Concealing a Mini Split AC

[Bubba L]

I'd like to install a mini split AC unit in my trailer (restoration thread is Tale of a '55 FC Whale Reno) for its efficiency and quiet operation. I've seen the condenser units placed on tongues or bumpers, but would rather have it concealed. My hope is to place it as shown in the drawing with the lines between the air handler and condenser running in the wall, but I'm not an HVAC expert and would like to know if this is viable. Can I get some input from those of you who have done this and/or considered it?





Essentially I want to extend the kitchen counter under the window to create a space to house the condenser. This would step the kitchen cabinet down and appear as a little coffee table at the end of the gaucho. The condenser will be isolated in a sealed and insulated plenum within the cabinet and will be sized to provide specified clearances. I will have a screened air intake below the unit with sides to isolate the cavity of the belly pan from the air intake. On the streetside I will have a screened, louvered hatch for the exhausted air. I hope to run the lines between the 2 units within the wall cavity and I hope to hide the air handler in a specially fabricated head locker. I realize this will take away from my cabinet space; however, it's a tradeoff I am willing to accept.

Appreciate your thoughts,
Bubba

[sgschwend]

To clarify, I see you have one side of the outdoor unit moving air to the outside, how are you getting fresh air to the input side of the outdoor unit? Through the floor?

[65CV]

Bubba,

Haven't done a mini-split, but we put in a casement air conditioner just like you're planning. Inspiration was from Toastie and Becky B's threads. Links to those threads and details of our install start at post 346 of this thread. The 6 6-inch computer fans really help get the hot air out.

It was a lot of work to get right, but it's so much quieter and I love the idea of keeping the center of gravity low.

John

[Bubba L]

Originally Posted by sgschwend

To clarify, I see you have one side of the outdoor unit moving air to the outside, how are you getting fresh air to the input side of the outdoor unit? Through the floor?

I planned on cutting through the subfloor and placing a screen for the air intake to the unit. I would have to know the CFM the unit needs to determine the required square footage of the screened intake. Thanks, Bubba

[perryg114]

Seems like it would work. You can have a louvered hatch on the outside and some sort of intake on the bottom of the trailer. You could just make a box on the intake side of the fan and run that below the belly skin. I would say the width of the fan and about 6 inches deep would to it. Those fans don't run real fast.

Perry

[Bubba L]

Originally Posted by 65CV

Bubba,

Haven't done a mini-split, but we put in a casement air conditioner just like you're planning. Inspiration was from Toastie and Becky B's threads. Links to those threads and details of our install start at post 346 of this thread. The 6 6-inch computer fans really help get the hot air out.

It was a lot of work to get right, but it's so much quieter and I love the idea of keeping the center of gravity low.

John

I started reading the posts. Sounds like a great system. How has it been working since you installed it? Anything you would do differently? I spent some time at Deerfield Academy a few years back. And why do you need AC up there? I like to have frozen to death. Thanks for the info. Bubba

[sgschwend]

I would say one to one, sized matched to the outdoor unit opening.

The units I have are 240 VAC, one ton which uses a 15 amp 2 pole circuit breaker. It takes care of my 32X20' first floor.

With the VFD controlled compressor the unit has a seven to one variable output power. It is that range that makes the so much more efficient. From memory it didn't seem to be as large a range with small units. I recall the smallest size is a 1/2 ton, however it has the same minimum cooling rate as the one ton and the prices are the same. I used the Mitsubishi brand. The outdoor units are the same size, the indoor unit the 1/2 ton is smaller.

[Protagonist]

Originally Posted by Bubba L

I planned on cutting through the subfloor and placing a screen for the air intake to the unit. I would have to know the CFM the unit needs to determine the required square footage of the screened intake.

Don't forget that for screened openings, you have to increase the size of the opening to account for the reduction in area due to the wires that make up the screen filling part of the opening. If you go with quarter-inch welded wire mesh, the wires themselves take up 24% of the opening, so you will need to make the opening that much larger to get the same airflow.

For your louvered opening on the side for rain-proofing, that will also mean that you need 24% more (or larger) louvers to get the required opening size if those louvers are also screened.

I don't recommend using a smaller mesh. Quarter-inch welded-wire mesh will keep out most rodents and nesting insects other than termites— and termites won't want to nest anywhere that there's no wood.

Side note: If you don't plan to run the a/c when the trailer is in motion, then instead of louvers on the side you could go with a top-hinged solid panel that you would open before starting the a/c. Then the only thing restricting airflow would be the wire mesh, not louvers. And the hinged panel could be weatherstripped to prevent water intrusion while driving. (your bottom panel could have a hinged cover as well, to keep out road grime in transit). If the hinged side panel is opened at a 45° angle, then the hinged panel will not restrict airflow at all.

