What does the pressures numbers on AC or Heat Pump units mean. For example they have the following on hteir nameplate.
Low Pressure 200 psig
High Pressure 440 psig
Other units have,
Tested to 420 psi High side, 150 psi low side.
Are these max system working pressures or max pressures that low and high side of the system sees regardless of if the unit is in operation or not.