Test 5

Question 1

Solenoid Valve

Answer 1

An electro-magnet opens and closes
the valve
– Used to stop and start refrigerant flow

Question 2

Magnetic coil energized (powered)
–

Answer 2

Plunger rises
– Refrigerant pressure lifts seat
– Fluid flows through valve

Question 3

Magnetic coil de-energized (no power)
–

Answer 3

Plunger falls
– Refrigerant pressure closes seat
– No fluid flow through valve

Question 4

Solenoid for Pumpdown
•(suction line)

Answer 4

Refrigerant in the suction line during off-cycle
can cause problems

Question 5

Refrigerant may migrate to the compressor oil

Answer 5

So Compressor will be damaged on startup
•

Question 6

A pumpdown removes refrigerant

Answer 6

before the
compressor shuts off

Question 7

Improper Installation

Answer 7

• Flow direction is marked on the valve
– Look for an arrow, or the word “IN”

Question 8

• If installed backward,

Answer 8

– Refrigerant will leak through

Question 9

Solenoid valves control refrigerant flow
•

Answer 9

By
– “Automatic” or “Continuous” pumpdown

Question 10

• The unit pumps down

Answer 10

until LP control stops compressor

Question 11

Hot Gas Bypass

Answer 11

Solenoid valves are used in hot gas
bypass to:
– Raise the evaporator temperature, or
– Defrost the coil in freezers

Question 12

Head Pressure Regulating (HPR) Valves
keeps what up in low amibient?

If refrigerant backs up what is this called and where does it happen?

Answer 12

head pressure
“flooding” the condenser
•

Question 13

HPR Acts like

Answer 13

an overcharge of refrigerant
–

Question 14

Compressor has to raise head pressure
Aka

Answer 14

Also known as “hold-back” valves

Question 15

What does Evaporator Pressure Regulator (EPR) Valve do in evaporator?

Answer 15

– Keeps evaporator pressure and
temperature up

Question 16

EPR also maintains stable…

Where would this be located…

Answer 16

• product temperature
• Located in the suction line

Question 17

Does EPR sense evaporator pressure?

Does it rise or open on inlet pressure?

Answer 17

Yes

Rise
–

Question 18

Sporlan calls EPR

Answer 18

an ORI valve

Question 19

Evaporator #1:

Answer 19

– Walk-in refrigerator (25°Evaporator)

Question 20

• Evaporator #2:

Answer 20

– Candy case (34°Evaporator)

Question 21

• Where do you install the EPR?

Answer 21

– Near the highest temperature evaporator

Question 22

What does a Crankcase Pressure Regulator (CPR) Valve look like?

Does CPR close or rise on of outlet pressure?

Hint: the C in CPR

Answer 22

• Looks like an EPR, but…
– Closes on Rise of Outlet pressure

Question 23

What does CPR stand for?

What is it sometimes also called?

Answer 23

Crankcase Pressure Regulator
Closes on Rise of Outlet pressure- CRO
•
–

Question 24

Does CRO ALSO sense crankcase pressure?

Where would this be located?

Answer 24

Yes
Located in the suction line near compressoe

Question 25

CPR Keeps crankcase pressure down to prevent what?

Answer 25

Prevents compressor overload during hot pull down
(after freezer defrost)

Question 26

Freezer Hot Pull Down

Answer 26

• Compressor shuts off during defrost
• Defrost heaters warm freezer evaporator

Question 27

Evaporator pressure and temperature rises
So what happens next?

And what can overload compressor?

Answer 27

So After defrost, the compressor starts
– High evap pressure

Question 28

Adjust CPR valve when

Answer 28

It is warm

Question 29

Water Regulating Valves
•

Answer 29

Used on water-cooled condensers
• Maintains head pressure
–

Question 30

Water regulatting valves also

Answer 30

Regulates water flow to condenser