Compressor types

[hoadster]

This might sound rudimentary, but could someone please explain, in simple english the difference between Hermetic and Semi-Hermetic Compressors. I am not a refrigeration mechanic.

[Chunk]

Hi Hoadster

Basically a Hermetic compressor is a sealed compressor and a semi-hermetic compressor is a sealed compressor with service valves.

[Toosh]

HI a hermetic compressor is sealed in a welded casing, where as asemihermetic can be stripped and repaired

Norm

[750 Valve]

Just to expand - both types contain an electric motor connected to the compressor whicj is contained inside a pressurized shell.

The hermetic compressor is often called a "dome" as it looks dome shaped, it may or may not have servive valves attached - the smaller ones have no valves, the larger ones do, sometimes a hermetic compressor contains an oil level sightglass but more often than not they do not and are always splash fed in their oil system (no oil pump). Suction gas surrounds the motor windings and aids to cool the electric motor and stop it from overheating. A hermetic can be a reciprocating compressor, a scroll compressor or even a rotary compressor - hermetic refers to the fact that they are sealed and unserviceable.

A semi hermetic is also sealed as far as it still uses the suction gas to cool the motor windings, however all essential parts of the compressor are accessable for removal and repair - these include valve plates, heads, oil pumps and motor windings. Typically only reciprocating and screw compressors come in semi hermetic variants, I have never seen a rotary or scroll although they may well exist, there is no reason that they can't. A semi can be rebuilt from scratch if necessary including pistons, connecting rods and crank on a reciprocating comp and rotors on a screw comp.

Usually semi's come in larger capacities and hermetics cater for the smaller loads, although there are sections of the capacity range where they can cross over. I have included 2 pics, they ones on the left are hermetic, the ones on the right are semi hermetic

[Chunk]

Just to expand - both types contain an electric motor connected to the compressor whicj is contained inside a pressurized shell.

The hermetic compressor is often called a "dome" as it looks dome shaped, it may or may not have servive valves attached - the smaller ones have no valves, the larger ones do, sometimes a hermetic compressor contains an oil level sightglass but more often than not they do not and are always splash fed in their oil system (no oil pump). Suction gas surrounds the motor windings and aids to cool the electric motor and stop it from overheating. A hermetic can be a reciprocating compressor, a scroll compressor or even a rotary compressor - hermetic refers to the fact that they are sealed and unserviceable.

A semi hermetic is also sealed as far as it still uses the suction gas to cool the motor windings, however all essential parts of the compressor are accessable for removal and repair - these include valve plates, heads, oil pumps and motor windings. Typically only reciprocating and screw compressors come in semi hermetic variants, I have never seen a rotary or scroll although they may well exist, there is no reason that they can't. A semi can be rebuilt from scratch if necessary including pistons, connecting rods and crank on a reciprocating comp and rotors on a screw comp.

Usually semi's come in larger capacities and hermetics cater for the smaller loads, although there are sections of the capacity range where they can cross over. I have included 2 pics, they ones on the left are hermetic, the ones on the right are semi hermetic

Yep.Thats exactly what i was trying to say,but not in so many words:cool: