Highest efficiency rooftop ac?

[Bus'n it]

Christopher, I'm looking at you! I decided to just get two rooftop units for my bus rather than dealing with cutting in mini splits and their unknown reliability bouncing around in a bus and/or dealing with installations constraints. So in my searches, I kind of like the Furrion 15.5k BTU units but they appear to be power hogs at 3500 starting watts. I do plan on shoving in many LifePo4 batteries as I can afford, but what in your experience can you recommend in terms of efficient roof top RV a/c units? I do plan on spray foaming the bus and doing dual pane RV windows.

[DeMac]

A similar discussion was recently started here:

https://www.skoolie.net/forums/f9/th...ion-36000.html

Houghton A3800 (nameplate below) is what we chose for both pump & fan efficiency.

[rossvtaylor]

Unfortunately, I can't answer your question...because we go the other way. I've not found an efficient rooftop unit, at least nothing that comes close to some of the mini splits (we like the units from, and support of, Alpine Home Air). We actually rip the rooftop units off old buses we get and put in mini splits, because I've not yet found a rooftop unit which I might be able to run off solar. And we're up the hill from you, where it doesn't get as hot as where you are.

I'll follow the thread, because I might learn about some new efficient rooftop unit. But we've been super happy with every mini split we've installed and have never had an issue with them in a bus.

[Simplicity]

Originally Posted by Bus'n it

Christopher, I'm looking at you! I decided to just get two rooftop units for my bus rather than dealing with cutting in mini splits and their unknown reliability bouncing around in a bus and/or dealing with installations constraints. So in my searches, I kind of like the Furrion 15.5k BTU units but they appear to be power hogs at 3500 starting watts. I do plan on shoving in many LifePo4 batteries as I can afford, but what in your experience can you recommend in terms of efficient roof top RV a/c units? I do plan on spray foaming the bus and doing dual pane RV windows.

I know nothing of this, yet, I did some research and got to thinking about this in relation to my bus. So, here's my freeflowing thinking.

There's two things at play here. One, the bus is a vehicle, second, the bus is a home.

Vehicles have very little to no insulation. Their metal components love to soak up heat. So, they get really hot really fast. In addition, in general, a vehicles AC system is made to work in SW desert or the cool coast of the PNW, and they have to cool the interior down quickly. In other words, a vehicle's AC has a huge job. They say for an average car AC generats, up to 40,000btu!

Vehicles used as homes have, comparatively, a huge amount of insulation in the ceiling, walls and floor. Add in energy efficient double pane windows and
a roof with a cooling coating and your vehicle is more like a home.

An average house room of say 150sqft. The rule of thumb is 20btu per square foot, so 3,000btu for this example.

Since a full size bus is ~250sqft x 20btu = 5,000btu.

So it seems like the 15.5k unit is more than adequate for general use.

Since you were talking about batteries, I'm assuming you're going to be wanting to run the AC off the batteries.

A soft start unit would seem to be the first feature I would want. This way your not surging your electrical.

The second thing I'd consider is similar to the battle of condensation. The best way to keep condensation at bay is to keep the air moisture content under control. I'd say this would be similar in wanting to keep the amount of time your AC cycles on to a minimum by keeping the internal temperature down through shade. If not shading of the bus, at least shading of the windows. Obviously you can make thermal window covers, but then you loose your view. I have yet to see them, but it would be cool if you had some kind of mini-awning for the windows. Of course, only practical when parked.

The other thing I'm wondering is how to automatically have the system fire up the generator a minute before the AC is going to cycle on. Then you would not need such a large battery bank.

Again, just random thoughts. Hope in some way it might help.

I'm going to work on that mini-awning idea for my bus.

[peterbylt]

I posted this on another forum as well, but applies here.

We first installed a 12k Pioneer Mini Split with the indoor unit over the top of the windshield.

We are very happy with this unit it is very quiet and efficient, sufficient to cool the entire bus most of the time.

The problems happen when the temperatures get into the upper 90’s then we start to lose ground (living in Florida this happens).

After much deliberation we decided to go the other way and installed a Coleman Mach 15 in the rear hatch in the back of the Bus, This unit Kicks A$$, can cool the bus from heat soaked to the 70’s in minutes.

Between the two we have the best of both worlds, Most of the time we run the mini Split, but when it gets real hot or we just want to cool the bus quickly we kick on the Mach 15.

