After some troubleshooting I determined that the ballast in my Lennox ureAir filter system had failed. Atomic had the part, at a very good price, and shipped it to me promptly. I will definitely be a return customer for my other air filter (and associated parts) needs.

This ballast was the exact Lennox part and fixed the problem with the UV lights not working in my PCO20-28 PureAir System.