It had been determined by one of the other 4-5 sparkys that looked at the problem that the fans on (there are 2) the tanning booths dims the lights. Blg. owner said he heard the term 'vibration' used to describe the source of the dimming. What does this mean? Light locations too far to be physical vibration. Units are Ruud lighting R7f26/32, have what looks to be xfmr fixed to outside of usual reccessed light conn. box. Owner was advised that incandescents would fix it.Thoughts?

Have you looked at the voltage when they dim?

Need a bit more info, the tanning booth is on the same circuit or just shares a neutral?

According to Ruud's website these fixtures have an integral class P ballast with automatic voltage senseing. It might be a case of reduced voltage during the fan motor start-up load causeing the can voltage sensor circuitry to fritz....it might be typical voltage drop on the circuit during fan start up if it is small conductors/long run/shared hot....

It might be all kinds of things but in your post you havn't given us a lot of info to go on....sorry

Sorry, the booths are in separate panel from lights.There are 4 panels serving this side of the building. (gonna be fun !!) Actually it's fairly recent construction. Prior sparky took fans off line then turned on booth; no dimming; fans on, they dim.

Unless these fans are monster power hogs as in 8 amps each or more....

Your saying that the lights don't share hot or neutral with the beds and are actually fed from a different sub-panel.

If the wireing is in fact completely discrete from the bed wiring then the only thing I could offer to look at is the neutral capacity/connections.

How two tiny fans starting could affect the tubes in a Recessed can when fed from a different subpanel I don't know. But my first thought would be to look at the neutral connections of the panels/service

I talked to a guy who services these booths and lots of others and HE said the problem is the duct size. Fan is 24" but the installer(?) necked the duct down to 12" before it goes thru the sheetrock ceiling. When he lifted the duct offf(while running) the dimming stopped. He said it's likely that the increase in air resistance is straining the fan motor messing up the harmonics and therefore the electronic ballasts. Sound right?

Reducing the duct diameter by a factor of 2 decreased the duct area by a factor of 4. No wonder why the fan current went up. I suspect that the fan motors and the dimming lights share the same circuit or the same phase in the same subpanel. Fix the fan ducting or reduce the fan size.

Larry C

If the fan was optimized for the duct size, making the duct smaller may actually decrease the current drawn by the motor. If the air is not moving the blades cavitate.
The same can be true of a compressor. When I put the amp clamp on my air compressor I found the peak current was when it had about 90 psi in the tank. It actually dropped quite a bit as the tank approached the 150 psi cutoff.