The Mini Split sips electricity, The Coleman gulps it, Mini split is so quiet you can’t hear it most of the Time, Coleman is pretty loud, Mini Split takes a while to cool, Coleman cools quickly.

Most of the time we run both to get where we want in the mid 70’s then maintain with the Mini Split.

I am currently in the process of building my Solar system (waiting on the batteries from China) and have sized the system to be able to run the Mini Split part of the day, The Coleman just eats too much juice to viably run off the batteries.

The Pioneer Mini Split was not too difficult to install, comes precharged with R410A, I bought a cheap vacuum pump off amazon and a cheap gage from Pioneer, The hardest part was bending the copper lines and not kinking them, it has been in the bus for 4 years without issue.

Peter

[Bus'n it]

I've got HVAC tools, flare, benders, pumps, fitting adapters, scale, micron meter, digital manifold. I just do not want to deal with finding a hidden place for the condenser. All space under the bus has been accounted for. I do have a 7.4kw diesel generator thats taking up a big chunk of change in the space department. Honestly, the rooftop unit will cut my build time. Wondering if those new 300amp lithium batteries can run it overnight if I put enough of them under the bus.

[joshrobertson1]

Originally Posted by peterbylt

I posted this on another forum as well, but applies here.

We first installed a 12k Pioneer Mini Split with the indoor unit over the top of the windshield.

We are very happy with this unit it is very quiet and efficient, sufficient to cool the entire bus most of the time.

The problems happen when the temperatures get into the upper 90’s then we start to lose ground (living in Florida this happens).

After much deliberation we decided to go the other way and installed a Coleman Mach 15 in the rear hatch in the back of the Bus, This unit Kicks A$$, can cool the bus from heat soaked to the 70’s in minutes.

Between the two we have the best of both worlds, Most of the time we run the mini Split, but when it gets real hot or we just want to cool the bus quickly we kick on the Mach 15.

The Mini Split sips electricity, The Coleman gulps it, Mini split is so quiet you can’t hear it most of the Time, Coleman is pretty loud, Mini Split takes a while to cool, Coleman cools quickly.

Most of the time we run both to get where we want in the mid 70’s then maintain with the Mini Split.

I am currently in the process of building my Solar system (waiting on the batteries from China) and have sized the system to be able to run the Mini Split part of the day, The Coleman just eats too much juice to viably run off the batteries.

The Pioneer Mini Split was not too difficult to install, comes precharged with R410A, I bought a cheap vacuum pump off amazon and a cheap gage from Pioneer, The hardest part was bending the copper lines and not kinking them, it has been in the bus for 4 years without issue.

Peter

Peter - I love the idea of having both. Do you run the mini split while you drive? I’m over near Cocoa Beach, and am just starting on my bus. Came with no factory AC, so I need some cool air! I’d love to come check your bus out sometime.

Josh

[cadillackid]

im of the mind to have 2 A/C systems.. one for the road, one for being parked. I dont know about the furrion systems yet.. of course coleman Mach's are tried and true and they are simple.. everyone makes parts for them.. Dometic makes a power-sipping Rooftop unit that runs on an inverter compressor but as of yet i think its still only sold for those who are "down under" (aussie).. a chinese company shows they have one. Aislu - RV Air Conditioner however I havent seen it on alibaba yet or id prob buy a couple for fun.



Minisplits to me on the surface are the best for power usage.. but longevity in a mobile application hasnt been tested.. somewhereinusa is prob one of the longest runners and I think his have been in 5 or 6 years and still work... of course the install work is much more intensive and not particularly space-saving.



me personally? running A/C on Solar / batteries is a slippery slope. you need a heck of a lot of charging capability to not only run your A/C on hot days but to also recharge the batteries from the night before.. thats a ton of solar.. and means leaving your bus out in the sun where the A/C must work harder...



at night when sleeping and in "quiet zone" of camping areas a minisplit is perfect as its quiet.. sips the power and doesnt constantly surge on / off with the compressor as it varies speed...

[somewhereinusa]

Just thought I'd chime in here. I checked the date and I purchased my mini's in June of 2015 so, they have been installed about 6 years. Other than some problems of my own making on installation they have been trouble free since then. I don't do it often, I don't feel the need, I have run the front one while driving and it works well. Biggest problem, when I still had lead acid batteries mounted in the engine compartment, was inverter shut down due to battery overheat.

