DC Air Conditioner (minisplit/rooftop/anything)

[Zwy]

He got right back with me on shipping. I was in no hurry so I sat back so you could lead the way. Write him again as he responded...

While he is asking, could he get a drawing with dimensions?

 

[eXodus]

While he is asking, could he get a drawing with dimensions?

DC Air Conditioner (minisplit/rooftop/anything)

These sleeper cab A/Cs are likely too small for an RV, unless it is one of those tiny canned hams, and that might still be a problem. These units would likely struggle to cool down a hot truck cab, but their use case is to run once the truck parks so they don't have to idle the engine to keep...

diysolarforum.com

I've uploaded them earlier to this thread. Dimensions, wiring etc.

 

[eXodus]

Something new just popped up. 12V 20.000 BTU from Truma only 1300w

That's almost 16 BTU / watt. For comparison any regular roof top RV unit gets a maximum of 10 BTU / Watt. So that's 60% better.

Truma is a very good company.

But the website is rather suspicious:

12V Undermount Air Conditioner for class B van or RV -Ducted Evaporator

In Stock. At your door in 5-7 days. *ALL Systems now come with Hush Fans* Complete UndermountAC.com 12V Split Air Conditioner Kit. Completely Battery Powered. New Condenser includes 90 degree brackets for horizontal or vertical mount and free built in rock guard! *This kit features our ducted...

trumaheaters.com

 

[curiouscarbon]

12V Undermount Air Conditioner for class B van or RV -Ducted Evaporator

In Stock. At your door in 5-7 days. *ALL Systems now come with Hush Fans* Complete UndermountAC.com 12V Split Air Conditioner Kit. Completely Battery Powered. New Condenser includes 90 degree brackets for horizontal or vertical mount and free built in rock guard! *This kit features our ducted...

trumaheaters.com

notation:
W = electrical watt
Wt = thermal watt

Compressor Speed 3, Evaporator Speed 7: 20,000BTU/h 1300W

20,000BTU/(3.412BTU/Wt) = 5861 Wt pumped with 1300 W input : COP = 4.51 very good

Compressor Speed 2, Evaporator Speed 7: 16,000BTU/h 1100W

16,000BTU/(3.412BTU/Wt) = 4689 Wt pumped with 1100 W input : COP = 4.26 very good

Compressor Speed 1, Evaporator Speed 7: 12,000BTU/h 900W

12,000BTU/(3.412BTU/Wt) = 3517 Wt pumped with 900 W input : COP = 3.91 pretty good

My dream cooling mechanism has Coefficient of Performance of 5-10.

5-10 watts of thermal energy pumped for each 1 watt of input power would be like magic, as far as i know it's not possible to reach CoP=10. but it's possible to reach CoP 5.

Divide EER by 3.412 to get CoP approximation for a given device.

 

[eXodus]

5-10 watts of thermal energy pumped for each 1 watt of input power would be like magic, as far as i know it's not possible to reach CoP=10. but it's possible to reach CoP 5.

50 years ago a CoP of 4 was magic. Now mini-split achieving those regularly.

Have you seen Solar Thermal Hybrid A/C units? https://offgridquest.com/energy/solar-thermal-hybrid-air-conditioners. They got a CoP like you are dreaming of.

I think they started in India and now making their way around.

When I understand the principle - that system actually uses the solar heat to move the refrigerant. So practically when you got enough heat - you don't need the compressor - at all. So only the two fans blowing. Could have some very high electric efficiencies.

 

[curiouscarbon]

50 years ago a CoP of 4 was magic. Now mini-split achieving those regularly.

Right?? CoP of 4 feels like an incredible feat to have normalized.

Have you seen Solar Thermal Hybrid A/C units?

Systems that use additional heat from the sun to increase dissipation and extract work? Never in person, only read about the concept of heat flow being proportional to delta T and solar thermal collector allows increasing of delta T and therefore increase heat flow..? Maybe I am still misunderstanding some aspects.. It’s a concept I want to learn more about, because it’s so interesting efficiency wise.

Some commercial places use water as a thermal buffer, freeze ice at night and thaw at day to quench heat load. That’s super neat because H2O is abundant and it sidesteps need for batteries.

Solar Thermal Hybrid AC sounds really interesting in a similar spirit of using a relatively accessible and affordable technology to improve the overall efficacy of the system.

Thanks for sharing!!

