Thursday, September 3, 2015

Balancing the New HVAC System Proves Challenging

Since the library's the new HVAC (heating, ventilating, and air conditioning) system was activated during the first weekend in August, the process of balancing the system to produce proper temperature and humidity levels has proven to be a long and challenging process.

Temperatures: floors 1-2
For about two weeks after the switch from the old "temporary" system, temperatures in the building were too warm--often near or above 80 degrees in some areas.  Eventually, engineers and technicians from two companies, the mechanical/electrical subcontractor MCC and the automation engineering firm Siemens, succeeded in getting air flowing from all the new HVAC blower units and with a sufficient flow of campus chilled water.  This produced the opposite problem, with temperatures falling to the mid and low 60s, and even lower in one location.  The adjustments at that point did produce lower levels of relative humidity, which was a positive step.

Yesterday the engineers and technicians began to mix steam (heat), generated from the campus physical plant, with the cold air circulating through the new HVAC system components.
Temperatures: floors 3-4
In some areas warmer air has already been emitting from air vents replacing the very cold air that had been circulating during the past couple of weeks. This could result in a subtle moderation of temperatures or, until the system is correctly balanced, it is entirely possible that some areas may become too warm.  The library's climate monitoring group (in operation since the library reopened after Katrina) is continuing to collect temperature and humidity readings to monitor the building's climate in multiple locations on all four lower floors, and is sharing these data daily with the construction project managers.

Meanwhile, the new mechanical system on the 5th floor basically connects to older duct and controls that for ten years have been dormant on the lower floors.  An MCC crew has been surveying the building to identify faulty pneumatic thermostats, disconnected or undersized horizontal pneumatic mains, faulty actuators on VAV boxes, and frozen or locked up damper shafts. They have developed a plan for repairs, which should address the remaining problems with distributing air flow throughout the lower floors. Siemens technicians have begun replacing about 30 faulty thermostats that had already been identified and more will be added to their list as MCC completes its survey. Some of the new thermostats needed are in office areas; the plan is for the work to be scheduled in advance as much as possible to give fair warning to occupants.

Tubes and Towers
Work has progressed relatively quickly on the removal of the old temporary HVAC system with its tubes and towers, and this includes glass replacement or repairs where overhead air distribution tubes ran through transoms, ceilings, or walls. Chilled water pipe and the older blower units have been removed from the back of the library building. Workers have begun separating the old towers from the building, as the first stage in the tower removal.

The library has been limping along with a single elevator since last November, in a phased operation in which all three elevators have been rebuilt and extended to also serve the new 5th and 6th floors. The other two elevators are now functioning and capable of traveling from the basement level to the 6th floor. Remaining work includes installing new elevator doors, modifications to the interior of each elevator car, and the installation of sump pumps required for the bottom of each shaft. The city inspector who will be reviewing the elevators before issuing certification allowing them to be operated for public use is being contracted in advance now in an effort to identify any potential obstacles to quickly passing inspection when the time comes, which is hoped to be soon.

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