[sambor]

Thought I would get some advice from the RV trailer guys here. I want to add a small roof A/C unit to the dressing room on my 8 horse trailer. Lots of different brands to choose from. Are these things reliable or maintenance pigs?
I am installing a 30 amp service in the trailer now but don't need any 12 VDC so no converters or inverters needed. Wife just want a couple of plugs and an A/C unit with heater if available.
Is the rood installation pretty straight forward and usually water tight?
Do the roof units come with the inside ceiling control/vent panels?
My trailer has a 4 ft. shortwall so its a small area to cool or heat but it isn't insulated. We weren't going to use it except for storage for the shows but situation has changed so she is going to sleep in it.
Any ideas or advice will be greatly appreciated.

 

[d9er]

you will need to glue a piece of Styrofoam on the the inside to build up roof it's sandwich together. Installation is fairley easy and water tight. yes come's with control/vents come with unit. Styrofoam needs to be 4 inch's thick.it will also help stiffen the flimsy metal roof.

 

[Ron Nielson]

d9er is correct. Should be easy.

Do the roof units come with the inside ceiling control/vent panels?

I note that there are many different units available and some are made for trailers that have built-in ductwork and those do not have ceiling panels. When you are shopping just make sure that the unit you choose either has a ceiling panel included or purchase the panel separately. Also, many units have a heat strip available, so check on that when purchasing. These heat strips do not put out a lot of heat so don't think they are a replacement for a furnace.

 

[cfell]

Some folks have added the free standing “spot coolers” where they get the condenser air ports mounted to a plate they mount in a side window. That can be removed to travel. For the size of your space to cool, the whole roof mount may be overkill.. and may not cycle enough to remove enough moisture leaving it clammy feeling.

 

[sambor]

I was concerned about the size as well. Space might be 28 sq.Ft. total. Smallest btu I have found so far is 13k.

 

[cfell]

I was concerned about the size as well. Space might be 28 sq.Ft. total. Smallest btu I have found so far is 13k.

Here is an overview.. of the portables.

 

[JimmyD]

I have seen some RVs with 10s but may have been a factory install. I had a 13k in our bedroom. When we used the bedroom a/c we didn't use the main one. Never had an issue with the bedroom feeling clammy even with the bedroom door being shut all night.

 

[jdwarren]

Thought I would get some advice from the RV trailer guys here. I want to add a small roof A/C unit to the dressing room on my 8 horse trailer. Lots of different brands to choose from. Are these things reliable or maintenance pigs?
I am installing a 30 amp service in the trailer now but don't need any 12 VDC so no converters or inverters needed. Wife just want a couple of plugs and an A/C unit with heater if available.
Is the rood installation pretty straight forward and usually water tight?
Do the roof units come with the inside ceiling control/vent panels?
My trailer has a 4 ft. shortwall so its a small area to cool or heat but it isn't insulated. We weren't going to use it except for storage for the shows but situation has changed so she is going to sleep in it.
Any ideas or advice will be greatly appreciated.

I've never done one from scratch but I don't think the installation is very complicated. A couple of notes:

1) Most RV roofs are "high crown" and the AC units are installed in the middle, at the highest point. As such, the AC-roof interface doesn't really need to be that watertight (it's usually just a big fat foam gasket) because water will naturally flow away from it. If you're doing this on a flat roof I would definitely shim the AC above the roof and ensure that the shim-roof interface is completely waterproof, so any standing water (the weight of the AC may create a very slight "dip" in the roof) will not enter the living space or ceiling.

2) I am almost -- although not completely -- certain that you will need a 12 VDC supply to make the thermostat work. Your amperage will be nominally zero, though, so this should be cheap to implement.

3) Relating to (2), I don't know of any units that can be controlled directly (i.e. without thermostat), but maybe there are some out there. You can definitely get non-ducted airflow, though (which is what you want since there is no ductwork). Cooling capacities less than 13k BTU/hr are out there but probably not very common.

