Rack Systems

Question 1

Large or small compressors on parallel compressor racks, which are usually dedicated to the coldest cases, are called?

Answer 1

satellite compressors
and
booster compressors

Question 2

What is a true statement regarding the operation of a parallel rack system?

Answer 2

A. it allows for better temperature control than a single condensing
unit
B. it allows for multiple evaporator temperatures to be maintained
C. it allows for greater operational safety versus a single condensing
unit
*D. all of the above

Question 3

Why is it important for the oil separator to be sized properly, insulated and located as close to the compressor as possible?

Answer 3

to minimize the chances for refrigerant vapor to condense into liquid inside the separator

Question 4

The capacity that a parallel rack will have during operation is determined by?

Answer 4

the coldest temperature evaporator

Question 5

On a parallel compressor rack what device is used to control multiple evaporators?

Answer 5

EPR

Question 6

What can cause the suction pressure on a parallel rack system to run higher than its setpoint?

Answer 6

a higher than design system load

Question 7

Auxiliary contacts would not be used to?

Answer 7

B. control a crankcase heater

C. control an interlock circuit

Question 8

What device would be used to cycle the condenser fans on and off as system head pressure changes?

Answer 8

a reverse acting high-pressure control

Question 9

A device used to damper out compressor torque to the connected copper piping is a

Answer 9

vibration eliminator

Question 10

A device used to maintain a minimum oil condition in a parallel rack compressor is

Answer 10

oil level control

Question 11

To maintain the correct amount of oil in each compressor on a parallel rack an oil system would require this/these components:

Answer 11

A. oil separator
B. oil reservoir
C. oil level regulator
*D. all of the above

Question 12

What device is used on an oil system on a parallel to control the pressure of the oil feeding the oil regulator?

Answer 12

pressure differential valve

Question 13

What is the best method for precharging an oil separator?

Answer 13

charge the oil directly into the separator before brazing into place

Question 14

A decrease in suction pressure of a reciprocating compressor will result in:

Answer 14

a decrease in volumetric efficiency

Question 15

For every 1ºF of additional liquid subcooling a systems capacity will be increased by approximately?

Answer 15

1%

Question 16

These lines should be insulated to help maintain subcooling

Answer 16

liquid line

Question 17

Additional liquid subcooling

Answer 17

reduces the amount of flash gas at the outlet of the TXV

Question 18

What is the purpose of a mechanical subcooling loop on a parallel rack system?

Answer 18

B. reduce the temperature of the liquid entering the metering device on the system being subcooled
C. increase the capacity of system to which the liquid is being subcooled

Question 19

Inadequate liquid sub cooling in a system can cause?

Answer 19

A. excessively high evaporator superheat

C. excessively high discharge temperatures