The sheet metal plate is drilled and painted for mounting the Honeywell UV100A1059 UV light to the air conditioner rigid duct board plenum. This project is continued from How to Install a Honeywell Ultraviolet Light Treatment System – Part 1.
Honeywell UV Light – Sheet Metal Mounting Plate
The 16 gauge sheet metal mounting plate will be attached to the rigid duct board plenum with aluminum foil HVAC tape because the fiberglass duct board will not hold screws and is not strong enough by itself to support the UV light. The metal mounting plate provides the needed structural support and distributes load across the duct board.
Using the tape measure and square, I measured and marked the center of the sheet metal mounting plate. The center of 2 inch hole for the UV lamp will be drilled in the center of the mounting plate.
I used a pencil to punch small holes in the paper template for two screws and 2″ inch lamp hole. The template sheet is carefully aligned with the center of the steel mounting plate and checked for square with the plate ends, then the pilot holes are marked on the steel with a marker:
The blue arrows indicate the green felt tip pen marks for the two mounting screws. A green dot is also marked on the center of the plate to confirm the template alignment was correct.
I set the sheet metal on two 2×4 blocks to protect the workbench surface, then dimpled the pilot hole marks with a hammer and strong screw. A 16 penny nail will also do instead of a screw. Use a center punch if you have one, I have one but didn’t bother to find it.
Be careful to support the sheet metal directly on the 2×4 block before making the dimple to avoid warping the sheet. The purpose of the dimples is to create a depression (or small pocket) for the drill bit point to rest in so it doesn’t “walk” across the sheet metal and cause the pilot hole to be misaligned.
Drill the three pilot holes using a 3/32 inch drill bit rated for metal. The 2×4 blocks protected my work bench from the drill bit.
Using my DEWALT cordless drill/driver, I drove the two mounting screws into the 16 gauge sheet metal plate while supporting it on the 2×4 blocks. The screws are significantly larger in diameter than the 3/32 inch pilot holes and cut threads in the steel plate. I found the screws held firmly.
Honeywell UV Light 2 inch Lamp Hole
A 2 inch diameter hole must be drilled in the center of the sheet metal mounting plate for the UV lamp to be inserted into the air handler plenum. Any 2 inch metal hole saw will do, but I really like the Milwaukee 3/8 inch Quick Change Arbor and Hole Saws. I already had the arbor and a 4-1/4 inch hole saw from a previous project, so I bought the Milwaukee 2 inch bi-metal hole saw 49-56-9624 for this job.
The Milwaukee 2 inch hole saw mounted my DEWALT cordless drill/driver:
The metal plate is slippery and must be securely clamped before drilling. The hole saw has a tendency to grab and spin the plate, and the metal plate can cut you! I drilled the hole by:
- Placing the two 2×4 blocks on the cement floor, spaced about 3 inches apart lengthwise.
- Laid the sheet metal plate across the 2×4 blocks with the center of the plate over the 3 inch gap between the blocks.
- Stood on the plate with each foot holding the plate on a 2×4 block.
My weight was centered on the 2×4 blocks so as not to bend the plate, clamping the plate to the blocks.
- Drilled the 2 inch pilot hole.
It helps to slightly rock the hole saw back & forth / side to side for better cutting. The hole saw generates a lot of friction heat, so don’t touch the metal when finished drilling. After the pieces have cooled, deburr the hole with a file (I’ve not yet filed the burrs in this photo):
Honeywell UV Light Sheet Metal Support Mount
Here’s the Honeywell UV100A1059 coil treatment UV light mounted to the 6 in. x 14 in. 16 gauge sheet metal plate. Tighten the two sheet metal screws by hand with a screw driver because a cordless drill/driver may over do it and strip the threads cut in the sheet metal.
Closeup of the sheet metal plate mount for rigid duct board structural support:
The plain sheet metal steel plate can rust. Wash the finger prints and oils off the metal plate with dishwashing soap and dry thoroughly. Then spray paint both sides and all edges with quality primer and wait until the paint is dry and cured. I used Rust-Oleum gray primer.
This project is continued in How to Install a Honeywell Ultraviolet Light Treatment System – Part 3.
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