residential hvac question?

Start at the evap and look at the inlet for the evap coil and trace back from there. If it is a fixed orfice metering device then each inlet to the coil off of a header may be a fixed orfice, you would be able to tell by looking for what appeared to be a slightly crimped piping on each inlet from the header. Carrier used to make package units this way but that was several decades ago, the reason for doing it this way was if one of the orfices became plugged it would only hinder that inlet off of the header and not the entire coil.

If this is a heat pump then look in the condensing unit access. You should have a fixed metering device for the heating mode and a TXV or AXV for the cooling mode and it will be in the outdoor unit.

Click here this si what it would look like http://www.bing.com/images/search?q=txv+valve&view...

If you have a nut on the outside of your evaporator coil you metering device is pistion.

Most all older system were metered with piston so typicall no txv would be present. not always true though

Expansion valve???

I have no clue,

hope u get more answers cuz it is hot in TEXAS,,,,