Installing a Mini-Split Air Conditioner on a Travel Trailer

welcome to our little blog.  Once you have read up on how we added a Mini Split to our travel trailer, check out a few of our other posts about the other upgrades we have done:

about adding solar

how to improve your RV’s water

better cellular connectivity when you are in the middle of nowhere and need to work

why we chose lithium batteries and why we love them

lots of other upgrades we have done to our travel trailer

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Update 01/2023 : we reinstalled our mini split on a different trailer (with video) we took a slightly different approach and its working out great so far.

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I’m not entirely sure when I first saw some info on folks using a mini split on a camper or trailer, but I think it was this fella from Gone Boondocking. His videos have enough info for most folks to come up with a plan to do this install.

In our case, once again, we enlisted the assistance of Eddie Glonek of Mobile Homesteading to help us with the install. Not only does Eddie also have a mini split on his custom built 5th wheel house on wheels, but Eddie used to be an HVAC installer / technician, prior to embarking on his current service offerings of Solar Installation and custom RV modification work.

What is a Mini Split ?

Before we discuss why we are making this modification, lets answer a common question that we get frequently… what is a mini split ? Basically, its a “heat pump” (meaning it can heat or cool) that features an outside unit (Condenser) and an indoor unit (Evaporator) which are connected by refrigerant lines (copper) and an electric line (so the Condenser can power the Evaporator, and the indoor unit can send thermostat information).

These types of units are very popular pretty much everywhere on planet earth EXCEPT in the United States. They are popular because there are very efficient, use loads less electricity than a conventional A/C unit, and you can place the inside unit precisely where you need the cool (or warm) air, assuming you can get your refrigerant lines to an outside wall (to reach the Condenser)

Generally these units have a built in inverter (no, not a standard inverter that inverts DC power to AC power) which regulates the delivery of AC power to the condenser at a variable rate depending on the demands of the condenser. This is key in how these units can be more energy efficient than a “normal” A/C unit.

Why do we want a Mini Split in our travel trailer ?

You may know from our other posts about solar power, that we don’t travel with a Generator for electricity. We like to dry camp / boondock, which means no “hook ups” to electricity, water or sewer. To that end, we are always looking for was to be more self-sufficient AND more comfortable “off-grid”

One of our missing pieces to the off-grid puzzle has been Air Conditioning when off grid. Our travel trailer came equipped with a 12,500 BTU A/C unit on the roof, which is plenty powerful and probably oversized for our tiny 21 foot trailer. This can be easily powered by a 2000 watt or higher generator, if you add an easy start (soft start) to the A/C unit. The reason this is needed : the amount of Amps of A/C power needed to kick on the compressor is pretty high, sometimes over 100 DC amps or more. Most small/portable generators cant supply a spike of AC high enough to start the A/C unit without a soft start modification.

Indeed, we had done just that, and added an Easy Start to our A/C unit back in the summer of 2017, which allowed us to run the A/C off of our solar power. However, with 200 ah of Battle Born lithium batteries, the A/C could only effectively run for 2 hours (max) and we would essentially drain our DC batteries to 0 %. So… yes, it worked, but it was comically inefficient, and totally impractical when off-grid.

Therefore, if we could replace the rooftop A/C unit with a mini split, we could do the following :

• downsize the BTU rating to more closely match our trailer size (12,500 to 9000 btu)
• reduce the power consumption from 2000+ watts to about 450-600 watts (while running A/C)
• increase available roof space for more solar panels
• reduce overall weight on the trailer / roof (the A/C units are HEAVY)
• reduce wind drag / height of our trailer
• reduce shadowing on existing solar panels from the A/C unit shroud in early morning / late afternoon
• add the ability to heat or cool, work as a fan, and add the feature of dehumidify

Which Mini Split did you buy and why ?

We decided to go with a Fujitsu Halcyon 9000 btu unit, mostly because Eddie Glonek has had experience with this model (his is the 12000 btu size) in his RV. This unit is Seasonal Energy Efficiency Ratio (SEER) : 16 with a quiet 23db noise level for the inside fan unit.

