Water cooled AHU tripping on start of system

[reftec021702]

Dear fellows:

I had inherited an interesting problem from another technician: a system of 14 water cooled TRANE Axiom 5-ton AHU, many of which trip on system starting. 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 AXIOM units begin to come on line at 1 minute intervals, some of them keep working, but most of them tripping the lockout relay. I had to reset them once, sometimes twice, and they keep running normally. Interesting is the fact that this behavior occurs mostly on saturday´s afternoons, when the system is switched on after a week long rest. I had all the water filters cleaned, and the problem remains.
Any clue?

Thank you!!

 

[AbbyNormal]

Several things can trip the lockout, could be high pressure, low pressure, freeze stat etc. Need to find out what is tripping the lock out in the first place

Maybe water is not flowing, system is air locked.

Take the "V" out of HVAC and you are left with a HAC(k) job.

 

[AbbyNormal]

Assuming it is a heatpump that is

Take the "V" out of HVAC and you are left with a HAC(k) job.

 

[lilliput1]

Check the water temperature. Entering water temperature should be anove 45°F and below 85°G.

 

[imok2]

If there is a pump down system on these systems and the load is small on startup it may take some time to buildup head pressure in some of these units and they go out on low pressure. You should make sure the water supply to the condensers is warm enough to get the head pressure up high enough to provide a full head of liquid to the low side. You might try to delay cooling tower fan to get water up to at least 80-85 degrees. Cooling tower fans should be controlled by controllers in supply water

 

[atlas06]

Just speculating, but are you doing any kind of electrical load shedding on week-ends? may be simply not enough juice (electricity) at the time? does your circuit breaker trip?