Mammoth BioShieldUV® Lite 18W 24V HVAC UV Light Air Treatment System Magnetic Holder AC Duct - UVC Light for Air Conditioner

My light failed after about 8 months. How do I use the warranty?

I notice alot of people ordering the 24v ballest shouldn't that already be in the central air unit? Also if their was a video on someone wireing this

The header states 18w 24vdc, but description states this is 24vac. can you please clarify?

Is it really 9 inches like in the picture? I need to know so it will fit.