Controls Final Flashcards
What is the branch pressure of a 2 pipe thermostat
0-20 psi
What control system has ultimate authority
Fire alarm
A pilot duty interrupts the current to the motor directly
False
Two position thermostats are analog
False Variable
Advantage of 3 pipe controller over a 2 pipe controller is
Greater capacity and ability to control multiple actuators
An actuator controls the dampers in an HVAC unit
True
When the high limit trips on a furnace it kills power to what
Gas valve
What is an electronic hygroscopic sensor made of
Resistance change polymer
Gold foil grid
Thin film polymer
In an electronic thermostat the length of time it takes for the control point and the setpoint to equalize is called
Deviation
Only semi hermetic compressors have an oil pump use an oil failure control
True
Mixed air controllers are typically set to
50F-60F
What do OFC protect in the system
Compressor
Why is the crankcase heater energized for the compressor during the shut down period
Prevent oil foaming on compressor startup
What is an acceptable temperature dry bulb setpoint for a change thermostat
50F-60F
In a freezer the fan delay job is to
Allow water to freeze on it after a defrost prior to the fans starting up
