More on variable flow piping

Engineers are doing everything to save energy for their clients by selecting the most efficient pump with the most efficient motor. These are responses to several questions that were not addressed during the live webcast.

By Kevin Anderson, Senior Technical Training Specialist, Grundfos Pumps Corp. December 2, 2014

Several additional questions were left unanswered at the conclusion of the webcast on Sizing Variable Flow Piping: An Opportunity to Reduce Energy. Below are the most common questions and their respective answers. 

Question: How did you generate an accurate cooling load profile?

Kevin Anderson: Trane TRACE or Carrier Hourly Analysis Program (HAP) can be used to develop the load profile. The information will be based on the location and design of the facility.

Question: Can you go into more detail into the back flow when using old three-way valves in variable flow piping?

Kevin Anderson: Three-way valves are designed for equal pressure in constant speed/constant volume systems in zoned applications with a bypass. When switching to a variable speed/variable volume system, the bypass is not needed. Once the bypass is disabled, the back pressure may lift the old three-way valve off the seat. Flow that should go to the return could go backwards through other zones depending on design.

Question: When would you use copper pipe versus steel pipe?

Kevin Anderson: In closed loop systems, either copper or steel piping configurations can be used. In open systems for potable water, copper piping is recommended.

Question: Can you really install two Alpha or Magna pumps in parallel? Can this work?

Kevin Anderson: Two Magna3 pumps can be mounted in parallel and can be configured to run at in alternating operation, backup operation, or cascade operation using either constant pressure or constant curve modes.

Question: The difference price between 3- and 2.5-in. shouldn’t that much that the smaller size to be selected. We want to use the pump and piping for the years. So for some example as such, we have to choose the bigger size. Is that right?

Kevin Anderson: The cost differential between 3- and 2.5-in. copper tubing can be $5/ft. This could result in substantial savings. As mentioned in the webinar, systems rarely operate at peak demand, making the smaller pipe a good choice in variable speed/variable volume systems.

Kevin Anderson is a senior technical training specialist at Grundfos Pumps Corp., Olathe, Kansas.