Wind disconnect switch construction, marking, and location rules
NEC 694.22(A) The wind turbine disconnect must be readily accessible, externally operable, plainly marked as a wind disconnect, and — for one- and two-family dwellings — located outside the building.
Q1 NEC 694.22(A)
Which requirement applies to a wind electric system disconnecting means per 694.22(A)?
- A It must be a fused disconnect only, never a circuit breaker
- B It must plainly indicate whether it is in the open or closed position
- C It must be rated suitable for use as service equipment
- D It must be located at the nacelle
Show answer & explanation
Correct: B — It must plainly indicate whether it is in the open or closed position
694.22(A) requires the disconnect to plainly indicate open or closed position. It explicitly does not need to be service-equipment rated, 694.22(C)(1) says the disconnect is not required at the nacelle or tower, and the section permits either manually operable switches or circuit breakers, not just fused switches.
Wind turbine wiring methods and flexible cords/cables
NEC 694.30(A) Turbine output circuits over 30 volts need raceways in readily accessible spots, and any flexible cord serving moving parts must be hard-service, extra-hard-usage, outdoor-rated, and water-resistant.
Q2 NEC 694.30(A)
A wind turbine output circuit operates at 45 volts and runs through a readily accessible location at the base of the tower. Per 694.30(A), how must this circuit be installed?
- A As open conductors if properly labeled
- B Only with turbine-listed flexible cord
- C In a raceway
- D Using any Chapter 3 method without restriction
Show answer & explanation
Correct: C — In a raceway
694.30(A) requires that turbine output circuits over 30 volts in readily accessible locations be installed in raceways. Open conductors would not meet this requirement, and while Chapter 3 methods are generally permitted, the raceway requirement is a specific added condition here, not an optional alternative.
Sizing conductors and overcurrent devices at 125% continuous current
NEC 694.12(B) Wind turbine output is treated as continuous, so conductors and OCPDs must be sized at 125% of the maximum current unless the whole assembly is listed for 100% continuous duty.
Q3 NEC 694.12(B)
Why does 694.12(B)(2) require wind turbine circuit conductors and overcurrent devices to be sized using a 125% multiplier?
- A Because wind turbine conductors are assumed to run at high ambient temperature
- B Because 694.12(B)(1) classifies wind turbine electric system currents as continuous
- C Because wind turbines always operate at their nameplate rating
- D Because the wind resource is considered unpredictable and requires a safety adder
Show answer & explanation
Correct: B — Because 694.12(B)(1) classifies wind turbine electric system currents as continuous
694.12(B)(1) states wind turbine electric system currents shall be considered continuous, which is what triggers the 125% sizing requirement in 694.12(B)(2). The 125% factor is not about ambient temperature, unpredictability, or assumed constant nameplate output — it's the standard continuous-duty multiplier tied directly to the continuous classification.
Disconnecting inverters, batteries, and charge controllers
NEC 694.24 Every source-connected inverter, battery, and charge controller needs a disconnect for all ungrounded conductors, grouped and identified when fed from more than one source.
Q4 NEC 694.24
A wind electric system has a charge controller energized from two separate sources. Per 694.24, what must be true of its disconnecting means?
- A A shorting switch must replace all disconnects in this case
- B The disconnects must be located in the turbine nacelle
- C Only one disconnect is needed since charge controllers are exempt
- D Each source's disconnect must be grouped together and identified
Show answer & explanation
Correct: D — Each source's disconnect must be grouped together and identified
694.24 requires that when equipment is energized from more than one source, the disconnecting means shall be grouped and identified. Charge controllers are not exempt (that exception applies only to nacelle-housed equipment), nacelle location isn't a requirement here, and the shorting switch/plug option is a substitute only for turbines that regulate speed using the turbine output circuit, not a general grouping requirement.
Calculating maximum circuit current for wind systems
NEC 694.12(A) Maximum circuit current comes from the equipment's own rating — turbine output at max power, inverter output rating, or stand-alone inverter input rating at lowest input voltage.
Q5 NEC 694.12(A)
Per 694.12(A), how many distinct methods does the NEC provide for calculating maximum circuit current in a small wind electric system?
- A One single method applied to all circuit types
- B Two, one for AC and one for DC circuits
- C Three, based on the specific circuit type
- D Four, including a separate method for battery circuits
Show answer & explanation
Correct: C — Three, based on the specific circuit type
694.12(A) directs the reader to 694.12(A)(1) through (A)(3) — three separate calculation methods, one each for turbine output circuits, inverter output circuits, and stand-alone inverter input circuits. There is no single universal method and no fourth method for battery circuits in this section.
Manual shutdown button and posted shutdown procedure
NEC 694.23(A) Wind turbines need a readily accessible manual shutdown button that parks the turbine, plus a posted shutdown procedure at both the shutdown means and the controller/disconnect location.
Q6 NEC 694.23(A)
Per 694.23(A), which wind turbine is NOT required to have a readily accessible manual shutdown button or switch?
