NEC applicable to Cathodic Protection DC Cables?

[Cathodic Civil Guy]

Greetings all. Long time lurker and finally joined up. I see there are a several cathodic protection (CP) posts, figured maybe I can start to give back to the community as related to CP. Y’all are an amazing wealth of knowledge and a big thank you is due for the guidance shared here.

Here is my question - Does NEC apply to DC wiring downstream of a rectifier?

When I started in the CP business, I was told by the old timers that NEC did not apply to these cables. I’m to the point now where I need to back up this theory with a real explanation / code interpretation.

For a typical example, the DC negative cable from the rectifier is bonded to a steel bulkhead and the DC positive cable runs to a deep well anode bed.
These systems typically run below 60 volts on the DC side.

I also speculate that NEC does not apply for other reasons:

• The CP world uses HMWPE cable almost exclusively and I can find no mention of this insulation type in Article 310.4 .(specifically Table 310.4(1)
• All I can find in NEC related to “Cathodic Protection” is isolation of objectionable ground currents.
• Section 300.1(B) ‘could’ be interpreted that the downstream DC cables are 'integral' to the cathodic protection equipment.

This would be analogous to low voltage landscape light wiring downstream of the LV transformer. Any guidance and/or opinions would be appreciated.

 

[tom baker]

The NEC is for premise wiring. IMO cathodic protection is not premise wiring

 

[tortuga]

Is this the system that protects building steel from rusting?
I'd say if the wiring is in a premises its premises wiring, probably class 1,2 or 3 depending on the rating of the power supply.
See article 725

 

[Cathodic Civil Guy]

Gents, thank you for your replies. This is the system that protects buried steel from rusting. Typically piping, tank bottoms, or a thousand feet of steel bulkhead.

In most applications, the wiring is all outside... typically a pole mounted rectifier with direct buried leads to a pipeline and an anode bed. In the scenario leading to this question, the rectifiers are wall mounted in a large warehouse and the wires are therefore "in a premises"

As per Article 725, looking at the Tables 11(A) & (B) for "power-limited circuits" a 160 amp / 60 volt DC output rectifier does not appear to qualify as power limited.