How To Install An HVAC UV Light (5 Step Guide)

Are you interested in learning how to install a sanitizing UV light inside of your HVAC?

You are in the right place because even hospitals use UV-C light to disinfect medical equipment and operating rooms.

I created this step-by-step guide on how to install a UV light to keep your A/C system free from mold and mildew protecting your air quality. 

In this article, you will learn...

how to install uv light for hvac
  • Why you should never allow a UV light to shine on your eyes or skin (a safety hazard)
  • How to determine the best location to place the UV light
  • How to use a hole saw to cut into the metal duct (and my top hole saw choice)
  • The best way to power a germicidal UV light unit
  • Important things to do before installing a UV light (if there is already mold)

The Five Steps To An HVAC UV Light Installation


#1. Choose Where To Install The UV Light

Perhaps the most important step is to choose where to install the UV light. You want it installed where it will be most effective and kill the most mold and mildew.


#2. Drill The Hole(s) For The UV Light

The biggest physical step is drilling the holes in the metal HVAC cover so that the UV light bulb can be inserted. Most holes will be 1-1/2" to 2-1/2" in diameter.


#3. Screw The Germicidal UV Light To The Furnace

In this step, you take screws and secure the UV light housing to the air conditioner. You don't want to tighten the screws too much where you damage the plastic housing.


#4. Power The A/C UV Light System

After the UV light is secured, you will want to add power to the UV light. Usually (and the easiest) is to just plug the UV light into a regular 120-volt outlet.


#5. Change & Clean The UV Light Bulb

After it is installed, the only real maintenance is to change the bulb annually (or at most every two years) and clean the light bulbs seasonally.

#1. Choose Where To Install The UV Light

The first step in installing a UV furnace light is to determine the best location on your furnace or air handler. If the germicidal UV light is installed in the wrong place, it will greatly reduce its effectiveness in preventing mold or mildew growth. 

Usually, you want to install the A/C ultraviolet light treatment system so that the evaporator coil gets the most amount of light. According to Lincoln Tech, it is the evaporator coil (and drip pan) that is usually the source of HVAC contaminants.

The evaporator coil is susceptible to the growth of biofilms which are communities of microorganisms that stick together on a surface. The amount of surface area of an evaporator coil is around 5,000 square feet.

The evaporator or A-coil is the part of the air handler that has the copper (or aluminum) tubing where the refrigerant runs through. It frequently has the shape of a tepee or "A" and frequently has the most dust buildup and mold growth.

However, if you have already had mold growth in your HVAC and there is a particular corner or area of the air handler that is prone to mold ---- then you should install the UV light so that it shines the most on the problematic mold area. There is no point in experimenting with locations if you already know that one spot of your A/C gets the most mold growth.

If you want to skip the hassle of installing a UV light on your own, you may want to check out my Contractor Search Tool — it will get you free quotes from local HVAC pros who have been screened and pre-vetted.

evaporator coil shape (3)

A-Shaped Evaporator Coil

The best location to install a UV light if in the A-shape is above, center, and downstream of the coil. This allows the A/C ultraviolet light to shine the most amount of light on the coil, while killing some of the airborne microbes.

The second best location is below the evaporator coil (if there is room). If none of these locations are feasible, then you can install the UV furnace light to either side of the coil.

N-Shaped Coils

The second most common type of A/C coil after the A-coil is the diagonal N-coil --- it is in the shape of an N or Z (depending on orientation). If the evaporator coil is in this shape, then there are only two options. You can either install the light above the coil or below it. Preferably, you should install the UV light closer to the drip pan and where there will be more moisture.

If you don't feel like the air handler is getting enough UV light, you can always install an extra UV light in a different location or on the other side of the coil.

Read Also: What Are The Best UV Lights For HVAC?

#2. Drill The Hole(s) For The UV Light

The next step is to drill a hole (or two) into the indoor air handler so that the UV light bulb can penetrate inside the unit.

All UV light sanitizing systems are installed so that the main part of the product is mounted to the outside, while only the long ultraviolet light bulbs enter inside.

Take Measurements Before Drilling Holes

It is advisable to remove the cover to the furnace, and take some measurements. You don’t want to drill a hole in the sheet metal only to find out that the location won’t fit for the UV light bulb.

