Service port location for sub cooling

[mjackson201022]

York split system condenser 10 ton single circuit tandem compressor.
I noticed the high side service port is located on the discharge of the compressor as opposed to outlet of condenser coil. I thought sub cooling pressures and temperatures should be read when the refrigerant is in a liquid state. I have also seen this port placement on packaged rooftops, is the only requirement when reading high side pressure is that it is after the compressor and before the metering device? Does it matter that pressure is read when the refrigerant is in a high pressure vapor state as opposed to high pressure liquid so long as temp is read at outlet of condenser coil?

[supers_5]

There's a few psi drop over the piping and Condensor. Usually not enough to even subtract from your readings, since it's under 1%

[jayguy]

Typically, the pressure drop is not going to be much, unless you have issues like: overcharge, undercharge, non-condensibles, mixed refrigerant, dirty coils, changes in refrigerant flow rates (multiple compressors, unloaders, bad valves, etc), low evaporator airflow, plugged filter/driers, metering device issues, etc. As long as you never have those issues, you won’t need a liquid line port.

[ehsx]

Commercial chillers may have 10-35 psid. Most smaller condensers have 3-10 psid. Check the ref tp chart and may be ~2* sat dif @ 10psid. Often the vendors will have charging charts instead of stating liquid subcooling number for charging. Would always add service ports if opening a system.

[Patech]

Commercial chillers may have 10-35 psid. Most smaller condensers have 3-10 psid. Check the ref tp chart and may be ~2* sat dif @ 10psid. Often the vendors will have charging charts instead of stating liquid subcooling number for charging. Would always add service ports if opening a system.

Agree. A 3-10 psi difference with r22 would be .7F-3F off. for r410 it would be 6.-2F off. so maybe you wouldn't charge by it but you could get a rough idea if there was adequate subcooling.