Low Subcooling Low Superheat?

[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.

[darmistead]

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

[HomesteadHVAC]

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

[ch4man]

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

[MIDCAM]

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

[Saturatedpsi]

We ran out of options and replaced the coil.

Which options did you exercise?

[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