Hey folks, let's start a discussion on your basic split system.

You all make me jealous with measuring SH or SC on cold rooms and chillers and being able to fine tune them with refrigeration fundamentals, but let's take a look at a basic split unit for comfort cooling:

It has a capillary after the condenser on the outdoor unit that feeds a partially expanded liquid to the indoor unit where it evaporates in the coil, and depending on pipe run, may or may not completely evaporate before returning to the outdoor unit. They chuck in an accumulator to mop up any liquid. They will come pre-charged for pipe runs up to 50m, but you may only have a 10m pipe-run.

Some of the very basic units will give you 1 access point for gauges on the suction valve on the outdoor unit.

A typical check for good running would be air-on/air-off temperatures on the evaporator with a delta-T of 12 to 14 degrees, and ensuring a suction pressure above freezing. (hopefully) In fact, some technical help desks tell you to ignore the pressures and work on temperatures only.
We all know that on critically charged systems, when performance is lacking, (after checking good airflow) we first do a "pressure test" and weigh out the charge and see if anything has been lost.

In general if the evaporator off-coil temperature is below 10 degrees in cooling I am happy, and if the heat rejection outside is in the 30 degree range (fixed speed compressor) I am happy. [Depending of course on ambient]

So the question is, do I need to get more technical with my measurements? Would trying to measure a subcooling value off the outlet of the condenser tell me much? The superheat values can vary so much.

Before answering, please remember I am talking about a BASIC BASIC split system. No EEV's, no inverter driven compressors, but I will allow you a condenser fan speed controller!