How to measure superheat and subcooling

[FEISTY]

Just a comment to " tonyhvacr " about soft soldering a speed valve on a refrig. system. Here in Chicago , code requires braze on any connection to a refrigeration system. If an inspector spots that solder, you're tagged and they pick the rest of the system apart. Relates to our code requirements for PRV valves on all refrig. systems mounted as close to compressor discharge as possible. It is an easy write-up violation these days. Inspectors look for " fake " PRV connections soldered on surface of piping. They carry pocket gauge and test to see if valve was pierced. Just a word of warning. Have a good day!!

[Crisbee]

Thank you Feisty for posting that I can't beleive people said as little as they did about tonyhvacr soft solder technic. It is code for a reason!!!!!!!!!! Soft solders can not withstand the pressures and temps related to HVAC/R systems. Yeah its no wonder he has to use soft solder. One short cut leads to another.

Just a comment to " tonyhvacr " about soft soldering a speed valve on a refrig. system. Here in Chicago , code requires braze on any connection to a refrigeration system. If an inspector spots that solder, you're tagged and they pick the rest of the system apart. Relates to our code requirements for PRV valves on all refrig. systems mounted as close to compressor discharge as possible. It is an easy write-up violation these days. Inspectors look for " fake " PRV connections soldered on surface of piping. They carry pocket gauge and test to see if valve was pierced. Just a word of warning. Have a good day!!

[nike123]

Although brazed joints offer higher joint strength in general, the annealing of the tube and fitting that results from the higher heat used in the brazing process can cause the rated pressure of the system to be less than that of a soldered joint. This fact should be considered in choosing which joining process to use.

Than why brazing in refrigeration is prefered? Short answer is halocarbon-based refrigerants are incompatible with lead-based solders. They will eventually leak.

[santhoshtrv]

...if specific manufacture data not available some suggested settings are high temp 10-12*F SH, medium temp 6-8*F SH, low temp 4-6*F SH.
I think these are reasonable, as long as the suction piping runs are long (like supermarkets). If the system has short runs or has capacity control, I would tend to stay with the slightly higher values of 8-10 as a minimum range.

Having said that, and as stated by Steve, if you can control a minimum suction superheat (at the compressor) the compressor discharge temperature can be much lower, than when used with a higher suction superheat.

The discharge temperature is a good one to get used to recording. After you develop a feel for "good" temperatures versus "bad" temperatures, it can really help nail down the best superheat (suction or discharge) for the system operation.