Fine Tuning a Dimmer Switch

[Little Bill]

Some dimmer switches have adjustment pots to fine tune the dimmer. I've used these for a long time, mostly with Lutron dimmers. I was looking on the instructions for a Legrand dimmer and it said you need to turn the power off when adjusting the pot/wheel. Why would that matter? It would be a royal pain to turn power off, adj the pot, power back on, test, rinse and repeat until it's where you want it.

I've never turned the power off on Lutron dimmers. Is this just a CYA thing from Legrand in case someone gets shocked adjusting the pot? Or would it damage the dimmer if adjusting with power on?

 

[hbiss]

Only one way to find out...

-Hal

 

[readydave8]

 

[brantmacga]

If it’s the tru-universal dimmer they recommend power cycling so it can recalibrate the minimum output voltage.


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[Little Bill]

If it’s the tru-universal dimmer they recommend power cycling so it can recalibrate the minimum output voltage.


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I don't know if it's tru-universal dimmer as I don't see anything in the documentation stating that.
It is a Legrand/Pass & Seymour
RHCL453P

 

[brantmacga]

I don't know if it's tru-universal dimmer as I don't see anything in the documentation stating that.
It is a Legrand/Pass & Seymour
RHCL453P

ok that's not the tru-universal. in that case its probably just a CYA note from P&S.

 

[Little Bill]

ok that's not the tru-universal. in that case its probably just a CYA note from P&S.

I just sent an email to the tech support at Legrand asking them why the power has to be off. I'll see if they give a logical answer, or even answer me at all.

 

[Flicker Index]

Totally CYA.. however, you do need to power down, wait 15-20 seconds, then start and do that 2-3 times before putting the cover back on to ensure predictable and repeatable startup. The reason for waiting 15-20 seconds is to allow the capacitors in the L.E.D. ballasts to discharge.

If you trim it down until you can barely see the glow, the lamps may fail to ignite or you may only have some of the lamps ignite upon restart.

The level at which all lamps on the circuit can successfully restart after a power down can limit the minimum dimming setting unless the user is ok with having to bump the level up and dim down. Some dimmers have a throttle blip feature to do this automatically to get around this.

My go to method is to start at the trim at maximum, dim the slider to minimum, then use the trim to bring it down to the desired minimum level.
Turn the switch off, wait 20 seconds... and power back on. Verify it starts reliably three times before reassembling.

 

[Little Bill]

Totally CYA.. however, you do need to power down, wait 15-20 seconds, then start and do that 2-3 times before putting the cover back on to ensure predictable and repeatable startup. The reason for waiting 15-20 seconds is to allow the capacitors in the L.E.D. ballasts to discharge.

If you trim it down until you can barely see the glow, the lamps may fail to ignite or you may only have some of the lamps ignite upon restart.

The level at which all lamps on the circuit can successfully restart after a power down can limit the minimum dimming setting unless the user is ok with having to bump the level up and dim down. Some dimmers have a throttle blip feature to do this automatically to get around this.

My go to method is to start at the trim at maximum, dim the slider to minimum, then use the trim to bring it down to the desired minimum level.
Turn the switch off, wait 20 seconds... and power back on. Verify it starts reliably three times before reassembling.

Thanks, wish I had saw this 2 hours ago before I played with the dimmers for an hour! I did the "turn breaker off" method. Luckily I had someone camped out at the panel.
I emailed Legrand but never got a reply.