Pipe Sizing Flashcards
What are the 3 main considerations when sizing refrigerant lines?
- Pressure drop
- Refrigerant velocity
- Oil circulation
Pressure drop is limited to a __F SATURATION temperature drop
2F
When sizing, find the pipes _________ length which includes all fittings
equivalent
Under sized and short lines cause a _______ pressure drop but excessively long lines also increase pressure drop
greater
Larger lines cause _____ pressure drop but require higher _______
velocity
Low temperature lines require _______ velocities to aid in oil return
higher
Condenser condensate line should be sized for ____FPM or less
100FPM
Inadequate oil return reduces system ________
capacity
When oil becomes trapped in the evaporator or condenser it acts as an _________
insulation
An oil logged evaporator can cause the metering device to send more _______
liquid
Where does the condensate line attach?
Outlet of the condenser to the inlet of the receiver
Condensate line pressure drop?
0psi
Causes of an undersized or excessively long condensate line?
Restricts flow of liquid causing high head pressure and back-up of liquid in condenser reducing efficiency
What information is needed for line sizing?
tonnage
equivalent length
refrigerant type
Explain static loss in pipe sizing?
Pressure drop occurring from there weight of the liquid refrigerant at the top in a riser
Static loss value in a riser per ft?
0.5psi/ft
Liquid line that is too small, long, or has too many fittings can create ____-___ due to pressure drops
flash-gas
Do you ever insulate a liquid line?
Only if it is exposed to extreme heat that may cause the liquid to evaporate
What may be added to a liquid line that is succumb to extreme pressure drop?
suction line-liquid heat exchanger to subcool the liquid
________ is the only way to reduce the effect of excessive pressure drop
sub-cooling
Oil in the suction line is at lower temperature making it more ______
viscous
If there is a conflict between pressure drop and adequate velocity for oil return, which do you pick?
Adequate velocity for oil return
Suction line
Vertical riser should have a ________ diameter than the horizontal section to aid in minimum velocity
smaller
The discharge line should be sloped toward the _______
condenser
___- ___________are commonly used when discharge lines include a riser (condenser on roof)
oil separators
Purpose of an oil separator?
Collects oil from vapour refrigerant and returns back to the compressor crankcase
What line is the oil separator installed in?
Discharge line
Vertical discharge line risers must have an __-____ to protect the compressor from flood back of liquid/oil
oil-trap
Compressor discharge line should slope toward the condenser a minimum of?
1/4” per 10’
Liquid line velocity is typically between 100 and _____FPM
100-300FPM
Excessive liquid line velocity causes
liquid hammering at the MD
