UV Light in an Air Handling Unit

Sam Klennert
4 min read
Face masks, hand sanitizer, and toilet paper - all things in high demand during the Covid pandemic. Perhaps one other thing that may be in high demand is UV lights in the HVAC world. UV light helps to disinfect air and surfaces. Not too long after the start of this viral pandemic, I got a tech call from someone that needed help. They were trying to find a relay device to turn on and off the UV light in their air handling unit. The reason: they don't want to get a sunburn or would rather not wear sunglasses to maintain the air handling unit.

Well, this is a new one out of the 5 years and nearly 6,000 calls that I've taken! I thought it worthy to write in a Tech Blog entry as well, so here you go. After talking for a little while to this caller about what kind of relay was needed, we formed a list of requirements:

  1. 10A contact rating
  2. 120Vac powered
  3. Can sense when the air handling unit service door is taken off
  4. Uses low voltage as the sensing voltage

Closet Light Controller To The Rescue

After the third bullet point, I knew what was needed, so I steered this individual toward our Closet Light Controlling relays with a magnetic reed switch - specifically, models CLC212 and ACLCMAGSM.

However, in typical applications of the CLC212, when the door is open, the light turns on. This application needed to work in the opposite way - when the door opens, the light turns off. With this understanding, two options arise: use the CLC212-NC, as it will act opposite of the CLC212. OR, make sure to use a "Form C" magnetic reed switch, like the one I mentioned above.

When using a Form C magnetic reed switch, the installer has access to a normally open or normally closed contact on the switch. With the normally closed contact, one can effectively invert the logic so that when the door opens, the light then turns on. Easy peasy! Why use the Form C switch and not the CLC212-NC? Well, the CLC212 is easier to come by compared to the "-NC" version. This makes it simple if more air handling units need UV lights to turn on and off in the future.

So, there you have it - using a CLC212 and ACLCMAGSM to control the UV light in an air handling unit. It was an honor to help that individual and the same goes to anyone else that needs help. Feel free to email or call in for assistance when choosing any one of our devices!

About Functional Devices, Inc.

Confidence and Peace of Mind

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.