Question 5. I have two questions. The first question is about NEC 225.30 and 230.2, which both refer to power supplies to a building or structure. Would you please explain exactly what the rules are trying to accomplish from a safety perspective?

The second question is about fire walls. The NEC definition of a building explains that it is a structure that stands alone or is cut off from adjoining structures by a fire wall. Can a fire wall be anything other than what the International Building Code defines as a fire wall? — K. M.

Answer 5. You have asked for a description of potential safety issues relative to the main rule requirement in Sections 225.30 and 230.2 for allowing only one source of electrical power to enter a building.

The first and foremost concern for both requirements is the ability of personnel who are responding to a public safety hazard, such as but not limited to a fire, to be certain that they are eliminating all power to a building when a decision is made to do so. To accomplish this, there is not only the main rule requirement for one source of power to a building as you have referenced, but there are also requirements found in Section 230.2(E) for the proper identification by means of a permanent plaque or directory at each disconnecting means for each source of power entering a building. You will also see here a reference back to Section 225.37 where the same requirements for the proper identification of feeders or branch circuits are located.

The other concerns with multiple supplies are more of a technical concern; however, they could relate back to safety concerns relative to shock and or fire hazards. These hazards could occur throughout a building whenever someone was exposed to circuits from different systems. There could be a shock potential between grounded conductors of the different systems; and if intersystem bonding was not properly performed, there could be a potential difference on grounding conductors and any non-current carrying metal objects that the grounding conductors were exposed to either intentionally or unintentionally. There were changes in both Articles 210 and 215 in this code cycle relative to proper identification of all system branch circuits or feeders within a building at the distribution equipment supplying the systems.

Your second question refers to the building code and I cannot render an opinion relative to this. I can state that Article 100, under the definition of building, refers to the term fire wall. To that extent, fire wall can be differentiated from fire rated construction. I have included below the definition of fire wall as found in NFPA 5000 and the appendices reference contained with the definition.

“Fire Wall. A wall separating buildings or subdividing a building to prevent the spread of fire and having a fire resistance rating and structural stability.

“A.3.3.566.4 Fire Wall. Portions of structures that are subdivided by fire walls are permitted to be considered separate buildings for the purpose of applying this code. The intent of the definition is that fire walls have sufficient structural stability to maintain the integrity of the wall in the event of the collapse of the building construction on either side of the wall.”

In addition, NFPA 221 is the standard that addresses the different types and construction methods of fire walls. Beyond this, it becomes a local issue depending on which model building your city, town, or state adopts for enforcement.

I hope that this adequately answers your questions. Please feel free to contact us for further information on this or any other issue. — James J. Rogers, CMP-4

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Question 6. I am currently on a job that has a 1600-amp, 3-phase, 480-volt service. The generator transfer switch does not have GFCI protection but the main distribution panel does. Can you tell me what year the NEC started requiring GFCI protection for equipment as per 230.95?

The engineer does not want the GFCI on the main distribution with the GFCI protection we are going to add at the generator transfer switch to make it code-compliant. Is there anything the downstream device must have, like a trip setting at a lower value, which would prevent this from being a compliant installation? The AHJ for this area is not strong in the electrical field; he wears a hat for all trades and makes all inspections for all crafts.

Any help would be greatly appreciated.— S.D.

Answer 6. To begin with, one important note that must be clarified is that you are dealing with GFPE or ground-fault protection of equipment and not with GFCI, ground-fault circuit interrupter. As indicated by their names, GFPE deals with protecting equipment from catastrophic failure due to a fault to ground; and the GFCI provides circuit protection for personnel from the hazards of electric shock.

To answer your question relative to when GFPE for service equipment first appeared as a NEC requirement, 230-95 first appeared in the 1971 edition of the Code. It was contemplated by the code-making panel for the 1968 edition; but in the final vote, it was held for further technical comment. Prior to giving you a comprehensive answer, some other information would be necessary, such as what type of facility is being supplied. If this installation is at a health care facility, the answer may be different. How is the generator connected to the system? Does it feed into the main service and supply the entire building, or does it connect on the load side of the service disconnect and supply only limited loads?

