CK-30-C16 Float valve / TXV / 134a conversion

Wow thanks for the great pics! I have so many questions!
It appears those are 2 different machines. What models are they?
Looks like one is a cap tube and one a txv?
Did you do a suction line restrictor?
How do they sound?
How long since the conversion and are they everyday user?

Very interesting! I guess you are using the original mineral oil? How much superheat are you maintaining with the txv valve? I have blown up part of your picture and can't figure out what this is. It looks like a weird Everdure tube that is coming out of the float tank, but it seems to have two very small copper tubes coming out of it. I am confused. Seen a lot of MT but not this 

That is to a large extent the way it came from the factory; I added a "T" in the float outlet tube to connect the TXV outlet tube.

The base of the float chamber has/had:
1) A larger than usual Everdure with a square cross section tube wrapped around it many times as a heat exchanger from the cold evap suction line to the warm valve base (incoming liquid).
2) The valve outlet tube going to the evap inlet.
3) A process tube next to it connecting the float chamber (not the valve itself) to the accumulator tank on the evap, crimped by the factory after evacuating and charging. 
This would have provided a path to allow the low side to evacuate using only the high side float tank service fitting.
This is a technique I have seen on GE refrigerators up to the date they stopped making their own compressors and started using Tecumseh.


Yes it's the original mineral oil, I've heard somewhere it's a bit thinner and contains the secret additive "Magic", so wherever possible I try to use it without mixing in anything else. 

The superheat is pretty small, the sensor bulb is only about 2 inches from the evap.  Basically I turned it as low as it would go and backed it out a half turn every few hours until I got a full frost pattern on all the refrigerant passages on the evap.  The last to fill in were the center passages below the accumulator, on the inside of the evap.  Then I turned it open an additional 1/2 turn, to allow for changes in loading, warm food, ice trays, etc.   Then watched the suction line to be sure it wasn't frosting back toward the compressor.

I pretty much assumed I would have to do some mucking around with it, several tries to get it right; the factory setting wasn't going to do it.  They somehow neglected to include instructions for G.E. SO2--134a conversions in the package.
I installed the adjustment fitting and a low-side service valve in a small panel at the front, so I could service just by opening the door instead of lifting the unit.


Some details on setting charge and superheat with TXV:

The TXV system won't show a slight low charge the same way a capillary or float system does (dropping frost line); the TXV will try to keep the frost line where it is set by superheat, as much as it can, by passing some gas (since there's a shortage of liquid).
So low charge will appear as less or no frost accumulation on the tube from the TXV to the evaporator, and on the first refrigerant passage of the evaporator (since they will be a bit warmer from the gas entering the evaporator from the TXV).
So full charge will be frost accumulation from the TXV discharge port to the frost line on the accumulator.
Theoretically you could charge until the receiver is nearly full, a great surplus, but if the TXV passes any liquid during the off cycle the evaporator will flood back to the compressor on start-up.  So in my opinion less is better.

Liquid refrigerant flooding back to the compressor makes a characteristic quite audible sound that I will describe as sort of like the sound of marbles rolling around in the bottom of a coffee can.  Not really, but you get the idea.

If the sound occurs immediately on start-up, the charge is leaking into the evaporator during the off cycle.  Smaller charge is called for.

If the sound occurs several seconds after start-up, the superheat is set too small; it's taking several seconds for the TXV bulb to respond to the suction line temperature.  Turn superheat adjust a half turn at a time and let it run to normal temp and try again.
(Setting to too little superheat is more pronounced if you let the unit go to shutoff and then turn off or unplug for a half hour or hour before restart.)

No, just coincidental positioning of parts in the space available.
The low side service valve is connected to the stub from the (previously) crimped process tube, so is connected to the accumulator tank.  You can see it as the dark tube hidden in shadow in the top of the pic going toward the back.
The large alumina block filter dryer serves as the liquid receiver, and feeds (filtered) high pressure liquid into the TXV.  It keeps the condenser and deck tube loop empty of liquid, just like the float valve used to, so the full condenser surface is available for heat exchange instead of partly filled with liquid like with a capillary system.  It is wrapped with 1/4 inch thick closed-cell foam insulation so it doesn't transfer high-side heat into the cooled space.  I tried it both ways, it didn't make any measurable difference in cycle times, but still seems like a good idea to insulate it.

Picture showing parts placement:

Placement of sensor bulb for TXV on suction line (wrapped in closed-cell foam insulation):