The Solar Air Conditioning unit works on a hybrid principle. It absorbs solar energy to heat the inside medium by utilizing a vacuum solar collector. The refrigerant from the compressor goes through a copper coil inside the collector and undertakes a heat exchange. The heated refrigerant then goes through a cycle inside the system for not only for heating but also for cooling too. Energy from the sun is fully utilized so therefore less power is required from the mains in this process, this, in turn, allows for smaller compressors to be installed that offer even better savings on power consumption. This system adopts a four-fold type heat exchanger as one of the core components of this air-conditioner. Its heat effective area is increased by 20-30% versus the usual V-type and flat plate heat exchanger, which greatly increases cooling efficiency.

found this helpful document about hybrid AC btw. warning: pdf link https://pdf.indiamart.com/impdf/8960243397/MY-1848302/hybrid-solar-air-conditioner.pdf

It is like your car going down a gentle slope. You can take your foot off of the accelerator for a longer period as gravity helps your car keep moving. Therefore it is using less energy for a longer period and will lower your power bills even further. But how do Solar Thermal Air conditioners do this? They absorb solar energy by using a thermal collector with copper heat conducting inner coils. The preheated refrigerant from the collector feeds directly into the compressor to reduce the amount of work needed and saves power.

excerpt:




most of the ones in that brochure seem to be CoP 3.6-3.9. I wonder how the solar collector works into the ratings and stuff.
Like, without the extra heat from outside, it will run at CoP 3.5-4 e.g. at nighttime.
Then during day it maybe run at CoP 4+++ :D

This might sounds weird but it reminds me of Marx generator. Due to using a weak potential (compressor) combined with a some natural phenomenon (heat flow proportional to delta temperature) to achieve a strong potential (more cooling than compressor alone).

Cheers!

edit: Originally overlooked this part you mentioned about the heat causing the refrigerant flow itself, that sounds super fun! Two fans and a thermal collector and an expansion valve or something..? With a compressor for kickstart or auxiliary use at night.? Cool! Copper heat pipes with low pressure atmosphere and a bit of water and a wick seem to do something similar. Really interesting concept module to try and integrate.

---

There was also a video on youtube of a liquid pump that was actuated by the phase change from liquid to gas convection but can’t find right now. The fluid seemed to be some high volatility liquid like alcohol or something. they said they don’t know what it’s charged with, but guess that it’s a low boiling point material. edit: found it. warning: linus tech tips. very commercial channel. video link to time where they start talking



Suppose for now I will have to abandon all hope of using magnetohydrodynamic drive based compressor ?

 

[Zwy]

What is being done is they are installing an absorption system onto a conventional condensing unit. Inside the unit, you will find a coil within a coil. Basically, it is a pipe run inside another pipe. This allows heat exchange into the absorption side lowering head pressure and compressor load thus reducing the watts needed for compression. This also allows for smaller wattage compressors to be used.

Would I consider such a system? Or one that trickles water over the condenser to get the same effect? As with anything, there usually is a cost involved whether increased weight/complexity/labor/maintenance.

 

[eXodus]

Cheers!

edit: Originally overlooked this part you mentioned about the heat causing the refrigerant flow itself, that sounds super fun! Two fans and a thermal collector and an expansion valve or something..? With a compressor for kickstart or auxiliary use at night.? Cool! Copper heat pipes with low pressure atmosphere and a bit of water and a wick seem to do something similar. Really interesting concept module to try and integrate.

With enough solar heat available you are basically building a absorption style RV refrigerator. Theoretical you could build one without any moving parts. (but fans make it more efficient)

I think those whole concept is very interesting since there are now Solar PV Thermal panels are coming out.

DualSun SPRING

DualSun designs and manufactures the world’s first certified hybrid solar panel (PVT): the SPRING 2-in-1 panel.

dualsun.com

So practically you get electricity and heat from the same space - which would be a lot of energy per sqft - which is very important for a RV/ Vehicle. Since we don't have a lot of space.

 

[Zwy]

With enough solar heat available you are basically building a absorption style RV refrigerator. Theoretical you could build one without any moving parts. (but fans make it more efficient)

Doesn't take much, my other pop up camper refrigerator uses a 12V/135w heating element for the 3 way. I think capacity is the limiting factor, look how long it takes to cool down a 3 way fridge using propane or 120V.

I think those whole concept is very interesting since there are now Solar PV Thermal panels are coming out.

DualSun SPRING

DualSun designs and manufactures the world’s first certified hybrid solar panel (PVT): the SPRING 2-in-1 panel.

dualsun.com

So practically you get electricity and heat from the same space - which would be a lot of energy per sqft - which is very important for a RV/ Vehicle. Since we don't have a lot of space.

