Notes Flashcards
If an oil pressure control should open due to lack of oil pressure, the voltage reading across the L and M terminals would read, if the supplied control voltage were 240v
a) 240v
b) 120v
c) 0v
d) 24v
a)
During evacuation, when should the gas ballast on a vacuum pump be closed?
a) only be open during venting of pressure from system
b) closed as soon as vacuum starts to pull
c) has no effect on operation
d) closed near the end of the vacuum process
d)
How to check if your level is level?
Use high point of floor
Open the gas ballast on your vacuum pump until the system reaches?
1000-3000 microns
What do you do to your vacuum pump when you go on vacation?
change oil and top it up higher than regular
Which is thicker?
valve plate gasket or cylinder head gasket?
valve plate gasket
What is the way to clean up the water lines in a shell and coil water cooled condenser?
chemicals only
Start sequence for a water cooled condenser AC unit?
Fan, water pump, compressor
How to cut capillary tube?
use a file and bend to break tube do not damage inside diameter
Name the four types of distribution duct systems
Radial
Extended plenum
Reducing trunk
Perimeter loop
Name 5 types of nonmetal ducts
fiberglass
urethane
plastic
sheetrock
textile
True or False? It is illegal to put screws in duct work
True
What is the R value used to describe?
rate the thermal resistance of insulation materials
The higher the R value, the ________ it is for heat to pass through the material
harder
If walls are made up of different materials, how is the R value calculated?
Each material’s R value is added to create a total R
The amount of heat that will pass through 1ftsq of material 1’’ thick in 1 hour when the temperature difference is 1F is known as ?
Thermal conductivity (K value)
High __ values indicate high rate of heat transfer
K
Amount of heat that will pass through 1ftsq of material that is NOT 1’’ thick in 1 hour when the temperature difference is 1F is known as?
C value
What is the difference between C and K values
K value is based on material that IS 1’’ thick.
C value is based on material that is NOT 1’’ thick
How to determine thermal conductance?
Find on chart and divide K value of each material by its thickness
When the compressor has adequate oil pressure the contacts between L and M are
a) open
b) closed
c) closed then open
d) open then closed
B
A term used to rate vacuum pumps is used to describe the pumps ability to draw a vacuum. Pump must create a vacuum within itself that is lower than a system, so that gases will flow from system to the pump. Point at which the pump can no longer create a pressure difference is the
a) dead head pressure
b) blank off pressure
c) blocked tight static pressure
d) point of no pressure difference
b
An imperial gallon of water weighs
a) 8.33lb
b) 10lb
c) 62.4lb
d) 64.2lb
b
Superheat is bad and only for mainly protecting?
compressor
Low ambient conditions lower head pressure which means less push of liquid into which component?
metering device
1deg of subcooling gives ___ more liquid and more cooling.
0.5
What is the liquid to vapour ratio in evap?
75 liquid to 25 vapour
Which type of oil is most hygroscopic?
A) POE
b) Mineral
A
Minimum and max air velocities and what will they cause if they are above or below the minimum requirements?
Between 20 to 65 FPM
- less than 20 you get stratification
- more than 65 you get drift
List four types of propeller fans;
- ___ disk
- ____ wheel (axial flow)
- ____ axial (spiral discharge)
- ____ axial (laminar discharge)
- fan disk
- fan wheel
- tube axial
- vane axial
What does laminar mean?
straight flow
List four types of impeller or centrifugal fans?
- backward inclined
- air foil
- backward curved
- forward curved
- radial
- fan wheel
What colour is a R22 bottle?
Green
Which refrigerant is a replacement for R12?
R-134A
What colour is a R507 bottle?
Teal
What colour is a R-410A bottle?
Pink
What colour is a R-134A bottle?
Blue
What colour is a R-404A bottle?
Orange/Red
Sentronic Oil Failure
Oil pressure differential falls below this range it will cut out the control circuit and open contacts L-M
7-9psig
Sentronic oil failure control will trip due to lack of oil pressure once the time delay has been reached - how long is this delay?
120sec
some manufacturers it is 90-120sec
When oil pressure rises above this range it will close the sensor (cut-in)
12-14PSID
PH Scale neutrality number & acidic high or low?
Neutral = 7
Under 7 is acidic
Name three types of copper, which is the most common?
K - heavy duty
L - Medium duty (most common)
M - light duty
Speeding up a compressor?
Decrease driven or increase drive
Inside (boat) of pressure enthalpy chart indicates the refrigerant is in what state?
Change of state (saturated)
Upper right of pressure enthalpy chart indicates the refrigerant is in what state?
Superheated vapour
Upper left of pressure enthalpy chart indicates the refrigerant is in what state?
Sub cooled liquid
Which desiccant has the best ability to remove acids in a refrigeration system?
a) methyl alcohol
b) activated alumina
c) molecular sieve
d) desiccants do not remove acids
B
If a refrigeration system is low on oil as well as low on refrigerant which would you add first?
a) oil
b) refrigerant
c) does not matter
B
Silfos melting temperature?
1100F-1400F
Oxy-Acetylene flame temperatures?
Up to 5400F
Acetylene (B tank) flame temperatures?
Up to 3000F
Approximate height of a thermostat?
5ft
Paragon Mechanical Defrost Clock
What load (s) are connected to the normally open contacts?
Defrost heaters
Paragon Mechanical Defrost Clock
What load (s) are connected to the normally closed contacts?
Compressor/Evaporator fans/Condensing unit
Where does line power go on a 208/240v mechanical defrost time clock?
To the Timer motor and each side of the NO and NC contacts
What is X for on a paragon defrost time clock?
X will terminate based on pressure or temperature (depending on control used)
What happens if Defrost X terminal is not used?
Defrost will terminate on time set only, not pressure or temperature
Paragon Mechanical Defrost Clock 208/240V
Explain Terminals 1,2,N
Terminal 1 + 2 are electrically connected and represent L1
Terminal N represents L2 on a 208/240v clock
Ideal evaporator superheats in low, medium, and high temp?
low: 6-8F
medium: 8-10F
high: 10-12F
Ideal compressor superheat for medium and low temperature?
25-30F
On a split heat pump, is O energized in cooling?
Yes, in Canada we fail to heat (disconnect O and it should switch to heating)
Are heat pumps in Canada conventional or non-conventional set up?
NON-conventional
