Mini-split in compartment

[Dirtyrhoades77]

Hi all, I'm in the planning stages of a Class C boondocker, loaded with solar panels, a big 24v battery, all that.

I'd like to install a mini-split up near the front of the vehicle, so when the sun is up and the heat is on, the living area is cool. I'm planning on a 9000btu unit as I think that would be enough if the roof is covered in panels providing some shielding from direct sun. I'd like to cram the external unit into a compartment nearby so it's close to the head unit, and on the driver's side so it's not disrupting the awning space on the passenger side. I'd have the fan exhaust blowing straight out the side, cutting a hole in the panel door for it.

The exterior unit's dimensions are in inches 32w*22h*14d.

Assuming I'm willing and able to remove the generator or propane if necessary, or modify whatever other type of compartment is in that area, are those compartments big enough to accommodate those dimensions?

I imagine the height is the biggest problem, it would hang down a bit. I'd have to bolt or weld in a frame for it to sit on, preferring to keep the rubber grommet to sit on to absorb some of the vibration.

Does that sound doable? I'd much rather make this work than do a bedroom/bumper mount.

[pianotuna]

Ask what the wattage is for the fridge.

You would need a DC to dc charger 24 to 12 or 48 to 12. The fridge may be perfectly happy at nominal 12 volts.

jc-refrigeration.com used to make 12 volt electric cooling units--but I could not find them at the site now.

[Dirtyrhoades77]

pianotuna wrote:

Dirtyrhoades77 wrote:

As for 48v, I can see what you guys are saying, but if I go 48, I'll then have to get a 48 to 24 converter for the fridge, and that's another component, and it's $150.

My system probly won't ever go over 2000w, so I won't be outgrowing 24v, so I can't see any real advantage over 24.
Maybe 48v mini splits are easier to find at the moment? Are 48v alternators easier to find? What other advantages are there besides more headroom for expansion?

A 24 volt inverter has to carry twice the current for the same output load as a 48 volt unit.

Your fridge is already 24 volt? That's a bit rare.

I've never seen a 24 volt mini split--but that probably means when I was searching for DC powered air conditioners that the 48 volt ones 'jumped up' first.

I don't have the 24v fridge yet, but jc-refrigeration.com sells replacement components for RV fridges. You pull it out, swap the components, and shove it back in. People seem to like them, and they have a 3y warranty, even up to 6 years. Best of all, no propane use and no inverter needed. I'm definitely doing that.

As for the DC minisplits, I think behind all the rebranding I think there are very few manufacturers actually producing 48v, and I've found only one so far for 24v, and I'm trying to clarify some of their info, as it's inconsistent.

[pianotuna]

Dirtyrhoades77 wrote:

As for 48v, I can see what you guys are saying, but if I go 48, I'll then have to get a 48 to 24 converter for the fridge, and that's another component, and it's $150.

My system probly won't ever go over 2000w, so I won't be outgrowing 24v, so I can't see any real advantage over 24.
Maybe 48v mini splits are easier to find at the moment? Are 48v alternators easier to find? What other advantages are there besides more headroom for expansion?

A 24 volt inverter has to carry twice the current for the same output load as a 48 volt unit.

Your fridge is already 24 volt? That's a bit rare.

I've never seen a 24 volt mini split--but that probably means when I was searching for DC powered air conditioners that the 48 volt ones 'jumped up' first.

[Dirtyrhoades77]

valhalla360 wrote:

pianotuna wrote:

I would jump right to a 48 volt battery bank.

Agreed, once you diverge from 12v may as well take good advantage of a higher voltage.

Also, keep in mind for the spacing, that the 12" manufacturer spec you mention is likely based on the condenser being completely outside with no other restrictions. If fresh cool air can only enter from a relatively small slot from below, it may not meet the needs. Talk to the manufacturer and explain exactly what you are doing.

Good point on the spacing. The opening would be the full 12" as the entire bottom would be open to the ground other than the two supports it would be sitting on, maybe unistrut, but maybe that's not enough. Surely any manufacturer would be against anything out of the norm so it's not worth the effort to explain it to them. There are guys on youtube that have done it to their Class As, and one manufacturer is even offering it as an option on a new model. Stuffed right into the compartment below. It's pretty cool.

As for 48v, I can see what you guys are saying, but if I go 48, I'll then have to get a 48 to 24 converter for the fridge, and that's another component, and it's $150.

My system probly won't ever go over 2000w, so I won't be outgrowing 24v, so I can't see any real advantage over 24.
Maybe 48v mini splits are easier to find at the moment? Are 48v alternators easier to find? What other advantages are there besides more headroom for expansion?

[valhalla360]

pianotuna wrote:

I would jump right to a 48 volt battery bank.

Agreed, once you diverge from 12v may as well take good advantage of a higher voltage.

