I should have asked whether it was on switch leveling or off switch leveling. Most off switch leveling causes a fault if both LU and LD are sensed at the same time. What kind of building is this? Office, apartments, doctors? Are there cleaning or maintenance people in the building doing something? Is there any other traffic in the building on the weekend? I know it is difficult, but could it be checked halfway through the weekend to see exactly when it faults? If you have a shutoff valve in the machine room, cut it off and wait 10 or 15 seconds and see if the pressure falls off. It it does, then you will have a relevel every 5 minutes or so, and this may cause your problem.
