Variable flow chilled water system
Variable flow chilled water system
(OP)
Hi friends,
I am currently designing a campus cooling system of about 8000 tons.I intend to use distribution pumps of following capacity:
a)2nos varaiable speed drive pumps each of 3350 gpm@ 200 ft head(eqvt to 2x2000tons based on a delta T of 14.4F)
b) 1 no constant spped pump of 6700 gpm@ 200 ft head(eqvt to 4000tons based on a delta T of 14.4F)
How should I control the speed of Variable speed pumps when both variable speed drive and constant speed drive pump are running? I see that in such an event both pumps will be developing different heads.How will it affect overall ssyetm operation?
Any advice will be appreciated.





RE: Variable flow chilled water system
For my chillers i have to maintain a designed flow of water.
If you want to use varible speed pumps you should go through a heat exchanger.Then you can use return water temp to control water flow.
hope this helps.
RE: Variable flow chilled water system
RE: Variable flow chilled water system
RE: Variable flow chilled water system
RE: Variable flow chilled water system
RE: Variable flow chilled water system
For parallel pumping to a common loop, your pumps should all be of equal capacity. Control sequence should be as follows - Start and run one (say P1) to control loop D/P. When P1 reaches >95% for 5 minutes (give or take), reduce P1 to minimum speed, start P2. Let P1 and P2 ramp together. When P1 and P2 together reach >95% speed for 5 minutes, ramp down P1 and P2, start P3. Then P1, P2, P3 ramp in parallel. Unload the pumps by reversing the sequence when pump speeds drop to a given setpoint, say <45% for 5 minutes.
If the pumps are supplying different loops, different sized pumps are fine, but parallel ops (I believe) mandate equal sizing.
RE: Variable flow chilled water system
Another arrangement, which I like, is to have unequal pumps, sequenced according to load, running one at a time. This allows the smaller pump to be selected with a lower head to match the system requirements at lower loads. Saves big bucks on pumps and on motor energy also.
RE: Variable flow chilled water system