chiller barrel dp

[mjm54]

Have a problem with low dp across barrel, dp switch wont make to start chiller. pump pressures 75lbs discharge 13lbs suction. only 4lbs dp at barrel, 5 story building. aaon chiller. found gycol pump not operational. pumped glycol in system with aux. pump suction side of pump went from 2lbs to 13lbs. still no change in dp across barrel. any ideas ?

[HvacCraftsman]

If the pump isnt passing enough water then the dP will be down.
Use the same guage on both inlet and outlet.
What is the Chiller design GPM and Pump Design GPM
Is the 4' the required minimum DP, or the design DP?

[klove]

What's your dp and GPM supposed to be? Where is the pump in relation to the building and chiller? What is the design head of the pump? At what GPM? You're makin' 143 ft of head (+) across the pump now (assuming your readings are correct). That's a fairly stout pump if this is nothing but a commercial a/c application or something of the sort.

[Shophound]

Is the chiller actually measuring DP via transducers or the like to determine if there's enough flow? Or is there a separate flow switch? Reason I ask is if so, could be something fouling the transducer, causing it to read low. Transducer itself could be reading low (if that is what the machine has).

Have you used a separate gauge to measure delta P...are there PT plugs on the inlet and outlet piping for this purpose?