I will begin with an answer for a non-healthcare facility where the entire service is supplied by the generator. In that case, then there would be no requirement for a second level of GFPE on the generator feeder as the protection is already provided in the service distribution equipment as you have described it. If the generator supplies selective loads in conjunction with a normal power feeder that is supplied from the service distribution equipment on the load side of the service GFPE, then the allowance of not requiring GFPE found in 215.10 Exception No. 3 would take precedence and, again, no GFPE would be required on the generator feeder. There is a reference to this type of installation found in 230.95 FPN No. 3 whereby it is noted that some type of interconnecting device may be required to assure that the service GFPE device will work in conjunction with the alternate power source. The technical information for an installation such as this would have to come from the manufacturers of the GFPE device and the generator transfer equipment.

You also ask a question relative to downstream protection at a lower rating. The issue of selective coordination of GFPE devices is addressed in 517.17(A), as referenced in 230.95 FPN No. 4. There is no mention in your question that the installation you have described is in a health care facility; however, if it were, then all of the requirements of 517.17 would have to be applied. NEC 517.17(B) specifically addresses generator supplies to essential electrical systems and contains specific language as to when GFPE cannot be applied to these feeders.

I hope that this has adequately answered your question. Should you need further assistance, please feel to contact me. You should also note that a great deal of technical information relative to GFPE devices is on the web sites of the companies that manufacture these devices.
— James J. Rogers, CMP-4
(March/April 2007)

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Question 7. I would like to ask for your interpretation of the following situation. Our office was recently written up by a new electrical inspector for an issue he perceives to be a violation of NEC 230.70(1), but which our office feels to be ambiguous because of the difficulty in determining what actually is a “readily accessible location” since the Code establishes the interpretation is at the discretion of the inspector.

The installation transpired as follows.We had an existing building that was to be divided electrically between two tenants. An existing electrical room that housed an 800-amp service with a CT/Term can, telephone board, house panel and fire protection riser.

 All electrical service equipment is confined to the main electrical room, which is roughly 12' x 5'. 

 Tenant No. 1 was the original tenant in the building and had a 400-amp distribution system that was fed from the existing CT/Term can that we did not want to touch.
 Tenant No. 2 required an 800-amp service; so we had a second 400-amp service brought into the room from the same TEP transformer and had an additional 400-amp CT/Term can installed next to the 800-amp to isolate Tenant No. 1’s service. We then took Tenant No. 1’s load off the 800-service and isolated it to the new 400-amp.
The 400-amp service was constructed by bringing into the room a 4" conduit 2 ft above floor level where it was then extended vertically 7 ft towards the roof, and then 6 ft horizontally along the wall towards the new service can, where it was then brought down 4 ft to the top of the new CT/Term can.

The inspector feels that under NEC 230.70(1) too much of the service is exposed, and that the new CT can could have been placed closer to the point of entrance. The new location required the relocation of smaller equipment not related to Tenant No. 2, which was ultimately moved due to the existing fire protection riser. Had the contractor located the new service can there, it would have reduced the nearest point of entrance by 13 ft (due to the conduits running up to the structure then back down to the new service equipment).

The services are energized and both tenants are operational.

We feel that since the Code does not delineate a maximum distance and leaves the decision up to the AHJ, the distance is subject to the official’s interpretation as to what exactly may have been the “nearest point of entrance” in an existing electrical room, especially with the existing conditions at hand. At this point, the service equipment and feeders could be rearranged to make the exposed runs shorter but the fact remains that we would still have 4 ft of exposed conduits.
 Attached is a rough sketch for your assessment. —S. P.

Answer 7. Before I actually attempt to address the submitter’s concerns, I think we need to establish a common understanding of the issues. As I understand this installation, two tenant spaces were being developed from a building with an existing 800-ampere service providing for one tenant space (Tenant Space No. 1) and a house meter. Tenant Space No. 1 was supplied through an existing 400-ampere service disconnecting means that was located in the north end of the electric room. Tenant Space No. 2 required a supply with an 800-ampere capacity so the existing service-entrance conductors were utilized for Tenant No. 2 and a new 400-ampere service lateral was run to the electric room to feed the existing 400-ampere disconnecting means for Tenant No. 1.

