1234yf operating pressures

[OMW John]

So I'm new to the forum but I've been servicing automotive AC systems for over 20 years. I run a mobile repair business in central Texas and this heat wave is keeping me busy. Anyhow, since I've already run into a few 1234yf systems I invested in dedicated gauges and a recovery machine. I've pretty much mastered r134a systems and have been working on them since 93' when they started coming out. All the literature I've read says 1234yf operates at lower pressures, bla,bla,bla but every one I've hooked up gauges to operate at 300 psi on the high side. Naturally the 100+ degree air temp isn't helping but it urks me that they run that high.

I went knee deep into a compressor swap on a 2016 ram 1500 where a customer wanted to go cheap. Bought a rock auto UAC compressor but got the kit with 134a pag oil. I told him the oil was a no go and added 3 oz to the system of 1234yf specific 46wt oil. After charging it, it was cooling well although pressure still at 275-300 on the high side. It has previously cooked the clutch so I told him, compressor only is a gamble. 4 days later, cooked the clutch again. Told him I'd warranty it but I think he just traded it in. On to another one today, 2018 accord 1.5. It also had a burnt clutch. This time the customer took my advice and we got the full kit. What annoyed me though was once again, 300 psi on the high side.

The kit came with pag46 which I did not use and an expansion block labeled r134a. Pissed me off because they'res no r134a option for an 18' accord. Anyhow I reluctantly installed it all and it cooled great but the 300 psi on the high side still worries me. Anyone with real world experience and advice ? I am an ASE master and hold MACS certification as well. I thoroughly flushed the core and everything else was new. Properly vacuumed, etc. Cooling at under 43 degrees from vents when running at 1500 rpm or driving it. Am I worried for no good reason?

[bohica2xo]

According to Honeywell 1234Yf has a P/T curve that closely matches the curve of 134a.

Initially the idea was to make it interchangeable with 134a, so your TXV should be fine.

Perhaps the system is a bit overcharged? Are you weighing small cans?

[Cusser]

He said he had a 1234yf recovery machine, so I assume he can add specified amount of 1234yf automatically.

[JohnHere]

As said, the P/T curves for R-134a and R-1234yf closely match. I don't think it matters whether you're looking at gauges for either refrigerant. At ambient temperatures above 100°F (like it was in Phoenix recently), the high side is going to read 275 PSI and above depending on the actual ambient temperature and the size/efficiency of the condenser.

[Tim]

At ambient temperatures above 100°F (like it was in Phoenix recently)

That was wintertime. 110 plus has been our norm lately. Currently, my AC is out in my home/office.

[JohnHere]

JohnHere wrote: ↑Wed Aug 09, 2023 11:43 am
At ambient temperatures above 100°F (like it was in Phoenix recently)

That was wintertime.

[Cusser]

At ambient temperatures above 100°F (like it was in Phoenix recently)

That was wintertime. 110 plus has been our norm lately. Currently, my AC is out in my home/office.

Heat is no laughing matter; Phoenix hit 119F several times so far this summer, and folks and animals have died from the heat.

[Tim]

Having trouble getting someone to come out and fix my Home ac as well. 99.8 this morning in my office. I had a company put refrigerant n it. Leaked. Then said the coil was bad. 8-week lead time. New system entirely, back-ordered. I calling BS. They don't want to go up in the attic where my coil is at. The second company was supposed to come out yesterday. 4:00 pm, they called and said the worker cut his hand, maybe today.

[JohnHere]

Just the "wintertime" part was funny, not the rest, which is why I didn't quote it.

[bohica2xo]

Tim:

Some of our HVAC techs here are working Midnight to 10am. With a huge percentage of units mounted outside on roofs they just can't take the heat.

Attic mounted systems around here are less common, but universally hated by the service techs. You say your unit is new - er? That must have been a fun replacement. All it takes here is a big crane and the cash to pay the crane driver.

To put us back on topic, Tim posted the YF1234 pressure curve in the Tips section.

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