4) As far as reliability goes, the 13.5k BTU/hr one that came with my old TT failed and I replaced it with a 15k that ran for years. The 15k one on my FW (it has a 13.5k in front and a 15k in back) didn't work when I got it home from the dealer; it had some loose spade connectors that just needed to be crimped down to make better contact. I think most of this RV stuff is garbage that runs on fumes and the aptitude of owners for troubleshooting.

5) For insulation, maybe consider the spray foam stuff. Probably worth it if you're trying to control the temperature.

6) Some of these units come with heat pumps which will have efficiency > 1 when the temperature is down to the 40s or so, but will have efficiency < 1 when it gets colder than that. Then there are some that actually have resistive heaters, which have efficiency of exactly 1 all the time. I don't know what's right for your situation but a small plug-in resistive heater is easy to throw in there separately, so I'd probably go with the heat pump option.

7) If you intend to run this thing off a generator you may need a "soft start" device depending on the generator's wattage. Due to high inrush current requirements a 15k AC will need at least a 3kw generator unless it has a soft start (even though continuous wattage is only ~1.5kw).

8) I don't know what the roof structure is like on your trailer; make sure it's capable of supporting the physical load of ~100 lbs.


Good luck and let's see some pics of your solution once it's implemented!

 

[sambor]

I'm thinking she can just use one of the oil-filled radiator type that Lowes sells. Have several around the farm and they work perfect and they are cheaper than the heater options on the a/c units.
On the units I have looked at the temp is controlled by one of the knobs on the front of the ceiling part.
The roof is crowned and it has 3"X 1.5" "C" channels running crossways on 24"
Centers. Reckon that will hold it up?
Just going to run it off shore power thats available at all the shows we haul to.

 

[Motofixxer]

Thought I would get some advice from the RV trailer guys here. I want to add a small roof A/C unit to the dressing room on my 8 horse trailer. Lots of different brands to choose from. Are these things reliable or maintenance pigs?

Many are now installing a Minisplit, the only issue is the condenser outside. Otherwise custom installed indoor hose units as well as window units built into cabinets with styrofoam duct that goes to a hole below. All depends on what you want to spend, skills and time. The roof units are horribly inefficient draw tons of power but some of the newer ones seem to be updating the tech they use...but pretty sure you'll have to sign over your first born and 2nd for a life of slavery
What is a Minisplit

What is a Ductless Mini Split Air Conditioner | What is A Mini-Split Heat Pump AC

Searching the web to find out 'What is A Mini Split?'. We have tons of information on Ductless Heat-Pump AC Systems, DC Inverter & More.

www.minisplitwarehouse.com

Minisplitwarehouse.com

 

[blythkd1]

Your roof sounds near perfect for a normal rooftop unit. I just pulled mine to put a new rubber roof on. It has 2x4's framed around the opening so that's about what your're probably shooting for on thickness. There are 4 long bolts that go up through the inside panel and thread into the main unit. I think that's pretty typical. I'm ordering a new roof gasket. It's 14 x 14" and 1" thick closed cell EPDM rubber. They seal up pretty well on a crowned roof. Stick the gasket to the bottom of the unit, Sit it down on the roof over the hole, hold the inside panel up to the ceiling and put the bolts in. Done except for wiring.

I have a Dometic. I've had Coleman. Being a small self contained unit there's not much to go wrong in my experience. Over the past several years, over 3 different units, I've replaced a capacitor and a limit switch. I think both were problems that I inherited when I bought the campers. They really don't give much trouble. Of course, I haven't had anything newer than probably 20 years old, so they used to be well built anyway. I think the new Dometics are still built pretty much like they have been though. I think they're head and shoulders above any window unit you can buy nowadays.

I had a 13k on a slide in camper. It would short cycle all night since as soon as it was blowing cold air, the thermostat was satisfied. I'm not saying it took the humidity down to an optimum level, but when you're cool, it's not that noticeable. I always liked when we got to a campground in the summer and it was like an oven inside the camper, it was cool in a couple of minutes.

As far as that roof holding the unit up? Have you seen what's in an RV roof? Mine has 1/4" OSB on top of OSB "trusses." The truss members are about 3/4" x 1 1/4", so like OSB firring strips. I always wondered why the roof felt so spongy under foot. But I never had a leak around my A/C.

