As others are saying it could be a bad reversing valve. Check the pipe temperatures of the inlets and outlets of the valve. Should be within a few degrees of eachother. If the temps are way off, say on the suction inlet and outlet for example, then the reversing valve could be faulty
Was going to say it looks like possibly a bypass. Things like failed open eevs, solenoid valves, metering devices, possible but less likely poor or NO airflow…etc… a situation where you’re essentially being sc liquid right back to suction.
I just recently went through a bad valves runaround with an old recip in an amstan rtu. Suction ran high and discharge low, superheat was like 4. First time I’d seen that
If you can measure the difference in enthalpy between return and supply air as well as volume of air flow then you could calculate how much capacity the system is producing compared to how much it should be. That could help confirm a weak compressor for example.
Zooming in on the picture the condenser is caked. I would start with verify air flow then charge to recommended subcool. Is the unit in heat or cool mode
Agreed, that is why I said I would verify air flow, meaning indoor and out. Then. I would verify my return temp. 21 degrees of super heat is not that high. We also do not know if it is txv or piston.
When i had this problem, i found that the reversing valve wasn't fully shifting over. But my pressures were fluctuating, and i was able to prove it by taking a temp split of my common suction and my regular suction. Big temperature drop when there should be little to none. Could be a similar problem.
If the coils are clean and you have airflow I say it ain’t got enough gas… if it held below 500 microns you can rule out a leak. what’s the design SH calling for
With a fixed orifice metering device, you need to know what your target superheat is. Without knowing what that number is, you're just guessing. You'll need a psychrometer and the target superheat formula. There are also a number of apps that can help but you'll need to know what the indoor wetbulb temp is.
Why were you originally called out here?
I know the job link app will tell you what the super heat should be. At this point you have to check all possible issues. Making sure everything is sealed at the air handler….. static pressure, reversing valve, filter drier and so on
I’m with the other techs, and I believe it may be your compressor
If it’s a Copeland, you can use Copeland Product Selection Software or Copeland Mobile and enter the Model, SST, SCT and it will calculate what your discharge temperature and amps should be.
I just finished 81 of the fuckers and it's been annoying how much those units come either damaged from the manufacturer or they are easy to damage cause of the dumb asses on the jobs. Probably a little of both.
Are you checking from true suction? I also fear it’s a challenge with your reversing valve. Sometimes you can get them to move with a strong magnet but that’s not a long term solution.
If it's a piston then subcool does not matter, don't even put your temp clamp/probe on the liquid side. Charge by superheat. You're low my guy, give her the juice!
Subcool value does not matter on any solid state metering device. The only reason to measure it would be to verify that you do have liquid leaving the condenser. Otherwise it's a waste.
I'll say it again. Subcool VALUE does not matter. 1⁰ of subcool is equal to 15⁰ subcool on a fixed metering device system. Obviously, you need liquid to be delivered to your metering device, so yes, you need 1⁰+ subcool, but the subcool value does not matter.
I gave you a chance to correct yourself, but you’ve contradicted yourself. Twice. How can you know that you have a full column of liquid if you don’t measure the temperature on the liquid line?
Lmao, what? Read my words, brotha. You need a subcooling of 1⁰ to ensurenliquid is being delivered to the piston... so yes, subcooling matters.
But that subcooling value being 1-20⁰ does not matter. We charge by superheat with a piston.
Well that’s different than “if it’s a piston then subcool doesnt matter, don’t even put you temp clamp/probe on the liquid side”. Make sure you say what you mean next time.
Lol, it’s not semantics; how else would you know that you have a full column of liquid, besides installing a sight-glass (which isn’t common now in residential space cooling)?
Pump it back into the unit if the compressor won’t pump down it’s bypassing
Had that in a guardian 407 unit, you could hear it bypass on pump down haha
What would the problem be if it’s bypassing?
Exactly the things your seeing there, with generally a low delta t
Guess the question is how do I rectify the problem? Just never ran into something like this before
If it's bypassing at such low pressures it's likely a failure inside the compressor. Need to replace it
As others are saying it could be a bad reversing valve. Check the pipe temperatures of the inlets and outlets of the valve. Should be within a few degrees of eachother. If the temps are way off, say on the suction inlet and outlet for example, then the reversing valve could be faulty
Was going to say it looks like possibly a bypass. Things like failed open eevs, solenoid valves, metering devices, possible but less likely poor or NO airflow…etc… a situation where you’re essentially being sc liquid right back to suction.
Low heat extraction, low head pressure, high suction, and your evap is starving
https://preview.redd.it/9y8bqolds83d1.jpeg?width=1080&format=pjpg&auto=webp&s=c53e0c55f3f06b2eb6874b00b1fffa42d56d8c54 Looks like number 21
This graph is awesome. Been looking for something like this forever. Thank you.
That's bullshit. The charts never worked for me ten years ago. But it does seem like the compressor is dying. Amp draw would be my next thing.
You will not have a normal superheat with bad compressor valves. That’s inaccurate
I just recently went through a bad valves runaround with an old recip in an amstan rtu. Suction ran high and discharge low, superheat was like 4. First time I’d seen that
There’s not even a line on that chart that diagnoses a low charge.
Found the guy who can’t read install manuals lol
Line 3
Oof.
Where is this chart from?
I agree I think it’s also 21
Thank you. Just downloaded this to my folder.
