Refrigerant high side vs low side

[MidStateVending]

I am Type I certified, and occasionally add 134a to drink machines... but they don't teach you about vending machines. Sometimes it is hard to distinguish high vs low side copper tubes.

 

Is there a way sure wat to tell on these Dixie Narco machines?

[lacanteen]

Since the Dixie Narco units are a cap tube type system, you pretty much have a suction line and a cap tube. Most techs add a shrader valve to the short stem that isn't used for anything. You're not going to get any high side info. 

[AZVendor]

On soda machines you only tap and attach gauges to the low side as LA said.  The low side runs on the larger tubes in your system.  You don't want to tap any tubes inside your cabinet.  The factory fill stub is the best place to tap but a suction line is fine.  The low side pressures should be between 18-20 lbs when your fans are running, the condenser is clear, you have low to normal ambient temperatures and your cabinet door is closed..  Colder ambientswill run 18 lbs and hotter ambients will run 20 lbs.  Don't overcharge above 20 lbs.  If you add gas and the low side doesn't change at all or goes up and back down you probably have bad valves.  

[MidStateVending]

So everything you said is contrary to what I have been doing for years. I never seen a factory tap (that would be convenient) . Also there are some 'fatter' tubes connected to the smaller tubes I tap, but they always end up being high pressure. 3rd, I was always told to pressure up to 10-11. I have never gone beyond that and seems to be enough. I guess I can try 20psi and see what happens.

[AZVendor]

Some moron gave you incorrect pressures. Only non-evaporator machines like Antares junk runs 10-11 on the low side.  Forced air-over evaps in medium temps run 18-20 and leaving them low on freon is what causes them to ice up.  1/4" tubes that reduce to capillary tubes are high side and you should not tap those.  The factory fill stubs are the ones that are pinched and brazed shut.  On DN stuff they are long enough to put a saddle tap on.  Vendo stubs are usually too short for that.