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memyselfandI

memyselfandI

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Hello everyone, it has been awhile since I have been here and I was hoping to get some feed back on a question that I have.
I have a control panel that feeds a piece of equipment. It is fed with a 50A 480V 3PH circuit. Inside this control cabinet are two transformers. One is a 480 to 120 1.5kva and the other is a 480 to 24v 3kva. Now according to 250.30(A)(4)(a), I need to pull a 3/0 CU grounding electrode conductor to my grounding electrode correct? Or does this particular article refer to service entrance conductors only? I know that Table 250.66 deals with sizing you GEC to the service entrance cables, but does it apply to this scenario? I mean the 250.30 article does not specify control transformers in an enclosure, just multiple separately derived systems.
 
This is not a separately derived system. See Art.100 definition and note 'premises wiring system'.
 
Its a control panel. It does not meet the requirements of the highlighted area of the definition below.

Separately Derived System. A premises wiring system whose power is derived from a source of electric energy or equipment other than a service. Such systems have no direct electrical connection, including a solidly connected grounded circuit conductor, to supply conductors originating in another system.
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chris kennedy said:
Its a control panel. It does not meet the requirements of the highlighted area of the definition below.
Click to expand...
If the control cables leave the control panel, they are premises wiring.
Premises Wiring (System). Interior and exterior wiring, including power, lighting, control, and signal circuit wiring together with all their associated hardware, fittings, and wiring devices, both permanently and temporarily installed. This includes (a) wiring from the service point or power source to the outlets or (b) wiring from and including the power source to the outlets where there is no service point.
Such wiring does not include wiring internal to appliances, luminaires, motors, controllers, motor control centers, and similar equipment.
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memyselfandI said:
Hello everyone, it has been awhile since I have been here and I was hoping to get some feed back on a question that I have.
I have a control panel that feeds a piece of equipment. It is fed with a 50A 480V 3PH circuit. Inside this control cabinet are two transformers. One is a 480 to 120 1.5kva and the other is a 480 to 24v 3kva. Now according to 250.30(A)(4)(a), I need to pull a 3/0 CU grounding electrode conductor to my grounding electrode correct? Or does this particular article refer to service entrance conductors only? I know that Table 250.66 deals with sizing you GEC to the service entrance cables, but does it apply to this scenario? I mean the 250.30 article does not specify control transformers in an enclosure, just multiple separately derived systems.
Click to expand...


Is this equipment in the same building as the panel from which the control transformer is feed? or is it located in a remote location? not that it should matter because the requirement is the same..

Here is from my 2008 handbook
Grounding Electrode Conductor. A conductor used to connect the system grounded conductor or the equipment to a grounding electrode or to a point on the grounding electrode system.
Grounding electrode conductors have always been used to connect to electrodes not only at services and separately derived systems but also where feeders and branch circuits require connections to grounding electrodes, such as at second buildings and other structures.
The grounding electrode conductor is covered extensively in Article 250, Part III. The grounding electrode conductor is required to be copper, aluminum, or copper-clad aluminum. It is used to connect the equipment grounding conductor or the grounded conductor (at the service or at the separately derived system) to the grounding electrode or electrodes for either grounded or ungrounded systems. Refer to Exhibit 100.5 and Exhibit 250.1, which show the grounding electrode conductor in a typical grounding system for a single-phase, 3-wire service. The grounding electrode conductor is sized according to the requirements of 250.66 and the accompanying Table 250.66.

I see it as a requirment with out even having to search hard. even though the comment highlighted is from the comments and not part of the code. Unless your system meets the requirements of 250.21 I believe you need a grounding electrode conductor (GEC)
 
I' sorry but I can't agree with this requirement for this type of application. IMO the purpose of 250.30(A)(4) is to provide a means of connecting the SDS to the GE when there is none readily available. I can see this in an application when we are dealing with a multilevel facility with no structural steel and no water piping system available for connection, but not for a control transformer whose derived circuit conductors are a piece of #12. 250.30(A)(4) also states that it SHALL BE PERMISSIBLE (not required to) to connect a tap from each SDS to a common GEC. I have no problem running 2 GEC's from each SDS to the GE, but to say that this is a requirement for this type of application needs to be reviewed and clarified and possibly an exception made because the reference to this article for this particular application is a very loose interpretation of the intent of what this article was intended for. A final note, 110.3(B).. I had to install it because it was a manufacturer spec.
 
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