Hopefully some of you can guide me on this- went out to check a 20 yr old 2.5 ton carrier straight cool - R22 system..,customer said company x came out 3 months ago and charged her because wasn't cooling. This time not cooling they called us. Unfortunately I only had gauges and handtools with me...left my meter, etc in another van...so already going kind of blind without being able to get sh or sc readings, but slapped gauges on and pressures were : L side 100psig and H side 285....but fluctuating rapidly up to 385 and back to 285 in 20 second intervals. Low side not doing anything except reading high. What would cause high side to move from normal up 100 plus psi and back as if its hunting like in a loose TXV situation - this was a piston system. Any help appreciated !
Fluctuating head pressure
squirrelshot
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Hopefully some of you can guide me on this- went out to check a 20 yr old 2.5 ton carrier straight cool - R22 system..,customer said company x came out 3 months ago and charged her because wasn't cooling. This time not cooling they called us. Unfortunately I only had gauges and handtools with me...left my meter, etc in another van...so already going kind of blind without being able to get sh or sc readings, but slapped gauges on and pressures were : L side 100psig and H side 285....but fluctuating rapidly up to 385 and back to 285 in 20 second intervals. Low side not doing anything except reading high. What would cause high side to move from normal up 100 plus psi and back as if its hunting like in a loose TXV situation - this was a piston system. Any help appreciated !
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I appreciate the reply- I went up into the attic and listened to the liquid line real close (sometimes I have heard non condensables pass through the line), but could not hear anything "swooshing" by....the head pressure was just bumping back and forth in very rhythmic 20-30 second intervals. Agree on the overcharge, but would non condensables also affect low side readings?
I think they are sold on a new unit anyway, but still just curious since I am still a relatively new tech....I really appreciate the feedback!
Usually, but not 100% of the time.
So non-condensables can be present without this effect? Or other things can cause this scenario? Or both?
Both. A small amount of air, may not cause the head to jump around. A condenser fan motor that is going out and varying its RPM can cause the head to move.
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Good thought on the condenser fan motor...how would I check that....amp reading and watch for fluctuation in amps?
Sound, sight and feel would cover that ide imagine
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That's an extremely high head presssure. Have you thought about cleaning the condenser coil? Do that, and then check your readings again. It could also simply be overcharged. Slugging causes both surging and high suction pressure. The rest of the numbers that you didn't get would tell the story. Pressures are mostly useless info without some temp readings to go along with them.
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10-4...all great suggestions and feedback. I appreciate how professional and helpful everyone is in this forum!
I too appreciate the conversation. Maybe one day ill get it in less than a blind guess. I figure fundamental knowledge is useless without experience and experience is useless without fundamental knowlage.
Would that alone account for fluctuations in pressure?
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yep- thought about that one as well....but this old carrier is a dinosaur! Tech would have had to of been purdy tired to do that....lol....although I know it happens!
On a maintenance call I had one doing this exact same thing, I had my 557's hooked up and the suction stayed steady, SH moved up and down only slightly, but 20sec time I would go from R22 LL 230 to 330 and SC was jumping from 15* to 35* sometimes 10* at a time, comp sounded like it was inverter style ramping up and down, at 330 it would crackle, its been a month still waiting on clearance to go back and pull charge and weigh in new. I suspect non-condensables after research and feedback from other techs.
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Just had this last Friday. Head just surging from 280 t0 330 about every 10 to 15 seconds. Talking with owner had Company X out on a service contract, he signed up on a year prior. Guess his system was freezing up and tech wrote down he found leak at schraeder core on LL valve. Replaced schraeder and added 2 pound and 3 ounces of NU22.
Asked HO if he saw jug and he said no, but it was a white box with a Dark Blue circle on it. Asked if tech used a scale, and he said no just sat it there on the curb.
So I have a tech who topped off almost half of the factory charge of 5 pounds and 10 ounces of R22 with NU22b. How he knew he added 2 pounds and 3 ounces without a scale is a trick I would like to learn.
Recovered entire mutated mix (6 pounds 5 ounces), vacuumed, and weighed in new virgin charge. System balanced out and stabilized perfectly.
Asked HO if he saw jug and he said no, but it was a white box with a Dark Blue circle on it. Asked if tech used a scale, and he said no just sat it there on the curb.
So I have a tech who topped off almost half of the factory charge of 5 pounds and 10 ounces of R22 with NU22b. How he knew he added 2 pounds and 3 ounces without a scale is a trick I would like to learn.
Recovered entire mutated mix (6 pounds 5 ounces), vacuumed, and weighed in new virgin charge. System balanced out and stabilized perfectly.
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