WATER CCOLED AHUs TRIPPING ON START

[refpro021702]

Dear fellows:

I have inherited a problem from a friend tech: a system of 14 TRANE AXIOM water cooled 5-ton AHU´s, most of them tripping on system start up. The sequence of the problem goes as follows: water pump starts, flow established, 10 minutes later cooling tower No.1 starts, 5 minutes later cooling tower No. 2 starts, then the AHUs start at one minute intervals, most of them tripping the lockout relay after a minute or so. I need to reset them once, some times twice, and they keep running OK. One interesting fact is that this behavior is observed mostly on saturday´s afternoons, when the system is turn on, after a week long rest. Any clues?

Thank you!!

[slimwoodie]

what is the HP, and the water temp at this time ...??

[Airmechanical]

you may need to adjust your water flow sensor to stay open until verified full flow is established!

are your condenser coils scailed up?



.

[absenceofheat]

what else is wired inot the lockout circuit ? too check for scale do a approach on the condenser.

[jimbob73]

Run loop pumps manually 24/7 and see if problems goes away. Units may be trying to run with no flow present.

[madhat]

Do you have Auto Vents in the system? One or more of them could be leaking air back into the system during the down time. Air bound coil trips the units out, till it's expelled. Our EnerCon & McQuay heat pumps were doing this after a new control system was installed. Everyone looked at, blamed the new controls. Running the system in "Hand" before had masked the problem. Had someone put the system in standby, while I went above the ceiling to find the defective Auto Vents.