R134A conversions

[stillsmokin]

I'm just curious, what kind of center outlet temps folks are seeing out of converted R12 systems in humid climates. Today I did one and got about 46 at the center outlet, full sun load @ 90F / approximately 70% humidity, on max high at road speed. This one has the 134A expansion valve and drier. The evaporator was cleaned when the heater core failed recently. I evacuated the system to 30 in/hg and charged it to 90% spec initially but, had to go to full charge to get the outlet temps lower. The condenser is located behind the intercooler.

My dually is an incorrect conversion, just labels and fittings. It pulled 55 under the same conditions today after I put 6oz additional charge in it. I got a 10F drop in center outlet temps but, I think the wrong components are pushing the high side numbers up. My system performance chart showed 50/360 as acceptable pressures for a clutch cycling system at the given temp and humidity. Adding 6oz put me at those numbers with reasonable cycling at 2000 rpm. But, it works good enough for now.

Not terrible in the cab under these conditions but it would be nice to get it a little lower. Hard to judge system performance vs dry climate reports in other threads. Sure do miss the days of R12 and 32F center outlet temps on hot humid days.

Tomorrows forecast... 95F and humid

[Mark Nixon]

IIRC, I understand that a certain percentage LESS R-134 in an R-12 system actually helps the efficiency.
There's still small cans of R-12 floating around on C/L, so if you take the pains to re-seal the system and you're sure your components like the compressor, condensor, evaporator and lines are leak free, grab some R-12 and put it in.

Sometimes a few extra $$ for the "good stuff" is cheaper than a retro fit.
I will add that I think the Cummins Intercooled Condensor is pitifully undersized.

Mark.