Thanks @nebulight

I have never really looked at AC for our vans, but I understand what you wrote & see your perspectives.

As I am unaware of the installs of these ACs, but I do know 12vdc “distance matters” & with your 120vac “distance is meh” kinda irrelevant.

The other matter around inverter use is standby consumption, but;

1) With bigger systems not as relevant
2) For AC, Type use the inverter might only be on when actively using it for AC (ie while parked).
3) Depending upon type of van use ,,, if @ a campsite with 120vac ,,, well better off with a 120vac AC (or heat pump)

I probably would not be interested in a 12vdc AC unit either.

A Van Fridge ,,, is a much different story ,,, that is all I am interested in for a fridge ,,, is a 12vdc.

 

Hi,

Have you looked into this one?

Velit 2000R - 12V/24V/48V Rooftop Air Conditioner

Download User Manual This super-efficient DC-powered rooftop air conditioner is designed from the ground up to maximize the comfort of your outdoor adventure. With the DC-powered twin-cylinder rotor compressor, Velit 2000R draws as low as 20A (at 12V) and is able to deliver fresh cool air to you...

velitcamping.com

These guys have yet to prove they can reliably deliver and support products, but the numbers look good?

https://cdn.shopify.com/s/files/1/0623/2840/6253/files/R2000_User_Mannual.pdf?v=1678857653

Gary

 

I received my Velit Heater in the mail yesterday, so they're starting to deliver products. I was impressed with packaging and all of the accessories, and read through the manual. But obviously the real test comes when it's installed and running. I purchased the Mabru 12V AC but I would consider the Velit too now that they're delivering products.

 

The energy savings from using a DC air conditioner compared to an AC air conditioner (if they are otherwise the same) are very limited. If you already have a good inverter, I am not sure why people are crazy about DC air conditioning. You are saving less than 10% and usually paying much more to do so, and having to use much larger wiring.

I have nothing against it, but I would not pay a lot more. I would consider one if the price was similar or it otherwise fit my needs, but I have a large quality inverter and that is what I run my current air conditioner off of.

As a side note on BTU capacity, I can keep my van cool with a 5000 BTU unit, but it is very well insulated with no windows in the living area (only the cab windows and one in the isolated cargo area). Insulation and lack of windows make this possible. Also I only said I can keep it cool, it would take many hours to cool it down when its already hot.

From 98-75 degrees when outside temps were 98 took 5 and half hours. My can was parked partially in the sun and the heat index was approximately 108 degrees (for those who will say this won't work in Florida or something like that, I did my test in the Texas summer)

In a promaster I would recommend the smallest AC unit you can get by with and plan on using the HUGE (comparably) dash AC unit to cool the van down, and then use the RV air conditioner to keep it cool. You can run the dash air and RV air together for 15 - 20 minutes and then just the RV air.

Having a smaller unit that does not cycle continuously is more pleasant than having a bigger unit that is constantly kicking on and off.

If you have a well insulated van, I would think a 7k unit would actually be a pretty good size fi you are willing to keep windows covered with insulated covers and don't open the doors constantly.

 

You’re finding out what alot of builders seem to be now reverting on. 2 years ago it felt like everyone was throwing these in builds. Now? Seems to be slowly shifting back to units like the RecPro. 12v ac seem to be good in select use cases but overall the cost to performance is not that much better in the long run over standard units.

 

I'll have real world numbers soon with the 9000 btu heat pump running on a 12v Victron MultiPlus. You are exactly right, there is no free lunch and if you want to cool a van it's going to take close to 1,000 watts per hour to do it unless you gave up some interior room for serious insulation. Getting an actual EER of over 10 in a van is not really practical with the space available. 1,000 watts will move about 10,000 BTU. When someone claims efficiency drastically better than that it's time to look behind the curtain and start asking questions.

Remember, this guy has a huge condenser and evaporator to move 18,000 btu and has an EER of 12.

 

You are exactly right, there is no free lunch and if you want to cool a van it's going to take close to 1,000 watts per hour to do it unless you gave up some interior room for serious insulation.

