HVAC Review Flashcards
The terminal labeled ‘W2’ on a seven-wire thermostat is used to connect to what?
Second stage heating
What is the ‘R’ terminal?
24V supply
What Is the ‘W’ terminal for?
Heat
What is the ‘G’ terminal for?
The fan
What is the ‘Y’ terminal for?
Cooling
What is the ‘C’ terminal for?
Common
Heating systems are rated according the amount of what?
Energy input into the system
True or false
A t stat is a controlling device that provides feedback to a load device
True
Convection is heat transfer in which form?
Through air
Four reasons for automatic control
Comfort, economy, convenience, safety
Cecs
What is a closed loop system?
A system that uses feedback to make a process automatic
What is high limit control generally set at?
80 - 100 degrees celsius
What are the typical fan settings
Fan on 49 - 60
Fan off 32 -38
Differential 17-22
List three types of contacts used in thermostats
Mercury ( most popular)
Spring activated or snap action exposed
Glass enclosed magnet and armature snap acting
How is the anticipator connected with the thermostat in a heating system?
In series
How is the anticipator connected with the thermostat in a cooling system?
In parallel
Where would a manual override switch be installed in a heating system?
In parallel with he fan control switch
What is a common name for a manual override switch?
Summer switch
What are the 3 main types of bi metallic temp sensing devices?
Spiral type
Strip type
Disc type
What is the open circuit voltage of a thermocouple?
26-32 mVdc