0-10 volt dimming: Mixed circuits?

Location
Portland, OR
Occupation
Electrician
This question is part code, part engineering. With current sinking (architectural) 0-10 volt dimming, what are the hazards and/or potential code violations of running the dimming circuit to fixtures running on different circuits.....potentially even from different line voltage sources?

Most commercial LED fixtures we install these days use universal drivers that run off 120/277 volt power. They produce a voltage which is then sent in parallel along with any other fixtures on the same dimming circuit to the dimmer, which uses variable resistors or PWM to drop the voltage, which tells the driver what percentage to dim. The drivers are designed to read the resistance/voltage drop across the dimmer without respect to the other fixtures that may be on the circuit. I've seen areas of open offices that have some 2x4 lighting on normal power mixed with other fixtures on emergency power, all sharing the same dimming circuit (using emergency relays to bypass dimming when normal power power drops out). This seems to work, but I'm not sure it's okay.

I'm guessing there may be a code issue here but I haven't been able to find one. I've also searched the literature online and I haven't been able to find anything from an engineering standpoint that says this is no bueno. Anybody here have any knowledge about the subject?
 

augie47

Moderator
Staff member
Location
Tennessee
It's poses some interesting Code issues.
To start, I might suggest you review this recent thread:
 
Location
Portland, OR
Occupation
Electrician
It's poses some interesting Code issues.
To start, I might suggest you review this recent thread:
I didn’t see anything in that thread that directly dealt with my question. Did I miss something?
 

augie47

Moderator
Staff member
Location
Tennessee
Likely I did (miss something). I guess I'm not exactly clear on your question.
I referenced that link as it discussed dimming wiring and Code,
Your post is still up and hopefully someone will address your specific question,.
 

hbiss

EC, Westchester, New York NEC: 2014
Location
Hawthorne, New York NEC: 2014
Occupation
EC
With current sinking (architectural) 0-10 volt dimming, what are the hazards and/or potential code violations of running the dimming circuit to fixtures running on different circuits.....potentially even from different line voltage sources?
I think he's asking about using one dimmer with a number of fixtures on different circuits and different voltages.

-Hal
 

hillbilly1

Senior Member
Location
Atlanta,Ga
I think technically they do not produce a "voltage" per se, introduce an external voltage such as a battery, all connected fixtures will react the same. Kinda like ghost voltage produced by open wires in close proximity of live wires. Short them together, they go to zero. Multiple circuits would not create "parralell" voltages in the sense we are used to.
 
Location
Portland, OR
Occupation
Electrician
I think technically they do not produce a "voltage" per se, introduce an external voltage such as a battery, all connected fixtures will react the same. Kinda like ghost voltage produced by open wires in close proximity of live wires. Short them together, they go to zero. Multiple circuits would not create "parralell" voltages in the sense we are used to.
That's what I'm thinking; even though the line level sources of each fixture may be different, they're not functionally interacting with each other. Simply put, they're reading the resistance value of the dimmer. BUT, in order to read that resistance, they have to put out a voltage of some sort, don't they?

I don't understand how the fixtures interact with the dimmer from an engineering standpoint, so I couldn't really say if there were potential dangers from mixing the circuits like that.
 

hillbilly1

Senior Member
Location
Atlanta,Ga
We’ve had no problems with multiple circuits, Home Depot dims the entire store with just a couple of zones, Walmart also does it. I built a battery bank to test the entire store at one time, in case any fixtures got missed in the loop. Shorting the dimming leads together will also send the fixture to full dim.
 

hbiss

EC, Westchester, New York NEC: 2014
Location
Hawthorne, New York NEC: 2014
Occupation
EC
I built a battery bank to test the entire store at one time, in case any fixtures got missed in the loop. Shorting the dimming leads together will also send the fixture to full dim.
Each fixture's controller provides 10VDC. Short it out and the fixture goes to full dim. I don't know why you use a battery bank. A VR would be more appropriate.

As long as you parallel all your 0-10V wiring from each fixture maintaining the correct polarity, (grays together and purples together) you've just parallel all the voltage sources. Shorting the junction out should dim all the fixtures. Using an appropriate VR for test should allow you to go through the entire range.

-Hal
 

hillbilly1

Senior Member
Location
Atlanta,Ga
Each fixture's controller provides 10VDC. Short it out and the fixture goes to full dim. I don't know why you use a battery bank. A VR would be more appropriate.

As long as you parallel all your 0-10V wiring from each fixture maintaining the correct polarity, (grays together and purples together) you've just parallel all the voltage sources. Shorting the junction out should dim all the fixtures. Using an appropriate VR for test should allow you to go through the entire range.

-Hal
Most dimmers are not rated for that amount of fixtures. HD uses a special high capacity dimmer module to dim their stores, even though the current is not that great. With the batteries, I can regulate the exact voltage through a step switch. We were doing a study for Depot against different manufactures outputs, so we needed a starting point to compare.
 
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