You can also just carefully insert the UV light bulb in the location where it will be installed to get an idea that it will fit correctly.

Remember to avoid touching the A/C UV light bulb. The oils from your skill will reduce the light of the bulb and may damage it.

Using A Hole Saw Drill Bit

Some HVAC UV light systems come with everything you will need to install a UV light--- including the hole saw drill bit---except of course an electric drill. If you bought a UV light without a hole saw, you will need to buy one so that you can cut a circular hole through the metal HVAC cover (or ductwork). 

Most UV lights will need either a hole in the range of 1.5" to 3" in diameter. I recommend buying a Lenox 2.5" Hole Saw because it already has a drill bit as part of the hole saw. The drill bit goes in first, which helps grab the sheet metal (and guide the hole saw), and then the hole saw cuts the actual 2.5-inch hole.

You can check out the price of the Lenox 2.5" Hole Saw on Amazon here. Lenox also has different sizes of the same model.

Shut Off Power & Use Paper Template

It is important to first shutoff the power to the HVAC system before installing a UV light---you don’t want to accidentally get shocked. Locate the breaker at the panel box, and flip the switch.

Most AC UV light products will come with a paper template for the mounting. Tape the template to the area where you wish to install the UV light. The template will help you cut the holes at the proper distance apart (if there are two bulbs).

Start slowly as you cut into the sheet metal, and as the hole saw makes a small groove, gradually push the saw into the ductwork to cut the hole. It may help to rock the drill bit back and forth to get a more effective cut.

Read Also: How To Prevent Mold in Air Conditioners (What To Do?)

does uv light kill mold in hospitals

#3. Screw The Germicidal UV Light To The Furnace

The third step is to screw the UV light to the air handler. The UV product should of come with a few screws for the install.  Simply use a cordless drill or a phillips screwdriver to secure the UV light to the metal.

Make sure not to install the screws too tightly where it may crack the plastic of the UV light. As a reminder, do not plug in the UV light bulb before it is fully installed. The UV light can burn your skin and may damage your eyes.

#4. Power The A/C UV Light System

With the UV light sanitizer secured to the furnace, now you want to power the system. Most new UV lights will come with 5′-7′ long extension power cords. All you will need to do is plug the unit into an existing outlet. Most utility rooms will already have an outlet. 

Another option is to hardwire the UV light into the furnace. You can even wire it so that the UV light only turns on when the furnace or A/C turns on so it isn't on 24 hours.

After you have plugged in the UV light, simply flip the power switch on the unit, and check the sight glass to make sure that the UV light is actually on. There should be a bluish glow in the sight glass.

The Best HVAC UV Light

My favorite UV lights for HVAC systems are made by a company called OdorStop.

This OdorStop UV Light will only turn on when your HVAC is on — which means it will save energy and extend the life of your bulb. It is also meant to be installed on the return duct side, which makes it less likely that the UV light will damage any critical HVAC wiring or other plastic parts. You can view the price of the OdorStop UV Light here on Amazon.

#5. Change & Clean The UV Light Bulb

Most UV light bulbs will last about one year. If there is blue light shining, this doesn’t mean that the bulb doesn’t need replacement. The actual UV-C frequency that kills mold is invisible to humans. There may be blue light emanating from the unit, but it is no longer shining enough UV-C light frequency.

It is also recommended to clean the UV light bulb every few months or after every season. To clean the unit, you will need to take out the bulb, and clean it with a soft lint-free cloth such as a microfiber rag. You can use regular glass cleaning solution to clean the bulb from dust and debris.

Read Also: Does UV Light Kill Mold? (How Effective?)

What's The Bottom Line On A UV Light Installation For The HVAC?

If you follow the steps in this guide, it shouldn't be too difficult to install a UV light to kill mold and mildew in your indoor air handler.  The basic idea is to cut a hole in the best location, insert the bulb, use screws to secure the light, and plug it in.

If you have all of the supplies, you should be able to install a UV light within 15min to 30min. However, if you want to hardwire the UV light to your furnaces power, it may take longer. Other than that option, using the hole saw to cut the hole(s) will likely be the most challenging aspect of a UV light install.