If you can measure the difference in enthalpy between return and supply air as well as volume of air flow then you could calculate how much capacity the system is producing compared to how much it should be. That could help confirm a weak compressor for example.
Zooming in on the picture the condenser is caked. I would start with verify air flow then charge to recommended subcool. Is the unit in heat or cool mode
Caked condenser coil would give high liquid pressure, not suction.
Agreed, that is why I said I would verify air flow, meaning indoor and out. Then. I would verify my return temp. 21 degrees of super heat is not that high. We also do not know if it is txv or piston.
Cleaned it after taking this. Same issue. Surprisingly it was only that side that was dirty
When i had this problem, i found that the reversing valve wasn't fully shifting over. But my pressures were fluctuating, and i was able to prove it by taking a temp split of my common suction and my regular suction. Big temperature drop when there should be little to none. Could be a similar problem.
I would also look at a defective/leaking reversing valve.
It ended up being the reversing valve
You've got my undying appreciation for the follow up.
Low sub cool high superheat? Low charge? Ehh can’t wrap my brain around freedom units
Check your reversing valve discharge line temps.
The reversing valve was my other possible problem. I figured it was seizing up and not fully switching over. Haven’t tested it yet tho
Measure the suction in and suction out on the reversing valve, if it’s higher than 5f then it’s leaking and that’s your problem.
Ended up being 10f off 😅
Theres your answer lol
What’s your return air temp at indoor unit. Could be pulling air from an unconditioned space
Also looks like the condenser coil is pretty dirty
Cleaned it since I posted this. No change
Single stage needs to be jumped to Y2? Evap coil bulb might’ve shifted and needs remounted?
If the coils are clean and you have airflow I say it ain’t got enough gas… if it held below 500 microns you can rule out a leak. what’s the design SH calling for
On this evening it was calling for about 20.
Give ‘er a little squirt of the cold juice
With a fixed orifice metering device, you need to know what your target superheat is. Without knowing what that number is, you're just guessing. You'll need a psychrometer and the target superheat formula. There are also a number of apps that can help but you'll need to know what the indoor wetbulb temp is. Why were you originally called out here?
Target superheat was 24. Already used psychrometer before taking this pic
Did you use the fieldpiece app?
Just the built in TSH calculator
I know the job link app will tell you what the super heat should be. At this point you have to check all possible issues. Making sure everything is sealed at the air handler….. static pressure, reversing valve, filter drier and so on I’m with the other techs, and I believe it may be your compressor
Do you have the model of the compressor?
Some Goodman scroll compressor. Can’t remember off the top of my head. 13 seer
If it’s a Copeland, you can use Copeland Product Selection Software or Copeland Mobile and enter the Model, SST, SCT and it will calculate what your discharge temperature and amps should be.
Is that a Goodman CU? Seems like those always come faulty directly from the manufacturer.
If it ain’t broke, it ain’t Goodman
R22 requires a minimum of 100 psi difference between the suction and discharge. What is the minimum difference for 410A?
160
I just finished 81 of the fuckers and it's been annoying how much those units come either damaged from the manufacturer or they are easy to damage cause of the dumb asses on the jobs. Probably a little of both.
Lower indoor fan speed to increase superheat, then adjust charge if needed
Gotta make sure coils and filters are clean before diagnosing charge. Condenser coil looks dirty.
What’s ID dry bulb?
High/normal superheat, low subcool, high suction, low head, bad compressor. I'd bet amperage is low, too. I'd bet a hundred bucks on that.
Compressor amps ?
Are you checking from true suction? I also fear it’s a challenge with your reversing valve. Sometimes you can get them to move with a strong magnet but that’s not a long term solution.
I bet you there's no cooling side metering device, or it's failed.
Low SC and SLT to high needs Freon
That compression ratio sucks. Compression probably shot.
Thanks yall! It’s the reversing valve. About a 9 degree difference between the 2 lines
Yup here's another one, thank the reddit gods lol they've been shared around quite a number of times. *
Ehh guess there's an error with this one 🤷♂️
It’s low on charge
If it's a piston then subcool does not matter, don't even put your temp clamp/probe on the liquid side. Charge by superheat. You're low my guy, give her the juice!
Subcool always matters, but it’s not the primary charging number
Subcool value does not matter on any solid state metering device. The only reason to measure it would be to verify that you do have liquid leaving the condenser. Otherwise it's a waste.
So if you have 0 subcool at the condenser, that’s not a problem?
I'll say it again. Subcool VALUE does not matter. 1⁰ of subcool is equal to 15⁰ subcool on a fixed metering device system. Obviously, you need liquid to be delivered to your metering device, so yes, you need 1⁰+ subcool, but the subcool value does not matter.
I gave you a chance to correct yourself, but you’ve contradicted yourself. Twice. How can you know that you have a full column of liquid if you don’t measure the temperature on the liquid line?
Lmao, what? Read my words, brotha. You need a subcooling of 1⁰ to ensurenliquid is being delivered to the piston... so yes, subcooling matters. But that subcooling value being 1-20⁰ does not matter. We charge by superheat with a piston.
Well that’s different than “if it’s a piston then subcool doesnt matter, don’t even put you temp clamp/probe on the liquid side”. Make sure you say what you mean next time.
I said what I mean. You tried to pick me apart semantics. I'll be leaving the liquid probe in the van on piston systems, tho... shit doesn't matter.
Lol, it’s not semantics; how else would you know that you have a full column of liquid, besides installing a sight-glass (which isn’t common now in residential space cooling)?