View Full Version : delta t issue chilled water system

25-01-2017, 06:05 AM
need expert advise as i am facing issues with delta T attained in one of the site to which FM services are given

District cooling supplies chilled water with 6 degree differential(supply 4.5 and return:11 degree Celsius)

In my load side we are able to get approx 4 degree delta T only

Supply been on a average of 7.5 and return 11 degree

When referred O&M manual design which was noticed was to attain 23-24 degree celcuis supply air through AHU and FCU

Client instructs to attain 20 to 21 degree celcuis on supply air

could this possibly results in getting low delta T or is it due to some other factors

25-01-2017, 02:29 PM
5-6 degrees delta T is fine, check for clean water filters and flow.

25-01-2017, 03:57 PM
Remind client that the system was designed for 23-24 and not 20-21.

25-01-2017, 06:02 PM
Delta t is directly related to water flow rate

28-01-2017, 07:40 AM
Thanks a lot for response given

whether trying to achieve low supply air temperature(like 20 and 21) limits impact delta t or does it results in starving of chilled water at the index lines

28-01-2017, 07:45 AM
Strainers on our secondary side got cleaned recently .

Constrain is that district cooling team supply the delta t as per the contract in the range 5-6 degree differential

When it comes to our side conditions are not met(like able to attain 3 degree celcuis max. delta T).Also supply temperature to our building get served @ 7.5degree celcuis with district cooling side been 4.5 degree

could you please help me in explaining why we come across such difference

28-01-2017, 10:30 PM
Check and reset if necessary the chilled water flow rates through chillers, higher flow rates will reduce delta T, due to high tube flow rates and water dwell / retention time, lack of heat exchange.
You have OEM manuals which should have commissioning settings per chiller set.