System Controls and Schematics Flashcards
What are the 5 parts of a relay?
Coil, core, return spring, armature, and contacts
What are the 4 most common arrangements for the contacts of a relay?
SPST-NO (single pole, normally open), SPST-NC (single pole, normally closed), SPDT, (single pole, double throw) and DPDT (Double pole, double throw)
What are the 2 most common capacitors used in HVAC systems?
Run capacitor and start capacitor
What is the material called that is used to separate the two plates in a capacitor?
Dielectric
What activates the pressure switch?
The inducer motor
What is flame rectification?
AC electrical current that sends a very small current from the CPU to the flame rod.
Where is the CPU located?
The electronic control board
In a cooling unit, where is the high pressure switch located?
In the tubing between the discharge side of the compressor and the condenser coil.
What is the function of the low pressure switch?
It monitors the refrigeration system for a loss of refrigeration charge.
What is a relay?
Is an automatic remote control device that uses one or more initiating devices such as a switch, to operate or control another device connected either in the same circuit or in another circuit.
A relay in a schematic is always shown in the ____ state and the contacts are said to be in their normal positions.
De-energized
Describe a relay coil?
A conductor formed into loops in such a way that, when current flows through the coil, an electromagnetic field is created.
Describe core?
A core is made of magnetic material. It is magnetized from the polarity of the magnetic field created by the energized coil.
Describe the return spring?
When the coil is de-energized, this spring returns the armature to its normal position.
Describe armature?
This is a moveable metal strip that provides the mechanical action to operate the moveable contacts connected to it.
