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Sun May 17, 2020 8:14 am

Has anyone here tried or heard of using a second AC condenser (behind the usual one) to improve the cooling capacity of R134a?

Both condensers would be the typical Nostagic Air 16x22 units and are connected in series (i.e. refrigerant passing thru the rear one then through the front one) with both condensers sitting in front of the radiator.

This has been mentioned to me by a shop with a stellar reputation working on Vanagons and AC systems so I consider it credible, but am looking for real-world experiences.

Yeah, I know about RedTek and have my reasons why I am not looking to go that route.

Sun May 17, 2020 8:23 am

My buddy just did this in his Consulier to resolve a pressure problem. We discussed series or parallel. In the end in series. Had to replace the smaller outlet with a larger one to match the inlet of the 2nd condenser. 1st condenser is behind the second. Pressure problem was solved. Works almost too well.

If your pressures are within spec, may not be worth the effort. Your trying to control hi side pressure with the condenser. I don’t see how it would hurt though.

Sun May 17, 2020 9:01 am

also consider the reduced air flow to the radiator. since so few have done this on a vanagon, you'll be doing some empircal testing.

Sun May 17, 2020 10:00 am

Your 2nd condenser doesn't have to be the same size (area) as the primary.

Sun May 17, 2020 10:28 am

I have a friend who did this, but the second condenser is behind the fuel tank, where there is a sort of bulkhead that things can be mounted to. His AC is original Westy headbanger (in the rear) but he's got a Subaru and a parallel flow front condenser. So far it seems to work well for him. I've given this some thought as well, as I want to control those high side pressures.

I've done Redtek and it's a disappointment in truly hot climates (Texas). Back to R134 and things are work well, but it's a higher pressure refrigerant.

kourt

Sun May 17, 2020 11:28 am

Didn't the original design have an upper condenser for the larger upper opening and a smaller one for the lower opening?

Sun May 17, 2020 11:45 am

Steve M. wrote: Didn't the original design have an upper condenser for the larger upper opening and a smaller one for the lower opening?

Some of the early dealer Ac had this arrangement. I imagine they believed there would be no air flow between the grills.

Sun May 17, 2020 12:18 pm

MarkWard wrote: Steve M. wrote: Didn't the original design have an upper condenser for the larger upper opening and a smaller one for the lower opening?

Some of the early dealer Ac had this arrangement. I imagine they believed there would be no air flow between the grills.

Yeah, but it was all one condenser. My '86 dealer a/c installation came with one. Actually smaller area/volume which is kind of the reverse of what's needed.

Sun May 17, 2020 3:07 pm

Hey Ahwahnee:
The magic that happens in the condenser is mainly accomplished by the phase change from refrigerant vapour to liquid. Routing the liquid refrigerant from one condenser to a second condenser will not achieve phase change, but it will achieve some cooling of the liquid refrigerant. My guess is that the supplemental cooling of the liquid refrigerant will not be as useful to you as would be the case with two condensers plumbed in parallel, because if plumbed in parallel, then each condenser would be achieving the phase change from vapour to liquid, together with the very large heat rejection accomplished. If you are set on having two condensers, it would be best to plumb them in parallel and not locate them one after the other in the same air stream.

Having said that, if you do not already have a parallel-flow condenser in your rig, you will likely be surprised by how big an improvement they are over the factory Vanagon condenser. I realize that Arizona temperatures are challenging, to say the least. However, when Mrs. Howesight and I were travelling through the Bakersfield area once in late June, at 100 degrees ambient, our system was cooling very nicely with the parallel-flow 22" x 16" Nostalgic Air condenser. However, I run RedTek refrigerant which does operate at lower head pressures, so your experience may differ. I strongly recommend RedTek or any of the equivalent hydrocarbon mixes. It is worth remembering that decades of home refrigerators ran on hydrocarbon refrigerant before Dupont created Freon.

When installing my condenser, I could see that if the radiator were to be re-located about 1" rearward of the factory location, then an even larger condenser could be installed. Even with the 22" x 16" unit, I did have to space rearwards the "L" brackets which support the bottom of the radiator, moving them rearwards by 1/2", using spacers.

Sun May 17, 2020 6:36 pm

Thanks for all the input.

I do have the parallel flow 16x22 condenser and R12 - a combination that cools very well (also have the later 3-speed fan).

The condenser has to be replaced because of collision damage at the grille and I am finding the shops I have previously used for AC work no longer work with R12.

I may just stay with R12 as there are some shops (new to me) that will do that but while the system is apart I thought I should consider R134a. A shop I trust mentioned their success with R134a and 2 condensers.

I am not going with Redtek because I prefer to be able to take it to a shop for AC service. Right now I could do it myself but my age is such (in my 70s) that the day will soon come when I will not want or be able to do that work myself. I don't think any reputable shop will work with RedTek.

Fortunately when the system was last worked on I had them use barrier hoses anticipating what the future might hold.

I will confirm with the shop whether they are connecting the condensers in series or parallel - though I think I hared them correctly.

Sun May 17, 2020 7:03 pm

khughes wrote: MarkWard wrote: Steve M. wrote: Didn't the original design have an upper condenser for the larger upper opening and a smaller one for the lower opening?