In his experience as an HVAC specialist, he recommended Fujitsu for their excellent warranty. This is NOT the cheapest option for mini splits. You can find them for under $700 on amazon, but in this case, we’re hoping we “get what we pay for” and chose reliability and warranty over cheap.

according to the specs from Fujitsu (for our 9000 btu unit) :

cooling current : 7.5 amps
heating current : 7 amps

maximum cooling current : 13 amps
maximum heating current : 13.5 amps

that means that with watts x 120v

that the max this thing would draw is 1620 watts (at 13.5 amps), and about 900 watts (at 7.5 amps) for cooling.

Other required items to do this installation :

in addition to the Mini Split, you’ll also need to purchase a “line set” which consists of 2 copper tube lines (for cycling the refrigerant), and some 14/4 control wire to connect the Evaporator to the Condenser. I purchased 30 feet of line set and control wire just to be sure we had plenty to spare. This of course was possible because Eddie could cut and create flared connections in the copper tube when necessary (the Gone Boondocking example video just uses the entire line set and doesnt cut anything to size).

also highly recommended, a vacuum pump (to evacuate the condenser lines, and a vacuum gauge to measure / test for leaks. You dont want any air , dust or moisture in your lines prior to adding the refrigerant, and you certainly dont want any leaks in your copper lines.. If you are doing a “one time” install of a mini split, you basically will never use this tool again, so it would just be easier to get an HVAC tech to do this part of the install.

If you watch a few installs, some DIY folks just skip the vacuum step, but depending on your install environment (very humid or near the ocean, dust, pollen etc.) you may be taking your chances on having contaminated refrigerant, which could cause future maintenance/performance issues.

Another item needed is a way to get AC 120 power to the Condenser. Obviously you’ll need an open breaker in your AC circuit breaker, and some 10/2 Romex wire to make the run from your breaker box, outside to the Condenser unit.

Optional items to do this installation :

You’ll of course need a way to mount this to your camper. In our install, we decided to use a RectorSeal Stainless Steel Wall Bracket. Later in this write-up you can see how we used this bracket. We have seen other folks mount theirs on triangle front tongue of their trailers, and even on a custom platform built over their LP tanks.

You’ll also need some sort of exit hole through the wall of your camper for the water drain. For this we used a SeaFlow Thru Hull fitting. The idea was to find something that matched the diameter of the drain tube, but also looked sorta nice from the outside.

Installation Consideration 1 : where to put the outside unit (condenser)

On our travel trailer, the only real option was to put the Condenser on the back of the trailer. We could have possibly created space by reconfiguring our propane tanks (or removing one?) to make enough space on the “A” of our trailer frame for the unit. Another possibility could have been to build a “shelf” frame above the propane tanks. That was outside the scope of this install so we just decided to put it “somewhere” on the back of the trailer.

There are some advantages to having the unit on the back of the trailer… mostly protection from road debris, wind wear and tear on the Condenser. Possible disadvantages : attaching the unit (bracket) to “anything” solid (our trailer is basically plywood, foam and glue), and being mounted on a big hollow wall…. possible vibration/noise from the condenser when ramping up.

Installation Consideration 2 : where to put the inside unit (evaporator)

Our Travel Trailer (2017 Rockwood MiniLite 2104S) is quite small, so the options for placement of the inside Evaporator unit are limited. The inside unit measures :

10 1/4″ high x 32 ” wide x 8″ deep

Additionally, the manufacturer recommends approximately 2 inches above the unit for proper airflow.

Inside our travel trailer, the obvious and possibly the ONLY choice for the inside unit was on the drivers side between the closet door and the slide-out. As you can see in the picture below, there is ample space to fit in the 32″ width of the Evaporator unit, and ample height for the unit, including the required space above the Evaporator. The depth at 8 inches doesn’t seem too deep where you might hit your head on it when getting in and out of the Murphy Bed in the middle of the night in a super dark camper.

This also places the unit directly above the bed, so that on a very hot night, the cool air will be blowing on the weary travelers trying to rest below on the Murphy Bed.

Installation Consideration 3 : how and where to run the refrigerant lines

Now that we know the Condenser will be mounted somewhere on the back of the trailer, and the Evaporator will be mounted on the drivers side between the closet door and the slide-out… where should the “line set” or refrigerant lines run, to connect the Condenser to the Evaporator ?

