A question was raised at a recent meeting that I attended. It started a search through both current and older versions of the National Electrical Code (NEC). The initial question involved a single-speed, 240-volt (V), single phase, 1-horsepower (hp), permanently connected swimming pool pump motor installed for a residential swimming pool and whether ground-fault circuit interrupter (GFCI) protection was required for the motor. A subsequent question expanded the scope of this issue to include a multispeed swimming pool motor of the same size and age with the same GFCI coverage question.
The initial question involving the single-speed motor was fairly easy to answer based on the 2011 NEC. The multispeed motor question became somewhat more difficult to answer and required a comparison of 430.52 in the 1993 NEC and the 2011 NEC as well as the new requirements relating to pool pump motors in Article 680 in the 2011 NEC.
Section 680.20 in the 2011 NEC provides the general introduction to Part II for permanently installed pools, and 680.21 covers the installation requirements for electrical swimming pool motors. In addition, consider the requirements for motors in Article 430.
Wiring methods for pool pump motors are in 680.21(A); 680.21(B) provides the requirements for cord-and-plug connected double-insulated pool motors. A new 680.21(C) was added for swimming pool motors that states, “outlets supplying pool pump motors connected to single-phase, 120-volt through 240-volt branch circuits, rated 15- or 20-amperes [A], whether by receptacle or by direct connection, shall be provided with ground-fault circuit-interrupter protection (GFCI) for personnel.” Based on the new text, a swimming pool pump motor does not require GFCI protection for branch circuits rated more than 20A in any circuit rated from 120V up to 240V.
To determine the rating of the overcurrent protective device for the branch circuit for the single-speed, 240V, single-phase pool pump, the electrician would refer to 430.52(C)(1) and the two exceptions for that section. According to Table 430.248, for single-phase, alternating current motors, the full-load current for a 1-hp motor is 10A. Table 430.52 provides the maximum rating or setting of motor branch-circuit short circuit and ground-fault protective devices. Assuming the electrician uses an inverse-time circuit breaker for this pool pump, the percentage of full-load current for this motor application would be 10A times 250 percent, equaling a 25A circuit breaker.
If this calculation had not conformed to a standard circuit breaker size or if the calculated circuit size did not allow the motor to start and run, there are two exceptions that immediately follow 430.52(C) that permit the circuit breaker to be raised to the next higher standard size (Exception No. 1) or to an even larger size (Exception No. 2). Since the circuit breaker is rated more than the 20A maximum required for GFCI protection required by 680.21(C), GFCI protection would not be required for this motor installation.
Now let’s examine the multispeed 240V rated pool pump motor. The text in 430.52 in the 1993 NEC and previous editions, dealing with multispeed motors, was located in 430.52(a). I have noted already that the exceptions, which permit the next higher standard overcurrent device [Exception No. 1 of 430.52(a)] or even larger values where the motor will not start (Exception No. 2), applied to multispeed motors. The exact same text was used for the 1993 and previous editions of the NEC as follows: “For a multispeed motor, a single short-circuit and ground-fault protective device shall be permitted for two or more windings of the motor, provided the rating of the protective device does not exceed the above applicable percentage of the nameplate rating of the smallest winding protected.” As can be seen in this 1993 text, the phrase “does not exceed the above applicable percentage of the nameplate rating” directed the electrician to go up to the two exceptions I have already discussed in detail. However, the 1996 edition of the NEC divided 430.52 into multiple subsections, eventually assigning each subsection a title. The text within 430.52(C)(4) is the same as in the 1993 and previous editions of the NEC; however, now the “above applicable percentage” in (C)(4) does not provide a clear direction to Table 430.52 or the exceptions in 430.52(C)(1) in the 2011 NEC.
To finish the multispeed motor calculation, a single short-circuit and ground-fault device is permitted for two or more windings, provided the rating of the protective device does not exceed 250 percent of the smallest winding. In other words, a 25A circuit breaker with no requirement for GFCI protection is permitted but only if 430.52(C)(1) and the exceptions can be used where necessary.
Section 430.52(C)(4) requires some changes for the 2017 NEC for clarity and consistency.
ODE is a staff engineering associate at Underwriters Laboratories Inc., based in Peoria, Ariz. He can be reached at 919.949.2576 and firstname.lastname@example.org.