Sorry, but that's a pet peeve of mine. It's "watts", not "watts per hour". Watts are power, which is already energy per unit time.
Watts per hour would imply some sort of load that starts out at a low power consumption, and over time increases its power consumption at a steady rate - it starts out at 100W, then in an hour it is 1100W, then an hour later its 2100W, etc.

 

We have several of our vans out on the road with the Kingtec KTD-1, 2& 3, Nomadic Cooling, Dometic RTX 2000, and the Mabru RV 12000. If a customer asks for the best air conditioner for an off-grid van I like the Mabru best. Although we don't yet have a full year of testing on the Mabru.

 

Logic and reason are may be coming back into this a little bit with builders. It was HUGE on social media for awhile. Brands are very smart for paying influencers to peddle this stuff now. It works very well. Make it seem like you aren't the cool kid on the block without an undersized DC A/C unit on your van.

But the power usage per btu difference just isn't there to justify the cost. And many of these, like Nomadic Cooling, are just off the shelf Aliexpress units. Mabru looks the best on paper but they would be breaking new ground in air conditioning if their numbers were accurate. They are claiming a 16 EER and 33db noise level. Which makes me think it may be nonsense. Why would they be focused on the RV space if they have figured out one of the most efficient A/C units on earth? lol.

I also dislike how all of these are not for 14x14 holes. And I dislike how they mount in general. Makes finishing the interior around them more annoying.

It's really difficult to overcome heavy influencer marketing. I mean....see "4x4" Sprinters for the best example of marketing being crazily effective on the general public.

 

No blm land in east, saudies cutting production for summer, me going shorter but need shore power, ac power cost paid for from savings due to wally world ac air

 

Strongly urge you to stay on your current pathway, especially if you plan to use it in a hot climate.

One of my customers has a Houghton (not sure which model it is right now) and it is very quiet and efficient.

It is in a full size sprinter powered from an 8 x battle borns wired 4S2P + a pair of inverters. (They wanted to be able to cook, be air conditioned, etc all at the same time). Pretty similar kW-hr capacity to your plan.

It worked very well during a cross country road trip through Nevada in the summer.

I chased the DC air conditioning concept with a lot of time and money - more than I care to admit.

In the end, what happens is that motor efficiencies are highly dependent on achieving very high magnetic fields and very short gaps between the rotor and stator.

In order to achieve high field strength and switch it on / off / reverse quickly, it takes very compact coil windings and high voltages, the higher the better.

_

Added - the peak voltage of a 12 volt system is 12 volts.

The peak voltage of a 120 vac sine wave is nearly 170 volts.

It is very difficult (not impossible) to achieve similar results in a motor.

 

I looked at it from a “how can I run AC without shore power” POV and not just the amp draw that they DC promoters like to show with the system ramped down making 2,000btu.

I went 12v to maximize alternator charging efficiency but if if you plan on doing a lot of solar charging the 24 or 48v inverters are quite a bit more efficient. Real world numbers to convert 12vdc to 120vac are around 87% efficiency with a Victron MultiPlus. The inverter and a Houghton are about the same money as an RTX2000 or Mabru and I’m not sure it’s even fair to count the cost of the inverter since most people spending $3k on an AC are going to go all the way and have a decent 120v system also.

 

I bought a DC air conditioner on AliExpress cost was under $1,000 including shipping. Has a danfoss compressor looks good so far. Did a test run in the living room over the winter very quiet will confirm power draw and performance if and when I ever get it installed. I don't have an AC system and have no need for it so the DC made sense to me.

Sent from my Pixel 5 using Tapatalk

 

Another not so huge factor for and AC powered by AC is that the losses in the inverter show up as added heat inside the van. So, if your AC is pulling 1500 watts, and your inverter is 85% efficient, the 15% inefficiency is 225 watt, or almost 800 BTU of heat added to your van that the AC has to take out.

These numbers are on the pessimistic side, but you get the idea.

