Article 725..."functionally related"?

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Electron_Sam78

Electron_Sam78

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Palm Bay, FL
Hey all, in reading posts about the issue of Class 1 and power/lighting circuits in the same conduit I would like some input on a situation at work. We have an evaporative cooling tower with two 480 VAC motors and a 24 VAC actuated valve that is located on the incoming piping just next to the unit. Is the functional relation between the valve feeding the water to and the motors for the evap. unit fans close enough to pass your interpretation of Article 725's requirement to allow the Class 1 and power wiring in the same conduit? :thumbsup: or :thumbsdown: :blink::huh:
 
Good question.

I can see it going either way depending on AHJ interpretation. FWIW, I would allow... but I suggest you contact them to get the pertinent opinion.
:p
 
Smart $ said:
Good question.

I can see it going either way depending on AHJ interpretation. FWIW, I would allow... but I suggest you contact them to get the pertinent opinion.
:p
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I would ask forgiveness not permission in this situation. Given the description, I assume the cooling tower would not function properly unless both the valve and the motors were operating. It would be a huge stretch for an AHJ to figure out how to call those, "not functionally associated".
 
Yeah I was leaning toward yes. Especially since the control system operating the valve will also be energizing the motor starter coils.

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Are you sure that the 24 volt power supply is a Class 1 power supply? If it is you are fine, as I agree with the others that the valve would be functionally associated with the power conductors. However if the power supply would be a Class 2 power supply, they can not be mixed with the power conductors, even where they are functionally associated.
 
don_resqcapt19 said:
Are you sure that the 24 volt power supply is a Class 1 power supply? If it is you are fine, as I agree with the others that the valve would be functionally associated with the power conductors. However if the power supply would be a Class 2 power supply, they can not be mixed with the power conductors, even where they are functionally associated.
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However, 725.130(A) states...
Exception No. 2: Class 2 and Class 3 circuits shall be
permitted to be reclassified and installed as Class 1 circuits
if the Class 2 and Class 3 markings required in 725.124 are
eliminated and the entire circuit is installed using the wiring
methods and materials in accordance with Part II,
Class 1 circuits.
Click to expand...
 
Smart $ said:
However, 725.130(A) states...
Click to expand...

You beat me to it. This is extremely handy when dealing with 0-10v dimming, as it means you can install it all in the same conduit. The caveat for those not as smart as Smart, remember that once you remove the Class 2 reference, all of the wiring from that supply must be run as class one, so for example, say you have a room with upscale dimming that also has a separate occupancy sensor, two sets of wall switches, and a photocell at the window. All the wiring must be enclosed in conduit and boxes.
 
Strathead said:
You beat me to it. This is extremely handy when dealing with 0-10v dimming, as it means you can install it all in the same conduit. The caveat for those not as smart as Smart, remember that once you remove the Class 2 reference, all of the wiring from that supply must be run as class one, so for example, say you have a room with upscale dimming that also has a separate occupancy sensor, two sets of wall switches, and a photocell at the window. All the wiring must be enclosed in conduit and boxes.
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The other key point is that any loads in the circuit must be rated for operation from a Class 1 source. In some cases the loads are only tested for safety with the power limited Class 2 supply. In those cases you cannot reclassify the wiring no matter how completely you do it. You may be able to supply alternative current limiting (Class 2 equivalent) right at the loads though.
 
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