Window Air condition venting?

[Bigballsofpaint]

Hey all, im looking to get a 8.2x24 next month and ill be taking it to Oklahoma in June for a week of paintball with my friends. I know im going to need A/C down there, and im pretty set on a window unit after reading a lot of things here vs portable units. My main issue is i really dont want to cut a hole in the trailer and slide this in and out, id much rather build it into the top cabinet of the V, and put a roof vent above it and maybe a side vent on the V to have almost an in and out for air flow. Would this be adequate? Im thining of an 8,000 or 10,000 BTU unit, ill make some type of drain for it as well in the cabinet since im sure it will drip.

Im just going for ease of use here. Any help is appreciated, thanks!

[Aguyfromohio]

It's best if you capture the hot exhaust air and direct it outside with a box or a duct. That will keep the hot air from recirculating back through through the hot side of the air conditioner, making it work harder and harder.
Here's a video showing how to capture that hot air flow with duct tape, cardboard, and dryer vent duct.
https://www.youtube.com/watch?v=JI3rviFUK-k
If you do something similar to direct the hot air out, and also let some fresh air in to replace it, it should all work.

[Bigballsofpaint]

Oh That could work. Do you still need some sort of drain for it at that point?

[Aguyfromohio]

Yes, you need a drain for condensate water in humid weather.
Just a shallow pan under the A/C and a way for the water to get out of the cabin. A little half inch tube run to the outside should do it.

[working on it]

It's best if you capture the hot exhaust air and direct it outside with a box or a duct. That will keep the hot air from recirculating back through through the hot side of the air conditioner, making it work harder and harder.
Here's a video showing how to capture that hot air flow with duct tape, cardboard, and dryer vent duct.
https://www.youtube.com/watch?v=JI3rviFUK-k
If you do something similar to direct the hot air out, and also let some fresh air in to replace it, it should all work.

Yes, you need a drain for condensate water in humid weather.
Just a shallow pan under the A/C and a way for the water to get out of the cabin. A little half inch tube run to the outside should do it.

• This is how I mounted my window shaker. The LG 5k BTU unit performs very well, does not drip (I have the drip pan jic), and actually only shakes the windows imperceptibly (solidly-mounted in the rear bulkhead). The advantage to the permanent mount inside the rear compartment is that it is secure from theft and damage, from insects and the elements, requires no effort to set-up and use, and can operate with the hatch locked for the night. I built the trailer for sleeping positioned head to the rear, feet forward, so the controls are in reach, while the airflow is circulated top-to-bottom of the trailer (cooling the hot roof first!). If needed, I use a separate fan to aid in the circulation. I've used this system in 108 degree heat, and in pouring rain. Only drawback, is the un-insulated exterior walls "sweat" in high humidity, showing a loss of efficiency, but in a 4x8 trailer, 5k btu's has plenty of cooling to spare.
• 
  below Right-angle ducting vents exhaust to side vent (shields from rain).
  
  below (1)LG unit with the master switch (a/c, in-line duct fan, exterior chassis cooling fan), (2)rear view with hatch open, (3)view of unit with deflector directing air forward under ceiling, (4)front shelf where airflow is re-directed back to rear by an ac-powered 3-speed fan.
  

• I chose to duct mine outside, at a right angle turn, with the rear hatch closed and locked at night. This necessitated an insulated exhaust duct, in order to not over heat my supplies inside the hatch (food in a cooler, a generator with 3.5 gallons of gas in an external tank, and Coleman stove, lantern, and two gallons of white gas). The right angle duct starts out by completely covering the exhaust end of the A/C, creating a plenum of over 1000 cubic inches, then turns into a 6" insulated duct (with a high flow axial fan inside, to get the hot air rapidly out of the duct), then thru the galley wall.
• I had to re-do it three times, since the hot air initially wasn't flowing out fast enough to keep the air in the plenum from getting over the thermal shutdown temperature. My struggles are documented here:http://www.tnttt.com/viewtopic.php?f=21&t=54945#p999038.
• The You-Tube set-up doesn't state whether or not his A/C shuts down from heat, but his plenum looks to be made of something other than the heat-retaining material mine is, and his outflow ducting my be larger in diameter, and also not insulated (he gets higher rate of heat transfer, not concerned with flammables within inches of his ducting). Also, my A/C has chassis cooling, and the intake is also isolated from external heat, his can still receive heat from the chassis, and given off from the un-insulated ducting. I built mine with special needs to be met (total security), but to do it all over again, I would've put a large open vent either straight back or to the sidewall nearest the A/C (shorter, larger, and quicker dissapation of exhaust heat).

[Aguyfromohio]

Thanks for all that excellent detailed info.

[aggie79]

It's best if you capture the hot exhaust air and direct it outside with a box or a duct. That will keep the hot air from recirculating back through through the hot side of the air conditioner, making it work harder and harder.
Here's a video showing how to capture that hot air flow with duct tape, cardboard, and dryer vent duct.
https://www.youtube.com/watch?v=JI3rviFUK-k
If you do something similar to direct the hot air out, and also let some fresh air in to replace it, it should all work.

