Low delta T

[MetroAir]

Working on a Amana 3 ton heat pump, 2 stage, 410 system with problems. I can only get 10 degree delta T across the coil. The system has a ex. valve and I am running a 10 degree subcooling. The pressures are running 145 over 300-310. I was told to change out the ex valve but still running only 10 degrees across the coil. The compressor is kicking into second stage. Amp draw is good. I am lost. Someone suggested to make sure the installer took out the piston..I did. Added 410 and adjusted the valve...still only 10 degrees across the coil. Static pressure is good considering we also changed out all the duct work. Any suggestions?? Has anyone else run across this? Maybe the compressor is going bad? The system is only going to be 1 year old next week. Confused and just want to make customer happy. also, the bulb is placed where is needs to be and fully insulated.

[amd]

Soon someone will tell you to get your post count up and apply for pro status.

Is the blower by any chance moving well over 400 CFM per ton on low? (Y1 and Y2 connected @ air handler? Dip switches set correctly?)

[beenthere]

Sorry, this is not a DIY site. So we are not allowed to give out advise of this nature.

Since answering your question in the open Residential Forums would be posting instruction for DIYers that may read this post later.

If your in the trade, get your post count up to 15, and apply for Pro Membership.
Use this link Apply for Pro Membership (http://hvac-talk.com/vbb/showthread.php?threadid=116113)

Once accepted, you have access to the pro tech forums. Where you can ask and get answers to technical questions.

Plus, you also have access to the Pro Educational Forums.

All of it is free.

Thank you, for your cooperation.

[beenthere]

Just because you changed out the duct work, doesn't mean the air flow is good.

Check duct work static pressure, and compare to fan data chart/install manual.

Since your head varies. How low of a vacuum did you pull when you changed out the TXV.
Did the installers pull a vacuum when they installed it.

Pressure reading without saturation and ambient temps don't tell us much.

[DavyB]

You should charge it.

[davefr]

What's delta T evap and condenser?

What's superheat and subcooling? (this tells you where the refrigerant is)

What's suction and discharge pressure?