Replace UV bulbs annually. The critical detail: the bulb keeps glowing long after its germicidal output has dropped below useful levels, so a lit bulb tells you nothing about whether it still works. Replace on schedule, not on appearance.
Why the Bulb Still Glowing Is Misleading
UV lamps produce germicidal ultraviolet output that degrades steadily with use. Meanwhile the visible blue-violet glow persists well past the point where the useful output has fallen off. Homeowners see the light on, assume the system is working, and leave a spent bulb in for years. It is the most common failure mode with this equipment, and it is entirely silent.
The Schedule
- Standard UV bulbs: every 12 months
- Some longer-life models: per manufacturer, occasionally longer
- Sooner if you notice musty odors returning or visible growth on the coil
Timing it with fall furnace maintenance makes it easy to remember.
What Else Needs Checking
The bulb sleeve or lamp surface collects dust, which blocks output — cleaning it is part of proper service. On coil-mounted systems, verify the lamp is still aimed correctly at the coil surface, since that positioning is what makes it effective.
Handle Bulbs Correctly
Do not touch the glass with bare hands — skin oils create hot spots that shorten bulb life. Power off the system before servicing, and never look directly at an operating UV lamp; the light is harmful to eyes and skin. Spent bulbs contain mercury and need proper disposal rather than the trash.
What Happens If You Skip It
Nothing dramatic — the system simply stops doing anything while continuing to draw power. Biological growth resumes on the evaporator coil, which affects both air quality and heat transfer. You paid for protection you are no longer getting.
Making It Routine
UV system checks are part of our maintenance visits. Care Club members get them scheduled, which is mostly a mechanism for ensuring it actually happens.