The lines could run outside on the roof, but we already have multiple solar panels on the roof. To properly make an outside run, we’d have have to reinstall our panels on the driver’s side roof edge. Also, having the refrigerant lines outside exposes them to heat, sun, possibly damage by a tree or overhead object. If we ran the majority of the lines inside the trailer, it would be visually unappealing, but overall, a more efficient (heat / cool loss) and more durable long term installation.

The picture below shows our solution which was to utilize the empty space above the slide out, to run the refrigerant lines towards the back of the camper.

After entering the wall (top left of the above picture) , the exact path of the line set run is still to be determined. This will be based on exactly where the Condenser will be mounted. At this point, we have enough of a concept as to how to move on to the next step.

Step 1 : Removal of original Air Conditioner Unit

At this point, Eddie jumped into action and started removing the original A/C unit. After removing the outer housing, the mounting screws for the roof top unit are exposed.

Once the inside plastic molding is removed, all that remains inside is the metal bracket

Once this bracket is free from the ceiling, the A/C unit can be lifted up and away. Eddie cut and capped the original AC power supply as well as all thermostat lines and tucked them inside the ceiling

Here we are walking the original A/C unit down the ladder from the roof. This this was HEAVY !

Step 2 : Replace A/C roof hole with a new powered vent fan

Now that there is a 14″ square hole in the roof, what was the plan ? Well… we could have built a custom cover to fill in this hole (and insulated) , but that would have added a bunch of install time and some custom materials. So… instead we decided to go with an inexpensive ceiling fan / vent. We chose the MaxxAir Mini Roof Vent because it is very thin (thats the mini part) as it extends only 2 7/8 inches above the roof line. We bought this fan from Gander Mountain as it had free shipping and cost only $119. The white plastic cover will also allow as much light in as possible (without being clear, which wasnt available)

Eddie was able to re-use an available 12 volt power supply from the A/C install to power the new fan. Also, we verified that after removing the A/C unit, the thermostat still worked as expected with the gas heat furnace.

Now that the A/C unit was gone the new Maxxair Mini fan was replaced in its hole. The purpose of the fan being only 2 7/8″ height off the roofline was because we planned to put a solar panel OVER the new vent. This will be covered in a later install post.

Eddie finishing up the sealing of the roof vent with Eternabond tape and dicor.

Step 3 : Test hang of the inside Evaporator unit

Here Eddie is doing a test hang of the inside unit. This metal bracket is screwed into the side wall, and the Evaporator hangs on top of it. We wanted to place the unit in its inside position so that we can start to come up with a plan for the line set (refrigerant line) run to the outside unit.

Step 4 : Assemble the Condenser Bracket come up with a plan for mounting bracket to the trailer

Here Eddie is assembling the stainless steel mounting bracket and aligning the rubber feet to fit the Condenser unit

here is a test placement of the condenser unit on the bracket. Taking a look at how it will sit on the bracket, allowing enough airflow between the condenser and the trailer

Below Eddie is doing a test for fit and position of the bracket. The idea was to use the vertical framing for the refrigerator (seen below near Eddie’s right hand). This means the left side of the bracket should have some “solid” wood framing inside the camper wall to sink in some lag bolts. The section near Eddie’s left hand, is an open “chimney” which we can access through the fridge access door. These attachments can be made with large size fender washers and bolts accessed inside the chimney.

Also, below… to be determined, what can we use as anchors for the horizontal bracket bar and the right side vertical bracket arm. Based on some measurements, it appears as though these “should” enter the camper back wall inside the bathroom cabinet. If so, we can access this area from the inside, using fender washers and bolts to “squeeze” the trailer back wall, creating an anchor for the condenser unit bracket.

just holding up the bracket for now, to see if we can come up with some solid anchor points

Step 5 : Investigate the vertical left side anchor point for the condenser bracket, drill a pilot hole to see if we can use the bathroom closet

At this point, Eddie drilled a hole from the refrigerator access door towards the bathroom closet to investigate the vertical framing for the fridge. Through this hole, we used my trusty boroscope remote camera to investigate exactly what was framing in the fridge. Turns out, as Eddie suspected there was some wood framing that “should” be enough to take a few lag bolts (for the left side of the condenser bracket)

