A newbie question

[Tony Hwang]

Hi, Once in a while AC unit needs refrigerant top up at the beginning of season during annual check up. Are they consumed or if there is no leak, how come it needs top up? Where does it go?

[The Daring Dufas]

There is a microscopic black hole in every AC compressor that sucks in Freon molecule by molecule expelling the Freon into another universe parallel to our own. ^_^

TDD

[Stormin Mormon]

Slow leak, some where. The system is under pressure, after all. Goes into the atmosphere. The sunlight breaks the chemicals into simpler chemicals, where they are absorbed by plants.

Christopher A. Young Learn more about Jesus

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[Stormin Mormon]

Well, that explains a lot about freon. The parallel universe sends wasp nests, and birds nests back to our universe?

Christopher A. Young Learn more about Jesus

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There is a microscopic black hole in every AC compressor that sucks in Freon molecule by molecule expelling the Freon into another universe parallel to our own. ^_^

TDD

[Tony Hwang]

Hmmmm, So is this quite usual thing? In three years they topped up once so far. (Puron system which has higher pressure?)

[Stormin Mormon]

Yes, it's usual. Most systems I've worked on, need top off now and again.

Christopher A. Young Learn more about Jesus

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Storm> Slow leak, some where. The system is under pressure, after all. Goes into

Hmmmm, So is this quite usual thing? In three years they topped up once so far. (Puron system which has higher pressure?)

[Steve]

A/C refrigerant systems are sealed systems.... if they need topped off, then there *IS* a leak. If the system is correctly installed, and a proper 400 micron vacuum is pulled, and holds for 30minutes, you should never need to "top off" the system unless there is a leak.

[Stormin Mormon]

Thanks for agreeing with me.

Christopher A. Young Learn more about Jesus

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A/C refrigerant systems are sealed systems.... if they need topped off, then there *IS* a leak. If the system is correctly installed, and a proper 400 micron vacuum is pulled, and holds for 30minutes, you should never need to "top off" the system unless there is a leak.

[john]

How much of a charge is in the unit and how much did you replace?

[john]

A vacuum test should never be used as a pressure test. Too many contractors purchase nitrogen test guages of 0-250lbs. This is not enough even for an R-22 system let alone a 410A. The high side should be isolated (not always possible) and tested at 450lbs (R-22) A small piece of debris can be sucked into a hole and provide a satisfactory vacuum only to be blown back out when positive pressure is on the system. The only idea that "nature abhors a vacuum" does not apply to our situation. Should always be careful testing a unit with a high pressure guage. A low side test of 100 lbs should be enough for a satisfactory test. I've found leaks in condensors that held 100lbs but at 200 lbs began to leak.

[The Daring Dufas]

I often replace the Schrader valves with the highest quality valves I can find. I've been using those having a polymer seal instead of rubber. The valves are inexpensive and I often find leaks at the service ports. Anyone who services AC/refrigeration should have the tool to replace the valves when a system is under pressure. ^_^

TDD

[Stormin Mormon]

Earplugs + left thumb? Hah, ha.

Yes, I've got one of those, some where.

Christopher A. Young Learn more about Jesus

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I often replace the Schrader valves with the highest quality valves I can find. I've been using those having a polymer seal instead of rubber. The valves are inexpensive and I often find leaks at the service ports. Anyone who services AC/refrigeration should have the tool to replace the valves when a system is under pressure. ^_^

TDD

[Steve]

Core tool and replacement cores are standard equipment on my truck. With a lot of new customers, I also routinely find cores that are just plain loose so the previous "tech" has job security. Yes I tell the customer all of the things I find when I do a complete system assesment as I do for any seasonal service.

[Steve]

I pressure test R22 systems to 350psi, and R410a systems to 500psi with N2 before I pull a vacuum. Only twice in 17 years have I found any leaks in a condenser that were not caused by stupidity(dropping crap in the fan when it was running), and only once have I had a leak in a *NEW* condenser.

[The Daring Dufas]

Steve, do you use the cores with Teflon seals? They cost a little more but I've never had them leak. I've seen so many AC/refrigeration techs ignore the darn things or even check whether or not the cores are tight. I like the home AC units that are manufactured with commercial type service valves because those don't leak unless the valve packing is loose. o_O

TDD

[Steve]

I prefer teflon, but pretty much have to buy what the supply house has in stock.

[john]

Solid practice. The leak I found in the condenser was on a 180° bend. I doubt it was hit by anything. The leak was on the weld itself. I spent hours on a 450T Dunham Bush machine where 95/5 solder was used instead of silver. Over the years, we run into many interesting things manufacturers let slip by.

A pebble in a shrader valve is what used to irritate me.

[Steve]

FWIW, if you have to repair any braze joints or unsweat/ resweat anything in a Rheem/RUUD condenser, the factory uses 45% silver. Silphos is not gonna do it for repairs.

[Stormin Mormon]

That's worth knowing. Thanks.

Christopher A. Young Learn more about Jesus

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FWIW, if you have to repair any braze joints or unsweat/ resweat anything in a Rheem/RUUD condenser, the factory uses 45% silver. Silphos is not gonna do it for repairs.

[PaxPerPoten]

While what you say is quite true... A deep vacuum in the 15 micron range or thereabouts will usually indicate at tight system. 5 Microns is used for airborne attack radar modulators. They are cooled with liquid refrigerant that loves to leak. Most good vacuum pumps can attain 15 microns. Don't do that to automobile systems though. sucks the seals out of them.