Ok, here it is. I was working on a Scotsman ice machine remote nugget. Changed the compressor on it, checked pressures and watched it make ice a bit and then left. A month or so later one of our other techs went out to look at it again because the customer said it was frosting. This technician only put his gauge on the low side and saw that suction pressure was high. I dont know what that was but he said he adjusted the txv but that we needed to replace it. They sent me back with new txv and I turned to machine on and diagnosed it for myself before just changing the part because that is how I was taught.
Upon start up I saw about 40psi suction and about 250psi head (404a). As it ran over the next 15 minutes the head pressure slowly started climbing to 320psi. At this time it was about 85 degrees ambient on the roof where the condenser is. I didn’t see any sub cooling and given the ever rising head pressure, decided I needed to go upstairs and check the head master. At 85 degrees the head master was bypassing about 25 degree difference between liquid line input to headmaster and liquid line out put from head master.
At this point I called my boss to let them know my findings and that the expansion valve was operating nominally, and that maybe we should wait for a new headmaster. Boss said just change the expansion valve.
So I changed the expansion valve and low and behold the same head pressure issues showed up upon start up. At this point it was 92 ambient and the headmaster had the exact same delta t across all input and output that it did before.
So, if you have made it this far, my question is this: is there anyway that the head master could have caused the frosting issue in the first place?
I’ve been doing this for a couple years now and am very hungry for any info you super smart peeps can give me. Thanks
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