R410A low side pressure not high enough

[den052]

We installed a USA Nordyne 2ton AC unit with a 25 foot line set and a 2ton A coil in my furnace. I evacuated the lines and opened the AC unit to charge the lines. The suggested orifice of .56 was installed in the A coil from the envelope attached to the Compressor unit.

In operation I am only getting a reading of 65psi low side and 285psi high side. The outside ambient temperature was between 80-90F degrees. I believe I should be getting a low side pressure of 118-145 psi. It seems to me not enough refrigerant is flowing with the .56 orifice and I am starving the A coil. If I remove the orifice and install a 410A TXV valve, do you think my problem would be corrected?

[monkey spanners]

What's sub cooling and superheat is the system running with?
What's the air on and air off temperatures?
What's the airflow cfm?

[den052]

Thanks for the reply. The superheat was way off scale. It turned out to be 1lb low of refrigerant. I didn't have an inventory of R410A available to test system response. Brand new unit from the factory was 1 lb low for a 25 ft line set. I could understand if I was using a longer line set. As soon as I started adding liquid refrigerant, the pressures stablized.
Thanks again (my first experience with R410A).
Dennis