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Running a true PF condenser in R-12 truck

TheApocalyptican on Mon June 10, 2013 2:27 AM User is offline

Year: 90
Make: Chevy
Model: Suburban
Engine Size: 5.7
Refrigerant Type: r-134a
Country of Origin: United States

I just recently read that if, in a conversion, you use a true PF condenser, then you can charge the system to the same weight as the r-12 was. Is this true? Reason I ask is that I am using a true PF in my conversion, and I've never really been able to get the right performance out of the system.

mk378 on Mon June 10, 2013 10:43 AM User is offline

Reading back through, a lot of people have tried a lot of things to make R-134a work in those late 80s early 90s 1500 class GM trucks, and it just doesn't.

Edited: Mon June 10, 2013 at 10:44 AM by mk378

ice-n-tropics on Mon June 10, 2013 4:39 PM User is offline

I still have one Kick A Modine 1 3/8 thick serpentine (not PF) condenser in my shop which was developed for the 5.7 Burb R-134a and tested by GM/Truck but it was toooo expensive. They tried it on 3 or 4 trucks w/ other changes and lowered the louver temp to 45 F (on recirculation) in Phoenix @ 111 F (like this week forecast). Makes the Burb into the butcher's meat wagon. My bro wants it for his Burb but he's in Colorado and doesn't really need it. It did not raise the H2O temp or have higher air restriction. Takes additional refrigerant Can charge orifice tube/accumulator A/C systems until evaporator outlet is 1 to 3 degrees colder than the inlet pipe (due to P/T relationship and evaporator refrigerant pressure drop).
Should insulate the accumulator. Keep on max or recir.
PF on Burb doesn't do Jack at idle but should help at higher compressor and road speed due to lower pressure drop.
hotrodac

-------------------------
Isentropic Efficiency=Ratio of Theoretical Compression Energy/Actual Energy.
AMAZON.com: How To Air Condition Your Hot Rod

Edited: Mon June 10, 2013 at 4:41 PM by ice-n-tropics

TheApocalyptican on Mon June 10, 2013 5:37 PM User is offline

Quote
Originally posted by: ice-n-tropics

Should insulate the accumulator.
I've read this before that it might be a good idea, and seen it on newer vehicles but any idea where to get one of the slip on kind of insulators like the newer vehicles have?

mk378 on Mon June 10, 2013 5:52 PM User is offline

You'll need 4 or 5 beer can coozies, a sharp knife, and a bunch of duct tape.

TheApocalyptican on Mon June 10, 2013 5:59 PM User is offline

Hahahaha. Didn't even think about the fact that can coozies are basically the same thing. I've got a medium size box full of them in my shed somewhere. Thanks for the idea!

TheApocalyptican on Mon June 10, 2013 6:05 PM User is offline

Quote
Originally posted by: ice-n-tropics
I still have one Kick A Modine 1 3/8 thick serpentine (not PF) condenser in my shop which was developed for the 5.7 Burb R-134a and tested by GM/Truck but it was toooo expensive.
Any idea whether these are for sale somewhere, or even something similar?

Smokey65662 on Tue June 11, 2013 11:51 AM User is offlineView users profile

You can always size a bigger universal PF condenser. There is lots of room up front for one that is bigger and its not hard to get them there. I am currently mounting one up on my 93 in hopes of achieving good temps with r134a.

ice-n-tropics on Tue June 11, 2013 11:59 AM User is offline

Prepper,
My 1 3/8" is up for Picker auction (w/ satisfaction guaranteed).
hotrodac

-------------------------
Isentropic Efficiency=Ratio of Theoretical Compression Energy/Actual Energy.
AMAZON.com: How To Air Condition Your Hot Rod

JeremyB on Thu June 13, 2013 1:13 PM User is offline

Quote
Originally posted by: TheApocalyptican
I just recently read that if, in a conversion, you use a true PF condenser, then you can charge the system to the same weight as the r-12 was. Is this true? Reason I ask is that I am using a true PF in my conversion, and I've never really been able to get the right performance out of the system.
Refrigerant charge is based on system volume, refrigerant density and to a lesser amount, how much of the refrigerant is liquid/vapor during operation.

PF condensers have less volume than tube/fin or serpentine condensers, so you'll reduce refrigerant charge when you swap to a PF condenser. If you swap to R-134a and a PF condenser at the same time, the "~90% charge" metric is no longer applicable. You'll be charging to less than 90% of the original R-12 amount.

Two SAE papers I read showed going from a serpentine to PF condenser resulted in ~20-30% less required charge, depending on the vehicle. (using the same size condenser)

Say you install go from serpentine to PF. You'll only need ~75% of original charge. You'll only need ~90% of the R-12 charge so you'll end up with 0.75*0.90=0.675 ... ~67.5% of the original R-12 charge when using R-134a.

TheApocalyptican on Fri June 14, 2013 9:58 PM User is offline

Thanks Jeremy. That's pretty much what I thought, but it was from a poster on here who has always seemed knowledgeable, and respected, so I figured I'd ask. Just further proves that it seems my system does NOT like to work well with r134a.

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