Automotive Air Conditioning Information Forum

Thoughts on putting a 12V AC compressor in-line to use when parked or 120V plugged in?

As I’m designing an AC system for the VW Vanagon with y'all's help, I see these RV AC kits available with 12V compressors.

How about putting a 12V AC compressor in line (or on a switched bypass loop) to move the refrigerant around when the engine is off?

It would run either off a battery bank when parked or off a 120V-12v converter when plugged to shore power.

Provide 12V to the condenser fan and the evaporator blower and should work, no?

If the 12v compressor isn't strong enough, how about a 120V HVAC residential compressor? - I get that the HVAC stuff is off forum focused - so I'm wondering from the view of how refrigerant lines would tie into the MVAC,

Thoughts?

Thanks,
Andy

IMO whichever comp is off, while the other is running, would actually block the flow of refrigerant.
It would actually be very difficult to plumb up a resi comp, the fittings are no where near compatible. Furthermore, careful attention would need to be paid to the type of compressor oil used in the system. There could also be compression ratio issues, as well, since an R410 comp (resi) might have a different comp ratio than R134 or R1234, whichever you are using. Bohica or John might know more about this.

tbirdtbird wrote: ↑Mon Aug 28, 2023 12:54 pm resi comp.

Thanks for the reply and I was familiar with those all the terms and concepts in what you wrote (and many were new considerations I haven't considered so thank you) and I'll look into those. I not familiar with this term "resi comp" and it doesn't google clearly. Can you point me in a direction to understand this?

Thanks

Tbird is talking about a RESIdential compressor.

Hey Tbird - when was the last time you saw a 2.5 Ton R12 rated compressor?

It is easy to lose track of just how big of a system we have in modern SUV's . A Ford Excursion has about 2.5 tons of A/C operating when it rolls down the highway at 65 mph. to swap in an electric compressor for stationary use you are talking about a single phase 240 vac unit with a 25 amp fuse.

You are putting together a system that can reach the same level as that Excursion for your VW van.

Sure there are some "12vdc" units on the market. In fact the Treelingo stuff is not all that bad. The 12k is optimistic, and you need a huge alternator and battery bank with a 65+ amp draw for that cooling. A class 8 truck with a couple of extra batteries, and some cooling for the sleeper is the target market.

Those 12v units use a 20cc scroll compressor with a 3 phase inverter to run it. I have looked at them and thought they might make an interesting freezer for a class A motorhome.

A better investment would be high efficiency insulation for the van, and a creative bracket to mount a small 110v window unit in a doorway or window when stopped.

Update – based on the feedback and things to consider so far, I’ve decided to not include this feature in the current design. Should it make sense in the future I’ll evac the system and add on this feature.

AND – it is still and interesting and valuable discussion and I wish for it to continue as the technology now exists which has not existed before.

It would be great to keep this conversation going and explore where it could go. This is a concept that is very likely to work.

(The quotes below are edited for concept flow)

bohica2xo wrote: ↑Mon Aug 28, 2023 6:28 pm
Tbird is talking about a RESIdential compressor

It is easy to lose track of just how big of a system we have in modern SUV's . A Ford Excursion has about 2.5 tons of A/C operating when it rolls down the highway at 65 mph. You are putting together a system that can reach the same level as that Excursion for your VW van.

a 2.5 Ton R12 rated compressor?......to swap in an electric compressor for stationary use you are talking about a single phase 240 vac unit with a 25 amp fuse

Thanks for the definition and yes, it would be hard to connect to that amount of shore power.

bohica2xo wrote: ↑Mon Aug 28, 2023 6:28 pm Sure there are some "12vdc" units on the market. In fact the Treelingo stuff is not all that bad. The 12k is optimistic, and you need a huge alternator and battery bank with a 65+ amp draw for that cooling. A class 8 truck with a couple of extra batteries, and some cooling for the sleeper is the target market.

Those 12v units use a 20cc scroll compressor with a 3 phase inverter to run it. I have looked at them and thought they might make an interesting freezer for a class A motorhome.

Re: Treelingo – I tried calling them and the number of their website did not connect. I sent an email inquiring about compressor oil type and capacity, I’ll post if they reply. I could not find any manuals or specific specifications. The closest is in the product description and even there it is interesting that the displacement rather than fixed is a range “displacement 14CC - 34CC, refrigerant R134a/R404a/R1234yf/R407c.” I would hope that the differing refrigerants compatible that it would allow for the PAG46 the FS10 compressor specifies.

bohica2xo wrote: ↑Mon Aug 28, 2023 6:28 pm A better investment would be high efficiency insulation for the van, and a creative bracket to mount a small 110v window unit in a doorway or window when stopped.

Yes, insulation would help. Issues are:
1) a lot of window area
2) insulation in body panels has the catch-22 of insulation vs. condensation being retained by insulation causing interior panel rust.
3) inside the body panels there is mechanicals that run or I, personally, like to find ways to use them for storage.

bohica2xo wrote: ↑Mon Aug 28, 2023 6:28 pm and a creative bracket to mount a small 110v window unit in a doorway or window when stopped.

Below is a pic of a temp solution I’ve tried (and others with vans do this successfully). It is a 6k BTU (maybe 8k? I’ll check) unit so if the 12V is close to 12k BTU, it would certainly be sufficient. This unit is good to about 100 on a van that was sitting in the hot afternoon sun. Also works with higher ambient in started before the heat of the afternoon. (somewhere on here y’all talk of ?retained? heat of parking in the full sun and then having to cool the vehicle including all the thermal mass of the seats, interior, etc. down from 160F

The biggest issue with a window unit like this, and thus the biggest advantage of the in-line 12V unit is storage, that the window unit has to be toted, stored, and set-up where as the in-line unit would be a switch to turn on and would just be siting somewhere hidden away.