# Fluorescent Dimmer Wiring



## TGGT (Oct 28, 2012)

My foreman came up with a wiring diagram for a dimmer switch to dimming fluorescent light that had the hot tie to the switch, but splice off of that and go directly to the ballast as well, then the "switch leg" comes off the light back to the switch again. Neutrals tie to both the switch and ballast.

This has me *really* confused. I'm really trying to understand this but it doesn't make sense to me how that would work. Does it have to do with electronics in the switch and ballast?

I've been looking for the past half hour to find a diagram on-line similar to his description.

It's a Focal Point light by the way, but I couldn't find relevant information on their website. FMA2-22-3-T5-D-277-G-WH


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## HARRY304E (Sep 15, 2010)

TGGT said:


> My foreman came up with a wiring diagram for a dimmer switch to dimming fluorescent light that had the hot tie to the switch, but splice off of that and go directly to the ballast as well, then the "switch leg" comes off the light back to the switch again. Neutrals tie to both the switch and ballast.
> 
> This has me *really* confused. I'm really trying to understand this but it doesn't make sense to me how that would work. Does it have to do with electronics in the switch and ballast?
> 
> ...


................


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## TGGT (Oct 28, 2012)

Dot dot dot what Harry.

Am I right in that it doesn't make sense or are you familiar with this kind of setup?


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## HARRY304E (Sep 15, 2010)

TGGT said:


> Dot dot dot what Harry.
> 
> Am I right in that it doesn't make sense or are you familiar with this kind of setup?


No,,,,,I bumped your thread then I got tied up in something else....:laughing:


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## HARRY304E (Sep 15, 2010)

I think that this is what you are looking for...

http://www.focalpointlights.com/downloads/reference/LowVoltageController_specs.pdf


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## TGGT (Oct 28, 2012)

Okay, this is what I found that most mimics the cardboard scribble he was showing me.

http://site.electricsuppliesonline.com/documents/Lutron/GrafikEye/fdbi.pdf

It's a Fluorescent Dimming Ballast Interface.

In this diagram it's spliced to feed the ballast interface _before_ it goes to the light.


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## TGGT (Oct 28, 2012)

HARRY304E said:


> I think that this is what you are looking for...
> 
> http://www.focalpointlights.com/downloads/reference/LowVoltageController_specs.pdf



I downloaded that earlier, not really sure if that's the route they're going or not. I'll study it more after dinner. Thanks, though.


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## drumnut08 (Sep 23, 2012)

TGGT said:


> My foreman came up with a wiring diagram for a dimmer switch to dimming fluorescent light that had the hot tie to the switch, but splice off of that and go directly to the ballast as well, then the "switch leg" comes off the light back to the switch again. Neutrals tie to both the switch and ballast.
> 
> This has me really confused. I'm really trying to understand this but it doesn't make sense to me how that would work. Does it have to do with electronics in the switch and ballast?
> 
> ...


I did dimmable compact flourescent recessed lights once and recall needing three wire from the dimmer location daisy chained to the lights . The ballast needed a constant hot , a switch leg and a neutral . The ballasts and dimmers were Lutron and meant to work together . I just followed the schematic and didn't question it and they worked great for dimming flourescents anyway .


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## HARRY304E (Sep 15, 2010)

TGGT said:


> I downloaded that earlier, not really sure if that's the route they're going or not. I'll study it more after dinner. Thanks, though.


Yup there is a lot to read there.


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## TGGT (Oct 28, 2012)

drumnut08 said:


> I did dimmable compact flourescent recessed lights once and recall needing three wire from the dimmer location daisy chained to the lights . The ballast needed a constant hot , a switch leg and a neutral . The ballasts and dimmers were Lutron and meant to work together . I just followed the schematic and didn't question it and they worked great for dimming flourescents anyway .


I hate that I don't have an official schematic, I haven't even seen the lights or the switches. It'd make pulling the wire a lot easier.


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## Electric_Light (Apr 6, 2010)

I can't figure out what you mean.
There are several different types of fluorescent dimming control. 

The traditional industry standard setup for electronic ballast is a pair of 0-10v analog, which are parallel wired. Each ballast provides about 0.5milliamps and the dimmer clamps across this to maintain a constant voltage.

If you have 200 ballast, the dimmer has to sink about 0.1A, so a small amount of heat will be generated at the dimmer. 

Another type is three wire setup where each ballast gets neutral, hot, and a dimmed hot that's controlled like an incandescent. The ballasts use the dimmed hot only for the purpose of "seeing" the phase angle (rather than voltage) which is used to tell the ballast what to do. This setup is primarily used by Lutron. If your lighting control system is 0-10v, you would have to use an interface to convert to this signal. Simple dimmers for this design is available from several vendors, but I think Lutron is pretty much the dominant player in 3-wire ballasts. Schematically, you treat it basically like a step dimming setup that uses two hot wires with three wires running to each box. 

Yet another type is called two wire, which is phase controlled dimming. This is the worst of all, because it causes poor power factor and is prone to flickering. This is used when pulling additional control wire(s) to each fixture is uneconomical. 

Then, there's DALI. Physically, wiring is like 0-10v setup. The low voltage wires are used for signaling and ballast does the dimming internally.


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