Behind the scenes of the buildings where we live and work are systems quietly humming away. In large-scale or industrial applications, you want these systems to run on autopilot (like lighting, HVAC, and security). That’s where a building automation system (BAS) comes in.
A BAS streamlines the management of commercial buildings, including upgraded efficiency, better occupant comfort, lower energy costs, improved security, and more.
Functional Devices offers a range of building automation products, including relays designed for a range of applications.
Contact our sales and support team to discuss your BAS needs.
Understanding the Role of Building Automation Relays
A relay is an electrically powered switch carrying, or relaying, electrical currents to other relays or components to switch them on or off. They can also amplify the strength of small electrical currents.
Many different systems work together in a BAS, meaning a lot of electricity needs safe management. Relays protect the electrical system, controlling and isolating low-voltage systems from high-voltage systems. With a relay, the twain shall never meet.
Not only do relays safeguard electrical components, but they also improve the reliability and longevity of a building’s systems, allow for a higher load capacity, and can be remotely operated.
Key Factors to Consider When Choosing a Relay
Although the idea of a “master switch” sounds simple enough, picking the right relay is more nuanced. Here are the top considerations to keep in mind when researching your options.
Load Requirements
Adaptability is the backbone of our success, allowing us to navigate challenges with agility and turn them into opportunities. Whether it’s responding to market shifts or adjusting to an increase in production, our team thrives in environments where change is constant. As one of our employees put it, “We don’t see obstacles as roadblocks; we see them as chances to innovate and improve.” This mindset has not only helped us grow but also ensured that we remain a leader in the ever-evolving building automation industry.An electric load is a device that consumes electrical energy to operate. The BAS’s load requirements, how much electricity it needs to run, and the types of loads will determine what kind of relay you choose.
There are three types of loads:
- Resistive. The electrical current and voltage are in phase, meaning the current is constant from switch on to switch off (e.g., incandescent lights, heating elements).
- Capacitive. The current and voltage are out of phase, with the current leading the voltage, meaning there’s a large inrush current at switch-on (e.g., devices with a capacitor, such as computers and TVs, capacitive load banks, long transmission or cable lines).
- Inductive. The current and voltage are out of phase, with the current lagging behind the voltage, meaning there’s a voltage spike at switch-off (e.g., electric motors, common household devices, transformers, solenoids, electromagnets).
For example, if you choose a relay only rated for resistive loads and try to use it for inductive loads, the voltage spike at switch-off will likely damage or destroy the relay and any accompanying control devices.
If you’re working with capacitive or inductive loads, choosing an oversized relay is essential to manage the switch-on inrush current or switch-off voltage spike. .
Contact Configuration
A relay contact is where the magic happens—electrically conductive pieces of metal touch to complete a circuit and allow the flow of electricity. Relays can have different contact forms suitable for different applications. The pole refers to the number of circuits the switch controls, and the throw refers to the number of positions that complete the circuit.
- Single Pole Single Throw (SPST). Completes one circuit in one “on” position.
- Single Pole Double Throw (SPDT). Completes one circuit in two “up” and “down” positions.
- Double Pole Single Throw (DPST). Completes two circuits in one “on” position.
- Double Pole Double Throw (DPDT). Completes two circuits in two “up” and “down” positions.
Voltage
Common control voltages in building automation include 120 VAC (Volts Alternating Current), 24 VAC, and 24 VDC (Volts Direct Current). The voltage rating of a relay must be equal to or greater than the voltage driving the load. For example, don’t use a relay rated as 12 VAC to operate a 24 VAC air conditioner.
Additionally, pay attention to the:
- Rated coil voltage. Operating a relay as close to this number as possible is safest.
- Maximum switching voltage. The voltage going across the contacts shouldn’t surpass this number even if the relay is closed.
Switching Speed and Frequency
Components of your BAS will require varying switching speeds and frequencies, so your relay must accommodate these requirements. Some systems, like HVAC and electrical control panels, need to switch quickly. Others, like automated test equipment systems, must switch often. Still others, like medical equipment, do both. Some systems, like HVAC, lighting, and safety, also need slow or time-delay switching.
Choose the relay accordingly, like those constructed for specialized high-switching applications or with built-in time delays.
Environmental Conditions
Don’t forget to consider your industry and where you’ll be installing your relay. Temperature, humidity, corrosive substances, and ambient vibration can affect relay performance. Therefore, install relays in an appropriate location and protect it with an enclosure.
Speaking of location, installation space constraints will help you determine the mounting type and size of the relay. Don’t select a relay that won’t fit in your available space. Also, consider the heat a relay will give off and its surrounding area. A larger relay may give off more heat.
To ensure your relay is up to the task of contending with your building’s environment, check its Ingress Protection (IP) rating. This rating measures how effectively an enclosure protects electrical components from solids and liquids that could damage the equipment or create a safety issue.
IP ratings consist of two numbers: the first, between zero and six, indicates protection from solids (e.g., dust), and the second, from zero to nine, defines protection from moisture. Higher numbers indicate better protection. For example, IP69 offers the best protection from water, dust, or debris.
Building Automation Relays Innovated: RIB Relays
Relays make a BAS run more smoothly, safely, and efficiently. When researching, select the appropriate relay depending on the load requirements, contact configurations and voltages, switching speed and frequency, and environmental conditions.
If you’re unsure about the best choice, consult the professional at Functional Devices, Inc. We’ve been in the relay game a long time, and our engineers have been innovating top-notch relays for specialized applications. Our “Relay in a Box” RIBⓇ relays come prepackaged and can cater to a variety of needs.
Choosing the right relay for building automation is necessary to run your building. Consider these key factors, and you’ll be on your way.
About Functional Devices, Inc.
Functional Devices, Inc., located in the United States of America, has been designing and manufacturing quality electronic devices since 1969. Our mission is to enhance lives in buildings and beyond. We do so by designing and manufacturing reliable, high-quality products for the building automation industry. Our suite of product offerings include RIB relays, current sensors, power controls, power supplies, transformers, lighting controls, and more.
We test 100% of our products, which leads to less than 1 out of every 16,000 products experiencing a failure in the field.
Simply put, we provide users of our various products confidence and peace of mind in every box.