Hi all I am just posting to ask if there are any refrigerant pressure charts out there that will tell me what pressure a certain gas should be running at for eg a cold room on 134a.. I know from going of my pt chart 0 deg is 28psi but im just not sure on what the head pressure should be runnning at? and I know all systems will be different but is there a rough guide to go off? any help would be good thanks