134a discharge pressures

I work on some old equipment (ice chests, from Leer). The older R-12 units used to run about 150 to 170 discharge pressure. The R-134a units run more like 225 to 250 or so. Anyone else seen this?

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Some online checking shows that's about normal. Seems a bit unusual, after working with R-12 all these years. For the first few degrees, the temp F and the PSIG are about the same. But when it gets hot, the pressure takes off.

I can tell that getting used to 410a is going to take a while.

Reply to
Stormin Mormon
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R410a is like any other refrigerant... it has to be charged by superheat and subcooling. The only real difference is that the pressures are approximately 1.6 times higher than R-22..... other than that, there isn't any "gettin used to". But if you had gone to any of the R410a classes put on by manufacturers and supply houses, you would know this.

Reply to
Steve

I think it may be because 134a was developed to work most effectively in higher temperature applications. I can't wait for HFO-1234yf to replace 134a. I'm going to have problems remembering all those darn numbers and letters. Sir, I'm sorry to inform you that your refrigerator needs 2,3,3,3-Tetrafluoropropene. Let me get my environmental suit and breathing air tank. Hey, I get to charge more!

TDD

Reply to
The Daring Dufas

I'm sure 134a works a LOT better at medium and high temp applications. Well, it keeps ice cubes cold enough. Sure was simpler when we only had four or five common gasses. Now, we've got a real nightmare.

Reply to
Stormin Mormon

I never said that I wasn't qualified or licensed. I never indicated one way or the other. I may have been at one time.

Reply to
Stormin Mormon

Every time you open your mouth its shows you're not qualified and the last time I checked NY doesn't require a license which makes it easy for hacks like yourself.

Reply to
The King

Have you seen the new square and triangular shaped snap on connectors for the new refrigerants? The manufacturers are trying to make sure new and old refrigerants don't get mixed up.

TDD

Reply to
The Daring Dufas

Not seen those. Never know, might be a good idea. Or, more gadgets to haul around. Offhand, I think it's bad idea for techs like me.

Thinking some more about 134a. When I start up the box, the inside can be 70F or hotter. The system is designed for evaporator temps more like 30F. So, the supeheat is way off the charts. Helps explain the high discharge temps.

Reply to
Stormin Mormon

Ah, you're just sayin that to make me blush!

Reply to
Stormin Mormon

In hot kitchens or in older stressed equipment, I charge them with R-416a. It runs a lower head pressure than R-12 or R-134a and can be used in place of either. I've had very good luck with it.

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TDD

Reply to
The Daring Dufas

How could any one miss those classes? They have free Pizza, pop, etc.

Reply to
Hermann

Thanks for the ideas, and information. One parts house near me has that. I've used 409a with great success. Advertised as a direct drop in for R12, with same mineral oil. But the

416a is noticably cheaper. I'll try that next time.
Reply to
Stormin Mormon

Busy fixing other stuff. I'll have to check at the parts house one day soon.

Reply to
Stormin Mormon

Not talking about a "subcooler", talking about *subcooling* where your looking for the Delta T between LLP converted to temperature, and actual LLT coming from the condenser. Normally for A/C and heat pumps, the Delta T should be between 10 - 14F to insure a solid column of liquid refrigerant to the TXV.

Reply to
Steve

Johnstone stocks it in 25lb cylinders and in the small 9.6oz cans. The screw on can adapter has left hand threads if I'm remembering correctly. I have a 25lb cylinder and haven't used the small cans in a long while.

TDD

Reply to
The Daring Dufas

I used a small can of one of the R12 replacements that was specifically sold for use in household ref/freezer applications. I'm thinking it was

414A, but I wouldn't swear to it. Anyway, I just used a side puncture can tap and it worked fine. If you bought a jug of every single R12 supposedly drop-in that is on the market, you'd be hard pressed to fit them all in an empty service van-- definitely wouldn't fit in a Pinto, even a wagon. Larry
Reply to
Lp1331 1p1331

You'd have some really nice jugs, though.

Reply to
.p.jm.

The only time we change gas, is if the unit had R-12, and then we use 416a. The older units are designed for R-12, and the newer units come with R-134 in them. Not doing any conversions.

Never worked on a two stage cooler.

Reply to
Stormin Mormon

Both sound convenient. I've toyed with the idea of mickey mousing up a cantap for 134a, so I can carry a duplicate set of tools in my other Pinto. Sometimes I have to come back home for the Van Pinto. Most of the time, it's just cleaning condensors and electrical repairs.

Reply to
Stormin Mormon

I hear you, with the explosion of mixtures and blends. It's not like the old days. I've specialized a bit, and only carry a couple refrigerants in my work pinto.

Reply to
Stormin Mormon

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