 

[eXodus]

Doesn't take much, my other pop up camper refrigerator uses a 12V/135w heating element for the 3 way. I think capacity is the limiting factor, look how long it takes to cool down a 3 way fridge using propane or 120V.

The issue I saw with powering a absorption fridge was not total energy, but temperature. The propane burns with above 1000 degree and a electric heating element reaches 300 degrees C easy.

A Ammonia fridge needs about 180 Celsius to run. That's something really hard to get with hot water on the roof.

https://www.arprv.com/dometic-ac-heater.php.

The highest I've ever seen a hot water system was 140 C. Most are staying below 100C for the explosive nature of things

A one square meter thermal panel delivers easy over 1kw of thermal energy - but only at below 100 celsius.

 

[Wtavern]

Something new just popped up. 12V 20.000 BTU from Truma only 1300w

That's almost 16 BTU / watt. For comparison any regular roof top RV unit gets a maximum of 10 BTU / Watt. So that's 60% better.

Truma is a very good company.

But the website is rather suspicious:

12V Undermount Air Conditioner for class B van or RV -Ducted Evaporator

In Stock. At your door in 5-7 days. *ALL Systems now come with Hush Fans* Complete UndermountAC.com 12V Split Air Conditioner Kit. Completely Battery Powered. New Condenser includes 90 degree brackets for horizontal or vertical mount and free built in rock guard! *This kit features our ducted...

trumaheaters.com

The unit is not manufactured by Truma, but by Proair. It was designed exclusively for Roadtrek before they went bankrupt. This reseller purchased all of the remaining stock when Roadtrek was liquidated. It features a 12 v Benling compressor that is used by multiple 12 v ac manufacturers. The kit comes complete and I’m in the process of installing it now in my Promaster based Hymer Aktiv Loft. I just finished ripping out the proprietary Ecotrek system and installing my own 1180 amp hour diy power system (detailed elsewhere on this forum) with the final goal of running ac overnight without hookups. I’ll create a post with the results once I’m finished. I’m waiting on some additional hoses due to come in tomorrow and should have the project completed by then.

 

[Zwy]

The unit is not manufactured by Truma, but by Proair. It was designed exclusively for Roadtrek before they went bankrupt. This reseller purchased all of the remaining stock when Roadtrek was liquidated. It features a 12 v Benling compressor that is used by multiple 12 v ac manufacturers. The kit comes complete and I’m in the process of installing it now in my Promaster based Hymer Aktiv Loft. I just finished ripping out the proprietary Ecotrek system and installing my own 1180 amp hour diy power system (detailed elsewhere on this forum) with the final goal of running ac overnight without hookups. I’ll create a post with the results once I’m finished. I’m waiting on some additional hoses due to come in tomorrow and should have the project completed by then.

Here's the COP data for the 12V Bengling.


COP of 1.9, for 6800 BTU capacity (2000 watts), we can see it uses about 1100 watts at 4500 rpm.

At the lower end of rpm, COP is still the same, and we have 2700 BTU's (800 watts).

Where is the advantage over a mini split with a COP of 3 or 4, even with inverter losses?

This is also only rated for 5500 BTU's (1600 watts). At it's rated full capacity, it will use 900 watts of power. This doesn't include fans needed for air exchange.

 

[Wtavern]

Don’t really care about cutting edge efficiency with 1180 amp hours of battery. I just wanted to have as much cooling as possible and be under mounted as I have a pop top and no room for anything on the roof. Also, I don’t like the look of a mini split mounted on the back or sides and have read about some problems with routing hoses in these configurations. My goal was to look as stock as possible as well. The compressor rating is low, but my understanding is that the condenser and the evaporator make up for it as they are both oversized. I could be wrong though as my understanding of ac systems is very limited. However, I wasn’t about to take a chance on a “no name” Chinese distributor without warranty for any amount of money. I will say that every component in this bundle seems like a quality made part and I’m more than happy with the ease of install. After I get everything working tomorrow will be the true test though.

 

[curiouscarbon]

I think those whole concept is very interesting since there are now Solar PV Thermal panels are coming out.

DualSun SPRING

DualSun designs and manufactures the world’s first certified hybrid solar panel (PVT): the SPRING 2-in-1 panel.

dualsun.com

So practically you get electricity and heat from the same space - which would be a lot of energy per sqft - which is very important for a RV/ Vehicle. Since we don't have a lot of space.