I have 2 12,000 btu Klimeair units and they do a great job. In temps of high 90's sitting in the sun inside temps are quite comfy. I now have built in shade on the back half of the bus (solar panels) and the lithium batteries are no longer in the engine compartment. I can run one air all night with battery power.

[LargeMargeInBaja]

On YouTube, check the ExpeditionVehicle build by EVERLANDERS.
.
They mounted a split a couple-three years ago.
Then, traveled to Alaska.
Then, all over the west US, up our favorite -- rough logger tracks.
Then, all over Baja, across deserts and climbing out of deep beaches.
After sitting 2020 in tropical Mexico, they are in Guatemala.
.
They may have an opinion about reliability.

[Bus'n it]

Well, I looked at RecPro which have the Australian designed Houghton units. Those seem to be the lowest amp draw for output available. Price on these is a published $1049.95. There is a company in AZ that makes 12v A/C's but the cost is $4400. I see no reason 6 300Ah LifePo4 batteries can't run one rooftop unit for 8 hours. I plan on covering the roof with solar to help and of course, I have the diesel generator to charge the batteries up in the late afternoons. Thats my plan in my dreamy world that I am sticking to! I should mention I will be using dual pane RV windows and spray foam walls with at least 4" in the ceiling. I did a roof raise so I could lower it again for efficiency. Knowing I had no road A/C made this my only wise choice and not for interior headroom alone.

[DeMac]

An efficient heat pump (installed) is an option with the A3800, for an additional $300ish. Some brands we considered only sold them separately or not at all.

[cadillackid]

the only problem i have with minisplit heat pumps and rooftop A/C with heat is that it blows the heat at your head.. your feet are frozen and you cant breathe...

[Bus'n it]

Originally Posted by cadillackid

the only problem i have with minisplit heat pumps and rooftop A/C with heat is that it blows the heat at your head.. your feet are frozen and you cant breathe...

I have two diesel heaters. The heatpump is more of a backup in my case.

[Bus'n it]

So in the end, I ordered two Furrion 14,500 units to be delivered for just over $1800. These have a 14.6 amp draw so close to the Houghton unit. No heat though, but thats ok. I doubt I would use the heat function due to having diesel heaters. Keep the A/C simple with less stuff to potentially go wrong. The Houghton unit I was looking at was out of stock. I see an impending price increase again with China closing up for the new Covid strain.

[DeMac]

Those are an efficient choice. Good reviews. Keep us updated. Looking forward to seeing the install & consumption tests.

[Bus'n it]

I’ve received my rooftop units the other day. Unfortunately they will sit in the garage for a while. Need to do some reinforcements and roof paint first. That may not happen until the heat ends which is somewhere in October. Gotta figure out how to get them up there. My bobcat forks will not go that high.

[cadillackid]

if you havent yet covered up your roof hatch holes the units should fit through the hole.. either build an anchor sawhorse type thing you clamp to the edges if said hatch hole.. pulley and pull AC unit on cable up through hole with bobcat?



or bungie cords and ratchet straps.. thats how I lifted those damn Mega sized bus air conditioners up to bount them.. the bungie cords lessen the amount of weight I have to lift and the ratchet straps hold where I have gotten it to so I can readjust the bungies..



unfortunately being a single man of 145 lbs has its disadvantages when it comes to strength or being in need of 4 hands..

[DeMac]

I carted the AC to Freddy in the bed of the farm truck and ramped it up, from there, using a battery wench. So, I could safely do it, lone.
The track is made from unistrut, 4-hole 90°s, 5/4"x6"x12' deck boards. The sled is a rear-seat-back, from Freddy and 2-hole 90°s, to guide the edge. Track is bolted through the bed rails. Wench anchored to opposing wheel.

[Bus'n it]

Thanks for the ideas guys! Chris, the hatches have been fitted with Marine skylights. The Furrion units are seriously wide. I am not far off in the weight department. 160lbs and being 51 make for a less than ideal weight handler...

The ramp idea looks like a feasible method and should work perfect. Did you do anything to reinforce the bus roof metal or just go with it as is? I was thinking of putting in square metal tube but that may not allow the roof metal to conform if I did that ahead of installing the units. Before I do anything, I need to figure out what roof paint/sealant is best that would not allow dirt pickup.