Also, keep in mind for the spacing, that the 12" manufacturer spec you mention is likely based on the condenser being completely outside with no other restrictions. If fresh cool air can only enter from a relatively small slot from below, it may not meet the needs. Talk to the manufacturer and explain exactly what you are doing.

[pianotuna]

Hi,

One of the largest heat sources is the engine, transmission, and tailpipe system on a class C. After a day's drive the roof air takes quite a bit of time to cool the RV down.

I would jump right to a 48 volt battery bank.

[Dirtyrhoades77]

Thank you for the detailed reply DrewE, it's exactly what I needed.

Thanks to everyone who replied. Definitely the generator and propane are imporant, I'm just trying to examine what is possible in this given scenario. I won't go boondocking without a generator or propane. Things just may get replaced, modified, or moved around a bit.

DrewE's suggestion to take some space from the inside may be the way to go. Nearly every model I've looked has the dinette there, it should be relatively uncomplicated to remove the dinette, cut and box out what it needs, as long as the mods stay below the cushion level of the dinette. Cut the dinette cabinet accordingly, and put it back.

As for tolerances, if I recall correctly the intake side needs 12". Given that I want the unit behind a closeable door, the exhaust will be set back maybe 2", 14" for the unit, then 12" intake clearance, makes a 28" deep box. Whichever compartment I mount it in will have an fully open bottom for air to move. I'd leave enough space on the sides to do the install and allow for vibration and flexing. Making it look normal from the outside will be more of a challenge.

In response to the solar panels adding heat, from what I've seen so far is that panels need sufficient airflow below them or they overheat and lose as much as 30% efficiency, so they should be mounted 2.5-3" above the deck for airflow. In that case, the air below the panels stays cooler, and the roof surface as well. With a lot of solar panels (1500-2000 watts), a significant percentage of the roof would be shielded from direct sun. That must help to some degree.

That said perhaps I should be considering a 12k unit, but I sure would like to know if 9k would do it, and somebody has to go first. I don't plan on hanging around any extremely hot environments (or cold for that matter), and I don't need it cooled below 75 degrees, so it won't be working too hard.

With a minimum of 1500w of solar, a 7200w lifepo4 battery, a mini split, a 24v amish hvac cooling upgrade on the fridge, an on-demand propane water heater, and an induction stove, the generator and propane loads should be much lower than usual.

I'm currently trying to clarify some details with a chinese company (royalstar) on some possible 24v Dc mini splits. It would be pretty great to keep that load off the inverter. Unfortunately there are spec discrepancies between their website, their catalog pdf, and a reseller's website. Not a good sign, but the idea is so tempting.

[theoldwizard1]

valhalla360 wrote:
OK, I'll also go down the rabbit hole...how do you plan to power it if you remove the generator to place the condenser in it's spot?

A generator is an absolute MUST ! The typical builtin generator in a Class C is very large. A 2500W-3000W portable or a pair of 2000W portables is the solution.

[theoldwizard1]

whemme wrote:
And what good is a big 24V battery when Class C appliances run on 12V dc?

They make 24VDC - 12VDC converters. The 12VDC loads in a modern RV are very low. Mostly lights and cell phone chargers. Slide motor can be run off of a 120VAC power supply

[Lwiddis]

Something “hanging down” and boondocking don’t go well together. Many Cs are low to begin with.

[theoldwizard1]

valhalla360 wrote:

wanderingaimlessly wrote:
The ones I've seen, they mounted the outside portion on the rear of the rig to allow sufficient airflow to cool it.

Yep, check with the manufacturer for airflow and spacing requirements.

This is going to be your problem !

Manufacturers specify a large margin on all sides for both airflow and serviceability. While it is possible to mount the unit on a slide out, flexing the lines will cause a failure over time.

[VA-Apraisr]

Hmmm....cloudy/rainy days don't allow much solar energy for your batteries. As mentioned above, I wouldn't consider boondocking without the option of running a generator to power a/c & heat as well as keeping your battery bank fully charged. What if you have a battery failure? No propane, no generator and you're in for an awful time. I spent 5 days on a deserted island with 40mph winds/rain/clouds and was sooooo thankful for my generator! Weather can change on a dime and your outdoor experience must be able to adapt. Good luck.

[whemme]

And what good is a big 24V battery when Class C appliances run on 12V dc?

[valhalla360]

wanderingaimlessly wrote:
The ones I've seen, they mounted the outside portion on the rear of the rig to allow sufficient airflow to cool it.

Yep, check with the manufacturer for airflow and spacing requirements. Typically they are mounted outside 6-10inches from a wall...that's why mounting on the rear bumper is more typically done if you retrofit to an RV.

Also, 9k btu is likely marginal in any kind of significant heat unless it's a very small RV. The black solar panels are likely to increase heat absorption over the typical white reflective roof.

OK, ;I'll also go down the rabbit hole...how do you plan to power it if you remove the generator to place the condenser in it's spot?