Track Lighting Current Limiting Panel

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Grouch1980

Grouch1980

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Location
New York, NY
A lighting designer wants me to draw up the electrical drawings for the following: a few hundred feet of track lighting connecting to a current limiting panel that has small circuit breakers... not sure how small they are, but i'm assuming around 3 or 4 amps.

I'm not entirely sure how to put this together. Is this correct?:

Design the feeder / main breaker that feeds the current limiting panel according to section 220.43(B), which is 75VA per foot. So I'll take the total feet of the track and multiply by 75 VA, and then multiply by 1.25 since it's a continuous load. Next size up would give me the breaker / feeder size.

Then I would have the individual tracks connecting to the small breakers on the current limiting panel. The breaker size for each track / circuit would be based on the actual bulb wattage divided by the voltage (120).

Do I have this correct?
 
hbiss said:
220.43(B) is for calculating the track lighting load, not for actually limiting the track current. The branch circuit (usually 20A) will do that.

The lighting designer doesn't know what he's talking about.



-Hal
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On the other hand, for energy efficiency standards it may be necessary to limit individual tracks or groups of tracks to less than 20A or to limit more precisely than a simple breaker can.
 
hbiss said:
220.43(B) is for calculating the track lighting load, not for actually limiting the track current. The branch circuit (usually 20A) will do that.
-Hal
Click to expand...
Isn't that what I'm proposing in the electrical design though? I'm sizing the feeder to the panel based on 220.43(B).
 
Grouch1980 said:
Isn't that what I'm proposing in the electrical design though? I'm sizing the feeder to the panel based on 220.43(B).
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And that is where you are making your mistake. The whole purpose of the current limiting panel is to not have to follow the 75VA per foot. Read the exception to that section. It directly addresses your scenario.

Exception: If the track lighting is supplied through a device that limits the current to the track, the load shall be permitted to be calculated based on the rating of the device used to limit the current.
 
211119-1358 EST

What is a current limiting device? A resistor, a fuse, an inductor, a capacitor, a circuit breaker, a transistor current limiter circuit, a fold back power supply, a thermistor, a positive temperature coefficient thermistor, a piece of copper wire, or many other things.

What is a good current limiter? An electronic constant current source.

Basically I have no idea what the original question is asking.

..
 
d0nut said:
And that is where you are making your mistake. The whole purpose of the current limiting panel is to not have to follow the 75VA per foot. Read the exception to that section. It directly addresses your scenario.

Exception: If the track lighting is supplied through a device that limits the current to the track, the load shall be permitted to be calculated based on the rating of the device used to limit the current.
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Thanks! I see the exception in the 2017 NEC... I had no idea it was there. In the 2008 NEC, which i'm following since i'm in NYC, we don't have that exception. What would you recommend I do since I don't have that exception?
 
gar said:
211119-1358 EST

What is a current limiting device? A resistor, a fuse, an inductor, a capacitor, a circuit breaker, a transistor current limiter circuit, a fold back power supply, a thermistor, a positive temperature coefficient thermistor, a piece of copper wire, or many other things.

What is a good current limiter? An electronic constant current source.

Basically I have no idea what the original question is asking.

..
Click to expand...
And I have no idea how your 2 responses are contributing in any way.
 
I would think you could still calculate the load based on the circuit breaker size. If, for example, you have a 2A circuit breaker feeding some track, it doesn't matter whether the track is 10' or 100' long, you can only have 2A of load on that track. The 75VA/ft calculation is based on the ability to add more or larger wattage heads to the existing track in the future. That ability doesn't exist with a current limiting circuit breaker feeding that track. The same logic works for low voltage track. If it is fed by a 300W transformer, for example, it doesn't matter how long the track is you can only put 300W of lighting on that track.
 
d0nut said:
I would think you could still calculate the load based on the circuit breaker size. If, for example, you have a 2A circuit breaker feeding some track, it doesn't matter whether the track is 10' or 100' long, you can only have 2A of load on that track. The 75VA/ft calculation is based on the ability to add more or larger wattage heads to the existing track in the future. That ability doesn't exist with a current limiting circuit breaker feeding that track. The same logic works for low voltage track. If it is fed by a 300W transformer, for example, it doesn't matter how long the track is you can only put 300W of lighting on that track.
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Got it, thank you for the feedback! It does make sense in that once you're limited nothing else will go through anyway.
 
Grouch1980 said:
Got it, thank you for the feedback! It does make sense in that once you're limited nothing else will go through anyway.
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Have you found a panel where you can use these small CBers?
Have you researched the track mfg’er web page…look for current limiting end feeds. They come in a wide range of wattages.
Have only seen them used where a project is being designed for a LEEDS certification.
 
MyCleveland said:
Have you found a panel where you can use these small CBers?
Have you researched the track mfg’er web page…look for current limiting end feeds. They come in a wide range of wattages.
Have only seen them used where a project is being designed for a LEEDS certification.
Click to expand...
This is what the lighting designer is proposing for the current limiting panel. Just see the attachment.
 

Attachments

  • Current Limiting Panel for Track.pdf
    706.7 KB · Views: 22
Finally able to view….new product I have not seen before.
I don’t see a bus rating option, so make sure to check with rep on options and compare to your total load x 1.25.
 
Given what that product is, basically a circuit breaker panel. I might consider sizing wiring based on panel's bus bar rating. That gives flexibility for any future changes.

I mean, who cares if current project is only four two amp breakers in a 16 space panel. If I was the building owner I'd want a circuit allowing me to fully load that panel if desired in the future.

But some customers only care about first costs so design/bid it both ways (based on actual connected load and panel's max amp rating).
 
gar said:
211119-1358 EST

What is a current limiting device? A resistor, a fuse, an inductor, a capacitor, a circuit breaker, a transistor current limiter circuit, a fold back power supply, a thermistor, a positive temperature coefficient thermistor, a piece of copper wire, or many other things.

What is a good current limiter? An electronic constant current source.

Basically I have no idea what the original question is asking.

..
Click to expand...
For example Juno has fused current limiting end feeds for their track. Different sizes depending on application. Just for that reason if you are using long runs but don’t want to follow the VA/ft spelled out in the code book.
Works well when using LED heads on long runs to satisfy the AHJ if they even pay attention to it.
 
Juno offers current limiting panels and current limiting track feeds, just fyi if that will save you some time.


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