HVAC 101
What is an example of a low refrigerant application?
Walkin Freezer.
What is the new refrigerant called?
A2L, R32, R454B
Motor speed is determined by?
Number of poles.
Which control wire operates the blower?
The Green G wire
Which color of the Thermostat energizes the outside contactor?
Yellow
Name two types of metering devices.
Piston, TXV
What is GWP?
Global warming potential
Start windings are placed ___ with run winding?
slightly out of phase.
What is Y2 on a tstat
2nd stage cooling
What is a potential relay?
Helps start a CSCR motor. Take the start capacitor out of the circuit.
How many BTUs in a 4 ton ac stystem?
48,000 btus
Why do some refrigerants have to be charged as a liquid?
they are a blend.
What does the centrifugal switch do?
Takes the start winding out of the circuit once to motor is at 75% speed.
Which terminal on the tstat does the electric heat strips get hooked to?
W terminal
2. Beside maintaining pressure on the contacts for current carrying capacity, the pressure springs have a second important function. This is to ____.
a.keep the contacts in line
b.help obtain equal contacts against the stationary contacts
c.slow dow the pull of the armature into place to reduce the noise
d.increase the power required to close the contacts
help obtain equal contacts against the stationary contacts
What is a manometer used for?
pressures lower that PSIG,
gas, static pressure.
What chart do we use to get saturation temps?
PT Chart
What type of starting torque does a shaded pole motor have?
low starting torgue.
Which terminal does the reversing value get hooked to on tstat?
O or B
T/F - A set of contacts are closed when the relay is energized. These contacts are classified as normally closed.
False
Why would you use the temperature rise method?
To measure air flow.
Why do refrigerants try to migrate back to the compressor?
Because it always tries to find the cool spot to stay.
How many capacitors does a PSC motor have?
1 run cap
Do low and high pressure switches operate on low or high voltage?
Low.
Technician “A” says that if you take a voltage reading from terminal "L1" to terminal "T1" on a contactor whose coil is energized, you should read zero volts. Technician “B” says that contactors can only have normally open contacts. Which of the following statements is correct?
A is correct
B is incorrect