Video of Roadtrek under floor Pro Air air conditioning option...

[gregmchugh]

https://m.youtube.com/watch?feature=share&v=wBF0xf6IxGk

[Davydd]

18,000 BTU dual compressors 12v system. They said running full out it uses 160a and when one compressor is turned off after getting desired temperature it drops to 100a. This is probably the system or similar Wendland and Campskunk have been testing for some time now.

I'm a little ambivalent about it. You are basically moving a mass of space to under the floor where other things can be utilized and then ducting it through potential cabinet storage space all clearing up roof space for more solar. I'm not sure that is worth adding maybe 100-200 watts of more solar. With high amp hour battery banks and under hood dual alternators I think solar makes much less contribution.

The stealth aspect would be interesting but immediately lost with that awning. The ceiling exhaust fan is still a must, IMO.

The 12v system is good. I was willing to be a test dummy for a 12v system Advanced RV was researching and testing but they decided it wouldn't work for them. Supposedly it would draw a low of 85a vs about 140a. My theory was I don't run air conditioning much anyway.

[avanti]

I am planning on a 12VDC under-chassis A/C upgrade eventually. My primary motivation is not extra solar, but rather quiet operation. ALL the roof-top units are unacceptably noisy. Extra run-time on battery will be nice, too. Stealth is just a bonus for us.

My problem with the RT setup is that it is WAY too big. 18K is just unnecessary. Indeed, it is not even desirable, since it reduces effectiveness at dehumidification, which is more important for comfort than temperature reduction. The ideal A/C size is the one in which the unit just keeps up when running continuously in a given environment. I'm sure this one would cycle constantly under most conditions. 160A is nuts--my current 11K unit is already probably too big, and it draws less than 110A even running through the inverter. There are very nice DC split units that use dual Danfoss compressors that max out at 6 or 8K. Makes much more sense, unless you live in Panama.

BTW: These systems are NOT ducted up from the floor. The evaporators are generally mounted in a cabinet. They are not overly large. I can easily fit one in the under-utilized top cabinet at the very rear of our Legend, while still having room for our bedding. I plan to have the air ducted downward toward the bed.

[gerrym51]

Originally Posted by avanti

I am planning on a 12VDC under-chassis A/C upgrade eventually. My primary motivation is not extra solar, but rather quiet operation. ALL the roof-top units are unacceptably noisy. Extra run-time on battery will be nice, too. Stealth is just a bonus for us.

My problem with the RT setup is that it is WAY too big. 18K is just unnecessary. Indeed, it is not even desirable, since it reduces effectiveness at dehumidification, which is more important for comfort than temperature reduction. The ideal A/C size is the one in which the unit just keeps up when running continuously in a given environment. I'm sure this one would cycle constantly under most conditions. 160A is nuts--my current 11K unit is already probably too big, and it draws less than 110A even running through the inverter. There are very nice DC split units that use dual Danfoss compressors that max out at 6 or 8K. Makes much more sense, unless you live in Panama.

BTW: These systems are NOT ducted up from the floor. The evaporators are generally mounted in a cabinet. They are not overly large. I can easily fit one in the under-utilized top cabinet at the very rear of our Legend, while still having room for our bedding. I plan to have the air ducted downward toward the bed.

one thing to keep in mind. 2 people-one a roadtrek owner and one a sportsmoblile owner have this system and say it is very loud underneath

[avanti]

Originally Posted by gerrym51

one thing to keep in mind. 2 people-one a roadtrek owner and one a sportsmoblile owner have this system and say it is very loud underneath

Right. Thanks for the reminder. That is another disadvantage of an oversized system. Some of the other alternatives are reported to be much quieter. Also, my main concern is indoor noise.

[BBQ]

.

Just turn on the fan,
open the window,
and enjoy the nature.

[cruising7388]

Originally Posted by gerrym51

one thing to keep in mind. 2 people-one a roadtrek owner and one a sportsmoblile owner have this system and say it is very loud underneath

What might be even louder underneath is the groaning from the poor pilgrim that has to repair or replace it. Right behind that decibel level is the groaning from the owner that has to pay for it. This whole thing seems like an expensive and overly complicated solution to a non-existent problem.

[WJones]

When I first heard about this I thought it was a great idea, because I thought it would be very quiet. Now, seeing it for the first time, I can't help but wonder what it will look like after a few years of driving around in the rain, dusty roads, and salt spray in the winter. Being behind the rear wheels seems like the worst place to be.

[gregmchugh]

I agree with Davydd that with the 100-160 amp draw there does not seem to be the power savings vs a roof air that Roadtrek is touting. With no power savings and not much quieter and the only benefit being room for 200 watts more solar and the stealth factor I don't see the point in having an A/C that will be a challenge to get serviced and under the van where it can be damaged.

They are not likely to offer a lower power option since people will complain that it cannot cool the van on a hot day no matter where it is located. ARV would do it if the customer wanted it and understood the limitations (e.g., Solar Womp) but the major Class B builders will stick with high btu, high power units to satisfy the majority of their customers.

