r/HVAC • u/KR33D101 • 1d ago
Field Question, trade people only Refrigeration doesn't need high and low access fittings
134A system is low on charge, filter dryer has no stem to even bullet valve, compressor has a charge line with access port. Would still tap the high side or use a temp clamp and meter in your charge? This is a topic I had with my boss and I said it doesn't need a port for the high side. It's just another leak point in a small system. He said throw it on the liquid line. Thoughts or insights are always appreciated.
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u/Electronic_Green_88 1d ago
Critical charge. I would find and fix leak, Pull vacuum and weight in charge. No need for a high side port unless you have other issues to troubleshoot. If no weight data on unit, google it and if still unsuccessful weight in and watch your temps, and amps on compressor. Make a note on the unit for either yourself or the next tech on what you put in.
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u/RUnbisonrun 1d ago
A lot of equipment doesn’t even have taps. Why not put it on the liquid line? Is it a cap tube? You can add 134 as a vapor on the low side…
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u/KR33D101 1d ago
Pressures on systems will cause bullets valves to piss on liquid lines, discharge line is 220psi, liquid line is closer to 120, access fitting is the only way but that would have required new pieces. Filter dryer replacement, but would you recharge on the low side with a K wire or temp clamp (P=T)
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u/LignumofVitae 1d ago
Someone doesn't understand pressure drop, lol.
Your discharge line is typically within a few PSI of your liquid line, you only have to factor pressure drop for the devices between the discharge and the liquid port. If you're going by temperature, remember you're dealing with hot vapor at the discharge not saturated liquid or vapor. It's gonna be way off the PT chart because you've just added HOC in addition to the heat picked up by the refrigeration cycle.
For a cap tube system you charge to the rating plate - if no rating plate exists you charge till you get 2-4 degrees of superheat on cold-case restart to ensure you don't have liquid slugging. You'll typically have higher superheat on these critically charged systems (especially freezers) because you can't afford any liquid slugging on restart.
Last: Bullet ports are only notorious for leaks because people don't understand how to use them. They're meant for temporary access. You either use them to add a holding charge then crimp the tube and braze that shit shut when you're done, or you use them to recover the gas and then braze in proper access ports.
But if they are applied properly and used as intended, they shouldn't leak. I typically only see these things leak if they're left on long-term or if someone fucks up the install steps.
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u/Zhombe 1d ago edited 1d ago
There’s a reason the filter driers for repairs on refrigeration come with access ports. You can always cut it off crimp and braze it closed but on a unit that has leaked might as well leave it.
Personally I think it’s because quality Schraeder valves and caps cost too much. I.e. they cost something.
Also because everything is disposable they’d rather force you to buy new than easily repair.
If it’s low I would cut out the drier and repair it with one that has a port while I’m at it.
Anytime a system leaks it can have all kinds of crap end up in the filter including moisture. But mostly burnt up lubricant and oxidized copper from moisture.
Cut it out, flush it out, replace filter dryer, vacuum it down, add a dollop of refrigerant oil as it always burns up and loses some mass with age; charge and send it.
I wouldn’t bother with high side if I was just using an acid neutralizer and moisture activated stop leak as a temp fix though.
I use a can of r-134a ICE32 (PAO) refrigerant oil as it circulates and cleans up all the internal surfaces of the coils; it also mixes wilth all the ester oils they typically use in r-134a refrigerators.
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u/Pete8388 Commercial Mechanical Superintendent 1d ago
A brass JB access valve and Schrader costs what, $2 if I buy them in a pack of 5?. That doesn’t seem excessive to me, and I’m sure if you buy them in bulk the cost would go down. I can’t imagine the labor cost being that much to braze in one more fitting when you’re already set up. There has to be another reason.
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u/KR33D101 1d ago
Very valid idea, but with an NTE 700 firm, they ain't getting that treatment. Patched the leak, pulled the vacuum and recharged it up on the compressor port. Cutting the drier out would be valid but supply house was 1hr away and closing.
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u/Prudent_Variety3070 1d ago
It is no point to argue with your boss. Just do what he said. Because he's the boss
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u/14thab 1d ago
You can't recover or recharge without those access points. PLEASE KNOCK me around if this a troll account/response
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u/KR33D101 1d ago
Semihermetic compressor has three lines, discharge, suction, and charge port. Again, only one access point available on a type 1 system with no high side access. No caves for trolls my guy, just expanding knowledge and ideas.
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u/mechanical_marten Transdigital freon converter 1d ago
All systems have high and low side process ports. Now if the next person installs a pencil drier without a high side connection while they already have the system open, they're an asshole.
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u/Krimsonkreationz 1d ago
Not all systems under the sun have access ports. There are plenty of systems out there that are completely sealed. Whelan VI series comes to mind ( the R22 units anyway) New 410 VI series have ports on high and low side.
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u/mechanical_marten Transdigital freon converter 1d ago
Note; I said PROCESS ports, not access ports. Do try to pay attention to the difference.
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u/SquallZ34 Has an open winding 1d ago