Another air compressor question

Check your storage tank for an ASME Code label plate...it should be tack welded to the tank somewhere. The plate should have the letters "MAWP" and a pressure indicated on it. MAWP stands for "maximum allowable working pressure". If that is indicated to be 125 psig, then your safety valve HAS to be set at no more than this. You will need a reasonable margin between your normal operating pressure and the MAWP to avoid premature blowing or weeping of the safety valve. A margin of 25 psig is not uncommon for this purpose. My own compressor cuts out at 175 psig and my tank MAWP is 200 psig. I would not consider increasing that cut-out setting on my machine and I don't think you should either...not unless your tank is good for a higher pressure than 125.

You also need a certain differential between the cut-out and cut-in settings on the pressure switch. I don't recall what that typically is but your 25 psig would not be unreasonable. Your manual should indicate that. If that is the case, you are probably limited in getting your cut-in any higher and therefore closer to your cut-out setting without also increasing your cut-out setting...something you probably shouldn't do.

Rod