[avanti]

Originally Posted by WJones

When I first heard about this I thought it was a great idea, because I thought it would be very quiet. Now, seeing it for the first time, I can't help but wonder what it will look like after a few years of driving around in the rain, dusty roads, and salt spray in the winter. Being behind the rear wheels seems like the worst place to be.

I haven't thought this through yet, but when I do my project I am going to investigate whether building some kind of weatherproof enclosure might be a good idea. A little complex due to air flow issues. I am not sure it is necessary, though. Compressors are sealed. As for the rest, it is not clear to me how much worse an under-vehicle location is than being stuck up front behind the grill in a traditional automotive setup, especially if there is some kind of deflector in the configuration. It helps that (at least in my case) it only has to run when the vehicle is not in motion. In the extreme, one could imagine an actuator-controlled door or grate that opens only when the unit is in operation. I really doubt that this will be necessary, though.

[Davydd]

I wouldn't worry too much about the "poor pilgrim" having to service from below. That is what lifts are for. Anyway, I found out when a Dometic rooftop went bad on my Great West Van, as in compressor, the whole unit had to be replaced. They don't repair them.

18,000 BTUs seems a bit high. Advanced RV puts in 15,000 BTU Mach 8 rooftops which is higher than other converters at 11,000 and 13,500. They do so because they think it more efficient and one person reported he got 13 hours in 90 degree weather running his air conditioner on the low setting in his ARV off an 800ah li-ion battery bank going from 100% down to 38% SOC. I never thought that possible so am a little skeptical about it yet. When you run on low it runs more continuously and way much quieter than my two previous Dometic units. So, is Roadtrek running 18,000 BTU because they found it more efficient or was the unit they installed just the smallest practical unit sold?

The Roadtrek unit does look very exposed. I have to hope the testing they did with Wendland and Campskunk proved OK. They have been out for more than a year and I would imagine more than 80,000 miles between them including Wendland driving in winter snow country. Wendland did report a failure last month in the Great Smoky Mtns. in 90+ degree weather.

[avanti]

Originally Posted by Davydd

When you run on low it runs more continuously and way much quieter than my two previous Dometic units. So, is Roadtrek running 18,000 BTU because they found it more efficient or was the unit they installed just the smallest practical unit sold?

Larger is certainly not more efficient, all else being equal. As I said, maximum efficiency is achieved when the unit runs continuously. Starting and stopping is bad for many reasons, definitely including energy inefficiency. My guess is that the A/C they use has multiple and/or variable-speed compressors. This would let the unit run efficiently (and, as you say, quietly) at "low". This is optimal under most considerations except cost, and cost is obviously not a priority for ARV.

This is certainly not the smallest practical unit sold. The split systems are definitely better, unless you want it on the roof. I suspect that the real issue is the "more is better" attitude that both RT and ARV tend to exhibit. The modest BTU numbers of these systems just don't make very good brochure copy. This is clearly important to RT--probably less so for ARV.

It is worth noting that the owner of the infamous "SolarWOMP" ARV unit recommends staying below 6000 BTUs:
Sprinter-Forum - View Single Post - No more RV hookups ever again

I haven't chosen my poison yet, but if I had to choose today, I would probably go with the IndelB Arctic Plus:
Stationary air conditioners for trucks - SW ARCTIC PLUS

It is native 12VDC and has dual Danfoss compressors; delivers up to 6160BTU, and consumes 41 amps normal and 62 amps at max cooling.

[gregmchugh]

Originally Posted by avanti

Larger is certainly not more efficient, all else being equal. As I said, maximum efficiency is achieved when the unit runs continuously. Starting and stopping is bad for many reasons, definitely including energy inefficiency. My guess is that the A/C they use has multiple and/or variable-speed compressors. This would let the unit run efficiently (and, as you say, quietly) at "low". This is optimal under most considerations except cost, and cost is obviously not a priority for ARV.

This is certainly not the smallest practical unit sold. The split systems are definitely better, unless you want it on the roof. I suspect that the real issue is the "more is better" attitude that both RT and ARV tend to exhibit. The modest BTU numbers of these systems just don't make very good brochure copy. This is clearly important to RT--probably less so for ARV.

If you watch the video you can see the two compressors and the info that the load is 160 amps with both compressors are running and 100 amps when a single compressor is running. It does get the van cooled down quickly with both compressors running which I expect is what the majority of the customers want but they still using a lot of power with one compressor off so I wonder why it is being touted as more energy efficient than the roof models. As you said, this thing is going to cycle a lot even with one compressor running in most cases

I think the lower power lower btu systems would work for many, me included, who avoid the heat and rarely need a high btu system but I don't see them being standard equipment from the high volume Class B manufacturers since they will disappoint the typical owner or even see them sold as an option since there would be too few buyers. I suppose you could have a special low energy usage boondocking model van but there would need to be customer expectation of a lower performance A/C unit as part of the sales job.