Two things to keep in mind:

1. Almost all newer window units do not have a condensate drain. Instead, the cooling fan is designed to "sling" condensate into the air flow onto the condenser cools to help in cooling the coils. This makes the unit more efficient. You can either use a water- resistant material for your exhaust duct or drill a condensate drain in the bottom of the pan and provide a condensate drain.
2. The ductwork shown in the video is not dryer vent hose (which is 4" in diameter). The hose shown is flex duct that looks to be 8" in diameter.

[Aguyfromohio]

Thanks aggie79, that's important information to us.
We just purchased our little window air conditioners, new Frigidaire 5,000 BTU units with remotes.
Ours will mount on the floor of the galley under the counter, and the cold end with controls is fitted into a square hole in the aft bulkhead.
The hot end is boxed in, venting down through screened holes in the galley floor.

We noticed it had no condensate drain hole and wondered where the condensate water was supposed to go. The manual says it normally doesn't need liquid water drainage.
We assumed they were somehow evaporating the water and forgot about it, planning on a drip pan with drain hole just in case.
Now that we know it's blowing a misty spray of droplets with the hot air, we'll take care to waterproof that exhaust plenum to avoid trouble.
We would not have expected water way up the plenum walls.
Many thanks.

[aggie79]

I'm in the process of "hacking" a similar Frigidaire window unit to put into my teardrop. I plan on drilling a hole for condensate drain in the bottom of the unit. The condensate makes a pinging noise when it hits the fan and I didn't want that.

[lrrowe]

I'm in the process of "hacking" a similar Frigidaire window unit to put into my teardrop. I plan on drilling a hole for condensate drain in the bottom of the unit. The condensate makes a pinging noise when it hits the fan and I didn't want that.

ohhhhh, I cannot resist this opportunity. Stuff usually does make a noise when it hits the fan!!

[flboy]

It may give you some ideas. The following is the start of my AC install. Will have to go through a few pages. This method requires you to cut a vent into the side and roof, but it uses the common vents you can get anywhere for am LP fridge. It has been working great for me, and I think it looks nice.

I did put a drain in and in Florida, it actually will drain. Humidity gets high, so the idea of flinging the water on the condenser coils via the fan, although a good idea for dry climates, just makes alot of noise when the water does not evaporate and builds up. Without the drain, it would otherwise start to overflow the pan on the most humid days.

http://tnttt.com/viewtopic.php?p=1176629#p1176629

[Bigballsofpaint]

Do you think sealing the sides hinders the performance of the unit? I also planned to install a roof vent above, but would have a wider cabinet to the sides are open too.

[aggie79]

In a window unit there are two separate air flow paths. Both air flow paths need to be maintained and separated.



On the "outside" air flow path, air enters the unit from the louvered sides and/or top, flows through the fan, across the condenser coil to extract heat from the compressed coolant, and out the back of the window unit.

On the inside air flow path, (return) air enters the lower louvered portion of the front of the unit, (usually) flows through a filter, across the evaporator coil to cool the air and extract moisture (condensate), through the fan, and out the vents (supply air).

As I noted in a prior post, I am in the process of "hacking" a 5000 Btuh Frigidaire window unit. Here are some pictures with the case removed.



In this picture, the back or outside part of the unit is on the right side of the picture. The front or inside part of the unit is on the left side of the picture. You can see the Styrofoam divider that separates the two air flow paths. For the outside air flow path, outside air enters through the top and side louvers near the middle of the unit, between the right side of the Styrofoam divider and the fan, goes through the fan, and then is pushed across the coils and back to the outside.



This picture shows the inside part of the unit. For the inside air flow path, air enters at the coil (after going through a filter - not shown), is "sucked" by the fan in the Styrofoam pocket through the coil, is cooled, and then is pushed out the top fan and forward through the front of the unit.

[Aguyfromohio]

Thanks again, aggie79, that looks like the very same unit we bought a pair of.
I assume:
- cold condenser water from the cold end (inside end) runs down the sloping metal case to the hot (outside) fan
- the bottom rim of the fan picks up the water and slings is out in the exhaust air flow, impinging the hot side heat exchanger fins
- you plan to build a little dam uphill from the hot fan to stop the water being picked up
- you'll drill a hole for a water drain tube near that dam.

We talked over what we'll do with our units, and decided not to modify them.
Instead we'll waterproof the entire inside of the exhaust plenums we've built with the spray rubber advertised on TV.

We expect that most of the water will get carried out in the hot air as little droplets, and whatever doesn't will dribble down the plenum walls and run out the 3 inch screened holes we have cut through the floor, onto the ground under the trailer.
Now that we understand how this air conditioner works, we'll be sure to waterproof and seal the joints and cracks, especially at our 3 inch exit holes, so the liquid water doesn't leak out into the galley floor and cause troubles.

We hope to avoid another of those frustrating moments where we are looking at a mess asking ourselves "where is all this water coming from?"

[McDave]

The condensate performs an important function in removing heat from the condenser. It is the vehicle for the heat to be absorbed and removed. Just as the evaporator removes heat in the form of condensate, the condensate removes heat in the form of evaporation. Draining condensate can affect the performance and the ability to "pump" the heat from the condenser, saturated air can absorb and remove more heat.

McDave