Superheat For Troubleshooting

[phxhvac]

According to the Sporlan bulletin on PT chart for troubleshooting purposes. Taking superheat to troubleshoot a system with refrigeration related problems, iced coil, warm box with working compressor etc. When is the proper time to take a superheat reading for troubleshooting? Before de-icing a partially iced coil, or a box that is pumping but not cooling properly, partially clogged cap tube, system capacity problems etc. Just s little confused, any help would clear things up a little.

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[welling service]

You can measure superheat any time you want but in the end you want to set the superheat when the box is close to set point. I have had people call and say my walk in freezer is running but never gets cold enough so one of the first things I do is visually inspect the system and determine if the coils are clean, fans running, system is fully charged and check compressor superheat. If I find it to high than I start lowering it and watching my gauges and the box temp until I get it where it is supposed to be and the box temp is at set point.

[phxhvac]

Thx!

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[J_Bridge]

Welling service is correct, box needs to close to temp. 8-10 frz and 10-12 on coolers, but make sure that at your comp you are no lower than 25 degrees. That is a coprland spec, you can go 20 but not really a good idea.

[spliskin]

but make sure that at your comp you are no lower than 25 degrees. That is a coprland spec, you can go 20 but not really a good idea.

Why is 20 not a good idea? Would you explain that some?

[J_Bridge]

I will find out. I know this is to ensure all the refrigerant is boiled off, but will get more details.

[J_Bridge]

Ok here it is. 20 degree superheat at the compressor during a load situation and no lowere. This ensures that at night under low load we still have superheat at the compressor and not a saturation point(liquid)

Another key is dicharge line 6 inches off compressor should never be greater than 225 degrees, this ensures that the head of the compressor isn't above 300 degrees (the point at which oil breaks down). May need to adjust superheat to keep discharge line below 225 degrees.