?

I made a diagram of my proposed plan. Also I would probably use 6" duct instead of 5". This gives me extra air volume in case I get a bigger unit later down the line. I figure if I will do this, I better do it now as in the next couple months when all the snow starts melting, it will be too hot to work in the attic.

I'd probably get something like this for the booster fan:

http://cgi.ebay.ca/6-Carbon-Air-Filt...item3cb6762b04

I may decide to not hook the AC unit directly to the pipe, I may just leave it in the server room where the fan will be and it will just grab the cold air from that room, and I will let other air enter. That room is not built yet though, but I plan to build it soon. By doing this I can let the AC unit's thermostat do it's job better. I can keep that room at 20 degrees which should result in a more or less constant temperature in the upstairs room that is getting this air.
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Old 03-29-2011, 08:55 PM   #6
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Convert portable AC to mini central AC. Any reason why this would not work?


If it gets hot in your attic, you'll need a ton of insulation on the ducts.

12k but isn't very much -- about a mid-sized window unit. If it doesn't get very hot where you live and you have good insulation, then 12k might be enough. Where I live 12k will work for a single room or maybe two.

You want your intake to be the relatively cooler, dryer air inside the house, not the outdoors.

I suspect your main difficulty will be getting good enough air flow through the small duct you are thinking about.
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Old 03-29-2011, 09:12 PM   #7
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Convert portable AC to mini central AC. Any reason why this would not work?


returns? just adding conditioned air will not cool.
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Old 03-29-2011, 09:13 PM   #8
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Convert portable AC to mini central AC. Any reason why this would not work?


Oh yes I will be using lot of insulation. I have to or I could get condensation and heat loss issues in winter. I will use insulated duct, air seal it very well with vb tape, and then lay lot of fiberglass over, probably R40 or so. (existing insulation which I'll be flipping over then putting back) A 500CFM unit should probably do the trick as far as air flow, I would think. The intake for the indoor air will be basement air. The intake in the picture is for cooling the condenser, so that air just goes back outside. The unit itself was used last year to cool my office and bedroom and works quite well, so hopefully it should be able to do the 2 rooms with this duct setup. I'm not too concerned about the spare, I will only open that duct on a needed basis and compensate. In fact if it can't cool even two rooms at once, I can just open/close the vents as required, still easier then hauling the unit around.

Think I should go bigger then 6" duct? I can easily do that, but I'm thinking that should be enough.
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Old 03-29-2011, 09:16 PM   #9
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Convert portable AC to mini central AC. Any reason why this would not work?


Quote:
Originally Posted by hvactech126 View Post
returns? just adding conditioned air will not cool.
The existing hvac ductwork should do I'd think. If I'm pulling basement air and pushing it through those vents, the easiest path for replacement air is through the ductwork, crack under the door, etc. If that theory really does not work, I can easily add dedicated returns too.
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Old 03-29-2011, 09:22 PM   #10
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Convert portable AC to mini central AC. Any reason why this would not work?


i'm done. its not a good idea thats all im going to say
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Old 03-30-2011, 09:23 AM   #11
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Convert portable AC to mini central AC. Any reason why this would not work?


Sorry to be a downer on this project, but 126 is correct, this is a bad idea.

Any time you are using one of these portable type units that vent out the wall you are depressurizing the space that the unit is cooling. That means you must be bringing air back into the space somewhere else. That air you are bringing in is likely the same temp as the air outside, which really means you are trading cool air in one room for warmer air in another.

Furthermore, to add ducting and a booster fan, control and power for said fan, make penetrations into your attic space in various locations, insulate ducting etc. Why not put the energy and or cash into purchasing a ductless split and be done with it? At least that way you know you will be happy with the result and your noise issues will go away.
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Old 03-31-2011, 01:39 PM   #12
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Convert portable AC to mini central AC. Any reason why this would not work?


This will only cost about 200 bucks, some aluninium pipe, insulated flex pipe, misc hardware, the fan itself. vs $5,000 and for the 2 months of the year that I'll use it, I can't justify paying for central AC or a ductless split unit. Maybe in the future.

But if this won't work, then I might stick to just hauling the unit around. As for the cooling of the compressor, I modded the unit so it uses outside air hence the intake/exhaust pipes. I found this made a huge difference last year.
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Old 03-31-2011, 02:45 PM   #13
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Convert portable AC to mini central AC. Any reason why this would not work?


Why not just get a window AC unit and call it done? If you only need it 2 months out of the year, that seems like the way to go to me.

You can easily get one for the price of materials your idea would cost.
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Old 03-31-2011, 02:50 PM   #14
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Convert portable AC to mini central AC. Any reason why this would not work?


I already have that big unit, and my windows are all crank, otherwise that's what I'd do.

I have considered getting a through the wall unit though, but I'd need two. the office and bedroom are the most critical to cool. Canadian tire had a nice one, it's like 30,000 BTU. Would cool the whole house, the garage, and the neighboor's dog house.
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Old 03-31-2011, 02:52 PM   #15
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Convert portable AC to mini central AC. Any reason why this would not work?


You could get one through-the-wall unit, and leave what you have now in the other room.

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