What Are HVAC Relays & Who Need Them?

An HVAC relay is a type of HVAC control system commonly used to monitor temperature, pressure, and humidity of large commercial and industrial facilities.

HVAC controls, such as in building automation system, are significant in the optimal start programs. When the program calls for a warm-up, the central air handling systems of the plant would start and operate with a recirculation air of 100 percent.

When it calls for a cool-down, the central air handling systems of the plant would start and operate with a return air of 100 percent.

An HVAC relay uses either one or perhaps more central controllers to regulate terminal unit controllers that are remote, communicating through an operator interface, usually one or more PCs. An HVAC relay is also often integrated with other systems such as smoke, fire, or light controls.

There are many types of HVAC relays available in the market. Temco Controls has actually three HVAC relays. Their MR3000 is a general-purpose mechanical relay and fits for both low voltage as well as excellent power switching.

To activate it, it needs only 10–12 VDC (voltage direct current) at 100ma (milliampere) for its low-power coil. Its double-pole, double-throw (DPDT) relay is estimated to be at 10A (ampere). Each relay consists of LED that indicates its voltage status. Its mechanical relay board is a slight modification of MR3000.

Types of HVAC Relays

They are actually two types of HVAC relays: 4- and 8-gang versions. Its features are very similar to that of an ordinary MR3000 mechanical relay in the sense that it still has a low-power coil and possesses LED lights for each relays.

Additional LEDs are used to monitor fuse loads. The mechanical board relay’s jumper can be set in two modes. It can be switched at 24 VAC on common ground, or you can use dry contact mode.

HVAC Relay Brands & Manufacturers

Temco Control’s SSR3000 features photo isolation of 4,000 volts and voltage turn-on, among others. It is a type of a solid-state relay. However, the word “relay” may be a misnomer as it isn’t a relay at all. It depends on electronics to do the actual switching. SSR3000 is known to provide solid-sate dependability for your HVAC systems.  For best performance, each relay is pretested before it is delivered.

Fujitsu Components America is one of the world’s leading manufacturers and distributors of electronic parts all throughout America. In 2004, it introduced and released into the market its newest type of HVAC relay named the FTR-K3. It is a slim relay with a power of 20 amperes and an operating power of 780mW (milliwatts), the lowest of among its class.

It has variety of uses, such as to switch compressor and inverter loads found in air conditioners and other appliances found in offices and in homes.

FTR-K3 is very durable and long-lasting, capable of 2 million operations (its mechanical life) or 100,000 operations (its electrical life) at its rated load.

Another leading company in the mechanical engineering industry is American Zettler. It boasts of being world’s no. 1 manufacturer and seller of HVAC relays. Its catalog or product list, which you can download, features over thirty kinds of relays for different purposes. Furthermore, each model has its own distinctive characteristic, allowing you to choose the best or the most appropriate for your need.

Omron has one of the best kinds of contactor relays. They consist of main contactors with an addition of contact blocks. Moreover, their components are finger proof and come in different sizes; definitely, you have almost infinite ways of possible configuration.

HVAC relays are sometimes manufactured as a part of “power packs.” We can take, for example, Leviton’s occupancy sensors, which are the most highly developed, functioning sensors in the market. These sensors, along with its own built-in HVAC relays, can actually place all control connections in one central location.

Computers can also be used to control HVAC relay operations through an open- or closed-contact representation. This is because PCs use binary logic—either one or zero, yes or no, true or false—that is transformed into electrical signals and eventually into true-or-false digital signals.