Achieving building comfort through proper controls, integration design
Homeowners often try to find a balance between thermal comfort and the energy cost
Consideration of thermal comfort within a building is often an afterthought, that is until there is a need to adjust the space temperature for more heating or cooling. Homeowners understand that the thermostat in their home is the means to make that adjustment, typically to a home furnace with or without air-conditioning, a home boiler radiant heat system or even a heating/cooling heat pump system. However, when away from home in a work environment or visiting a building, the same simple adjustment may seem more daunting, complicated, confusing or even unknown.
Homeowners often try to find a balance between thermal comfort and the energy cost. Outside of the home, often in commercial buildings, facility owners or managers are often tasked with finding means to minimize the energy costs for providing occupant thermal comfort and the outdoor ventilation air required by code.
Each temperature-controlled zone within a building has a thermostat or space temperature sensor associated with a microprocessor-based direct digital control (DDC) controller that is associated with a Heating Ventilating Air Condition (HVAC) system. The system may have self-contained heating and cooling capability or be associated with a building plant that provides heating and/or cooling to individual HVAC systems. The temperature control system associated with the building equipment include occupied and unoccupied control strategies to minimize energy costs, while achieving thermal comfort. Depending on the location of zone temperature sensors and building management policies, there are many temperature display and setpoint options for space sensors including the option of having a hands-off blank cover.
A building automation system (BAS) is generally used to network the individual equipment controllers and thermostats (if network capable) to provide a management level graphical interface to the building’s entire temperature controls. This allows for the scheduling of building occupancy, space temperature setpoint adjustments, systems monitoring, alarm notifications, and trending of equipment operations and temperatures. Building lighting, fire alarm system monitoring, security/access, elevator system monitoring, electrical metering are examples of other systems that can also be integrated into the BAS, typically through open communication protocols such as BACnet, LonWorks, and Modbus, which are industry standards. The additional information is meant to further improve the operating environment in an energy efficient manner.
Control Suppliers and Installation Coordination with Building Owners
There are several brands of BAS and controllers developed by industry leading manufacturers, some of which are considered proprietary that can only be installed and serviced by select area representatives/installers. Other available BAS and controllers are openly distributed and installed by certified installers giving facility owners more options for their building controls installation and service requirements. All systems utilize an open protocol for controller network communications and integration capabilities.
There are many successful installations of these systems, each with their own pros and cons. Several owners have successful relationships with controls providers and other owners seek alternatives to move in a different direction. For owners with multiple buildings and continuing construction projects, a Master Systems Integrator is sometimes utilized to maintain consistency with their BAS data configurations and graphics.
BAS technology continues to progress. Current control systems leverage the owner’s Information Technology network to provide a good communication means for owners to monitor and maintain their building’s HVAC systems. Controller communications that have been traditionally wired to a building supervisory controller, serving as a router, with a single or minimal IP connection are now taking advantage of ethernet technology. Controllers are now capable of utilizing Cat-6 network cabling for communication that handles more data at higher speeds.
Some IT departments are accepting of providing multiple IP data drops to individual controllers; however, some do not, which has led the controls industry to create Operational Technology (OT) networks to be used specifically for BAS communications with minimal IP drops to the IT system in a secured manner. The networking requirements require coordination with the owner’s IT departments.
More HVAC equipment is being produced today with packaged DDC controls migrating away from past built-up control installations. Owners and construction managers are interested in this delivery method as a way to reduce costs associated with installing controls. Equipment controls have configurable programming in lieu of custom programming and have open protocol capability to be integrated with the BAS to provide monitoring, operating schedules and setpoint adjustments for owners. Equipment with self-contained controls provide a lower cost solution for material, but also adds some installation labor. The additional labor involved with the installation includes equipment technician time for setting up proper configuration, TC contractor technician time for mapping over logical information to the BAS for owner’s graphical interface, and more coordination between the installation contractors, the design engineers, and many times, a commissioning agent. In the end, the installed cost for equipment may be lower; however, the owner needs to understand what service provider may be needed, equipment or BAS service representative, for future maintenance and repairs.
As the equipment and controls are being determined and coordinated for a project design, much attention is required to ensure that systems can be programmed or configured to provide overall building thermal comfort while adhering to building energy and building ventilation-related codes and standards. Example strategies include, but are not limited to:
- Building occupancy scheduling for occupied/unoccupied heating/cooling setpoints,
- Unoccupied standby modes during building occupancy to relax space setpoint and reduce outdoor ventilation where applicable,
- Demand Control Ventilation to reduce outdoor air ventilation when large spaces are lightly occupied,
- Air Handling Equipment Static Pressure Reset to save fan energy when remote zone heating and cooling demands are reduced, and
- Water Supply Temperature Setpoint Reset for Hot Water Heating Systems and Chilled Water Systems to save energy at source plants.
Original content can be found at blog.peterbassoassociates.com.