Knowing that our plan was pretty solid so far, Eddie drilled an exploratory hole on one of the right side bracket holes, hoping to land in the bathroom cabinet

Step 6 : Anchor Condenser unit bracket to the camper tail wall, Attach Condenser to bracket

Eddie’s measurements and guess work paid off as the exploratory drill hole indeed ended up inside the bathroom cabinet ! This meant we had a way to drill through the tail of the camper wall, and have an easily accessible area to attach the hardware to secure the bolts. (the arrow below shows the pilot hole). Eddie started drilling out three of the bracket holes. In total, inside the cabinet, there would be four bolts across the top, and three bolts along the left side (along the wall of the cabinet)

Knowing the position of the inside cabinet, Eddie could now pre-drill for the bolt hardware, as well as put down a healthy layer of silicone to seal around the bolt holes as well as offer some adhesion of the bracket to the wall

Here are the final bolts, nuts and fender washers (that hold the right side of the condenser bracket). The bolts got cut down (post-install) to a shorter size after the install (so that we’d have more storage room)

With the bolt hardware attached inside the cabinet, and the bolt hardware attached inside the refrigerator chimney access door, Eddie could now use lag bolts on the left side of the condenser bracket. These are the lags that are going through the fiberglass, luan (plywood), foam, luan and then the wooden vertical fridge frame.

With the bracket securely attached to the back of the camper, it was time to attach the condenser to the bracket. This was done with the hardware that came with the condenser bracket, but Eddie also added some nuts inside the bracket arm, to be sure they wouldn’t easily back out and possibly cause the condenser to jump up and down

Step 7 : Plan and prepare for the line set to run from the inside evaporator to the outside condenser

The basic idea was, as previously mentioned, to run the refrigerant lines above the slideout (top right corner arrow in the picture below), punch a hole through the pantry, then run down the right side of the pantry, across and underneath the fridge, past the water heater, and into the bathroom cabinet.

Eddie taking a look with his drill as a flashlight… for a good entry into the bathroom cabinet. the target was a to be drilled hole in the left side wall, creating an opening in the bathroom cabinet

In the picture below (to the left of the water heater), we bust open a “false” wall, that was just covering a huge space behind the toilet. Basically, the Rockwood installers just paneled over this space, because they couldnt be bothered to create another storage space. As you can see, the space is quite large, basically only covering some plumbing and wiring.

Now that we had a plan in place, it was time to start drilling holes for the refrigerant lines to pass through. Here Eddie is making a hole to access the pantry cabinet. The door will have to be re-hung to accommodate the space needed for the line set.

Step 8 : Run the refrigerant lines and control wire from the Evaporator inside unit to the outside condenser

Now that the holes were drilled along the path of the lines from inside to outside it was time to run the refrigerant lines and control wire.

Below, we carefully uncoil the line set from the shipping box. You have to be very careful not to crimp either of the copper tubing lines, as any hard bend or crimp would mean a refrigerant leakage point.

Now for the tricky parts. feeding the refrigerant lines from outside to inside. Due to the nature of our run, we need to make 5 turns along the course. Each time you need to make a 90 degree turn, you have to be absolutely sure you dont crimp the copper lines. Feeding the lines through sharp edges means that the foam outside insulation collar gets chewed up and chopped up.

Suffice it to say, the more turns you have to make, the harder this process is. On top of that, Eddie indicated multiple times that the quality of the lineset that I purchased was not top notch. Mainly, the insulation tubing was very thin and crumbly and the copper was of only acceptable gauge and quality. This made making the twists and turns along our run very frustrating and difficult. This was the second-most time consuming part of the install.

As Eddie has noted many times during our installs (past and present), the smaller the camper, in general, the harder the install. This is mostly just due to space constraints, but also you have to be creative with your problem solving and prepare for unforeseen roadblocks along the way.

Step 9 : Run AC power from the breaker box to the outside condenser unit

I have no images for this part of the install, but it wasn’t all that fun to say the least. While Eddie was working on making the final connections to the inside evaporator, and installing the drain, I was working on the electrical wire.

Basically, all that needed to happen was to make a run from the breaker box / distribution panel (on the side of our oven, but the outside door) to the outside condenser unit.

