a-coil wont get cold enough

[ultitech]

got a 12yr old lennox split system 2 1/2 ton. A-coil will only get half way cold. A-coil is clean, recovered freon, replaced liquid line dryer, removed, cleaned and check orfice, flushed out with nitrogen, pumped unit down to 300 microns and recharged with r-22. pressures are perfect, about 80 low and 225 high but no matter how much more freon i put in the pressures keep going up but the line set temp wont come down, stuck at about 80 degs. also when charging the unit, the low side needle goes in to retard like normal but when i close my gauges the needle very, very slowly goes back up. its about 85-90 degs here and im out of ideas. it was running about 325 on high side before i replaced the dryer and was causing the compressor to over heat and shut off but still the a-coil will not flood with freon and will only give me a 10 deg temp drop across the coil. any help would be appreciated dont know what else to check for.

[dandyme]

which half gets cold????

might want to try another set of gauges.

how does psi go above retard?

[jim147]

What tells you when you have perfect pressure? <pressures are perfect, about 80 low and 225 high>

Is there a chart for that?

jim

[jpsmith1cm]

It always needs more gas, doesn't it?

[Six]

More gas is the panacea for all HVAC issues.......

or is it ?

[jpsmith1cm]

Now, I'll be serious for a bit.

You've provided a bit of information but, since you're asking for help, you've got to do a little better.

Let's have some more data.

Airflow, actual air on and air off temps with wetbulb, actual line temps would be a good start.

[r404a]

what is the return wet bulb temp, may have a high humidity load on the coil


404

[ultitech]

im saying my pressures are in range of where they should be for a 90 deg day. they are not indicating a problem but the line set temp is stuck at 80degs which is not in range and i said the needle goes into retard when charging a r-22 unit with r-22 gauges not pass retard but when you close your valve the needle should quickly go back up not take 3mins to go back up ( i replaced the valve core as well). the unit is 12 yrs old and is just now having a problem, its not a airflow problem and it doesn't matter how much more freon i put in, the pressures will keep going up like normal but the line set temp will not budge. After i replaced the liquid line dryer and got my head pressure down the compressor doesn't overheat anymore and has been running for 3 days but still the evap only gets cold and sweats on the bottom of the coil, its completely dry on the top half. It doesn't matter what my cfm, wetbulb or temps are, the coil should be saturated top to bottom. for some reason the freon is just not flooding the coil. Im leaning toward a compressor problem.

[stay gold jonny]

Sounds like to much air across the coil, can't tell without more data.

[jaypslugger]

Is the house very warm inside? Is there a panel open on the air handler? At 80 psig on the low side, you would have a coil temp of close to 50 degrees.
You specified that the a-coil is clean; how about the condenser? Assuming a 12 year old condenser is likely somewhat dirty, on a 90 degree day, 225 psig would be a little low, which combined with 80 on the low side (a little high) WOULD point to leaking compressor valves probably caused by - you guessed it - overcharge.

[jpsmith1cm]

It doesn't matter what my cfm, wetbulb or temps are, the coil should be saturated top to bottom. for some reason the freon is just not flooding the coil. Im leaning toward a compressor problem.

You're wrong about that.

[yunggun]

A compressor isnt going to change a thing but the amount of the repair. Are you sure you have the right size piston for that system. Without measuring airflow, wet bulb inlet temp diff across coil. What else can i tell you?

[dandyme]

well, if all the other information doesn't matter enlighten us as to why.

i'm all up to figuring out how to work smarted than harder

[jpsmith1cm]

im saying my pressures are in range of where they should be for a 90 deg day. Pressure alone is not a good diagnostic metric. they are not indicating a problem but the line set temp is stuck at 80degs I assume that you mean the suction line temperature.which is not in range and i said the needle goes into retard when charging a r-22 unit with r-22 gauges not pass retard but when you close your valve the needle should quickly go back up not take 3mins to go back up ( i replaced the valve core as well). I think this is a red herring. Forget it for now. the unit is 12 yrs old So what? and is just now having a problem, its not a airflow problem and it doesn't matter how much more freon i put in, the pressures will keep going up like normal but the line set temp will not budge. After i replaced the liquid line dryer and got my head pressure down the compressor doesn't overheat anymore and has been running for 3 days but still the evap only gets cold and sweats on the bottom of the coil, its completely dry on the top half. It doesn't matter what my cfm, wetbulb or temps are, the coil should be saturated top to bottom. for some reason the freon is just not flooding the coil. Im leaning toward a compressor problem.

I've made some more notes in red. I was in a hurry earlier to go to dinner with my family.

I also highlighted what I believe to be the error in your logic in blue. Could you please explain to me why you believe that a compressor problem, with what you claim to be "perfect pressures" could be causing your problem?

The compressor is pumping, you needn't ask more from it at this point in time.

As requested, please take the requested readings and post back. We'll explain what the problem is and WHY we know it to be the problem from the information that you haven't yet provided.

[OldSchoolMech]

So Blowing a Ton of Hot air across your coil wouldn't cause it not to be wet? I think you better run the unit close the liquid line valve and see if your gauge Retards.
Or just listen to JP advice cause he knows his Refer
We need more info to help you

[pacnw]

I will say air flow is MOST DEFINITELY something to check.

Had an almost same situation today, low TD, low pressures, warm coil, SH & SC off and they wanted on one of our maintenance policies.

Mind you, this unit was installed as a package with a furnace in 1995 by others. We have serviced the furnace since 2002, but only replace the capacitor in the outdoor unit and nothing else done according to the service sticker.

Well it was a 75K furnace with a 1.5T a/c with blower tap for cooling on high.

I found an old invoice with a reading of 11555 CFM, 50/120 PSIG, 74° AMB and a
16° TD. This was also after he added a LB of refrig because he replaced the core due to a leak( maybe low pressures due to improper, too much, airflow?).

Duct work is spotty at best.

Lowered to heat tap, which was 752 CFM, lowest possible, got a 16° TD, but it is, was and will always be WRONG!!!

So YES airflow matters!!!!!!!

[TriplePoint]

This is just a wild guess from a new student. I am thinking oversized orifice because of low superheat with high suction side pressures.


JASON sent this from his DUMB-PHONE

[Bsmith816]

Definitely need all your data:: return dry bulb, return wetbulb, supply temp, outside ambient, low pressure, high pressure, liquid line temp, suction line temp, condenser saturation temp, and evap saturation temp, with all those numbers you can tell exactly what is wrong, no ifs ands or butts. Science doesn't lie

[jpsmith1cm]

This is just a wild guess from a new student. I am thinking oversized orifice because of low superheat with high suction side pressures.


JASON sent this from his DUMB-PHONE

Where did he post about low superheat?

[carmon]

give the guys want they want.... superheat wet bulb dry bulb and you will get help..... no info we cant help.... and 80 suction is not really all that normal