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I am having a problem with a Soft serve ice cream machine that runs too long. It has an automatic expansion valave which is set for 20 PSI. The machine was originally charged with 502... I have retrofitted it with HP 80, (R-402A). I weighed in the correct charge and the machine will not shut off. The ice cream comes out a degree or two above the recommended dispensing temperature. How can it keep running without freezing up solid?
Never used 402A but from the book
Condenser discharge temp will go up and evaporating and condensing temperatures/pressures will not be stable.
Slightly higher operating pressure and glide effects.
Suggest reselection of the expansion valve and then re-check your conversion.
Who did the charge weight calculations? Is it simply overcharged... You can't always use the sight glass with blends especially ternaries.
Personally 404A would seem a better bet, it's not a drop in and the expansion valve would need to be reselected. POE lubricant required and check high side pressure components.
Terry, I too have used 402A which I have found to be an exceptional interim replacement refrigerant. You mentioned that you weighed in the correct charge... I always start out with no more than 70% of the original charge and watch the system for a full cycle if possible before adding additional charge should it be required. Many HCFC and HFC refrigerant manufacturers suggest that 80% of the original charge is normal for replacement but that is not always the case. Check your pressures and evaporator outlet temperature... I suspect you may be overcharged.Quote:
I weighed in the correct charge and the machine will not shut off. The ice cream comes out a degree or two above the recommended dispensing temperature.
R404A also operates with a glide, as did R502 but most tech's never knew it had one... it was never posted on the PT charts.
Keep us posted. ;) If you correct the charge and still have problems... post your findings... pressures, line temperatures, ambient, compressor amp draw -vs- rated, visuals, drier placement, sight glass condition, fan motor amps -vs- rated, condenser coil condition, filter condition if it has one etc, product temperature, etc.
Just a note.... HP80 was intended for ice machines and does run with substantially higher discharge pressures and temperatures.
In my opinion a better selection of refrigerant for this type of application would be R-408a... pressures and temperatures are nearly identical to R-502.
When compared to R-404a and R-402a you will find R-408a has the closest operating characteristics to R-502 than any of the other refrigerants, including discharge temperatures and pressures as well as being able to operate with a mineral oil charge. ;)
Cost is comparable to R-404a. Check it out for yourself... I think you will like what you find.
I have used HP-80 in several machines previously with good results. I went back to the job today and found the customer having problems with the auger motor overload tripping, yet the ice cream wasn't too cold. He said he had replaced the capacitors on the motor a couple weeks earlier. I found a 35 uF run cap where there should have been a 12.5. The start cap was wrong too. I changed them and it runs like a new one now! Chalk another one up for the do-it-yourselfers! Thanks for all the responses. I love this website!
I agree that R-408 is the best replacement for R-502. I have used it in Walk-in freezers, Ice Machines, and soft serve machine without problems
Most of the "interim" refrigerants are a real pain, particularly if the system isn't completely evacuated and re-charged (new sporlan drier of course)
Truman;)