School Integrates DDC for VRF to Improve Control, Energy Management

School Integrates DDC for VRF to Improve Control, Energy Management

For more robust and consistent control, the HVAC-solutions provider integrated the VRF with Alerton’s VLD-362 communicating sensor-controller combination.

Magruder Elementary School. (Photo courtesy of Hudson + Associates)

When York County School Division renovated Magruder Elementary School in Williamsburg, Va., in 2015, it chose to install variable refrigerant flow (VRF) for heating and cooling. The wall controllers supplied by the VRF manufacturer, however, lacked dual set points, night setback, and consistent interoperability across competing systems, restricting the school division’s ability to manage energy use.

For more robust and consistent control, the HVAC solutions provider/dealer, Air Conditioning Equipment Sales Inc. (ACES) of Richmond, Va., integrated the VRF with Alerton’s Visual Logic Display (VLD) 362 communicating sensor-controller combination. The BACnet-enabled VLD provides the direct digital control (DDC) commonly lacking with VRF wall-sensor displays.

Because it is programmable, unlike many VRF-manufacturer-supplied wall controllers, VLD makes possible the control of a host of HVAC equipment.

“The VLD units allow us to apply our energy-management protocols to the VRF,” Russell Payne, supervisor of resource and security control for York County School Division, said. “These include 73-79°F cooling and 64-70°F heating set-point ranges, dynamic night setback, and more.”

Paul Butler, ACES sales engineer, added: “Some mechanical engineers thought this couldn’t be done, but our controls programmer has developed a powerful and reliable way to provide DDC for VRF. We’re not replacing the VRF control panel, but are using a powerful and adaptable wall controller to manipulate the VRF’s programmable data.”

VLD-362 has built-in temperature and humidity sensors and an easy-to-use interface. Unlike typical VRF-manufacturer-supplied wall units, it features:

  • Customizable set points (single or dual range).
  • Easy-to-use fan-speed control.
  • The ability to schedule overrides in 30-min increments.
  • The ability to add carbon-dioxide monitoring and extra inputs and outputs.

VLD’s programmability provides user flexibility, Butler said.

“With VRF manufacturers’ wall units, we usually can’t customize the displays the way users want,” Butler said. “For example, one school district might want its teachers to see temperature, time, and set points, while another only wants the wall units to display temperature. With the VLD, we can provide each customer with what they want.”

With a VLD unit installed in each classroom, Magruder Elementary teachers are able to better control the temperature of their rooms within set points programmed by the district. Additionally, teachers have reported liking VLD’s easy-to-read digital display because it resembles the ones in their homes, Payne said.

“The VLD allows the user to have a seamless experience from space to space, regardless of the equipment we are controlling, whether it is bathroom heaters, large rooftop units for gyms and cafeterias, or small indoor VRF units located in the classroom ceiling grid,” Payne said.

The 12,000-student York County School Division has deployed this DDC-for-VRF integration solution for its last three school HVAC renovations and additions and plans to implement it in three more schools in 2016. In addition to better building control, the Alerton products provide data for thermographic floor plans the district has developed for each school, which allow facility managers to view room temperature and equipment status. Eventually, the school division plans to put all of the schools’ floor plans on one display for more comprehensive energy management.

 

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