Question about Serarately Derived System Bonding

[JJWalecka]

The structural steel is used as one of Grounding Electrode (per 250.52 Grounding Electrodes) for the building service. Do I need to bond the steel for a Separately Derived System, derived from that service equipment [per 250.30 exception to (1)(2) and (3)]?
250.52 Grounding Electrodes.
250.52(A)Electrodes permitted for Grounding
250.52 (A)(2) Metal Frame of the building or Structure. The metal frame of the building or structure, where effectively grounded.

250.30 Grounding Separately Derived alternating current systems.
250.30 (A)(2)Grounding Electrode Conductor. The grounding electrode conductor shall be installed in accordance with (a) or (b). Where taps are connected to a common grounding electrode conductor, the installation shall comply with 250.30(A)(3)

250.30(A)(3) Grounding Electrode Conductor taps. It shall be permissible to connect taps from a separately derived system to a common grounding electrode. Each tap conductor shall connect the grounded conductor of the Separately derived system to the common grounding electrode conductor.

250.30(A)(3)(d) Bonding where exposed structural steel that is interconnected to form the building frame or interior metal piping exists in the area served by the Separatelys derived system, it shall be bonded to the grounding electrode conductor in accordance with 250.104

250.30 (A)(4) Grounding Electrode. The grounding electrode shall be as near as practicable to and preferably in the same area as the grounding electrode conductor connection to the system. The grounding electrode shall be one of the following:
(1) an effectively grounded Structural member of the structure
(2) An effectively grounded metal water pipe within (5ft) from the point of entrance.

EXCEPTION to (1)(2), and (3): Where a separately derived system originates in a listed equipment suitable for the use as service equipment, the grounding electrode used for the service or feeder shall be permitted as the grounding electrode for the Separately derived system, provided the grounding electrode is of sufficient size for the separately derived system. Where the equipment ground bus internal to the service equipment is not smaller than the required grounding electrode conductor, the grounding electrode conductor shall be permitted to be made to the bus.

Thank you for your time and effort.

Justin W.

 

[iwire]

Re: Question about Serarately Derived System Bonding

Justin.

What exactly is the question here?

No offense intended.

Bob

[ April 02, 2005, 07:05 PM: Message edited by: iwire ]

 

[JJWalecka]

Re: Question about Serarately Derived System Bonding

Iwire,

No offense taken. I wanted to know if I was understanding the code correctly. The main service uses the structural steel as one of the grounding electrodes and it is installed to the main ground bar in the switch gear. A separately derived system that is feed from that system has to be bonded to the structural steel or a metal water pipe. If the grounded electrode conductor is installed from the main service ground bar to the separately derived system would that constitute as an appropriate grounding conductor to the Structural steel? Or would an addtional grounding conductor be needed to bond the structural steel from the sepraratly derived system. You have always helped me. Thank you for your time and effort.

Justin W.

 

[mc5w]

Re: Question about Serarately Derived System Bonding

Is your separately derived system a transformer or a generator?

If the neutrals for a service and a generator are solidly connected at the transfer switch the generator is NOT a separately derived system.

 

[JJWalecka]

Re: Question about Serarately Derived System Bonding

mc5w,

A Switch Gear and Transformer located in the main Electrical room. The main switch gear that is feeding the Transformer is located less than ten feet away. I currently do not have the size of the Transformer or the size of the Primary or Secondary conductors in front of me. I encountered the issue on a previous job. I was not the general foreman. I was wondering if the application was to code. It saved time by not having to run an E.M.T. to the structural steel for the Transformer Bond.
Unless I'm interpreting the Code inappropriately as long as it was sized correctly for the derived conductors that it could be installed from the Transformer to the main switch gear ground bar. The ground bar would have all the Grounding Electrode conductors installed to it including the structural steel. Thank you for your input.

Justin W.