RVs as Dwelling Units, Fire Pump Motor Supply and More

By Jim Dollard | Oct 15, 2021




Jim Dollard has an extensive background in codes and standards. Send questions about the National Electrical Code (NEC) to Jim at [email protected] Answers are based on the 2020 NEC.

RVs as dwelling units

Do the new rules for surge protection in services for dwelling units apply to recreational vehicle (RV) parks? In many cases, an RV goes into a park and sets up camp for a solid year, or even several. When replacing the service equipment for an RV park, is surge protection required?

The application of NEC rules in this case comes down to definitions. A dwelling unit is a single unit providing complete and independent living facilities for one or more people, including permanent provisions for living, sleeping, cooking and sanitation. An RV contains all of the elements in a dwelling unit as defined.

However, Article 551 contains modifications and supplemental requirements to the general rules in the NEC for RVs and RV parks. An RV is defined in 551.2 as a vehicular-type unit primarily designed as temporary living quarters for recreational, camping or travel use, which either has its own motive power or is mounted on or drawn by another vehicle.

Where an RV is occupied, it serves as a temporary dwelling unit, but it is, by definition, not a dwelling unit, and the general rule for surge protection (as well as many other general rules) does not apply. See 551.72(E) that permits, but does not require, listed surge protective devices in equipment supplying RVs. There are similar issues raised in marinas where larger boats are lived in as dwellings on a permanent basis.

Fire pump motor supply

In an area that is supplied by the local utility with 2-phase 240V, is it permissible to supply a 3-phase fire pump motor by converting 2-phase to 3-phase? The requirement in 695.3(I) prohibits phase converters. It is very difficult to find a fire pump controller and fire pump for 2-phase systems. What are my options?

The prohibition in 695.3(I) is for phase converters, not transformers. A phase converter is defined in 455.2 as an electrical device that converts single-phase power to 3-phase electric power. In this case, a transformer (typically called a Scott-T type transformer) can be used to transform the 2-phase supply to 3-phase power. It is important in this installation to review the permitted power source for the fire pump in Article 695. Section 695.3(A)(1) permits a direct connection of service conductors to the fire pump controller.

However, in this installation, a transformer is required to supply the fire pump with 3-phase power. This installation is permitted to be supplied in accordance with Section 695.3(A)(3). This requirement permits a dedicated feeder, provided that it is derived from a service connection as described in 695.3(A)(1). See the requirements of 695.4 for the permitted single disconnecting means, 695.5 for transformer requirements and 695.6 for the feeder conductors.

Panelboard location

On a plan review, a hand-drawn sketch showed an outside feeder entering a new detached garage. They planned to enter the garage where a half bathroom was being installed. The owner wanted the panelboard located in the bathroom because it was the only part of the garage that would be heated and cooled. The garage was not connected to the dwelling unit, but as an inspector I felt it was associated and made them take the panelboard out of the bathroom. Was that correct?

The requirement that you are referencing is in Section 240.24(E), which prohibits overcurrent devices, other than supplementary overcurrent protection, from being installed in bathrooms that are located in dwelling units, dormitory units and guest rooms or guest suites. The garage is not a dwelling unit; see the Article 100 definition. The panelboard could have been located in the bathroom in this installation. It is interesting to note that during the first-draft stage for the 2023 NEC , Section 240.24(E) is modified significantly. This revision will prohibit overcurrent devices, other than supplementary overcurrent protection, from being installed in any showering facilities or locker rooms with showering facilities.

Marking the high leg orange

In service equipment, I know that the high leg in a 120/240V 3-phase, 4-wire system has to be marked in orange. I am being told that in all junction boxes and terminations, the high leg must be identified by orange tape. Is that correct? Even at motor terminations?

Section 230.56 specifically addresses 4-wire, delta-connected services where the midpoint of one-phase winding is grounded. These systems result in one service conductor having higher phase voltage to ground. This requirement mandates that the service conductor having the higher phase voltage to ground be durably and permanently marked by an outer finish that is orange in color, or by other effective means. This marking is required for all junction points and terminations of service conductors. This requirement applies only to service conductors. A similar requirement exists in Section 110.15, High-Leg Marking. This is a general requirement and applies to service, feeder, branch circuit and tap conductors. Section 110.15 generally requires the higher phase voltage to ground be durably and permanently marked by an outer finish that is orange in color at each point on the system where a connection is made if the grounded conductor is also present. A 3-phase motor termination would not require the high-leg identification because the grounded conductor is not present.

Single conductors for temporary installations

To begin removing temporary feeders and branch circuits in new construction, we supplied the permanent switchboard with single-conductor 500 kcmil conductors in parallel on the ground behind the switchboard. This is something we have done for years, but the GC informed us that was a violation and forced us to install PVC conduits. Does 310.10(A) permit such an installation?

No. General requirements for the installation of single conductors are located in 310.4, and this includes those listed in Table 310.4(A). They are permitted for use in any of the wiring methods covered in Chapter 3 and as specified in their respective tables or as permitted elsewhere in the NEC . Article 590 provides modifications and supplemental requirements for temporary installations. All of the general requirements in chapters 1–4 still apply, allowing all types of raceways and conductors within to be used for temporary feeders. See Section 590.4(B) that modifies the general rules allowing conductors within cable assemblies or within multiconductor cords or cables of a type identified in Table 400.4 for hard or extra-hard usages.

Additional modifications in this section permit types NM and SE to be used in a manner not permitted in Chapter 3. The exception following 590.4(B) permits single insulated conductors only where installed for emergencies or tests as specified in 590.3(C), and only where accessible solely to qualified persons. Additionally, 590.4(J) prohibits cable assemblies and flexible cords and cables installed as branch circuits or feeders from being installed on the floor or ground.

Pool shell bonding

During a pool remodel at a dwelling unit, all of the concrete around the pool was removed, which exposed rebar that turned out from the pool shell. It is an older pool, and the rebar was ¼ or 5/16 inches in diameter. There were no listed clamps available to bond to that size rebar, so we tied 4-foot pieces of ½-inch rebar to the rebar that turned out from the pool shell in all four corners and bonded to that before concrete was poured. Is that acceptable?

Yes, the structural reinforcing steel (rebar) in the existing pool can be simply tied together by steel tie wire or equivalent. See 680.26(B)(1)(a) that specifically permits tying rebar together with steel tie wire or some equivalent.

About The Author

DOLLARD is retired safety coordinator for IBEW Local 98 in Philadelphia. He is a past member of the NEC Correlating Committee, CMP-10, CMP-13, CMP-15, NFPA 90A/B and NFPA 855. Jim continues to serve on NFPA 70E and as a UL Electrical Council member. Reach him at [email protected].


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