Because the conditions that caused it have not changed. In Florida the coil produces condensate through most of the year, so within days of cleaning it is damp, dark, and receiving organic dust again. Cleaning resets the surface; it does not alter the environment. Continuous UV is what slows the rate of return, which is the argument for pairing the two rather than choosing between them.

Both do the same job — UV-C directed at the evaporator coil. BLU QR adds quick-release lamp technology for tool-free replacement and more flexible mounting. On an accessible air handler either works well. Where access is awkward, the quick-release version is worth the difference, because it determines whether annual replacement actually happens.

Yes, and it is the part worth understanding before purchase. UV-C output declines gradually while the lamp still looks lit, so a lamp two years old may be producing little useful output while appearing to work perfectly. Annual replacement is the guidance we give, and we check lamp age during maintenance visits rather than leaving you to track it.

Where the installation allows, yes — we illuminate the drain pan too. It is worth doing because the pan holds standing water in a dark enclosed space, which is arguably a better environment for growth than the coil itself. Whether it is practical depends on the air handler layout, and we will tell you which applies to yours.

Indirectly, by keeping the coil cleaner than it would otherwise stay. Biofilm insulates the coil and reduces heat transfer, so preventing that buildup preserves efficiency you would otherwise lose gradually. It will not make a clean system more efficient than it already is — the gain is in what you avoid losing, which is real but less dramatic than it is sometimes sold as.

When installed correctly, yes. The lamp sits enclosed within the air handler, so the light is contained inside the equipment and there is no exposure during normal operation. Safe 24V electrical integration and proper enclosure are part of the installation, and are among the reasons this is not a suitable DIY fitting.