HVAC Upgrade at the Mt. Hope Christian School
Weston & Sampson is providing MEP engineering and design services along with associated architectural work for the complete HVAC renovation of this school, which serves toddlers through fifth-grade students. The Mt. Hope Christian School and Church has a long-term lease to occupy this 1950s vintage single-story brick building in Burlington. As the landlord, the Town of Burlington is undertaking this comprehensive HVAC system upgrade.
The existing HVAC system is original to the building and consists of three Smith natural gas-fired (converted from number 2 fuel oil in the 1980s), Smith cast-iron sectional, induced draft, hot water boilers with continuously modulating Webster burners provide heat to a combination of classroom unit ventilators and various convectors and propeller unit heaters. One of the boilers is non-functional and the two remaining have recently had their refractory replaced. One boiler is capable of heating the entire school, thereby effectively leaving a spare boiler in the event of a failure. The hot water system is segregated into three zones via individual zone pumps. Unit ventilators are heating-only draw-through; as a result, there have been several coil freeze-ups. Classrooms are exhausted by a combination of bathroom exhaust fans and individual classroom registers tied to ganged exhaust fans. Controls are pneumatic and largely non-functional. Domestic hot water is provided by gas-fired hot water tanks.
The new HVAC system will include all new components but reuse the existing hot water distribution piping and exhaust ductwork. New boilers will be high-efficiency gas-fired low temperature condensing hot water boilers operating with full hot water temperature reset at fuel to heat efficiencies greater than 90%. Pumps will be variable speed. The new heating-only hot water unit ventilators will be blow-through design to alleviate potential coil freezing. New convectors and unit heaters will be provided and properly sized for low temperature operation. New exhaust fans will also be provided.
The entire system will be controlled by a new Web-based direct digital control (DDC) system that allows the owner and occupant (password protected) to view the current operating status and make scheduling and other system adjustments from any computer connect to the Internet. Although the existing York-packaged rooftop air conditioning that serves the sanctuary is not part of the HVAC renovation project, the DDC system will be integrated into the existing air conditioning to ensure proper holistic HVAC system control and prevent simultaneous heating and cooling of the air conditioned spaces.