Precise Radiant Thermostat Controls Maximize Comfort and Save Energy
Let's Be Precise
Controls are vital to achieving radiant comfort and optimizing energy consumption. They’ve become a lot more intelligent and their capacity far exceeds the basic thermostat. Available controls allow precise design of radiant systems for very specific end user wants and needs.
Radiant controls — which include thermostats, zone controls and actuators — are required to properly regulate the flow of the heating fluid through the radiant piping system in order to maximize radiant comfort. Radiant systems are designed for a variety of low-mass, medium-mass and high-mass floor construction methods.
Each type of floor system has a different control methodology to reach and maintain the desired set-point. For example, a low-mass radiant installation which consists of aluminum plates applied over the subfloor, quickly reaches the set-point, but has a high potential for fluctuation. In contrast, a high-mass radiant installation, in which radiant piping is embedded in the slab, reaches the set-point much more gradually, and then is easily stabilized. Mid-mass installations fall somewhere in the middle.
Radiant controls are designed with high- and low-mass settings to mitigate over- or under-shooting the desired set-point. This is one key distinction between radiant controls and forced-air thermostats, which lack the error correction programming that maintains a stable set-point in a space.
Knowing what a control can do up front allows the installer to develop a system for optimal comfort. Projects with a goal of optimizing energy consumption require more advanced controls strategies that can respond to weather conditions and room occupancy. Employing outdoor reset controls and mixing devices, a radiant system can take into consideration heat losses and gains to the exterior of the building and raise or lower the supply water temperature accordingly. By avoiding over-heating and under-heating, this controls strategy not only maintains occupant comfort, but also makes the system more energy efficient.
Many advanced features are used to provide complex home automation solutions. Features such as voice control, and remote monitoring and control are becoming more accessible and easier to use with Smartphone apps and smart speakers. Wireless thermostats can be installed without having to run the right number of wires or using unsightly conduits.
Advanced controls can provide zoning and setback for end users. Zoning allows users to divide large areas into smaller areas of control, typically individual rooms. This allows each zone to be controlled separately from all the other zones.
Setback allows users to save energy by reducing the temperature of an area when it is unoccupied. The setback can be enabled manually, on a schedule using a timer, or more advanced controls can automatically determine a schedule based on detected occupancy. Combining zoning with setback allows for efficient use of energy, operating the radiant system only when and where it’s needed.
Another available feature is a “connected house,” offering remote connectivity from a smart device. This provides the ability to change the set-point temperature from a smart phone, tablet or computer. With home automation interconnectivity there is the option of tying the heating system into other devices in the home. For instance, if the windows are opened in a room, the system can automatically turn off the heat to that room.
There’s also the option of energy consumption feedback. This offers the homeowner the ability to monitor energy consumption and fine-tune their system to maximize energy savings. Systems also can be connected to weather forecasting. Advanced radiant controls can be connected to weather information from the National Weather Service or Environment Canada to maximize energy savings. If the outside air is predicted warm over the next couple of hours, the system does not have to work as hard to maintain comfortable temperatures in the house. Conversely, if a cold front is coming, the system can raise the water temperature ahead of the front so that there is no lag in response from the radiant system.
Also an option, radiant heating systems can employ IFTTT (If This Then That), a free web-based service that consumers use to create chains of simple conditional statements, called applets. The applets could use geo-locators on smart phones and motion sensors to trigger turning the heating system on and off, or adjusting the set-point.
Residential vs. commercial
Small commercial systems typically use the same controls found in residential systems. Large commercial systems use a building management system which controls and monitors all of a building’s systems, not just mechanical systems. A BMS enables facility maintenance staff to identify and resolve issues proactively.
In commercial buildings, radiant controls systems are typically tied into a comprehensive BMS that controls the entire indoor climate including heating/cooling loads, dehumidification and air quality. In this case, the radiant controls strategy can consist of simple temperature sensors in the wall, slab and relays that turn the radiant system on and off in response to the heating calls from the BMS.
The BMS system is the overall conductor of all the equipment in the indoor comfort system. The radiant contractor usually needs to provide a lot of support to the BMS supplier who is responsible for integrating the two systems, which typically talk on a Modbus or BACnet protocol. Residential systems are much easier to install because they do not need much interoperability with other systems in the house, unless the house is large enough to have a commercial BMS. Radiant contractors can independently install the typical residential controls system.
(Appeared as "Let's Be Precise" in print.)