Commissioning Integrated MEP Solutions| August 5, 2015
Powering your Building Management System
One of the things often overlooked in a construction project that incorporates a Building Management System (BMS) is the final location of the head end. The head end is the supervisory application for building controls that can reside either on a singular computer (such as in a maintenance office) or possibly on a virtual server somewhere within the organization’s IT infrastructure. The importance of the proper location of the head end cannot be disregarded for multiple reasons. Important questions to ask when determining a location for the BMS head end are: Will you require an emergency power circuit for the BMS? Who is the primary user of the BMS? What data provisions are required for the BMS head end location? Will the head end need remote access from multiple users, or just one at a time on a singular computer?
So, does a BMS head end require an emergency power circuit? If remotely located equipment controllers have battery back-up, the head end may not need an emergency power supply because they will continue to control from the last signal they received from the BMS. If the head end is going to operate on an emergency power circuit, typically the system will also benefit from an Uninterruptable Power Supply (UPS). The UPS will prevent the brief shutdown of the BMS head end in the event of a utility power loss and allow equipment receiving information from the head end to receive them real time until the emergency generator can supply power back to critical controls systems.
Fitzemeyer & Tocci’s commissioning team typically facilitates determination of the BMS head end location with the owner and controls contractor in the design phase or early in the construction of the project. Locating the head end early allows electrical contractors to determine what power and data provisions will be required for proper head end can operation. It is also important to keep in mind who will be accessing the BMS head end and operating building controls systems. Putting the BMS head end in an electrical closet on the opposite end of a project site from the facilities office may not be the most practical solution. On larger project sites, a remote BMS head end location can be desirable to enable local assistance in equipment troubleshooting.
Always be sure to work with a the owner’s facility operational personnel and the project commissioning agent to determine the best head end location and clearly set expectations for the BMS head end functionality during a loss of power. Both location and power requirements ultimately affect members of the construction team and determining BMS head end needs early will help prevent unnecessary changes later in the project.
Monson Town Hall and Police Department
“Fitzemeyer and Tocci was a key member of the Monson team. They were on hand throughout the project to work collaboratively with the owner, designers and contractors. Their knowledge and expertise of the commissioning process was a key factor to the success of the project.”
Shane Nolan, Senior Project Manager, Daedalus Projects, Inc.
Scope of work:
Fitzemeyer & Tocci was contracted by the Town of Monson to provide commissioning services for a new 14,000 sf combined use facility. The facility provides space for the new town hall and police department. The project consisted of the commissioning of mechanical, electrical, plumbing and life safety systems. Systems commissioned included air handling units (AHUs), energy recovery ventilators (ERVs), variable air volume (VAV) boxes, boilers, pumps, split air conditioning units, exhaust fans, emergency generator and radiant heating panels.
Functional testing of the air handling units revealed that the AHUs were balanced by the testing, adjusting and balancing (TAB) contractor as 100% outdoor air (OA) units and initially programmed by the Automatic Temperature Controls (ATC) contractor as 100% OA units based on the balancing data provided by the TAB contractor. The design called for the AHUs to operate at a minimum outdoor air position to increase the efficiency of the equipment, allow economizer mode of operation and incorporate space carbon dioxide control.
The original design specified discharge duct static pressure optimization sequences for both of the AHUs in order to provide additional cooling to the VAV terminal boxes in the event multiple zones within the building required it. The execution of functional testing revealed that the ATC contractor was not monitoring the position of the VAV box’s primary air dampers which prevented the AHU from increasing speed when the VAVs required additional air flow for cooling.
Contract documents required the installation of an additional outdoor air duct on one of the AHUs that tied directly back into the return air duct work of the unit. This additional ductwork was causing unnecessary outdoor to be provided back into the return air stream of the unit reducing efficiency of the temperature control of the unit.
- Fitzemeyer & Tocci conducted a controls integration meeting early in the construction of the project and identified the discrepancy between the ATC submittal and the contract documentation. The commissioning team also worked with the ATC contractor during acceptance testing to incorporate these minimum OA positions for the AHUs to allow economizer and carbon dioxide sequences of operation.
- Through the controls integration meeting and coordination among contractors, F&T was able to identify that the VAV boxes damper positions were not being monitored. In response, the ATC contractor programmed a supply duct static pressure optimization sequence based on carbon dioxide concentration to reset the duct static pressure up and down for when the carbon dioxide level of any space was above 900 PPM.
The design team was informed of the extra ductwork early in the construction of the project by the commissioning team and was able to provide supplemental information to the contractors, thus isolating this section of ductwork from the return air ductwork. This change allowed the unit to operate more efficiently and according to design intent.