IN-PROGRESS STILL_____UV-C Germicidal Furnace "Filter"
Having suffered from allergies most of my life, anything that promises to "help with "allergens" tends to be of great interest!
Premise
Ultraviolet "C" band light is well known to be "toxic" to almost any living organism; such as mold, bacteria, viruses, & people. (See some stupidity here: https://www.nytimes.com/2023/11/07/style/bored-ape-nft-eye-burn.html )
I wanted to use this same "Kill EVERYTHING" approach toward any living contaminants that may have found their way into my home HVAC system. UV-C is already used for this exact purpose in commercial products and systems,systems but the pricing can be prohibitive for an off the shelf unit. MyComparing priceprices comparisonskinda went from ~$500 for what I consideredstank; an under-powered unitconsumer product started about $500, but went sharply up to ~$50004000 for a cool fluorescent system that MUST be installed by approved HVAC tech to have any warranty.
LessBeing moneya spent...acceptablehuge qualitynerd, etc.....................I asked myself the ultimate question: "How hard can it be?"
Design
This only qualifies as a design in the strictest sense, since even a table lamp has a switch!
- 2x - 50W+
E27E26 size UV-C COB LED bulbs- Edison #26 is the most common light socket in the US
- https://en.wikipedia.org/wiki/Edison_screw
- 2x - Ceramic
un-switchedE26/E27 light outlets- Un-switched type are cheapest
- 2x - 1" deep electrical light boxes
- Metal would be fine, but I used PETG-V0
- 6' - 18/2 home wire (18ga with black, white, ground)
- 3-wire service cord would work equally well
- 4' - 1/2" weather stripping
- Anything "UV resistant" and soft since the metal is fairly thin
- Right Angle 3/4" clamping box fitting
- Points the cable the right direction and holds it tight
- 24"x12" 22ga steel sheet
- Gotta make a plate out of something sturdy and UV resistant
Build
We begin by looking at the furnace system we want to modify; can we find a place about 6-8 by 10-16 inches? it is recommend to go with a standard "off the shelf" vent size such as 8x16", which would enable easy retrofitting if the home is soldsold, etc.
Once we have the location and size chosen, cut and smooth the edges of our sheet metal plate to match a 1" overlap on all sides so our plate overhangs the hole we will cut in the HVAC system. I used some 3mm screws with nuts to mount the electrical boxes onto the sheet metal plate. I used some PETG-V0 Flame Retardant filament to 3D print the electrical boxes, to ensure I added a little fire load to the furnace as possible!
Both light fixtures are connected in parallel with the grounds each being terminated to the metal sheet inside each box for extra safety.
Notes
Wiring was harder for me than it should have been since I used "scrap" materials wherever possible, this left me wiring 130W of total power lighting with 12ga heavy wire instead of the 18ga or similar that could also have been used.
I ended up going the LAZY way and wired these in as "on all the time", since my HVAC system blower motor is Variable Frequency Drive meaning there is no convenient place to hook up the lights to a switched 120VAC output like I hoped.