Res furn 2 Flashcards
What is the main difference between an intermittent pilot gas valve and a direct ignition gas valve?
The direct ignition gas valve has no pilot connection.
When using electronic ignition, what is the process of proving the flame called?
Flame rectification
What is the minimum flame rode to ground electrode area that is immersed in the flame?
1:4
Why have flame conductivity systems not been used for proving the flame?
The system will not distinguish between a flame and a short to ground.
What is the first step in the sequence of operation for any heating application with electronic ignition?
There is a call for heat at the thermostat.
What is the importance of the connection diagram?
It shows where the wires go and the colour of the wires.
What is the importance of the ladder diagram?
It shows how the appliance works for troubleshooting.
What is the function of the device identified as ILK?
The ILK device shuts off the appliance if the blower door is removed.
What device has a capacitor connected to it?
The blower motor.
How many speeds does the blower motor have?
4
What color wires are connected to the limit switches?
Red
What is the voltage output of the transformer?
24 VAC
Which motor speed is not used as the unit is received from the factory?
MED HI
What size of fuse should be used as a replacement?
A three-amp fuse
How many trials for ignition does this unit have?
Four
5 parts of a Relay
Coil Core Return spring Armature Contacts
List four most common arrangements for the contacts of a relay
“SPST - NO” single pole throw normally open contacts
“SPST - NC” single pole single throw normally closed contacts
“SPDT” single pole double throw
“DPDT” double pole double throw
Two most common capacitors used in HVAC systems
Run capacitor
Start capacitor
What is the material called that is used to separate the two plates in a capacitor?
Dielectric
What activates a pressure switch?
The pressure switch is activated when the IDM starts turning and creates enough pressure, it will force the diaphragm to move toward the microswitch, closing it.
What is flame rectification?
Flame rectification is an AC electrical circuit that sends a very small current from the furnace electronic board-up to the flame rod. When the flame is established, the flame acts as a path or conductor, which allows the current to flow across the flame from the flame rode to ground (burner), thus completing the circuit.
Where is the CPU located?
The electronic control board contains the CPU in most modern day HVAC equipment.
In a cooling unit, where is the high pressure switch located?
The switch is located in the tubing between the discharge side of the compressor and the condensing coil.
Explain the function of the low pressure switch.
The low pressure switch monitors the refrigeration system for a loss of refrigerant charge and may also be helpful in stopping the evaporator (indoor) coil from freezing up due to a dirty filter or low airflow over the coil.