The new service conductors enter the electric room on the same end as the fire protection riser (south end) and were run to the north end of the electric room to a new 400-ampere CT cabinet, and then to the existing 400-ampere disconnect switch. Additional information obtained from the submitter indicated that there was sufficient working clearance and headroom to accommodate the new 400-ampere CT cabinet and the 400-ampere disconnecting means at the south end of the electric room. The electric room was not constructed as a vault. For now, we will assume the installation is customer-owned and therefore covered by the NEC.

The main concern of the submitter is with the application of the terms readily accessible location and nearest the point of entrance. In my opinion, the reasons for the use of these two terms is to make sure the service disconnecting means can be reached quickly for operation and that we have the shortest possible length of unprotected conductors (without ground-fault and short-circuit protection) inside a building or structure.

Section 230.70 requires that a means be provided to disconnect all the conductors in a building or structure from the service-entrance conductors. Section 230.70(A) tells us to locate the service disconnecting means in accordance with 230.70(A)(1), (A)(2) and (A)(3). Section 230.70(A)(1) requires the service disconnecting means to be installed at a readily accessible location either outside a building or structure or inside, nearest the point of entrance of the service conductors.

In analyzing 230.70(A)(1), we find there are two basic requirements. First, whether the service disconnecting means is located outside or inside a building or structure, it must be readily accessible. This means that the disconnecting means must be capable of being reached quickly without one having to climb over, or remove obstacles or resort to the use of a portable ladder (see Accessible, Readily in Article 100). Second, when the service disconnecting means is located inside a building or structure, it is required to be located nearest the point of entry of the service conductors. I have always found it interesting that this is a rule about the disconnecting means, but its intent is to limit the length of the service conductors.

Without considering 230.6 regarding conductors considered outside the building, the nearest readily accessible location for the 400-ampere service disconnecting means for Tenant Space No. 1 would be at the south end of the electric room. However, in accordance with 230.6(2) and (3) respectively, if the 4" conduit were encased in concrete or brick not less than 2" thick within the electric room, or if the electric room was a vault meeting the construction requirements of Article 450 Part III, the 400-ampere service disconnecting means could have been located at the north end of the electric room.

I agree with the submitter that the NEC assigns the responsibility for interpreting the Code to the authority having jurisdiction. This is especially true where parts of the installation are exiting and/or there are no hard-and-fast measurements specified. In these cases, much is left to the discretion of the AHJ.

In my opinion, the requirement for a service disconnecting means installed inside a building or structure to be at a “readily accessible location, nearest the point of entrance of the service conductors” has always meant the disconnecting means must be installed at the first point inside the building or structure that has sufficient working clearances and headroom so that one does not have to climb over something or use a portable ladder to reach it. This location is intended to be the one that results in the shortest length of conductors.

Now that we have discussed the main concern of the submitter—the application of the terms readily accessible and nearest the point of entry, let us consider another issue. As with many existing installations, the actual circumstances can present significant and unique challenges for the AHJ as well as installers and designers. In this case, the submitter noted in his inquiry that the service-entrance conductors had already been energized. Further telephone correspondence with the submitter established that by the time all these issues became known the utility company had already taken over ownership of these conductors before the inspector had looked at them.

Unless the installation is being made by the utility and the conductors are terminating in utility-owned equipment, the installation is not under the exclusive control of the utility company at the time it is installed and the NEC applies (see 90.2 (B) (5)). There are many cases where the installation is not made by the utility but it will assume ownership once the system is completed, hopefully inspected and approved by the AHJ, and energized. In these cases, the installation must meet the requirements of the National Electrical Code. Significant challenges in obtaining compliance can be expected if the equipment becomes energized prior to inspection and approval by the AHJ, and if the utility has taken over ownership. We will leave that discussion for future issues of IAEI News, but I felt it was worth mentioning. — Mark R. Hilbert, CMP-4
(November/December 2007)

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