mg test nov 2
automatic pump down systems are equipped with a what valve to prevent refrigerant from reaching the evaporator
solenoid valve
snap acting valve that open and close very fast with the electrical energy to the coil
solenoid valves
the one time relief valve is cased to relieve by
temp, hear or fire
what prevents the oil pressure safety control from DE energizing a compressor immediately after start up
time delay
define a king valve
valve that is at the outlet of the reciever with a diptube
what is a check valve
valve that only lets refrigerant to flow in one direction
random defrost is accomplished with
when the refrigeration system has enough reserve capacity to cool more than the load requirement
the refrigeration compressor motor can be operated at about what percent over its rated capacity without harm during this pulldown
10 %
what is the temperature range in medium temperature refrigeration
34 to 45
a suction line accumulator is used to ensure that liquid refrigerant enters the compressor
False
helical oil separators are about 98% efficient in separating oil
True
oil separation work on the principle of low refrigerant and oil velocity
True
the crankcase pressure regulator puts a limit on the pressure that can return to the compressor
True
two-temperature operation is desirable when more than one evaporator is used with one compressor
True
refrigeration systems are designed to operate year round for this reason they are equipped with
a low ambient control
where is the refrigerant sight glass normally located
after the filter dryer in the liquid line
which of the following is another type of low ambient temperature head pressure control?
air volume control using shutters and fan cycling
frequently on smaller condensing units, one fan will run continuously and the other fan will be cycled on and off
ambient temperature controller
the normal position for a suction service valve during normal operation
back seated
how does the receiver ensure that only 100% liquid refrigerant enters the liquid line?
by means of a dip tube
orit is what kind of valveq
cpr valve
to protect the compressor during periods of hot pull down, a what valve is used
cpr valve
what is the crot valve also called
cpr valve
what valve is a mechanical control that keeps the refrigerant pressure in the evaporator from going below a predetermined point
epr valve
what are the two forces that contorl the epr valve
evap pressure and valve spring pressure
which of the following is a type of low ambiet temperature head pressure control
fan cycling
list 5 methods of providing low ambient controls for refrigeration units
fan cycling, fan speed control, condensor splitting, condensor flooding, air volume control
defrost using internal heat is accomplished using
hot gas from the compressor
what does a cool liquid line filter dryer indicate
its blocked
what is the crank case pressure reg valve used for
keep the low temperature compressor from ovberloading on a hot pulldown
where is the refrigerant filter drier found
liquid line after the king valve
list four causes of liquid floodback
low evap loads evap fan frozen dirty evap coil evap fan not operating
to protect a refrigeration compressor when refrigerant loss occurs
low pressure control
the epr valve is installed in the suction line at the evaporator outlet and it?
modulates refrigerant vapor to the compressor. prevents the boiling point in the evaporator from dropping below a pre set point and when used with a tx valve the system has the characteristic of maintaining a constant superheat and keeping the pressure from going to low
two temperature operation of a refrigeration system is necessary when?
more than one evaporator is used with one compressor.
crot is special why
needs ammeter to adjust it
the spring loaded type of relief valve is normally brass with a what seat
neoprene seat
formula to remember
oil pump discharge pressure - crankcase pressure = net oil pressure
how can you tell if your float is stuck open on the oil seperator
oil return line
two types of relief valves are the spring loaded valve and the what valve
one time or fusible plug
epr valve are also referred to as what valve?
ori valves
what valve is used as a epr valve
orit valve
low ambient control valve
oroa valve
when a system pumps down, where is the refrigerant stored
receiver and the condensor
