HVAC general knowledge

Question 1

What is superheat?

Answer 1

Saturations above boiling point

Question 2

What is sub cooling?

Answer 2

Temperature below saturation point

Question 3

How to determine discharge pressure?

Answer 3

Ambient +10-35

Question 4

How to measure resistance in fan motor?

Answer 4

Using a ohm meter

Question 5

How to charge unit with fixed orifice?

Answer 5

Using superheat

Question 6

TXV is charged by?

Answer 6

Subcooling

Question 7

Run winding reading is.

Answer 7

Lowest .5

Question 8

Start Winding reading

Answer 8

Is in the middle. 1.0

Question 9

Common winding reading measures?

Answer 9

Total reading run + start 1.5

Question 10

What temperature is comfort cooling?

Answer 10

40-50 degrees F

Question 11

How to determine superheat?

Answer 11

Suction line temperature

=superheat

Question 12

How to determine sub-cooling?

Answer 12

High side pressure (converted to temp)
-subtracted by
Liquid Line Temp
=sub-cooling

Question 13

Formula for CFM?

How is velocity measured?

In what situation is Pi used ?

Answer 13

Area x Velocity = CFM

Velocity is measured in FPM

Circle object Pi x radius x2

Question 14

What does a overcharge indicate in a system?

Answer 14

High head pressure

High sub-cooling

Low superheat

Question 15

What 2 actions happen in the evaporator?

Answer 15

Latent heat of vaporization
&
Superheat

Question 16

What 3 actions happen in condenser?

Answer 16

Removal of superheat

Latent heat of condensation

Sub-cooling

Question 17

How are circuit breakers rated?

Answer 17

In AMPS

Question 18

Reading voltage across fuse means?

Answer 18

Fuse is bad

Question 19

Reading voltage drop across contacts while closed means?

Answer 19

Contacts are dirty

Question 20

If circuit breaker is open and you Ohm out contacts you should read?

Answer 20

OL

Question 21

How to check MF? (MicroFerrite)

Answer 21

2654 x AMPS x Volts

Question 22

A good contractor will measure?

Answer 22

Some resistance

Question 23

Ohms law is?

Answer 23

If AMP draw goes up

Resistance will drop.

Question 24

How many ohms per volt?

Answer 24

1000

Question 25

Run compositors are in ? With start windings?

Answer 25

Series

Question 26

How many BTU per ton?

Answer 26

12000

Question 27

A closed contact has ?

Answer 27

0 resistance

Question 28

A single compressor to operate 7evaporators at different temps is?

Answer 28

EPR

Question 29

Where is the glass sight located?

Answer 29

Discharge line