Motor Control Circuits and Circuit Classification

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makoester1

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Hello,

I have a combination starter with a 480-120V, 500VA control transformer tapped from the load side of the branch circuit protective device. Within the 120V control circuit is a remote sensor that requires a factory assembled cordset.

Based on the transformer specifications, I believe this would be classified as a Class 1 remote-control and signaling circuit. If the circuit is classified in this way, the factory assembled corset would not meet the requirements of 725, as it is rated 250V, 4A.

However, I believe a solution would be to find a cable specified as ITC (Instrumentation Tray Cable). This would fall under the provisions of article 727 and article 725 would not apply.

Am I applying this correctly?

Thanks.
 
iwire,

Thanks for the reply. However, can you elaborate a little more? The sensor is something that is being added to the control circuit as an interlock function.
 
makoester1 said:
Hello,

I have a combination starter with a 480-120V, 500VA control transformer tapped from the load side of the branch circuit protective device. Within the 120V control circuit is a remote sensor that requires a factory assembled cordset.

Based on the transformer specifications, I believe this would be classified as a Class 1 remote-control and signaling circuit. If the circuit is classified in this way, the factory assembled corset would not meet the requirements of 725, as it is rated 250V, 4A. ....
Click to expand...
Please explain how you interpret the sensor with factory assembled cord set as 725 noncompliant.
 
The sensor will be powered via the 500VA transformer. Based on the transformer specs, it is not a class 2 or class 3 circuit. Therefore, wouldn't the requirements of class 1 wiring be required? The cordset consists of a PUR cable, 5-22awg conductors, and is rated 250V. Based on these specifications, how would the cordset meet the requirements of class 1 circuit conductors?
 
makoester1 said:
The sensor will be powered via the 500VA transformer. Based on the transformer specs, it is not a class 2 or class 3 circuit. Therefore, wouldn't the requirements of class 1 wiring be required? The cordset consists of a PUR cable, 5-22awg conductors, and is rated 250V. Based on these specifications, how would the cordset meet the requirements of class 1 circuit conductors?
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Class 1 wiring is required for field wiring. The remote control sensor with cord set is a manufactured product. Is it a listed manufacturer accessory for the combination starter? If yes, the cord set wiring does not have to meet the NEC requirement for Class 1 field wiring. (This is what iwire was referring to)
 
makoester1 said:
The sensor will be powered via the 500VA transformer. Based on the transformer specs, it is not a class 2 or class 3 circuit. Therefore, wouldn't the requirements of class 1 wiring be required? The cordset consists of a PUR cable, 5-22awg conductors, and is rated 250V. Based on these specifications, how would the cordset meet the requirements of class 1 circuit conductors?
Click to expand...

When you plug an appliance in the wall does the NEC apply to the internal wiring?
 
This is not an accessory for the combination starter. I am interlocking a separate flow sensor into the start/stop circuit of the combination starter. Therefore, power is being supplied to the flow sensor via the cordset from the 500VA control transformer within the combination starter. Sorry for any confusion.
 
makoester1 said:
This is not an accessory for the combination starter. I am interlocking a separate flow sensor into the start/stop circuit of the combination starter. Therefore, power is being supplied to the flow sensor via the cordset from the 500VA control transformer within the combination starter. Sorry for any confusion.
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Got some make model part number or better yet links to doc's?
 
makoester1 said:
Here is the make and model of the flow sensor and cordset.

IFM Effector SI1006
IFM Effector E18026

http://www.ifm.com/products/us/ds/SI1006.htm
http://www.ifm.com/products/us/ds/E18026.htm

Thanks.
Click to expand...
If you are dead set on using that flow sensor, I only see three possible ways:
  1. Make up your own custom cord set with 18AWG
  2. Use a separate Class 2 power source for the flow sensor and interface to the starter control system with an ice cube or similar relay
  3. Change your starter control transformer to one that is rated Class 2 or 3.


BTW, using ITC does not change your power source Class rating.
 
Smart,

I really appreciate your advice. The flow sensor has already been purchased so I would like to try to utilize it. To your last point. I understand that ITC cable does not change the power source class rating and this is where I find some confusion. Based on what has been previously discussed, I don't see how ITC would meet the requirements either. However, please find the links to a few articles below.

http://ecmweb.com/content/making-sense-necs-rules-industrial-controls
http://www.cabletrays.org/pdfs/techbl16.pdf (page 2, item 2)

These points basically state that ITC is classified as an unidentified type of circuit and Article 725 doesn't apply.
 
This is the first I've heard about ITC "negating" 725 requirements, so I'm still on the fence on the concept. Need to hear more from the experts before completely accepting the idea. Otherwise, it looks quite promising for your scenario. However, it is as I said, using ITC does not change the power source Class rating... and your the one saying the factory assembled cord set is required. Does it use ITC? If not, are you going to make a custom cord set with ITC? This takes us back to possibility #1 that I listed earlier.
 
Thanks Smart. Hopefully we can get some feedback regarding this. The flow sensor requires a 1/2" connector (I believe this is what some manufacturers consider a microfast connector). With that said, I don't necessarily have to utilize the one shown earlier. Turck makes a corset that should connect up to the flow sensor and is rated PLTC/ITC.

http://pdb2.turck.de/repo/media/_us/Anlagen/B2007.pdf (page 141-142)
 
makoester1 said:
Anyone have experience with Instrument Tray Cable (ITC)? I am curious if and how it negates the requirements of 725?
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ITC cable is frequently used in heavy industry for instrumentation circuits as an alternative to Art 725. The caveat is you cant combine them in the same tray with power, lighting and Class 1 circuits that are not power limited or non-power limited circuits. Also, they may not exceed 5A and 150V. The advantage is, at least I'm told, ITC cable is easier to install than 600V TC cable.
 
Dale,

Thanks for the information. So is ITC an acceptable means of wiring for a class I circuit operating at or below 150V, 5A? Again, this is a control circuit interlocking a motor starter based on a flow switch.

If it is an alternative wiring means to 725.49, how can it be backed up? Possibly based on 725.3(G) referencing ITC and article 727?

Thanks.
 
Dale Horstman

Dale Horstman

If the Class 1 circuit is limited to 5A and not more than 150V...AND if installed where maintained by qualified personnel then ITC cable can be used.

Sent from my LG-K330 using Tapatalk
 
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