Gary

 

Darn Parasites on the wrong side of cold 👿 ,,, 85% efficient pulling 1500 watts ,,, I have not looked very close at this but I always assumed 1500/85% would require 1765W from the battery so 265 watts going mostly into added heat from the inverter ,,, is that wrong?

When considering all electronics with heat sinks ,,, solar chargers, transformers (boost/bucks), & other equipment like isotherm or other HWT I think about the possible added heat as we got no AC.

 

OK - if he AC actually needs 1500 watts to runs, and the inverter is 85% efficient, then

(0.85) * ACout = 1500, or ACout = 1500 / 0.85 So, ACout = 1764 watts
That is, for the inverter to output 1500 watts, it has to consume 1764 watts with 85% efficiency.

So, the Inverter is wasting 1764 - 1500 = 265 watts.

In BTU this is: 265 watts * 3.412 BTU/watt-hr = 904 BTU

So, yes you are correct - sloppy math on my part.

This is somewhat conservative in that some inverters (but not too many) do better than 85%, and the AC won't be drawing 1500 watts all the time. But, you can plug in your numbers.

Gary

 

OK - if he AC actually needs 1500 watts to runs, and the inverter is 85% efficient, then

(0.85) * ACout = 1500, or ACout = 1500 / 0.85 So, ACout = 1764 watts
That is, for the inverter to output 1500 watts, it has to consume 1764 watts with 85% efficiency.

So, the Inverter is wasting 1764 - 1500 = 265 watts.

In BTU this is: 265 watts * 3.412 BTU/watt-hr = 904 BTU

So, I guess both of our first attempts were wrong

This is somewhat conservative in that some inverters (but not too many) do better than 85%, and the AC won't be drawing 1500 watts all the time. But, you can plug in your numbers.

Gary

Even “Victron” publishes their maximum efficiency % ,, Not Average or Mean

My multi shows 93% “max” ,, I just don’t feel that lucky in “real world” 😳

I think 85% is conservative ,, but without actual testng I believe that is the right way to analyze it 👍

 

Awesome, I can't wait to run my heatpump off my inverter, lol! Free heat!!

 

To me, AC is a shore power luxury. I'll be getting a cheap portable AC that I can vent out the window. If I lived in the van and actually needed to run it off batteries and wring out every watt of efficiency, I'd have already spent so much money on a lithium battery bank to power it that I'd just take the rest of my lumps on the 12V AC.

 

I think the real potential benefit for 12v A/C is one with a variable speed compressor. This allows the unit to adjust its output (and power consumption) to match the cooling requirement just like an Espar or Webasto heater does. This eliminates the temperature swings and the frequent starts of a single speed 120vac compressor that typically require up to twice the normal running current.
I recently installed a variable speed heat pump - A/C in my house and it's a night and day difference in comfort, noise and electric consumption.

If somebody makes a variable speed 120vac RV air conditioner that might make a viable alternative but you still have the heat and power loss from the inverter.

 

And Trane, who makes some **** efficient nifty equipment, says we are years away from efficient equipment suitable for something the size of a van. R&D is working on units with dual and variable speed compressors for larger RV's.

 

i'm with @rjcarter3 . It's a power luxury. In my travels so far, I have never wished for AC. Following the weather is the best way to enjoy what vanlife offers. I love having all the doors and sunroof open with a good fan moving the air around. The AC takes away the outdoor magic a van offers.Now, if I lived in the van full time in a southern/hot climate where I couldn't follow the weather -- I'd have a bigger van, maybe even a skoolie, with a giant battery bank, lots of windows, dc ac and all the other luxury comforts of home.

EDIT: I also hate AC in my house. When I lived in Los Angeles, I almost never used it. In PA, the humidity makes it a necessity.

 

We got sold on the 12v benefits, and got a Dometic RTX 2000.

Tested it on some hot muggy days last summer, and even kept our half insulated van pleasant with ~700w power usage. Our solar was pulling 680w, so our effective runtime was days at that point. Since then, we've added an insulated curtain at the back and ceiling insulation (which we didn't have yet!) so I'm excited to see how it does.

