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HVAC

Module 2

term
On an open drive compressor the motor is separated from the compressor.
The suction valve closes in a reciprocating compressor when the piston reaches its lowest point.
Oil scoops can be found in a reciprocating compressor.
A rotary compressor has no suction valve but does use a discharge valve.
In some scroll compressors the internal discharge- temperature safety devices are actually valves that bypass refrigerant.
The motor drives the male rotor in a screw compressor.
The centrifugal compressor often uses multiple stages of compression to increase the pressure difference.
Open and semi-hermetic reciprocating compressors often use a cylinder unloading as a popular capacity control method.
The compressor displacement equals the rpm of the drive motor multiply by the piston displacement.
Scroll compressors have typically used a refrigerant bypass method to control capacity.
A screw compressor uses a method that provides capacity steps of 25%, 50%, and 75% by using a plug valve this is called simple capacity control.
Slide valves allow screw compressors to vary capacity from full capacity to as low as 10%.
Throttling valves are used for capacity control on a centrifugal compressor.
A failed crankcase heater could cause flooded starts.
Moisture in the system can cause freezage of the systems expansion device.
In order to prevent copper oxide formation you should purge refrigerant lines with nitrogen during brazing.
If a three-phase compressor motor is single phasing about how many times above the normal running current value will be measured? X1.5
Internal line- break overloads are automatically reset.
A current-transformer monitors current in a single-phase compressor on the common lead.
High and low pressure safety switches are installed in series in the compressors control circuit.
A differential pressure oil safety switch is used on semi-hermetic compressors.
A dirty condenser coil may be a condition that causes a compressor motor's overload device to open.
The system condition that can cause the vapor returning to the compressor to be super-heated beyond normal is an un-insulated suction line.
The maximum voltage imbalance allowed for a three-phase system is 2%.
RLA is the unit nameplate value that should be consulted to compare the measured compressor running current.
Created by: rosi_23
 

 



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