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The same situation was happening to me: 410-A condenser, Low SuC and Low SuH, i struggled to find out why. A super dirty conders coil and air in system where 2 things that pop in my head. Coil was not dirty and gauges did not show signs of air (noncondensible). I read the $&@n manual where it asked for Service Access door to be attached while checking pressures so as not to deprive coil of air flow and all my pressures were perfect. Hope this does not happen to anyone. 🖖

Running low superheat and low subcool....txv stuck open.....you can add and add refrigerant....need new txv.

Originally Posted by MIDCAM

The TXV was changed from the factory Danfoss to a Sporland, The equalize line was check for flow. All checked good. Air flow was double checked by checking pressure drop a crossed the coil. .58”wc the valve checked good the heat added and then dip into and ice bath, responsive to both

Fair enough...for a while there, I thought you had burned down the house to get rid of the cockroaches.

the valve checked good the heat added and then dip into and ice bath, responsive to both

tXV

The TXV was changed from the factory Danfoss to a Sporland, The equalize line was check for flow. All checked good. Air flow was double checked by checking pressure drop a crossed the coil. .58”wc

Originally Posted by MIDCAM

We ran out of options and replaced the coil.

Which options did you exercise?

Fixed

Sorry for the delaying in posting, While I was on vacation, another tech replaced the indoor coil. After replacement the system ran at spec's 12 deg s/c 9 deg of s/h. althought the coil would frost evenly when the blower was off. We ran out of options and replaced the coil. I am requesting an RMA back to Carrier to have the coil tested. If I get anything back I'll post thier finding.
Thanks all

its been 6 days, the OP hasnt been back, guess he fix it.?!?

so we can all benefit, it'd be nice to here how these threads end up

have you tried testing the txv by heating and cooling the bulb?

verify air flow using mini vane or equev.
what is the amp draw at compresor
is the evap coil / blower clean
what is return wb and
supply wb
how did you figure capacity

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.

Originally Posted by 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.

Originally Posted by skidoox800

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.

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

Sounds like more air flow is needed to me.

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.

TXV problem

Txv stuck open

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?

Originally Posted by 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

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.

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