Tag: primary/secondary

IPS® Retrofit: Discover the Simple, Effective Solution for Chiller Plant Energy Efficiency

Did you know that if your chiller plant features a primary/secondary (P/S) design, you are likely not operating at maximum efficiency?

With the introduction of variable speed drives in the 1970s, the P/S design was created to take advantage of the newfound ability to modulate flow with load and the added flexibility for chiller staging. At the same time, the system met the requirement for constant evaporator flow.

Quickly becoming the standard, the primary/secondary design continued to be used in new plant construction, even after microprocessor chiller controls unlocked previously unreachable efficiency gains in the 1990s. The main shortcoming of the P/S layout is that its cooling strategy is solely focused on the hottest day of year, creating inadequate energy efficiency for the remaining 364.

P/S bypass blending represents one of the biggest energy efficiency drawbacks of the P/S system because:

  1. Chilled water not used by the load flows through the bypass and blends with warm return water
  2. Blending decreases the temperature of the return water into the chiller, thereby lowering ΔT
  3. Chillers must work much harder than necessary to maintain the designated temperature setpoint

Find the simple, effective solution

Fortunately, these existing systems do not need to remain inefficient thanks to the tekWorx Integrated Primary/Secondary (IPS®) retrofit design. The IPS® retrofit requires only minor mechanical and control system modifications, a short installation time and minimal system disruption. The result? Major energy savings and utility rebates.

Key aspects of the IPS® retrofit include:

  • Minimizing bypass flow and associated return water blending that degrades system ΔT either by insertion of bypass valve or by controlling loop flow
  • Adding variable speed controls for pumps, fans and chillers, as needed
  • Adding new instruments to measure process variables affecting operation and efficiency (usually flow and kW) as needed
  • Using adaptive control algorithms for continuous online equipment adjustment

How the IPS® retrofit design provides maximum energy savings

tekWorx offers a unique blend of Approachable Expertise,® increasing operational efficiency and reducing energy costs while designing pragmatic solutions to meet unique client needs. As a result, the IPS® can be implemented in one of two ways:

  1. The most common application of the IPS® is via the addition of a valve that eliminates bypass flow and improves system control.
    The most common application of the IPS® retrofit is via the addition of a valve that eliminates bypass flow and improves system control.
  2. In instances where inserting a bypass valve is not an option – because it requires plant shutdown or other circumstances make this modification impractical – there is an alternative. Instead, tekWorx matches the primary and secondary loop flow to minimize bypass flow.
    tekWorx matches the primary and secondary loop flow to minimize bypass flow in an IPS® retrofit.

    For more information

    To see how tekWorx utilized an IPS® retrofit to reduce cooling costs by 28% at Chrysler’s North American headquarters, read our case study. Then contact us to discuss how our IPS® retrofit design can save money and earn utility rebates for your company.

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tekWorx Empowers JCI Client to Slash Operating Costs 68%



  • 480-bed private hospital
  • 75,000 ft2
  • Over 3,000 employees
  • (4) York chillers
  • 2,575 tons installed cooling capacity


  • Convert plant to Integrated Primary/Secondary® design
  • Reconfigure tertiary pumps to alleviate system pressure problems and eliminate wasted energy
  • Add VFDs to all building pumps to eliminate wasted pump energy
  • Design and install PLC based adaptive control algorithms to ensure maximum chiller loading, optimal control of all CHW pumps and proper balance of cooling towers and chillers


  • CEO ® system connected directly to JCI Metasys system via BACnet IP protocol, allowing tekWorx to gather real-time data on temperatures, flows, etc., and to fully control all plant equipment
  • Failover sequence developed and implemented to address control redundancy
  • No plant downtime during the course of this project
  • All major equipment remained in operation during commissioning


  • Manually operated system operating at 1.1kW/ton is now a real-time adaptive control system operating at .75 kW/ton
  • System experiences much less wear and tear
  • Operators are now freed up to perform other important tasks
  • CEO® User Interface has provides the staff with better insight into the system for diagnostics and trouble shooting

To learn more about this study and to see how tekWorx can help to optimize your plant, visit www.tekWorx.us

Issues with Primary and Secondary Chiller Plants

plumber fail-resized-600

An energy efficient design is the last thing on a property owners’ mind during the construction of a chilled water plant. Typically, the chief concern revolves around keeping construction costs to a minimum, ignoring future utility costs and energy efficiency considerations that are critical once a building is fully functioning. Due to this altered focus, chiller systems have historically been built using the classically inefficient “primary/secondary” (P/S). This configuration simply makes sure the building doesn’t run out of cooling on the hottest day of the year and gives no consideration to the expense of this strategy.

With respect to energy, one of the greatest causes for concern with these P/S systems is what is known as blending. Blending occurs as the chilled water combines with warmer water, thereby decreasing the temperature of the return water into the chiller. Because the chillers outputs are spec’d based on a designated temperature set point, energy is being wasted as the system fights to maintain its set point with the influx of warmer water.

To combat this issue, tekWorx has developed an “Integrated Primary/Secondary” retrofit design (IPS®) that brings valuable primary energy benefits to existing primary/secondary systems. Depending upon the specifications of a system, the IPS® substantially improves flow and reduces blending. The IPS® requires minor mechanical/piping changes and control system modifications, keeping the overarching facility infrastructure intact with minimal interruption to the current cooling operations. To see how tekWorx IPS™ can improve your ∆ T, fill out our Chiller Plant Evaluation Form.