It does get loud in boost, though you really can't hear it from inside the van. Outside it sounds like a drone (on boost, normal is fine)

 

For the climates where you need AC in a van I don't think the variable speed compressors are much of a benefit when it comes to power consumption. If you only need 2-3k BTU to maintain the temperature the battery capacity problem gets really easy to solve. It does help a lot with noise and humidity though. I'm not sure if RV roof AC's are even using TXV's yet...

As far as inverter efficiency, everyone is spot on. Even Victron overstates their efficiency, plus the standby is closer to 30 watts when the inverter is ON. Real world is around 85% at 12v when you account for all of the losses. Our 9,000 BTU heat pump pulls between 825 and 875 watts depending on temperature and uses 950 to 1000 watts from the batteries. If we are also heating water and running the Nespresso machine the efficiency drops to around 80%. The batteries, wiring, and inverter share a space with the heat pump so that 400 BTU of waste heat goes straight to the return air of the heat pump and is not felt in the van. Compared to the windows its a fart in the wind, but it definitely cuts down on the overall efficiency.

 

For the climates where you need AC in a van I don't think the variable speed compressors are much of a benefit when it comes to power consumption. If you only need 2-3k BTU to maintain the temperature the battery capacity problem gets really easy to solve. It does help a lot with noise and humidity though. I'm not sure if RV roof AC's are even using TXV's yet...

An exception would be if you camp mostly during days at campgrounds with shore power, and can therefore power A/C with 30A service so installing a larger unit makes sense; but at same time occasionally boondock at night and need to power A/C from batteries (with or without inverter).

Some units that can operate down as low as around 30% of rated capacity by use of variable speed also gain efficiency by running much slower, similar to mini-splits. I’m interested in 8,000 BTU/hr dual inverter window air conditioners because they are inexpensive, and EER are +/- 15. It also means SEER rating for nighttime use should be even higher.

 

Interesting views all round on the AC units. For us folks in the southeast it's a must-have rather than nice-to-have. Here the temp is less of an issue than humidity so I don't think variable speed (even if available) will be useful.

For selecting a unit it's like the old project manager's dilemma: there are four important variables and you can only optimize two..... For RV air conditioners these variables are :

• BTU cooling capacity
• Noise
• Price
• Size - ie weight and height on the roof

Bigger units are inherently quieter since they have more space to direct air flow which is what creates noise. Compact units - often are too low a BTU capacity and/or too noise... etc.

Note that 12 V vs 120 V is not even one of the main variables - the other four govern and 12V loose on price every day!

Everyone's use is different but I would opt for the larger Rec Pro because it works, is quiet and relatively affordable. The smaller Rec Pro is a second place but is less capacity in a compact casing and therefore noisier and less efficient.

 

Everyone's use is different but I would opt for the larger Rec Pro because it works, is quiet and relatively affordable. The smaller Rec Pro is a second place but is less capacity in a compact casing and therefore noisier and less efficient.

Since a lower-capacity air conditioner does not need to move as much air flow, and heat exchangers don’t need to be as large, doesn’t it follow that a 9,500 BTU/hr unit can be much smaller than a 13,500 unit while still having similar sound and efficiency performance? I’m not that familiar with RecPro efficiency data yet, but expect smaller size doesn’t necessarily mean extra noise or less efficiency when cooling capacities are much different.

I helped install two 9,500 recently and know they are fairly quiet compared to most common RV units. If 13,500 is even quieter, that would be great, though probably difference would not be that noticeable. The 9,500 is so quiet that there’s not as much room for improvement.

 

In case some of you are not following the old thread about it I cut the van up and put the heat pump in today. It’s the quietest air conditioner I have ever experienced in an RV and that’s without the ductwork or bed…

Pioneer 9000 BTU Floor Mounted Heat Pump

When I was planning our build I wanted to avoid things on the roof that would kill MPG and have a very quiet HVAC system that would be able to run on batteries. I had experience with a Dometic Cool Cat and was looking for a modern replacement...

www.promasterforum.com

 

This is basically a window air conditioner with a reversing valve in a foam box.