However, installing a UV light can be a pain if you don't have the equipment or the DIY skill. You may want to check out my Contractor Search Tool which I created so my readers can get free quotes from local contractors who have been pre-vetted.

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10 thoughts on “How To Install An HVAC UV Light (5 Step Guide)”

  1. Great step by step guide, however, you really need to update this 5 Step guide to include images of an installation in regards to a N Coil and recommended UV light mounting locations. As I’m sure you know, high-efficiency N Coils are quickly becoming the norm because they use enhanced, more efficient tubing materials inside the coil, utilize a better fin design on the external portion of the coil and incorporate a better thermal expansion valve (TXV), to meter how much refrigerant the coil needs at any given moment.
    UV light placement in regards to an N Coil can be confusing, with most installations needing two lights minimum to reach most areas impacted by mold growth.

    Reply
    • Hi Noway,

      Yeah, I will update the article to include N-coil info in the future — two lights will probably be necessary.

      However, even with A-coils, I don’t think one light is going to cover 100% of the area either. I think UV lights are really more preventative measures, and that the air handler still should be thoroughly cleaned every 1-3 years. From all the homes that I have inspected, homeowners really have no idea that their furnaces should be cleaned which means; the coil, the plenum, blower fan, wiring etc.

      But if I had an N-coil, I think I would just install a return side “air treatment” HVAC UV light. The air treatment UV lights also tend to be more powerful and higher quality than the “surface treatment” UV lights that are installed on the supply or coil side of the air handler.

      I will need to update this article on that aspect as well. I did touch upon the difference between air & surface treatment UV lights in this article here: Best Honeywell HVAC UV Lights.

      Thanks for the tip!

      Reply
    • Hello Jack,

      I haven’t heard of UV lights not being able to take the heat. Usually, it is the other way around — the UV light is damaging certain furnace components. You may want to consult your furnace manual to see if there are any areas that need to be protected or sensitive to UV light. You could also install air treatment UV lights which are installed on the return side of the furnace so it won’t be exposed to as high a heat such as this one by Honeywell.

      Good luck!

      Reply
  2. OVC ideally installed after the cooling coil. How do you install it in a cassette type FCU?

    For Free Blow FCU if you install, the Lamp and the light can be seen thru the grills?

    Reply
    • It may be tough to install conventional UV lights in FCUs, I did find one product claiming to work with cassette and mini-split AC systems — it’s called the UV Light LED System for Mini-Splits by a company called Fresh-Air UV. They put the UV lights on a LED strip. I imagine it would be seen through the grill, but with the room lights on, perhaps not visible.

      Reply
    • Hello Tito,

      The typical amount of UV coil exposure is in the 50-100 microwatts per cm^2 — but exposure between 30-50 μW/cm2 is reported as sufficient to kill most micro-organisms.

      Directly from Ashrae.org “A UVC installation that produces a maintained, uniform distribution of UV irradiance averaging between 30 and 50 μW/cm2 is effective in inactivating most airborne droplet nuclei containing mycobacteria, and is presumably effective against viruses as well (First et al. 2007a, 2007b; Miller et al. 2002; Xu et al. 2003).

      Good luck!

      Reply
    • Hi Charles,

      In general, if the UV light has an air flow sensor, like some of the OdorStop products, then these are installed on the return side of the furnace which is prior to the coil — so UV light doesn’t even hit the coil. The other type of UV light is installed above the coil on the supply side — and it is always on. So the air treatment UV lights are meant to kill microbes in the air stream which is why they only turn on when the furnace is actually running. I think they both do a good job, though I think the air treatments lights are of a higher quality.

      Good luck!

      Reply

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Arie Van Tuijl

Arie Van Tuijl

Arie is the founder of Home Inspector Secrets, an online resource dedicated to helping people understand how homes work. He is a licensed home inspector in two U.S states and owns a residential and commercial inspection company (read his full bio on the About page). To ask Arie a question, please use the comment box at the bottom of the relevant article.

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Home Inspector Secrets is an online resource for owners, buyers, and sellers to understand all aspects of home maintenance. We have detailed home guides, product reviews, inspection advice, and much more.