HVAC Expansion Valve vs Piston?

Some techs burn up the new valve trying to solder it in. They don’t use good ol wet rags or enough of them. They overheat the sensor and blow the actuator diaphram. Must have a good experienced tech without his boss riding him to hurry up.

Piston/Orifice is a much simpler refrigerant metering device than a TXV (thermal expansion valve), and the pros of a piston is its simplicity and it is reliable and will not fail, the con it is not quite as efficient as a TXV in regards to metering refrigerant into the evaporator coil with changing conditions. The TXV when working properly controls refrigerant superheat within a narrow range which is an advantage to HVAC efficiency, but I’ve read where that increased efficiency may not be that high, and the con as you’ve found out is that they can fail.

For a single stage HVAC, as you have, particularly if it is an older unit, I’d give serious consideration to having him install a piston. It should be a cheaper repair. If it’s a newer unit with many more years of anticipated life, I’d probably go back with a TXV.

I’m not a HVAC professional but I’ve watched several video of HVAC tech replacing bad TXVs with pistons and I’ve seen this suggestion on several occasions by HVAC techs on the HVAC-Talk forum. For example this is a direct quote from a tech on the HVAC-Talk forum to a similar question as yours “Some guys like TXVs others like pistons, just like some like Chevys and others like Fords. The main difference is a TXV will make your system more efficient and provide some protection to the compressor by controlling superheat.”

TXV more efficient, less reliable over long term. Piston, less efficient but bullet proof ! Go with TXV !