ventilation for thru wall AC - please help...

[jying]

I have a thru-wall AC unit in my condo, but after about 5 minutes of use, the compressor shuts off. The fan keeps blowing, but no cold air.

I thought it was a ventilation issue with something overheating and an auto shut-off triggering, so I pulled the unit out of the window and ran it completely unobstructed. The unit operated beautifully and so I know it's definitely a ventilation issue rather than a busted AC.

I think the problem is the exterior vent, which looks to be too small for the unit I have. It's only the size of half the back-face of the AC and there's metal slats and metal mesh across it to keep out water and bugs. I'm assuming one solution would be to make the vent bigger, but since I live in a condo, I can't easily rip out the vent without talking to the condo association about changing the exterior of my unit. I also don't want to pay for major work if I can avoid it.

Here are some pictures of the unit, the hole/setting in the wall and the exterior vent. I think another possibility is that that maybe the hot air is getting stuck in the gap between the back of the AC unit and the vent.

Questions:

• Will it help if I build a funnel that leads from the back of the AC unit to the vent?

• What other options would I have for venting the unit?

• Am I on the right track with what's causing the compressor to shut down after a few minutes?

The AC unit is an AMANA AAC182STA

Thanks in advance for the help!

Jim

[HayZee518]

there is absolutely NO air circulation at the rear of the unit - of course its gonna trip out on high temp.

[pushkins]

I'm thinking that, that unit would require an open hole to the exterior, not the louvers going to the exterior.
In wall units like that are built to have their rears in free air, they are not constructed to drag air in like your asking it to do, it's simply too much work, therefor your overheating problem.

You could remove that louver vent cover, that would allow a little more free air movement and see if that solves the problem, but I think your best option would be to remove it all together and make that hole as big as the A/C unit.

Lucky for you so that most electrical devices are built with overheat protection devices, if not that would be a major fire hazard.

[jying]

So would you say the problem is:

• that it's not pulling in enough air from the top and sides or
• that there's not enough venting out for the hot air coming out the back?

If it's the 1st, then I could drill some holes in the top of metal frame that's set in the wall to hopefully let it pull in more air. (any other options?)

If it's the 2nd, then I need to figure out a way to vent the hot air in back more effectively. Either by increasing the size of the vent in back or maybe adding in a fan in the current vent to blow out the hot air. (any other options?)

[HayZee518]

do other people share the same vent? is there a roof exhauster for the vent? does makeup air come in at the bottom of the vent column? if there is an exhauster on the roof, is it powered as in a fan?

[jying]

Answers to q's:

The vent is for my AC unit only.

There isn't a roof exhauster for the vent. I'm assuming this is a fan/vent above the AC.

Makeup air comes in through the top and sides of the metal frame that the AC unit sits in (visible in the pics). I'm assuming makeup air is air that goes into the AC units besides the air that is sucked in from the front.

There is no separate exhauster. It's a standalone, through-the-wall unit.

Thanks!
Jim

[pushkins]

I think your problem is : not enough room for the unit to push the hot air away from it. What is in that chase that the A/C unit sits in or in other words what's in that void between your inside wall and that small vent with the stack beside it ?
Does that chase go anywhere (to the roof and out or is it just a void with only air access via that small vent ?

[jying]

There's nothing there. It's just an open area between the back of the AC and the vent. It doesn't open up to go anywhere.

[pushkins]

Can you make that vent larger ?
The problem your having is that the A/C unit cannot get enough cool air to disapate the hot air, so it overheats and shuts down.

[HayZee518]

A/c Vent

Look at my diagram. First of all the design of the condo stinks!. To have a sheet metal trunk line that doesn't go anywhere is absurd! It is in essence a closed box. If it exhausted at the top outside somewhere it would make sense but it doesn't. Look at your a/c pictures. the front box is the evaporator part the rear is the condenser part. Now use your head -- between the two boxes is a motor with a double shaft. one fan is for the front the other fan is for the condenser. the condenser is in a box that's supposed to remove latent heat from the coils of the condenser. In your case it has no where to go. it is stagnant in that enclosed space you call a vent. In free air the unit gets all kinds of air to cool and remove heat. put that inside a closed box, it trips. Does that tell you something??

[jying]

Definitely agree that the design of the layout is horrible. The question now is how can I fix it.

Will it help if I build a metal/wood funnel that leads from the back of the AC to the vent? That way, the hot air gets blown straight out the building instead of stagnating/swirling in the enclosed space.

I'm also thinking of drilling some holes on the top of the sheet metal enclosure so that it pulls in more air from the middle section.

Other options I'm considering are installing an exhaust fan in the vent so that it pushes the hot air out of the back. or ripping out the current vent, expanding the hole in the back and putting in a larger vent.

Which of these would you say have the best chance of working?

thx,
Jim

[pushkins]

Make the vent bigger, as big as possible.
Adding an exhaust fan as well would be a good idea too, BUT the problem you face there is you don't want the exhaust fan running all the time, just when the A/C is, so you may well need to get in contact with an electrician for the appropriate wiring needs.
If this is a condo unit you probably won't be allowed to make the vent bigger anyway. CHECK WITH MANAGEMENT FIRST !!!!!!!