Jim Dollard has an extensive background in codes and standards. If you have a query about the National Electrical Code (NEC), Jim will help you solve it. Questions can be sent to firstname.lastname@example.org. Answers are based on the 2017 NEC.
OCPD for a fire pump
I am inspecting a fire pump installation with a reliable power source (utility service connection) where the fire pump also is being fed by a generator. We have a 200-horsepower pump with a full load current (FLC) of 240 amperes (A) and a locked rotor current (LRC) of 1,450A. Normally, we want the fire pump to continue running, so we size the overcurrent protective device (OCPD) to carry the LRC. The engineer had the installers place a 400A breaker at the generator for the feeder to the fire pump transfer switch.
For normal motor applications, we size an inverse-time circuit breaker at 250 percent of the FLC; 600A in this case. Section 695.4(B)(2)(b) appears to allow you to size the OCPD for the feeder between the generator and fire pump transfer switch based on the requirements of 430.62. It does not seem right that the installers could size the OCPD at 400A, but, if it starts, I’m not sure a Code section requires a larger overcurrent device.
Section 695.3 requires fire pumps to be supplied with a reliable power source. This section recognizes individual sources that are permitted to supply the fire pump without a standby source, multiple sources where reliable power cannot be obtained and permissive requirements for multibuilding campus style complexes. As illustrated in your question, this installation is in accordance with 695.3(B) for multiple sources.
Where a reliable, individual source can be obtained, multiple sources are not required. Individual sources that are considered reliable must also be capable of indefinitely carrying the sum of the LRC of the fire pump motors, the pressure maintenance pump motors and the associated fire pump accessory equipment FLC. The determination of reliability is a significant challenge for the installer and inspector.
See the new informational note following Section 695.3 that sends the Code user to sections 9.3.2 and A.9.3.2 in NFPA 20 2013, Standard for the Installation of Stationary Pumps for Fire Protection, for guidance on power source reliability determination.
Section 695.4 contains requirements that are necessary for power continuity to the fire pump. Direct connection to the fire pump controller is permitted in 695.4(A). Connection through a disconnecting means and OCPD is addressed in 695.4(B). OCPD selection in 695.4(B)(2) requires individual sources, such as 695.3(A)(1)(a) utility service connection, to be rated to indefinitely carry the sum of the LRC of the largest fire pump motor and the pressure maintenance pump motors and the FLC of all of the other pump motors and associated fire pump accessory equipment.
However, the OCPD between an on-site standby generator and a fire pump need only be sized to allow for instantaneous pickup of the full fire pump room load but cannot be larger than the value selected to comply with 430.62, which essentially takes us to the values in Table 430.52. You are correct that Table 430.52 shows a maximum of 250 percent of the motor FLC where an inverse-time circuit breaker is applied. However, it is not required to be at 250 percent and can be a smaller value if it is sized to allow for instantaneous pickup of the full fire-pump room load.
Surge protective devices (SPDs)
Sections 285.23, 285.24 and 285.25 contain requirements for Types 1, 2 and 3 SPDs respectively. How do I know what type SPD I am working with?
SPDs will be marked with a type number. Article 100 contains a definition for “surge protective device” and an explanation of each SPD type. Type 1 is permanently connected between the secondary of the service transformer and the line side of the service disconnect overcurrent device. Type 2 is permanently connected on the load side of the service disconnect overcurrent device. Type 3 devices are used at the point of utilization, and Type 4 are component SPDs.
Supporting Type MC cable
We are in the middle of an ongoing dispute with an engineer that concerns support of Type MC cable. The project is a new, single-level shopping mall. After drywall ceilings were installed, there were multiple extras that required us to fish a very limited amount of Type MC cable across drywall ceiling spaces. The engineer claims that, since the job is not a renovation, we should have found a route where the cable could be supported, and he pointed one out. That would have added more than 200 feet to the branch-circuit length. Is he correct?
No, Section 330.30(D) permits Type MC cable to be installed unsupported and unsecured under limited conditions. The permissive requirement in 330.30(D)(1) allows Type MC cable to be fished between access points through concealed spaces in finished buildings or structures where supporting is impractical. The space above the ceiling was by definition a concealed space. Spaces that are rendered inaccessible by the structure or finish of a building are considered concealed spaces. This requirement is not based on the type of project (new construction or renovation) involved.
Dwelling-unit kitchen peninsular countertops
While attending a recent seminar to keep up my continuing education credits, the instructor stated that the 2017 NEC contained significant revisions to receptacle outlet requirements on peninsular countertops in dwelling units. He said that a receptacle outlet installed in the wall for the wall-mounted countertop is all that is necessary. This means a receptacle outlet on the adjacent wall is all that is necessary without regard to the length of the peninsular countertop. We get involved in some high-end dwelling units where such a countertop may be 15 feet long or more. Allowing the wall receptacle to suffice just didn’t sound right. Now that I have a copy of the 2017 NEC and have had the chance to read the revised text, I am even more confused.
There has been significant discussion on the application of the revised text for receptacle placement on dwelling-unit kitchen peninsular countertops. While clarity is most certainly needed, the revised requirement is clear.
Most NEC users will focus only on the revised text and not the title of the section or the subdivision that they are applying. The revision you refer to occurred in second-level subdivision 210.52(C)(3) for “peninsular countertop spaces.” It is essential to focus on that title. The countertop along the wall is addressed by 210.52(C)(1), which provides receptacle placement requirements for wall countertop and work surfaces. The peninsular countertop space extends from the wall countertop and work surfaces. These spaces and associated requirements do not overlap. The requirements of 210.52(C)(1) and 210.52(C)(3) stand alone.
The revision here is only in how we calculate the peninsular countertop space length. It is a significant expansion of the existing requirement, not a reduction. Peninsular countertops are no longer measured from the connecting edge. They are measured from the connected perpendicular wall.
For example, consider a short peninsular countertop extending from a wall countertop that measures 22 inches from the connecting edge. The connecting edge is where the peninsular countertop space meets the wall countertop space. The 2014 NEC would not require a receptacle in that peninsular countertop space, but the 2017 NEC will require one. The only change here is how we measure to determine if a receptacle outlet is required.
This issue is similar to previous confusion created where an installer tried to use a wall countertop and work-surface receptacle—required in 210.52(C)(1)—to count as a wall space receptacle, as 210.52(A)(2) requires. That was never permitted because the existing requirements addressed different spaces. The moral of the story here is that all Code users should read all section and subdivision titles to correctly apply the contained requirements.
The 2017 NEC is revised with a new 210.52(A)(4) that clarifies a wall countertop and work-surface receptacle cannot be counted as a wall-space receptacle. While similar text is needed to provide clarity with respect to peninsular countertop spaces, understand that this is not a relaxation of receptacle requirements in peninsular countertop spaces.
Panelboard circuit identification
Why does the NEC prohibit a directory in a panelboard from containing information on transient conditions of occupancy? What does that mean? If an owner provides the name for a conference room, do we list something different? While building panelboard directories on a recent commercial tenant fit-out, we were told we could not refer to the names provided on the contract drawings for individual rooms and work stations. Why?
The requirement in 408.4(A) requires field identification of every circuit supplied by the panelboard. The intent here is for the installer to provide an approved degree of detail that allows for future identification of the branch circuits and outlets supplied. The requirement prohibits naming a room or space in a manner dependent on transient conditions of occupancy.
For example, if the drawings provide both room numbers and names of people who will occupy the rooms, the panel directory must list the room numbers because the occupants will change over time.