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Too hot or too cold?

The Heating Plant is continually looking for ways to improve occupant comfort and minimize energy consumption. Staff regularly analyze work orders created due to temperature control problems and look for areas that would benefit from upgrades.

The fourth and fifth floor perimeter rooms at Milner Library were areas identified as needing improvement since these rooms historically had poor temperature control. After careful study of this issue, a project was designed to improve this situation.

Milner Library room temperatures are controlled using a zone reheat system. In this type of system–which is used in many places on the campus–air handlers supply air at a fixed temperature (typically between 55 and 60) and the temperatures in the various building zones are controlled by adding additional heat to get the zones to their set points. At Milner Library, the Heating Plant staff found many of the heating coils used for zone reheat were excessively plugged. This reduced HVAC air flow causing hot rooms in the summer and cold rooms in the winter. In addition to the coil restrictions, the control system did not work properly for the fifth floor perimeter zones because the sensors used to control these areas were located remotely from the areas being controlled.

The project included the replacement of 10 reheat coils that were restricting the HVAC air flow by an average of 45 percent below original design flow rates. Efforts to clean the coils resulted in little or no gain in air flow. Replacement provided an additional benefit in that the Heating Plant could make a design change so the coils would have even less air flow restriction than the original design. The coils were replaced by the in-house pipefitter staff.

In addition to the coil replacement, new temperature sensors were installed so the temperatures in the fifth floor perimeter rooms could be accurately monitored and the zones controlled based on actual conditions. The HVAC control program also was modified and all controls evaluated to make sure systems were operating in a reliable and stable manner.  This work was done by in-house automation technicians with assistance by the University’s electricians.

Milner Library staff coordinated the schedule of work to minimize disruption to the occupants and moved library materials out of the way to provide clear access to the work areas. They also provided valuable feedback as the project progressed so the Heating Plant could fine tune our systems.

The result of this project was a 41 percent increase in air flow, and greatly improved temperature control in the affected areas. In addition to improving occupant comfort, the project allows the Heating Plant to slightly reduce the speed of the main building fans to save electrical energy.

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