Pipe Sizing

Question 1

What are the 3 main considerations when sizing refrigerant lines?

Answer 1

1. Pressure drop
2. Refrigerant velocity
3. Oil circulation

Question 2

Pressure drop is limited to a __F SATURATION temperature drop

Answer 2

2F

Question 3

When sizing, find the pipes _________ length which includes all fittings

Answer 3

equivalent

Question 4

Under sized and short lines cause a _______ pressure drop but excessively long lines also increase pressure drop

Answer 4

greater

Question 5

Larger lines cause _____ pressure drop but require higher _______

Answer 5

velocity

Question 6

Low temperature lines require _______ velocities to aid in oil return

Answer 6

higher

Question 7

Condenser condensate line should be sized for ____FPM or less

Answer 7

100FPM

Question 8

Inadequate oil return reduces system ________

Answer 8

capacity

Question 9

When oil becomes trapped in the evaporator or condenser it acts as an _________

Answer 9

insulation

Question 10

An oil logged evaporator can cause the metering device to send more _______

Answer 10

liquid

Question 11

Where does the condensate line attach?

Answer 11

Outlet of the condenser to the inlet of the receiver

Question 12

Condensate line pressure drop?

Answer 12

0psi

Question 13

Causes of an undersized or excessively long condensate line?

Answer 13

Restricts flow of liquid causing high head pressure and back-up of liquid in condenser reducing efficiency

Question 14

What information is needed for line sizing?

Answer 14

tonnage
equivalent length
refrigerant type

Question 15

Explain static loss in pipe sizing?

Answer 15

Pressure drop occurring from there weight of the liquid refrigerant at the top in a riser

Question 16

Static loss value in a riser per ft?

Answer 16

0.5psi/ft

Question 17

Liquid line that is too small, long, or has too many fittings can create ____-___ due to pressure drops

Answer 17

flash-gas

Question 18

Do you ever insulate a liquid line?

Answer 18

Only if it is exposed to extreme heat that may cause the liquid to evaporate

Question 19

What may be added to a liquid line that is succumb to extreme pressure drop?

Answer 19

suction line-liquid heat exchanger to subcool the liquid

Question 20

________ is the only way to reduce the effect of excessive pressure drop

Answer 20

sub-cooling

Question 21

Oil in the suction line is at lower temperature making it more ______

Answer 21

viscous

Question 22

If there is a conflict between pressure drop and adequate velocity for oil return, which do you pick?

Answer 22

Adequate velocity for oil return

Question 23

Suction line

Vertical riser should have a ________ diameter than the horizontal section to aid in minimum velocity

Answer 23

smaller

Question 24

The discharge line should be sloped toward the _______

Answer 24

condenser

Question 25

___- ___________are commonly used when discharge lines include a riser (condenser on roof)

Answer 25

oil separators

Question 26

Purpose of an oil separator?

Answer 26

Collects oil from vapour refrigerant and returns back to the compressor crankcase

Question 27

What line is the oil separator installed in?

Answer 27

Discharge line

Question 28

Vertical discharge line risers must have an __-____ to protect the compressor from flood back of liquid/oil

Answer 28

oil-trap

Question 29

Compressor discharge line should slope toward the condenser a minimum of?

Answer 29

1/4" per 10'

Question 30

Liquid line velocity is typically between 100 and _____FPM

Answer 30

100-300FPM

Question 31

Excessive liquid line velocity causes

Answer 31

liquid hammering at the MD