Article 725 Class 2 device

[hutch75]

I am reviewing some panel build drawings, and have run into a disagreement with a panel shop concerning a Class 2 network(devicenet) being fed from a Class 1 transformer. The vendor is claiming that the class 1 transformer is outside the scope of 725.41, and is calling out a class 2 listed 4 amp circuit breaker as the other(725.41(A)(3)) listed equipment power source. Reading the FPN, it does not specifically list a fuse as being a class 2 listed power source.

Has anyone had any luck in contacting a CMP or the NFPA for a formal interrpertation? This item is beyond the interest of our local AHJ, and has far reaching considerations in future builds.

 

[tom baker]

Re: Article 725 Class 2 device

An answer from the NFPA would be slow.
The best resource that I have seen on Device Net is from Allen Bradley, Device Net Media Design and Installation Guide. It does discuss NEC Class 1 and 2 circuits and wiring guidelines.
Its publication DNET-UM072c-en-p
Search for it here:
http://literature.rockwellautomation.com/idc/groups/public/documents/webassets/browse_category.hcst
Under networks and communications, its

 

[tony_psuee]

Re: Article 725 Class 2 device

hutch,

I had a similar situation at my last job. The power supply was listed, but not as a class 2. We presented the power supply UL file number and fuse information to our UL inspector and he approved the combination as a class 2 supply within the listed 508A panel.

Tony

 

[hutch75]

Re: Article 725 Class 2 device

The Allen Bradley literature makes reference to Article 725, and makes it clear that the maximum current allowable is 4 amps on any branch. Our vendor has each circuit protected with a four amp class 2 breaker, but the power supply is a class 1 rated device, and is outside of the enclosure. My main concern is that does a circuit breaker comply with 725(a)(3)FPN(4)?

We do not have the avenue for a UL listing on this equipment, so we need to rely on the NEC to tell us if this is a correct installation. We are hesitant with this installation since if this power supply fails, we will need to stock a very large supply in the crib instead of a few smaller(4 amp) ones.

Thanks for the feedback