Last September I change the full condensing unit on a cold room. System ran up fine, no problems at all. Christmas time the client went on holiday and emptied the cold room and left it switched off. When he came back 3 weeks later and switched it back on, it was tripped on LP. I went down, and sure enough no gas in it. Pressure tested over night and the pressure didn't budge at all. I was thinking maybe the leak could have been from the service valve, as I left my gauges on over night. So I put some of that red dye stuff in, replaced the valve caps with brass flare nuts and bonnets, vacced out and charged. That was mid January. Called into the place about a month ago, Room 2šC, sight glass full, everything looked good. Client went into Hospital 3 weeks ago, so again switched the system off. Client returned yesterday and again tripped on L.P. Iīve just got back from site. No gas in it again. No red dye anywhere, no oil anywhere.

Itīs got me puzzled as to why it only leaks when itīs switched off and why there is no dye or anything traceable? Anyone any suggestions?