Hello everyone,

My background is that I have NVQ level 2 in refrigeration and have been working as a service engineer for 12 years.

What is unusual is that I have only ever worked on environmental chambers. Never A/C never on refrigeration.

I work on R23 systems every day.

Other than touching on superheat and subcooling during college or FGAS, I never have to use them.

Diagnostics are different in my field. For example if the chamber has tripped it's low stage HP switch that means there's a problem with the high stage not working properly.

If the high stage compressor has frosted up, the low stage has lost all it's gas.

R23 is usually charged to a standing pressure and the high stage is charged to the sight glass.

I became a bit unsure of myself when I had to charge up a single stage R404a chamber...

Don't worry, I do know what I am doing it's just more common to work on cascade!

I cleared the sight glass and was looking for a box temp of -40'C but could get no lower than -32'C.

I just closed down the expansion valve to evaporate at a lower temperature and soon got -40'C.

What I'd like to know is what would be a more scientific way of doing what I did? what superheat/subcooling should I have been looking for?

It's all very well measuring these variables but unless you know what they should ideally be then the readings can be a bit meaningless.

cheers,

Cascademan.