To do this, I had to cut the power, pull out the breaker box, fish a line from the breaker box, behind the furnace, underneath the kitchen sink, through the wall to the bathroom, under the bathroom sink, under the shower pan, and out into the newly opened cabinet behind the toilet and out the hole created for the refrigerant lines to the outside.

Sounds easy enough, until its time to actually fish the wire through this run. Luckily, the Romex 10/2 wire is very stiff, so you dont need a fish line. In generally I could force a decent path with the wire itself, all the way to the end of the run.

All that said, it probably took me almost 1.5 hours to get this done, and get it connected to the original breaker for the Air Conditioner on the AC panel.

The picture below shows the final pass-through of the power, refrigerant lines and control line. On the left side, is the AC wire coming up from underneath the shower. On the right side is the refrigerant line and control wire coming from the water heater compartment. All of these lines go outside through a new hole to make the connection to the outside condenser unit.

Step 10 : Create a drain hole, connect refrigerant lines, control wire and drain hose to the inside Evaporator unit

Using the installation instruction measurements, Eddie drilled a hole in the sidewall to accommodate the Evaporator drain.

To make a nice closure with a waterproof seal from the outside of the camper, Eddie used a SeaFlow Thru Hull fitting. The inside of this fitting hooks into the drain tube of the evaporator.

Here is what the Seaflow fitting looks like on the outside of the camper. If there is significant moisture in the Evaporator, it will drain out the sidewall to the outside and drain to the ground

At this point it was time to connect the refrigerant lines, drain hose and control wire to the evaporator unit. This was unfortunately the hardest part of the install for a few reasons. For one, it seems the instructions from Fujitsu for drain position, and refrigerant line positioning were incorrect. This meant that Eddie had to do some custom fitment (cutting away some of the plastic housing) and just generally manipulating the lines so the unit would sit flush on the wall.

This was an extremely frustrating waste of time for Eddie, one that we had not planned on, naturally. After a considerable effort, Eddie wrangled all the connections and was able to get the unit secured flush to the wall.

Just to be sure the unit wouldn’t jump up and off its wall bracket when driving on bumpy road, Eddie added two little wooden shims above the evaporator unit. This lock down the unit so it cannot lift off when in transit

Step 11 : Connect the refrigerant lines, control wires and AC power to the outside Condenser unit

As you can see from the fading light, its about to call it quits for this day. But before darkness fell, Eddie connected both refrigerant lines, connected the control wire for the Evaporator (black cable below) as well as the AC power for the Condenser. The picture below shows the work in progress, but almost complete. Things were starting to come together !

Step 12 : Vacuum the refrigerant, check for leaks, release refrigerant into system, test system

Here Eddie set up a vacuum pump to the system to pull out any air and moisture from the lines. This also allows for a pressure check to be sure that after getting a good vacuum, the system can hold it steady. This way, you’ll know if you have any leaks. Luckily for us, with 5 turns in the lineset run… there were no leaks !

After removing the vacuum pump, we could now release the refrigerant from the condenser unit into the system. The refrigerant is contained in a reservoir within the Condenser, so that when your system is closed and ready, you can fill with the refrigerant.

At this point, with the mini-split connected to the AC power (via the old Air Conditioner circuit) and the system leak free and filled with refrigerant, it was time to test.

We tested both the cooling and heating modes, all fan features (swing, hi/lo fan) and everything was working as expected.

Here, Eddie is filling all the gaps with expanding foam. This hole in the picture is the entry point for the lineset as well as the AC power as it comes out from the bathroom lower cabinet

While it isnt the prettiest thing we’d ever created, we needed a way to “hang” the lineset above the slideout. The copper needs to be protected from puncture or crimping, and the lineset needs to be out of the path of the dinette slides as it opens and closes.

We chose this plastic gutter channel, because its lightweight, and easily anchored on the top to the sidewall of the trailer above the slide out.

This was actually a little trickier than anticipated because, when the slide goes in and out, at the VERY end of the slideout, it actually raises UP about one inch.

This was workable, but only just barely. We just needed to reposition the ugly wooden top moulding (horizontal across the slideout face) down slightly. Its really just for looks, and those looks are ugly anyways. It barely noticeable after moving down low enough to clear the last slideout movements and clears the lineset with ease.