That's pretty cool, no pun intended.

I don't really have room for this thing and already have heating covered anyway, but I could fit something smaller. I'd love to find a cleaner way to install an inexpensive window AC that didn't involve cutting a hole in the side of the van. Not saying I'd do this, but would it even be possible to lay a window AC flat on the floor leaving the bottom to hang over a similar square hole in the floor then build an insulated box around the top and sides of the vents to keep all the hot air going out the bottom of the van? Seems like it could work, although having it blow cold air that low in the van is less than ideal. Maybe there'd be other problems with rainwater splashing up from the road into it.

I wouldn't have the nerve to try it anyway and would just end up replacing my Maxxfan with a 12V AC before doing this, but just a thought.

 

Not saying I'd do this, but would it even be possible to lay a window AC flat on the floor leaving the bottom to hang over a similar square hole in the floor then build an insulated box around the top and sides of the vents to keep all the hot air going out the bottom of the van? Seems like it could work, although having it blow cold air that low in the van is less than ideal. Maybe there'd be other problems with rainwater splashing up from the road into it.

Here is more information about installing a window AC on the floor. Window Air Conditioner to Cool an RV – Build A Green RV

 

Since there's good discussion going.
How about "a dream system" - it is expensive, but has benefits.

12/24/48 Volt DC Air Conditioners..Battery Powered..Solar Powered..Hand Made In Arizona Since 2010<br/> — Battery Powered Air Conditioners 12/24/48 Volts DC

We manufacture DC powered air conditioners in various voltages for various applications..... Off grid living, solar powered, energy efficient...... Made in Arizona.... Custom applications welcome.

www.cruisencomfortusa.com

It doesn't take any space on roof
It doesn't drip on your head
Only coolant lines go through the floor, means
- flexibility with placement
- no need for a huge hole
It is efficient

cons:
the pricetag
need to run ducts (although, can mount it in a cabinet up high = no floor space sacrificed and no ducts needed)

 

Since there's good discussion going.
How about "a dream system" - it is expensive, but has benefits.

12/24/48 Volt DC Air Conditioners..Battery Powered..Solar Powered..Hand Made In Arizona Since 2010<br/> — Battery Powered Air Conditioners 12/24/48 Volts DC

We manufacture DC powered air conditioners in various voltages for various applications..... Off grid living, solar powered, energy efficient...... Made in Arizona.... Custom applications welcome.

www.cruisencomfortusa.com

It doesn't take any space on roof
It doesn't drip on your head
Only coolant lines go through the floor, means

• flexibility with placement
• no need for a huge hole

It is efficient

cons:
the pricetag
need to run ducts (although, can mount it in a cabinet up high = no floor space sacrificed and no ducts needed)

I was looking at them 10 years ago when I put the battery powered AC in our boat. It seemed like a good solution but the high cost drove me to a 120v AC and Inverter. They got their start in go-fast boats where you want the cabin to stay cool but don't want a bunch of weight or an inverter. I looked at them again for the van but this time the noise and chances for refrigerant leaks drove me back to a packaged unit again. If it was not so loud I would have gave it a shot, especially since I already have the tools for the refrigerant line install.

I think this system gives up a little efficiency and is noisy because of the evaporator and condenser fans. Moving the air quietly is trickier than you would think and where the foam boxes really shine.

The packaging with this system is a huge win though.

 

Hi RV,
In the cabin, if its dry when its hot, you might try and evaporative cooler...

Lots of choices - they don't use much energy.

Or, a small minisplit with high SEER?
I have an earlier model of this one, and it works well. Easy to DIY.

Or, one of the Energy Star inverter model window AC with CEER16 ish (probably better than the minisplit above).

Gary

 

This one is pretty nice - low drag and no interior space taken up when its deployed.

GAry

 

That is pretty nice. If my cargo doors weren't already windowed, I'd consider it.