[Andrew T]

You might want to look at the Dometic Cool Can unit that is made for through the wall installations. We have these in our Alto units and they work quite well. You don't have to go through the floor with them and the vent area can likely be smaller.

https://www.dometic.com/en-ca/ca/pro...ol-cat-_-20787

Andrew T

[55AS]

Originally Posted by Andrew T

You might want to look at the Dometic Cool Can unit that is made for through the wall installations. We have these in our Alto units and they work quite well. You don't have to go through the floor with them and the vent area can likely be smaller.

https://www.dometic.com/en-ca/ca/pro...ol-cat-_-20787

Andrew T

I looked at those a few years back before deciding on a mini split. At the time they were pretty pricey. What does that unit cost?

[Bubba L]

Originally Posted by Andrew T

You might want to look at the Dometic Cool Can unit that is made for through the wall installations. We have these in our Alto units and they work quite well. You don't have to go through the floor with them and the vent area can likely be smaller.

https://www.dometic.com/en-ca/ca/pro...ol-cat-_-20787

Andrew T

I did consider the Cool Cat at one time, but found it hard to get detailed information. I even called Dometic to find out how noisy (in dB) the unit operated and they said it was not something they could divulge?!!?!?! I like the size and easier installation, but am worried about the noise, efficiency, and price.

Can you provide more detailed information? Installation guide? That sure would help.
Thanks,
Bubba

[55AS]

Attached pic shows clearances recommended in the installation manual for my unit.

[toastie]

Vent my ac out of the back license plate, also add a big 12v fan for those very hot day. There was no way I was going to cut a big hole out the side and roof top ac was not even an option.

see post 799, 786 and 532
http://www.airforums.com/forums/f36/...-38289-58.html

toastie

[55AS]

Originally Posted by toastie

Vent my ac out of the back license plate, also add a big 12v fan for those very hot day. There was no way I was going to cut a big hole out the side and roof top ac was not even an option.

see post 799, 786 and 532
http://www.airforums.com/forums/f36/...-38289-58.html
toastie

Rooftop A/C was not an option for me either since I needed to squeeze through a 9 ft garage door. I have installed mini splits on two trailers so far. Fortunately the hole in the shell is only 2" in diameter and easily hidden.

[Bubba L]

Originally Posted by toastie

Vent my ac out of the back license plate, also add a big 12v fan for those very hot day. There was no way I was going to cut a big hole out the side and roof top ac was not even an option.

see post 799, 786 and 532
http://www.airforums.com/forums/f36/...-38289-58.html

toastie

Interesting concept. The typical questions. How has it worked thus far? What would you do differently? What is the noise level? Thanks, Bubba

[65CV]

Originally Posted by Bubba L

I started reading the posts. Sounds like a great system. How has it been working since you installed it? Anything you would do differently? I spent some time at Deerfield Academy a few years back. And why do you need AC up there? I like to have frozen to death. Thanks for the info. Bubba

Bubba,

You were in Deerfield at the wrong time of year! It can get warm up here and VERY humid.

I'm happy with our install as is and would only add a rain gutter over the exhaust fans in the former battery access door. That said, I've only had to run it full blast once -- in Southern California. In full sun, mid 90's, the unit was only able to reduce the interior temperature by 21 degrees. We didn't have an awning at the time, which significantly added to the heat load. In temps like that, we have no trouble reaching set point with the awning in use.

We have a 26' Overlander and have used multiple layers of Prodex, being very careful to maintain air gaps between each layer. Our awning is 16' and is extra wide so that we get great shade from it. As critical to your choice of AC is the insulation decision you make and the resultant heat load.

Our AC is a 12000 btu unit that runs directly into the forward area of the trailer. We use a small fan to distribute cool air through the trailer, if necessary. If I lived in Texas, I'd be looking for 15000 btu if possible. I hear that it gets a little warm down there in the summer.

[Andrew T]

Here is a cool cat installation manual.

Andy

[Bubba L]

Originally Posted by Andrew T

Here is a cool cat installation manual.

Andy

Thanks Andy. This helps a lot. I may end up going to a dealership and measuring the Decibel level. Thanks again for your help. Bubba

[Andrew T]

I would say the noise level is similar to a roof top ac. It is hard to tell in an Alto as everything is a hard surface. And there isn’t much fabric. If you had room to put an inch of sound deadening around it I think it might help.

[DFlores]

Being that the noise level of the Cool Cat and the traditional roof top unit are similar, the Mini Split should be the preferred choice. I have been doing some reading on people's installations, due to variations in humidity, any unit will condensate on the inside. Saw a video of a guy with a Cool Cat type installation battling condensation leaks ruining his wooden walls. He suggested a drip pan and a drain as a solution. May as well have a hole in the bottom for a Mini Split if it is true that they all will create condensation at some point.