Basic Heating/Cooling Systems 080305b Flashcards
Where is the low pressure switch located on a cooling system?
Located in the compressor suction line
A low pressure switch is what kind of switch?
Normally open
A high pressure switch is what kind of switch?
Normally closed
A low temperature switch is what kind of switch?
Normally closed
Most often, a single rooftop unit would be controlled using what kind of thermostat?
5 wire or 7 wire
What happens when a thermostat calls for cooling on a cooling unit without an economizer?
- the indoor fan contactor and compressor contactor are energized
- indoor fan motor, compressor and outdoor fan start
How long does an indoor fan continue to operate once a cooling call has been satisfied?
30-45 seconds
What state is the refrigerant in once it passes the tx valve?
Low pressure, low temperature vapour/liquid
What is the purpose of the condensor coil?
Cool compressed hot refridgerant vapour and turn it into a liquid
What state is refrigerant in as it leaves the condensing coil?
High pressure medium temp. liquid
What is the purpose of the compressor on an AC system?
Adds pressure and temperature to vapour
What state is refrigerant in when it leaves the evaporator coil?
Low pressure medium temp. vapor
What is the purpose of the TX valve?
Lowers pressure and temp.
What is the putpose of the evaporator coil?
Adds temp to refrigerant liquid
What is temperature?
Measurment of the speed of molecules
