I am working a system with a 3o ton trane chiller with 2 chilled water pumps in parrallel. It has a standard m&m paddle type flow switch on chilled water loop. The bas monitors pumps with current sensors and shuts off chiller call if no chw or cond pumps. The flow switch is part of the actual chiller control. We just replaced it several months ago. the switch failed today not so much a paddle issue. This chiller is very critical for a rare books area(humidty/temp control). My question what other options do I have that may be a little better more reliable. I understand I have seen this style flow switches 20 years old?? The customer is always trying to improve things. I was thinking diff pressure. also the pumps are on hand off auto switches.the way we are runnig them now is pump is on hand valve open while the backup pump is off with valve closed. we rotate bimonthly. I have suggested switching them automatically. thanks for your input.