fluctuating/restriction?non-condensibles?

[thewoodman]

hey guys, what do you think. Troubleshooting a 2 ton Ac, R22, low side psi goes from 40 up 73, then drops to 40 and gradually climbs to 73, then drops to 40 repeat, repeat. The odd thing is the head psi remains constant at 223. I pulled the cover from the evap coil and it is a 2 ton coil orifice metering device. Coil is clean as a whistle.?????

[xe1000]

Does it have a TXV?

[xe1000]

Sorry! Didnt read your post good enough you say fixed orif.

[beenthere]

If the air filter is just as clean.
They just took out the plugged air filter, and put a new one in, after they had no a/c.
And now from freezing up, the evap is oil logged.

Blow it out.

Then measure how much, and add new oil.

[airworx]

ears could be worn down on orfice causing it to tilt and then straighten. but what we need to know to more accuratly diagnose is subcooling and superheat. is superheat going up or down as pressure drops. is subcooling going up or down.

[thewoodman]

I didn't check the super heat or sub-cooling, I usually do, but the pressure changed too quickly to really justify me trying to get a super heat reading. 73psi for a sec, then gradually dropping to 40psi, how could you know what your saturation temp would be? It would be moving all the time right?

I did pull the piston and found another a coil just like the one installed and compared the pistons. WEll they were different..both .60 same brand coils (nordines) but one was flat ended the other had a bull-nose. Same looking orifice just different on the front end. Could this have had the wrong orifice installed?

[thewoodman]

to beenthere, the unit never froze up, and this was a move out, I maintain duplexes and apt. No one ever complained while living there, but that doesn't mean anything. I am checking things out for next move in. And the air filter was dirty, but again the coil is clean. But the evap doesn't sweat and doesn't get cold. Pressure just don't add up. Head stays the same. Which is odd. I can see head and low changing together if I have a restriction but low changing and not high.??? I haven't come across this exactly. Thanks for your thoughts.

[simpleman]

I had a bad connection on a fan lead do that to me once.




[Edited by simpleman on 06-18-2005 at 12:22 PM]

[beenthere]

Pump the unit down to its self.

Remove the piston.

Back flush the coil with nitrogen, and see if you get alot of oil out of it.

And then put a new piston in it.

And see if it works better then.

Also check the screen while you have it open.

[thewoodman]

thanks beenthere, I have the unit pumped down and checked the screen, put in another piston, and thats it for now. Off work,,till monday, Very good suggestion, only one problem.. these people I work for just refuse to buy me any nitrogen...of course I never vent or purge. I know it is a problem,, but I work there and I am not taking money out of my pocket for them.

[beenthere]

Woodman, thats understandable, you shouldn't have to provide comsumables for them.

Are you having alot of a/c failures, or troubles.

If so, try to get them to understand that good practices can cut down on the number, and cost of repairs.

[thewoodman]

beenthere, yeah, we are experiencing many problems. But I love every one of them. The Prior maintenance installed 248 2 ton units without evacuation. They are gone now. But we come to work the next day and compressors are blown, no refrigerant and oil blown out to boot. Before they left I couldn't convince them that some apartments that where bigger required 2.5 ton units. But thank goodness I have a supervisor now that knows better. These boys had the management fooled for a long time. Sloopy and unprofessional... where is the integrity?

[tinknocker service tech]

did you look for kinks in the lineset if there is a kink it can cause this.