Wow that’s a really neat product. Great point about RVs and space optimization. Extracting heat from the PV cells should extend lifetime too and maybe even boost voltage slightly…



edit: this has me wanting to play around with designing a system that extracts heat from the panels during day and uses them to dissipate heat at night. curious!

of course the surface area will pale in comparison to a 12 FPI aluminum radiator, but that’s why i’m curious ?

 

[eXodus]

Here's the COP data for the 12V Bengling.

View attachment 55853
COP of 1.9, for 6800 BTU capacity (2000 watts), we can see it uses about 1100 watts at 4500 rpm.

At the lower end of rpm, COP is still the same, and we have 2700 BTU's (800 watts).

Where is the advantage over a mini split with a COP of 3 or 4, even with inverter losses?

This is also only rated for 5500 BTU's (1600 watts). At it's rated full capacity, it will use 900 watts of power. This doesn't include fans needed for air exchange.

The Roadtrek Truma System has apparently 20.000 BTU @ 1300w
You must have a different data sheet.

20,000BTU/(3.412BTU/Wt) = 5861 Wt pumped with 1300 W input : COP = 4.51 very good

 

[eXodus]

Wow that’s a really neat product. Great point about RVs and space optimization. Extracting heat from the PV cells should extend lifetime too and maybe even boost voltage slightly…

Most of the total energy usage in an RV is actually thermal.

Thermal Appliances:
Water Heater,
Furnace, (Heating in general)
Stove,
Microwave.

Fridge (just the other way around)
A/C

The only things which are different - are fans, entertainment and lights. But on a KwH basis those uses are tiny in comparison.

Using and storing heat directly - should be much cheaper then batteries.

 

[Timdog]

Anyone considering the new midea/toshiba dual hose inverter portable heatpump? Not dc, but even with inverter losses seems like it's by far the cheapest, quietest, most efficient, and most roof friendly(and stealthy) option. It's as efficient as most window acs and vastly cheaper, smaller, lighter and easier ton install
than mini splits.

Edit:. Here's the link(also on Amazon for similar price) https://www.homedepot.com/p/Toshiba...eat-for-up-to-550-sf-RAC-PT1411HWRU/314730948

 

[curiouscarbon]

Anyone considering the new midea/toshiba dual hose inverter portable heatpump? Not dc, but even with inverter losses seems like it's by far the cheapest, quietest, most efficient, and most roof friendly(and stealthy) option. It's as efficient as most window acs and vastly cheaper, smaller, lighter and easier ton install
than mini splits.

Edit:. Here's the link(also on Amazon for similar price) https://www.homedepot.com/p/Toshiba...eat-for-up-to-550-sf-RAC-PT1411HWRU/314730948

Thanks for sharing.

Seems like it’s a dual hose type. Intake for ambient cool air, exhaust for hot humid air.

Even has heating mode.

I couldn’t find information on that page about whether the condenser coil is prepared to be anti-corrosive. Reading the reviews, most were glowing and most of the bad ones were DOA frustrated stories.

I looked at the midea duo as an alternative to that one, but kept looking because people said the dual hose was very difficult to laterally bend. But that was a hose embedded in a hose type.

Saw the whynter brand for this but there were lots of bad reviews about the condenser coil corroding with the condensate.

Personally I like the two separate hose type the most.

Anyways thanks for sharing. That toshiba looks really good and I might move on it after some more research. Been using a midea-u 8000BTU/hr unit for a while and want to increase cooling capacity and change form factor.

 

[Zwy]

The Roadtrek Truma System has apparently 20.000 BTU @ 1300w
You must have a different data sheet.

20,000BTU/(3.412BTU/Wt) = 5861 Wt pumped with 1300 W input : COP = 4.51 very good

The datasheet is right off Benling site.

https://benling.coowor.com/shop/product-detail/20170802103009087VFAMP1.htm

That is the COP data for the DM18A7 that ProAir uses on their unit here.

https://trumaheaters.com/collection...ss-b-van-trailer-or-camper-cabinet-evaporator

which they claim is 20K btu but I doubt it is.

I've worked on ProAir systems over the years in RV's and buses. I can tell you they do tend to stretch the performance a little, it is a company I'd steer clear of. ProAir is now Undermount AC. While the undermount condensers might seem like a good idea, reality is they aren't that great and I've relayed this to you before.

So it is claimed it has 20K btu's at 1300w which gives us an EER of 15.4, that translates to a COP of 4.52. Do I believe this figure after looking at the Benling data for the compressor? I really don't but I'll let you decide for yourself.

 

[curiouscarbon]

By the way I was just regurgitating those numbers from the webpage, I didn’t look at the core component spec before posting ?