The gutter is pretty ugly too ! so we have already begun to decorate this part of the install with tiny pictures that cover the gutter perfectly. We put on a long strip of velcro to the plastic gutter, and then each picture can be stuck on, reordering and updating pictures as we go along. None other then Eddie Glonek pictured in the first slot on the left below.

The mini split in action ! testing the unit in some late fall sun and heat in western Colorado.

Final Install Thoughts

This install was very complicated, super involved and required a lot of expertise. We are grateful for Eddie Glonek’s hard work and extensive installation knowledge. As expected, he did an incredible job, and did it right the first time. For the average DIY person, I’d say… you probably should have some assistance for this install, and highly recommend including an experienced HVAC installer, ideally someone with Mini Split experience. Or.. just hire Eddie Glonek do it !

How is it working so far ?

Well, we installed this unit at the very end of September 2020. So we haven’t used it a whole bunch thus far. But we have the following info to share so far :

• the indoor and outdoor units are securely connected to the camper (inside and out) , we have had no issues with the units staying put. We really don’t even think much about them when going off the highway.
• the unit does work well (off grid) when running off of our 2000 watt inverter. In 90F weather, it takes about 1200-1400 watts for initial cooling, then approximately 350-400 watts to keep the camper at temperature (on Economy, quiet fan setting)
• also at 90F, when initial cooling is completed, our incoming solar can supply the entire minisplit energy needs, when we have full solar incoming. This means when we have approximately 30-35 amps incoming, we can run the mini-split at a “net zero” where its only consuming the incoming DC solar power.
• the inside evaporator unit is more or less silent on quiet mode.
• the outside condenser unit is NOT silent, especially when “ramping up” when the system kicks up its power temporarily to “catch up”. Because its attached to the back wall of our camper, which is essentially a gigantic foam box, there is some vibration sound on initial ramp up. However after “ramp up” it is not really noticeable, especially if you aren’t trying to sleep in total silence.
• that said, even at its loudest, the indoor unit plus the outdoor unit condenser vibration sound is drastically quieter than our original roof-mounted 12,500 btu unit.
• the sizing of the 9000 btu unit is more than adequate to cool our 21 foot trailer. However, we haven’t tried in anything more than 90F heat. But we never used anything but economy (lowest) settings and it cooled the camper to an “uncomfortably cool” inside temp (during testing)
• Using it as a heater is also possible of course, and we did test that, but to be honest, we’d be more likely to use the unit as a dehumidifier than a heater. We do like the ability though, to have a third heating option (in addition to our furnace, and catalytic heater)
• removing the roof unit saves weight and frees up more roof space for more solar !

What would you have done differently, given the choice?

Well, I’d say, even though running the lineset inside the camper was extremely time consuming, I’d probably go that route again.

But I think, knowing now how much vibration is created by the condenser on start up / ramp up, I probably would have spent the time and resources to create a custom mount / shelf on the front of the trailer A-Frame. This would have made the refrigerant line run much shorter (from a-frame front to inside). Mounting the Condenser on the front of the trailer also increases the risk of debris or rock strikes from the tow vehicle.

Another option, build some sort of contraption off the back of the trailer that hangs on the trailer frame I-Beams.

The idea being, in theory, that having the condenser not physically attached to the sidewall of the camper, but rather to the steel frame, it should be much much quieter.

In the end, this would have drastically increased the complexity and cost of this install, as well as required custom fabrication and welding. You’d have to weigh the options of cost vs a little bit of vibration noise, knowing that in comparison, I’d say the mini-split is probably about 15-20% of the noise level of your common roof mounted A/C unit.

In summary… the vibration noise is not that big of a deal vs being uncomfortably hot (or cold) when dry camping

Im on the fence… do you recommend this mod ?

This is clearly not for “everyone” but rather for folks who want to extend their dry camping into places where air conditioning would make camping more comfortable and don’t want to rely on a generator for electricity to power a high-energy, traditional A/C unit.

Its a bit too early to report our findings, but so far… its doing exactly what we had hoped for.

We will update our long term usage and let you know more about how we use this unit and if its meeting our expectations.

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Update 12-2021 : check out a related video by Eddie about how he installed a Mini Split on an Alto travel trailer