A/C: Suction in retard, Liquid at 175.

We recently had our air conditioning serviced by a professional contractor. Was low on R-22, no leak found so he charged it up.
Since then we have had some intermittant problems (no cooling). Put some meters on the outside unit with the low side > 120 psi and the high side ~175 psi.
I called our air conditioning contractor (1 week backlog) and he believes it is probably the reed value in the compressor and the compressor needs replaced. For those who care, this is Lennox.
Wanted to double check if this makes sense. Any input appreciated.
Thanks. Direct replies to: firefly24 comcast net (insert @ and .) Gary.
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are you saying the low side is in retard (vacuum) or is greater than 120 psi?
the title says one thing and the text of your message says the other
either way, it is VERY unlikely that a "reed valve" in the compressor would cause either reading
please post the correct high & low side pressures you measured and the ambient temperature they were measured at
PS - if your unit was truly "low on R-22", then it has a leak, they just don't use up some like a car uses a little oil!
sounds like you need an A/C contractor who is competent

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This is Turtle.
What you have stated here means nothing. If the compressor was not running and you got these readings. It means nothing.
Now have it running and then get the readings ! Also a model & Serial number of the unit and what type system it is Split, Package, or heat pump split or package would be nice to see.
TURTLE
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OK, I get what you mean, it is showing in the "retard" area, because you pegged the meter 360 degrees around!
if the freon level was correct, and the system was running when you took the measurement, you have a worn compressor, although it would be the primary compression area of the compressor, not the reed valves.
before jumping to any conclusions and tossing what might be a perfectly good compressor, insist that your contractor completely evacuate the system, leaving the vacuum on a full hour, then WEIGH IN the freon charge as per the amount listed on the information plate.
there is no other way to accurately determine the correct charge, other than weighing it in, no matter what any contractor might incorrectly tell you.
it is not like the gas gauge of a car, no meter or gauge set can tell you if the freon level is correct, weighing it in is the only precise way, due to reasons of chemistry & physics, all other methods are a guess.
freon level must be correct to be sure a compressor is the actual culprit
cheers!
wild bill

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Hi cowboy, hope you are having a nice day
On 15-Jun-05 At About 15:24:47, cowboy wrote to All Subject: Re: Suction in retard, Liquid at 175.
c> there is no other way to accurately determine the correct charge, c> other than weighing it in, no matter what any contractor might c> incorrectly tell you.
Actually there is a way to check the charge properly. depending on the metering device superheat or subcoooling. weighing the charge in is a start but you should always check with the proper method above to insure that you are correct.
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Hmmm my guess... OP, those reading were taken with the unit not running... and if it has pure R-22 in it, the temperature of the equipment that day was about 95F, is that right? :)
Got that info from the "vapor pressure scale" on my gauge set. ;)

Yeah cowboy, what HvacTech2 said. :/
I'm still in the process of getting a handle on this super-heating and sub-cooling thing myself. It's kind of tricky but is "the way" the engineers figured out what the charge weight should be to start with. First things first. Know what I mean, Verne?
What I want to see is an explaination on how to measure and adjust SH and SC using only the pressure readings, the R-22 scales on the gauges and a thermometer.
Definition basics to get out of the way:
Water boils at 212F at one atmosphere of pressure.
The heated-boiling pan of water stays at that temperature only the vapor/gas can be brought above that 212F so water vapor/gas at 220F (and one atmosphere pressure) is super-heated 8F.
Sub cooling: Water at 200F is 12F subcooled (at one atmosphere pressure). Different pressures, different boiling points, different numbers.
To measure SH and SC you got to know (what the liquid really is and so its characteristic boiling points, at what pressures and also the existing/measured temperatures and pressures.
With that, we are getting dangerously close to my limit of knowledge on the subject. ;) (assuming I even got it worded right)
Alvin in AZ ps- where you at cowboy? pps- my first post here on a.h.r!
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BTW, looking in at the label that came with my system... they left the "total charge" area blank! :/ The system was sold without the evaporator which varied with what would fit into my furnace? I guess.

Hey cowboy, I think I've got a handle on it now but while reading different sources they have different temperature ranges as to being the "best". Still learning. :)
This is my guess at this time...
For capillary tube type metering use the "super heat" readings. For those with expansion valves use the "sub cooling" readings.
Ok, so you got it up and running with your gauges on it etc. :) If it's R-22 with capillary metering look at the low side and read off the number on the R-22 vapor pressure scale. Subtract that number from the actual temperature of the suction line (at the compressor). That's the "super heat" reading.
Using that information and looking at the table that came with my cap-tubed Rheem they want ~20F of super heat.
Ok, so again you got it up and running with your gauges on it etc. :) This time it's R-12 with an expansion valve metering, look at the high side and read the R-12 vapor pressure scale number and subtract that number from the actual temeperature of the condenser's exit line (can be read at either end). That's your "sub cooling" reading.
Ok, at least that's my understanding so far. What I want to know is how close to right is that?
Hey! I've only been working on this for a friggin week. :/
I don't really know shit about it. :/
HvacTech2?
What have I got wrong there?
Alvin in AZ
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Why don't you take an amperage reading of the compressor while it is running and compare to the rating plate. If reed valves are shot you should be getting a pretty low number, as the compressor is not working very hard. High suction and Low Discharge are a good sign of a bad compressor. Of course you could sink hundreds of dollars into fixing a problem whereas that couple hundred dollars could go to a new condensor. Sometimes you just have to look at how old the unit is to determine it's time to put it out of it's misery. Also make sure filter is clean, and inspect evap in plenum to make sure it is clear of dog hair, dust or anything blocking air flow.
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Yeah but. ;)
He's never got back and told us that when he took those readings the sucker was actually running. :)
Look at the post again? I see it as... it wasn't running and the temperature was 95F (if it's pure R-22 ;).

For sure, always the first things to do, the obvious and easy little things.
"when you don't know what's wrong, first, before you figure it's something big or complicated, -make all the little things right- then see where you are" -Jack Duncan RR signal maintainer
What I'd like to see is his pressure readings with the thing running this time? ;) Also the temperature of the suction line at the compressor and the temperature of the line exiting the condenser.
Alvin in AZ
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I presume these pressures were with the outside compressor running?
Yep, those pressures do suggest bad valves.
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Please.
We refer to them as mentally challenged and not retards.
And why are you checking his suction???
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