×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

Chillew water pump
2

Chillew water pump

Chillew water pump

2
Secondary pump speeds should modulate in response to the remote secondary loop differential pressure signal. The set point will need to be refined after testing and balancing, but 10 psi is a typical starting point. The differential pressure signal is typically measuring the pressure difference between the chilled water supply and the chilled water return at the point in the secondary loop that has the greatest pressure loss between it and the secondary pumps.

RE: Chillew water pump

Ideally i would place the DPT at the farthest unit in order to get the real picture at the end of the loop. and you can do testing from time to time and try to reduce the speed of the VFD as long as you dont go below your minimum delta P at the farthest unit  

RE: Chillew water pump

(OP)
can you please let me know what will be my pump setpoint (psi) if I have 30mAq total head?

Also the diff. press transmitter will give signal to VFD to modulate the pump water flow? or pump will modulate base on temperature difference?

RE: Chillew water pump

(OP)
How to find the value of Differential Pressure Transmitter that will give signal to VFD to modulate?

Thanks in advance.

RE: Chillew water pump

The set point for the differential pressure must not be too high or control valves will not close properly and pump energy is wasted. Too low and some units will not have adequate performance because the control valve can't accurately control the required flow to maintain the air-side set point.
To begin with, look at the unit closest to the sensor. Estimate the pressure differential through this unit's coil, control valve and piping to and from the header. Assume the control valve is 80% open at maximum design flow. This amount is the pressure differential needed at that unit. Use that value as a starting point. If possible, test, adjust and balance the entire system and refine the set point as needed.
 

RE: Chillew water pump

(OP)
Misterdonut,
When you say estimate the pressure differential through the units coil, control valve and piping to and from the header - does it mean the Total Pump Head?

If I have 30m Aq (~100 ft of water) total pump head does it mean that is my diff. pressure sensor setting?

Thank you in advance.

RE: Chillew water pump

The differential pressure at the remote sensor will not be the same as the pressure developed at the pump because of the losses between the pump and the remote sensor.
The head required at the pump must overcome the losses in the supply and return piping as well as the losses through the control valves and coils. Some units are near the pump, so the piping losses between the pump and these units is lower. Some units are far from the pump, so there is more piping, and thus more piping losses, between the pump and these units. Each unit needs a certain amount of pressure differential between the supply and return piping so that water will flow through the control valve and coil. The set point to be maintained at the remote sensor must be enough to overcome the losses through the most remote unit.

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources