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Types of compressors rotary vs recip - OLD fridges

ChrisJChrisJ Posts: 3,232Member ✭✭✭
I'm curious what the advantages and disadvantages of reciprocating and rotary compressors are?



As many know, I have been restoring two 1930s refrigerators for a while now and I've studied everything I can find on them.



One thing that had me wondering for a bit was why GE switched from SO2 to methyl formate for 2 years and then back to SO2. From what I've found it was due to non-condensibles causing problems due to moisture breaking the refrigerant down. This lead to service calls where repairmen would "bleed" the system and let the non-condensibles out without letting much if any refrigerant out. Either way it lead to angry customers.





What I don't understand is why GE used reciprocating compressors with SO2 but used a rotary design with the methyl formate.



I'm hoping someone may have an idea why? What I can tell you is SO2 is similar to R12 as far as operating pressures where methyl formate operates under a substantial vacuum on the evaporator side. My guess has been a rotary is better at low pressure operation but I have no clue honestly. Both use what appear to be called flooded evaporators where refrigerant flow is regulated with a highside float.



I have a 1933 and 1934 unit which are both methyl formate \rotary units and all I can say is I have never heard such a beautiful sounding pump anywhere else.



On a side note, both reciprocating and rotary compressors used on these have a unloader than holds the intake valve open until oil pressure reaches a certain point. This actually allows the pump to start with a high head pressure and I have personally tested it by unplugging the fridge for a second, allowing it to stop and plugging it back in. It started right up.
Weil-McLain EG-40 connected to 392sqft of radiation via two 2" risers into a 3" drop header and 2" equalizer. EcoSteam ES-20 Advanced Control for Residential Steam boilers. Rectorseal Steamaster water treatment Typical operating pressure 0.5 - 1.0 inch wc.

Steam system pictures updated 1/25/15.
https://picasaweb.google.com/thetube0a3/Boiler?authkey=Gv1sRgCImUxIqv9436MQ#

Don't push the envelope, eliminate it.
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