Sam wrote:
Does anyone Know what HVAC Stands for?
Also what is a Thermal expansion valve for?

www.myinfoviews.com

Google is sometimes your friend:

HVAC = Heating, Ventilation, and Air Conditioning.

"A thermostatic expansion valve (often abbreviated as TXV or TX valve) is a
component in refrigeration and air conditioning systems that controls the
amount of superheat at the outlet of the condenser. This is accomplished by
use of a temperature sensing bulb filled with a similar gas as in the system
that causes the valve to open against the spring pressure in the valve body
as the temperature on the bulb increases. As temperatures in the evaporator
decrease so does the pressure in the bulb and therefore on the spring
causing the valve to close. An air conditioning system with a TX valve is
often more efficient than other designs that do not use one."