Shop Flashcards
Current relay type of wire and resistance
Heavy wire low resistance
Current relay S=?
S= start
Current relay L=?
L=Line voltage
Current relay M=?
M=run
In a current relay what position are L and S
Normally open
Potential relay what is it called when the coil is energized?
Pick up voltage
What shuts off a potential relay secondary coil after being energize?
Back EMF
What kind of resistance does a solid state relay have?
Low resistance
Order of calculating open compressor pulleys?
2 sames on top divided by the one by itself
Liquid charge and cross charge have a MOP
NO
Height limit for evaporators away from condensing units
20 feet
Hot gas bypass line sizing should not exceed a
6-12 psi pressure drop
Bypass pressure activation
58 psig
How does hot gas bypass valve open
Open of differential pressure ORD
When using hot gas bypass for capacity control what must be used
De superheating TXV is liquid injector valve
Should hot gas bypass line be insulated?
Yes
Is hot gas bypass the last unloader
Yes
What kind of valve operates heat reclaim
Pilot operated valve
Are head pressure control valves necessary when using heat reclaim valves
Yes
Epr and cpr shouldn’t be together
More often than not
When does a CPR close
Closes on a rise of outlet pressure
CPR is normally?
Open
What amps is the cpr set for
FLA or 10% higher than RLA
Where is a CPR installed?
Always downstream of other control devices
EPR opens…
On a rise of inlet pressure
What is a common hold back valve?
An EPR
Can an epr be considered a 2 temperature valve?
Yes
What does an EPR maintain
A minimum evaporator pressure
Epr keeps a constant pressure
No it doesn’t
It limits the minimum evaporator pressure
Where must a EPR be installed
Upstream of all suction controllers devices
What is a hear pressure control also known as
A low ambient control LAC
Head pressure control helps…
Oil return to the comp
Prevent TXV hunting
OROA=
Headmaster
Head pressure control opens…
On a rise of outlet pressure
Head pressure control is usually used on temperature operated systems or pressure controlled systems
Temperature
Valve selection pressure drop should be in between…
2 abs 14psig
2 types of receivers
Flow though
Surge type
Receivers capacity and temperature
90% at 90F
How much % must a distributor be able to handle
50-200%
Oil filters must be mounted…
Vertically
At what pressure drop should you replace a filter?
40-50psig
3 types of oil separators
Helical
Impingement
Coalescing
Mixing valve mixed how many things
2
Diverted valve
1in 2 out
Direct acting solenoid valve is how small
1/4 or less
3 way solenoid valve/mixing valve
Heat reclaim
Split condenser and 2 more
Hot gas defrost
Pilot control valve
3 types of desiccant
Loose fill
Compressed beads
Solid core
Adjust clockwise an epr what happens
Increase set point of valve
Clock wise on a cpr
In increases
