Unloader

[Abe]

Would anyone care to offer some spiel on unloaders, the ones fitted on the head part of compressors

I see them installed on the compressors I work on, but Ive never had to commission one, ie: set the pressure switch settings, etc

I know they kick in on start up, apart from that Im green on this subject

Ok........who said I was an ace tech anyway? But Im getting there............. ( with your guys help!!)

[reggie]

Most internal unloaders in the cylinder head are operated by oil pressure which lifts the suction valve ring plate from its seat via lift pins. Once the valve is seated then the cylinder can seal. If the valve is lifted off its seat then the refrigerant pressure is pumped straight back into the suction line hence no compression.

The oil pressure which is responsible for the seating of the valve is generally controlled by an actuator which can be adjusted
by the tension of its internal spring. This in turn moves a floating piston which fires the oil to each individual unloader in stages.

So the compressor is regulated by back pressure. The higher the suction pressure the more unloaders activated by the actuator.