External EGC around LFMC in Haz Area for flow xmtr

[David Lundquist]

Hi Mike,
Thanks for a great webinar on the 2011 NEC Top Code Changes. Thanks for starting with glorifying God. Prov. 16:3 & Prov. 3:5-6 support this.

My question is;
Is an external Equipment Grounding Conductor (EGC) required across Liquidtight Flexible Metal Conduit (LFMC) in a Class I Div.2 Group B,C&D Hazardous Area for a 4-20ma loop powered flow transmitter?

NEC Article 250.118(6)a thru e critia is being met and indicates that the EGC is not required. Article 501.35(B) indicates that LFMC cannot be used as the sole ground fault current path, but we meet the criteria for the Exceptions 1 thru 3. However, Article 250.100 indicates that bonding in Hazardous Locations are required "Regardless of the voltage..." I do not think that a 4-20ma loop powered flow xmtr needs a ground fault current path as there isn't enough energy to cause an arc even when deliberately grounded.

I believe that the LFMC is sufficient as an EGC for a 4-20ma loop powered flow transmitter and that an external EGC is not required across the LFMC.

Do you agree?
Thank you.
Dave Lundquist
Electrical Lead Designer

 

[tom baker]

No, and Mike does not hang out here much.
There is no exceception for your 4-20 MA loop. And there is sufficent energy to cause an arc in a hazardous location, and thats why there is no rule to disallow bonding. The 4-20 MA loop power can be an Article 725 Class 1 or Class 2 circuit depending on the power supply.
Your only out from bonding is a if this would be an IS system which it is not.