Dimmer bypass needed if neutral available?


#1

I’ve seen it said a couple of times that a dimmer bypass may not be needed if a neutral is available at the switch.

I’ve found this not to be the case and a bypass is needed, that or swap out a couple of 4W Leds for 35w halogen.

Can anyone confirm whether they have successfully installed a dimmer 2 without a bypass on a load such as 4 x 4w GU10 Leds?

Also, as the led bulbs (when they are the only load) remain slightly lit when the dimmer is “off”, when the bypass is installed is this current still present but just soaked up? I.e am I actually consuming power when the switch is “off”.

In this case would I be better with FGS-213 as a relay without dry contacts to switch an led load (dimmable not required)


(John Crighton) #2

I think I’ve said it before. If there is a neutral, then the Dimmer module can use it to complete the circuit for powering itself, and doesn’t need to route any power through the lighting circuit.

That was my assumption anyway, I don’t understand why it wouldn’t be the case.

Any module will take some power (whether it’s a dimmer or relay) as it will need it to be ready to respond. A relay always has a neutral as it needs it to be truly off, whilst still giving the module power.

The amount of power consumed by this is miniscule.


#3

It would seem then that the dimmer never truly turns off.

Even when powered directly with its own live and neutral the led lights still glow slightly when the module is set to off.


#4

There seems to be some confusion about the bypass. Although it can be helpful when there’s no neutral, that’s not its purpose. Its purpose is to add a dummy load to the circuit so that you will meet the minimum load required for the dimmer to function efficiently. Without it, LED lights may flicker, buzz, or not turn completely off.

Adam Whistler has a good explanation:

And from the official manual for the dimmer 2:

FIBARO Bypass 2 prevents flickering of the lED lights and glowing of the turned on compact fluorescent lamps.