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Check the air temperature entering the outdoor coil, all 4 sides, make sure you are not getting recirculation of air at the outdoor unit.

Remember It only acts up during the afternoon, in the morning and eairly afternoon pressures amp draws and sc/sh is normal, so the airflow restriction would make sense but I'm just not seeing it

Both *factory driers*

I removed both driers in the heat pump and put in a biflow drier, I've washed the coil several times, no restriction in airflow around heat pump, fan motor is good its pulling out air, amp draw normal blades balanced. And unfortunatly tranes tech support is few and far between. My supervisor is coming out with me tommorow. This one has just stumped me for sure, we'll see if we can come up with the culprit

Originally Posted by mark beiser

Have you checked the air temperature entering the condenser on all 4 sides?

Are there any obstructions that could cause the unit to recirculate its discharge air?
Unit installed in a corner?

One of the reasons we switched from Trane to American Standard was to get away from that god awful top. It is great for keeping leaves out of the unit, but terrible for efficiency if the unit is not out in a wide open area.

Yeah, i had a few of those too!! What a terrible design. I guess they were going for looks!!! Very easy to pop the top and watch the head pressure fall!

sounds like a fun service call. did you cut out the factory drier and install one on the outside of the unit? you may have a restricted outdoor coil. i would try blowing it out with nitrogen. make sure there are no resitrctions in the piping at the outdoor unit. make sure discharge line of compressor isnt kinked.

Sorry Gunslinger. I re-posted the water mist thing. I missed it when I read through the first time.

This may sound a bit unorthodox but have you tried a light water mist on the condenser to see if if that helps bring your readings more in-line. May help eliminate what it's not and help find what it is.

Have you checked the air temperature entering the condenser on all 4 sides?

Are there any obstructions that could cause the unit to recirculate its discharge air?
Unit installed in a corner?

One of the reasons we switched from Trane to American Standard was to get away from that god awful top. It is great for keeping leaves out of the unit, but terrible for efficiency if the unit is not out in a wide open area.

Liquid line drier

Are you sure that you don't have two liquid line driers on this unit? One is factory installed on the inside of the panel and if you aren't looking for it can be easily missed.

Did you remove the panels on the condenser and see that the coil is clear????? try misting the condenser with a water hose. Does the pressures fall into place? Has the fan/motor been changed? On most Tranes, the fan blade hub is flush with the end of the motoer shaft. Check the heat rise of the condenser. It should not be more than 10 or 12*, This realy sounds like a restricted condenser coil. Been there....done that.

havent been on here in a week or so i was on-call and busy busy. So this customer got back into town,today i replaced the txv, the drier, charged all new refrigerant. the system symptoms are the same and didnt change anything, the compressor still over amping and pressuers the same... not good.

It's a matched size wise I did check on that, yeah boss man said replace txv so that's what I'm doing next week, we'll see how it goes... I personally have a hard time saying its the valve according to all my readings but I'm not sure what else it could be.

Also what trane sometimes forgets to tell people is sometimes with the 15 to 20 seer outdoor units you must use a much larger indoor coil or ahu. trust me. Ive had to uninstall brand new equipment because of inadequate cooling. The smaller coils that are the same tonnage cannot properly handle the amount of refrigerant. Call trane tech support and run all of your #'s to rule it out

Also what trane sometimes forgets to tell people is sometimes with the 15 to 20 seer outdoor units you must use a much larger indoor coil or ahu. trust me. Ive had to uninstall brand new equipment because of inadequate cooling. The smaller coils that are the same tonnage cannot properly handle the amount of refrigerant. Call trane tech support and run all of your #'s to rule it out.

The 16 seer i believe has a two stage scroll compressor. By looking at your pressures it looks like it was in second stage but i would still check the switch in the outdoor unit.The only other thing is if it is a trane evap coil. there was a recall on a series of expasion valves. there is a service bulletin about it too through tranes comfort site. Run the serial #. The valves were made with moisture in the sensing bulb and run a 35 to 45 degree superheat. That looks like your problem to me. good luck remember TXV

Great information! I would rule out your non-condinsable, your discharge temp vs pressure is right on.

So the 2 areas I would focus on:
1) Solid column of liquid getting to the TXV (dryer most suspect, but any restriction in the liquid line should be considered - or flashing)
2) TXV

Good luck!

Yup in the morning the system is fine and operating normally, im within my refrigerant curve but it gets all wonkified (technical term) in the afternoon lol

Fan motor on particular unit isn't var. Speed or multi-speed, amp draw normal.. motor working within specs. The boss man says replace txv so I'm gonna do what I'm told, the customers out of town so I'm gonna replace the txv, drier and refrigerant next week. I'll post what happens.

my first arrival 3:00pm (first day)
my pressures @ 143/463psig
40sh-6sc
ambient temp 104'F
delta t 19'F return temp 86'F supply temp 67'F
wet bulb 78.3
system shows symptoms of low charge due to high superheat and low subcool readings. condensor coil clean washed several times to make sure. decide to return in the morning to see what changes.

The head pressure is around 70 psi higher than it should be for 104˚ ambient, according to the service literature. But the SH and SC do suggest undercharge.

8:30am (second day) system maintaining
my pressures 121/344psig
35sh-5sc
ambient temp 93'F
delta t 19'F return temp 77'F supply temp 58'F
compressor amp draw 13.5 fan motor amp draw 0.9 fan is on high speed.
i decide to charge the system to get 10'F sc and drop my superheat and raise my subcooling at this point my main concern is my head pressure. i decide to return in the afternoon again to see my changes

Head pressure is about right for 93˚ ambient

3:00pm (second day)
my pressures are fluxuating between
154/520 and 149/500psig
my subcooling and superhead are also doing the same (but much better)
11-14'F sc - 13-16'F sh
ambient 104'F

The fact you were able to get decent SH and SC by adding refrigerant seems to eliminate the TXV. But the head is obviously way high now, and looks like it's due to low condenser air. You cleaned the OD coil. I'm wondering if the condenser fan motor is running the correct second stage speed???