 

[jlawles2]

The new ones out are Furrion. Dometics have a known issue with the capillary tubes plugging up (had 2 fail on me). Coleman Mach are on my current rig. The ones with roof top controls do not need DC power as the thermostat is a resistive type not wall mount. They are not as efficient as you think for cooling quickly but they will get the job done and pull loads of moisture out. As for the heat strip vs the oil filled, the heat strip is probably faster at raising the temp than the oil filled, however the oil filled may be nice since you can drop a shirt on it to have that our of the drier warm.

If you want ducted, you will need at a minimum a double roof (You may want to do this anyway as it helps reduce the heating) don't forget to vent the space between the roofs. Lots of the newer high end campers are doing double roof some with double insulation.

 

[blythkd1]

Yeah you're right, mine is ducted, that's why the roof is framed with 2x4's under the unit. 2" thick ducts run through the roof trusses. Didn't mention that part.

 

[jdwarren]

I'm thinking she can just use one of the oil-filled radiator type that Lowes sells. Have several around the farm and they work perfect and they are cheaper than the heater options on the a/c units.
On the units I have looked at the temp is controlled by one of the knobs on the front of the ceiling part.
The roof is crowned and it has 3"X 1.5" "C" channels running crossways on 24"
Centers. Reckon that will hold it up?
Just going to run it off shore power thats available at all the shows we haul to.

I guess it depends on the wall thickness of the C channels. If the roof is designed to be walked on then you're definitely good.

However, the openings for these units are generally 14" by 14", and you don't want this thing just sitting on sheet metal, so I would probably plan on adding one additional cross piece 14" off from one of the existing ones and then connecting them to form a supported 14" by 14" square. That will guarantee equal pressure along the length of the perimeter gasket.

 

[Bruizza]

I can’t stress enough how much I agree with point 7 made by @jdwarren A soft start is an absolute game changer for RV AC units. We installed one on our camper last summer and we never had a generator trip since. The compressor and fan kicking on at the same time on a hot say was brutal on our generator. 4500 peak 3700 watt onan Cummins generator.

 

[sambor]

I am just going to install 2 duplex plugs and whatever I decide for an A/C unit. We don' t use a genset so will always use shore power. Pretty simple wiring. Total wire length won't be over 10 ft. so voltage drop is nil and I have 25 ft. of 10/3.

 

[jdwarren]

I am just going to install 2 duplex plugs and whatever I decide for an A/C unit. We don' t use a genset so will always use shore power. Pretty simple wiring. Total wire length won't be over 10 ft. so voltage drop is nil and I have 25 ft. of 10/3.

Sounds good. Personally I would recommend using a small load center and backfeeding one side with a 30A and then use a 20A for the AC circuit and either a 15A or 20A for the outlets. The screw terminals on the breakers will also work well with the portable cable you'll use for shore power. Without the load center you're relying on the shore power's overcurrent protection and you have to figure out how to join portable/stranded cable to romex (if you go this route I have some ideas; definitely don't use wire nuts).

 

[sambor]

Get outta my brain JD.
Thats exactly how I am going to wire it except I hate romex!
Going to use gray pvc and the gray flex conduit. Using a 20 for the a/c circuit and a 20 for the duplex's. With 10ga wire on short run loads aren't a concern.

Many thank you's to all who answered my questions and gave great advice. Kept me from spending too much, building a monument to my ignorance and trashing the trailer.
John

 

[Jasong]

Here are my thoughts: the construction is a bit cheap on a RV AC unit. The freon system is not serviceable. They are not very efficient. While I prefer Dometic's build quality (since the Carrier AiRV was sunsetted) they are a bit noisier than the other brands.
Going with a mini-split gets you a range of 6/9/12/15K BTUs. They are much more efficient. You won't need to spend $2-300 on a soft starter. Mini kits can be found in the $6-700 range, rooftops start at $800 (the inside part is sold separately as it depends on whether it is ducted or not).

 

[jlawles2]

Domestic sucks. The capillary tube they use gets plugged. Had 2 units fail on me same way.