head pressure

[wirerunner]

im just learning about hvac not for work but because its the only trade that i haven't done as a job and love to learn new things my question is what is head pressure and what should it be in commercial units (10-15 ton units) how do i find this out im looking for a night school to eventually go to probably ittech again all answers would be appreciated

[rango]

Roughly the same as it would be in a 2 to5 tonner.

[jdenyer]

Head pressure depends on type of refrigerant used, it's application ie high, medium, or low temp. Also depends on ambient temp if air cooled condenser or water temp if water cooled condenser, whether or not the condensor is clean etc, etc, etc.

[airworx]

just remember this, you cannot charge or diagnoses systems with pressures. because pressures do not tell you how much liquid is in your condenser or how much superheated vapor is exiting the evaporator or actually how much liquid is in evaporator.

ill give you an example. say we have a low suction pressure with a normal head pressure. so whats wrong. low on charge, restriction, dirty evap coil. we don,t know. so we look at our subcooling and superheat and that tells us whats wrong. like a small liquid line and low charge. indicated by high superheat. study refrigerant circuits and youll pass most techs within a yr.