A/C Fundamentals

Question 1

What is comfortable air temp?

Answer 1

70-75 F

21-25 C

Question 2

What is comfortable humidity level?

Answer 2

40-45 %

Question 3

What is purpose of HVAC system?

Answer 3

Provide exchange of air
Control humidity
Heat and cool cab
Allow filtered fresh air to enter

Question 4

Heat intensity

Answer 4

Also called sensible heat. Measured in temperature

Question 5

Heat quantity

Answer 5

Amount of heat energy, measured in BTU’s

Question 6

Latent heat

Answer 6

Is the energy that is required to change the state of a substance without changing the temperature.

Question 7

Superheat

Answer 7

After latent heat of evaporation, when the refrigerant continues to absorb heat energy, however the vapour ref. will only increase in temperature and not pressure.
TPT-SAT = S/H, measured at lowest low pressure

Question 8

Subcooling

Answer 8

Occurs after latent heat of condensation, ref. continues to give off heat energy with no change in pressure.
SAT-COT = S/C, measured at highest high pressure

Question 9

TXV specs

Answer 9

H/S pressure : 2-2.5 x amb temp
L/S pressure: CC - 15-30 PSI, VD - 29 PSI
S/H: 6-12 F
S/C: 10-20 F

Question 10

Orifice tube specs

Answer 10

H/S pressure : 2-2.5 x amb temp
L/S pressure: CC - 20-45 PSI, VD 29 PSI
S/H: 0-4 F
S/C: 10-20 F

Question 11

R134A

Answer 11

Tetrafluoroethane
HFC
Light shy blue container

Question 12

Mineral based A/C oil

Answer 12

Used with R12, amber in colour

Question 13

polyol ester POE

Answer 13

Used with all ref., clear in colour

Question 14

polyalkylene PAG

Answer 14

Used R134A only, light blue in colour

Question 15

What two ref. oils do not mix?

Answer 15

PAG and MIN

Question 16

Expansion

Answer 16

As refrigerant travels through the metering device, it expands and the pressure is dropped.

Question 17

Evaporation

Answer 17

Because the pressure has been dropped the liquid ref. undergoes a state change to a vapour. As the change occurs latent heat is absorbed from the surrounding air

Question 18

Compression

Answer 18

Vapour ref. is compressed which adds pressure and temperature to the system.

Question 19

Condensation

Answer 19

The heat of compression is removed turning the ref. vapours into a liquid

Question 20

VD compressor

Answer 20

Compressor control valve uses low side pressure to control the swash plate