Some of the early dealer Ac had this arrangement. I imagine they believed there would be no air flow between the grills.

Yeah, but it was all one condenser. My '86 dealer a/c installation came with one. Actually smaller area/volume which is kind of the reverse of what's needed.

Hmm...yes and no. If you added a second condenser it would be connected by rubber hoses, but both running on the pressure from one compressor..
The lower condenser is a separate set of condenser fins from the larger upper one just connected by tubing, but both running on pressure from one compressor.
Same difference isn't it?

Sun May 17, 2020 8:11 pm

I'm on (one) 16x20" parallel with 134 and it does very well in NM 100+deg heat.

Mon May 18, 2020 8:07 am

Here in hot and humid Miami i am running r134a with a parallel flow condenser. It is not cool enough for me. I do need to retint my windows with that new ceramic tint. My old tint has faded to nothing. I had my system redone a feww years ago with barrier hose, 709 sanden compressor etc. my AC guy (an AC only shop) who is very good and has worked on vanagons suggested a second condensor under the van with an electric fan. This would be opposite the propane tank in the frame rails. He also said he could do dual AC, front and rear with 2 condensers and 2 evaporators. I am going to repaint my tan windows out and replace the window seals and retint first. If that doesnt work then i will consider dual AC or dual condensors. I have also noted heat comes through the uninsulated poptop. Any suggestions on how to insulate the poptop? Mine is painted tan. We have 8 months of brutal heat and humidity in Miami.

Mon May 18, 2020 8:37 am

Steve M. wrote: khughes wrote: MarkWard wrote: Steve M. wrote: Didn't the original design have an upper condenser for the larger upper opening and a smaller one for the lower opening?

Some of the early dealer Ac had this arrangement. I imagine they believed there would be no air flow between the grills.

Yeah, but it was all one condenser. My '86 dealer a/c installation came with one. Actually smaller area/volume which is kind of the reverse of what's needed.

Hmm...yes and no. If you added a second condenser it would be connected by rubber hoses, but both running on the pressure from one compressor..
The lower condenser is a separate set of condenser fins from the larger upper one just connected by tubing, but both running on pressure from one compressor.
Same difference isn't it?

Actually, no, it was all hard tubing - a single integral condenser. There were no horizontal tube/fins behind the tin separating the grills, just the vertical tubes connecting the upper and lower fin areas. Not two separate pieces at all. Overall dimensions were the same as the later condensers, just a chunk of fins/tubes missing in the middle. So less heat transfer area than the later condensers with the same dimensions, but with added fins behind the tin. Adding a "second" condenser would increase heat transfer area even further. Here in Phoenix, I wouldn't want to add anything else in front of the radiator, so it would need to be elsewhere. But when it's 118F, I could certainly use some extra condenser power.

Mon May 18, 2020 8:42 am

Westified wrote: Any suggestions on how to insulate the poptop? Mine is painted tan. We have 8 months of brutal heat and humidity in Miami.

Apologies to the OP for the hijack.

This really helped cut down the heat from my pop top. Easy to do with spray paint if you go this route.

Mon May 18, 2020 10:26 am

Westified wrote: ...I do need to retint my windows with that new ceramic tint...

That made a huge difference in mine.

Mon May 18, 2020 6:51 pm

Thanks for the tips Dobryan and Ahwahnee. I was thinking of white vehicle wrap for the top of the poptop instead of paint. Also insulating the undersode of the poptop with a new headliner. Going to see if they can get Aerogel insulation. Used by NASA. I am also considering a double layer top like the tropical top I had on my Land Rover. Get a sheet of Starboard and mount it on my roof rack bars. The only downside of that is it probably wont fit in my garage unless I remove it. I will test a couple of these this summer sith my heat gun. This wiil be cheaper and simpler than dual AC or dual condensers.
I am hoping the tint will solve the problem. I am getting like Ahwahnee
since I am 72 and want to spent less time fixing and more time enjoying life. This corona virus has made me realize even more how precious our time is here on earth. Since I am stuck at home now I am doing some Vanagon work so I am ready to go when this is over.

What Temps are you guys getting coming out of the evaporator in the rear?

Mon May 18, 2020 9:10 pm

Try the white paint or wrap first. I think you’ll be surprised and may avoid the other measures.

Tue May 19, 2020 6:51 am

Just curious. If one does a wrap, can it be taken off for the winter months without harm to the paint?

Tue May 19, 2020 7:46 am

kourt wrote: I have a friend who did this, but the second condenser is behind the fuel tank, where there is a sort of bulkhead that things can be mounted to. His AC is original Westy headbanger (in the rear) but he's got a Subaru and a parallel flow front condenser. So far it seems to work well for him. I've given this some thought as well, as I want to control those high side pressures.

I've done Redtek and it's a disappointment in truly hot climates (Texas). Back to R134 and things are work well, but it's a higher pressure refrigerant.

kourt

Kourt, what type of improvement did you see w/ the r134? I'm in a similar boat here w/ the Austin weather. I kept the rear evap unit, but did a full referb on the system 2 years ago.
- new hoses
- new condensor
- flushed old evap out, etc...

Things work really well up to about the high 80s, but then the system doesn't keep up.

I also have a NOS expansion valve that I may try in the system in case my original one is no longer up to snuff.