Case study: Pressure-independent control valves will update HVAC system
The Field Museum in Chicago will incorporate pressure-independent control valves to help regulate its chilled water system
As The Field Museum in Chicago implemented its master plan, its chilled water system would change as more and more air handling units were consolidated onto the system over the past 20 years. The net result was an improperly balanced system, which became worse over time.
During a recent investigation, the two-way modulating valve controlling flow to the coil hydraulically closest to the distribution pumps were operating as on-off valves. With its location so close to the distribution pumps, the valves would crack open and the pressure would immediately overflow the coils, which also prevented good heat transfer. This wasted energy was prevalent at nearly all the units, which were tested.
A balancer was called out to the site to calibrate the valve to meet the specified flow requirements. After doing so, the valve was able to operate as intended and modulate flow to the coil in lieu of acting as an on/off valve before balancing. Further, more flow was seen at the coils hydraulically furthest away from the distribution pumps.
Air handling units serving critical storage rooms with tight temperature and humidity controls were experiencing issues maintaining values within the required range. While the chilled water valve would open to 100%, discharge air temperature was still not met further verifying issues that flow through the system was compromised.
The goal is to install pressure-independent control valves moving forward so a properly balanced system can be maintained as air handling units throughout the building are upgraded. During these replacement projects, complete system rebalancing is not necessary after future equipment upgrades.