Low Subcooling Low Superheat?

[MIDCAM]

I am working on a two stage heat pump with a varable speed air handler.
The system runs about 1.5 deg S/C and about 2 deg S/H The delta T is 22 deg. A capacity check shows systems is operation at 122% of publish Capacity. Adding refregerant does not change the S/C much at all.
My question is how is this possable? low subcooling and low S/H
This is a matched system, and all test equiment was checked for accuarcy.

[jpsmith1cm]

Moved to Tech to Tech residential

[shaka]

Is the compressor and evap motor at 100% ?
What kind of airflow to your air handler?

[jpsmith1cm]

You've got multiple problems, I think.

Please provide all of the readings that you took on the unit along with model and serial and maybe we can see a problem.

[MIDCAM]

25HNB624 with an FE4ANF003 Air Handler.
90 deg ODBD Pressures 298/138# liquid line@ service valve 93deg vapor @ service valve 52 deg.
air flow @ 700 CFM +/- 20 cfm
RA 76 deg db 67 Deg wb
SA 54 deg db 52 Deg wb

[MIDCAM]

Compressor @ 60% of fla air flow @ 700cfm

[skippedover]

You may have a flooded everything due to a gross overcharge. Start by recovering all the refrigerant from the system. The start with a fresh charge to factory specs and see where things are at that point.

[MIDCAM]

The Refrigerant charge was recovred and weight back in @ factory specs added 5 lbs more. and removed 10lbs. still little change is s/c

[timebuilder]

The Refrigerant charge was recovred and weight back in @ factory specs added 5 lbs more. and removed 10lbs. still little change is s/c

I would have loaded just the factory spec amount and continued the diag from there. No need to add 5 more lbs....

[jpsmith1cm]

Where, exactly, are you measuring the liquid line pressure and temperature?

Where, in relationship to the liquid drier?

[Nytefog]

I'm guessing it's metered by a txv? Could the txv be causing the issue?

[jpsmith1cm]

The Refrigerant charge was recovred and weight back in @ factory specs added 5 lbs more. and removed 10lbs. still little change is s/c

No offense, but a part of me is questioning your instruments.

I just can't see adding 5 pounds of refrigerant without affecting subcooling unless you have an extraordinarily long lineset.

[MIDCAM]

As did I with three different instruments A cooper digital. Field Piece digital. And my old standby yellow jacket and fluke temperature probes. Nothing makes sense. How can a evap show flooded and the condenser be starved?

[Nytefog]

Txv stuck open

[Huntinwalkerstyle]

TXV problem

[jarganda83]

Read the book on that cond. Unit. I know with some Carriers, they have to be running in high capacity or you'll get funny pressure reading. Also check if the indoor blower is running in high speed.

[Kevin Weaver]

Sounds like more air flow is needed to me.

[skidoox800]

TXV Problem, Airflow is good at 700 CFM for a 2 ton. Newer systems call 350 CFM better dehumidification. Seems stuck open.

[ch4man]

I am working on a two stage heat pump with a varable speed air handler.
The system runs about 1.5 deg S/C and about 2 deg S/H The delta T is 22 deg. A capacity check shows systems is operation at 122% of publish Capacity. Adding refregerant does not change the S/C much at all.
My question is how is this possable? low subcooling and low S/H
This is a matched system, and all test equiment was checked for accuarcy.

TXV Problem, Airflow is good at 700 CFM for a 2 ton. Newer systems call 350 CFM better dehumidification. Seems stuck open.

the only way he's getting 122% rated capacity is that there is actually less airflow than the number he used in the capacity calculation.

[wanttosee]

I believe your compressor is still in first stage. IIRC there's a five minute delay from signal sent to compressor engage in addition to the delays in some thermostats. I've seen those same pressure/temp/sh/sc conditions on a carrier two stage system that would not engage full capacity.