- A A turbine with a swept area of exactly 50 m2 (538 ft2)
- B A turbine feeding a dedicated branch circuit regardless of swept area
- C A turbine with a swept area of 60 m2 (646 ft2)
- D A turbine with a swept area of 40 m2 (430 ft2)
Show answer & explanation
Correct: D — A turbine with a swept area of 40 m2 (430 ft2)
694.23(A) exempts turbines with a swept area of less than 50 m2 (538 ft2) from the manual shutdown button/switch requirement. A turbine at exactly 50 m2 or above 50 m2 still needs the shutdown control; branch-circuit configuration isn't a factor in this exemption.
Working clearances for wind system electrical equipment
NEC 694.7(G) Wind system equipment follows standard 110.26(A) working space unless it's a large turbine maintained only by qualified persons at 1000 volts or less, which can use Table 694.7(G) instead.
Q7 NEC 694.7(G)
A wind electric system's electrical cabinet needs working clearance. Absent any exception, which requirement applies?
- A No clearance requirement — Article 694 exempts wind equipment
- B The standard working space rule in 110.26(A)
- C Table 694.7(G), regardless of turbine size or voltage
- D The hazardous-location clearance rules in Article 500
Show answer & explanation
Correct: B — The standard working space rule in 110.26(A)
694.7(G) requires working space per 110.26(A) as the default. Table 694.7(G) is only available under the large-turbine, qualified-persons-only exception described in that same section — not as a blanket replacement. Hazardous-location rules aren't the basis for wind system clearances.
Disconnecting all current-carrying conductors of a wind system
NEC 694.20 A disconnect must open every current-carrying conductor from a wind turbine, but never one that leaves the grounded conductor ungrounded and still energized.
Q8 NEC 694.20
Per 694.20, which arrangement is a violation for a wind electric system's disconnecting means?
- A A single disconnect that opens all ungrounded and grounded current-carrying conductors together
- B A disconnect that isolates the wind source from all other building conductors
- C Omitting a turbine output circuit disconnect when that circuit regulates turbine speed
- D A device in the grounded conductor whose operation leaves it energized and ungrounded
Show answer & explanation
Correct: D — A device in the grounded conductor whose operation leaves it energized and ungrounded
694.20 specifically bars a switch, circuit breaker, or other device in the grounded conductor if it can leave that conductor energized and ungrounded. Isolating all conductors together, or skipping the output circuit disconnect when it regulates turbine speed, are both permitted under 694.20.
Voltage limits for wind turbine circuits in dwellings
NEC 694.10 In one- and two-family dwellings, wind turbine output circuits can run up to 600 volts, but anything over 150 volts to ground must be guarded from anyone but qualified persons.
Q9 NEC 694.10
In a one- and two-family dwelling, what is the maximum voltage permitted for a wind turbine output circuit?
- A 300 volts
- B 1000 volts
- C 150 volts
- D 600 volts
Show answer & explanation
Correct: D — 600 volts
694.10(A) permits wind turbine output circuits in one- and two-family dwellings to have a maximum voltage up to 600 volts. The 150-volt figure is instead the threshold in 694.10(C) that triggers added guarding requirements, not the maximum allowed voltage.
Diversion load controllers and over-speed protection
NEC 694.7(C) A diversion load controller can't be the only thing standing between a wind turbine and over-speed — a second, independent protection method is required.
Q10 NEC 694.7(C)
A wind electric system uses a diversion load controller as the primary means of regulating rotor speed. Per 694.7(C), what else does this system require?
- A A second diversion load controller wired in parallel with the first
- B An additional, independent, reliable means to prevent over-speed operation
- C Nothing further, since the diversion load controller already regulates speed
- D Confirmation that the utility interconnection can absorb excess rotor energy
Show answer & explanation
Correct: B — An additional, independent, reliable means to prevent over-speed operation
694.7(C) requires an additional, independent, reliable means of over-speed protection whenever a diversion load controller is the primary speed regulator. A second diversion controller isn't independent in the way the rule requires, and relying on the utility interconnection is explicitly disallowed since it isn't a reliable diversion load.
Wind turbine equipment listing and field evaluation
NEC 694.7(B) Wind electric system equipment must be either listed or field-evaluated with a field label applied before it goes into normal service.
Q11 NEC 694.7(B)
Per 694.7(B), what must be true of equipment used in a wind electric system?
- A It must be listed, or evaluated for the application with a field label applied
- B It must be approved by the local AHJ verbally before installation
- C It must be listed only; field evaluation is not an accepted alternative
- D It must be manufacturer-certified but does not need listing or a field label
Show answer & explanation
Correct: A — It must be listed, or evaluated for the application with a field label applied
694.7(B) permits two paths: the equipment is listed, or it is evaluated for the application and has a field label applied. Listing alone is not the only route, and neither verbal AHJ approval nor manufacturer self-certification satisfies the section.
Equipment permitted on turbine side vs. non-readily-accessible mounting
NEC 694.22(B) Rectifiers, controllers, isolating/shorting switches, and overcurrent devices can sit on the turbine side of the disconnect, and rectifiers, controllers, and inverters can be mounted in nacelles or other spots that aren't readily accessible.
Q12 NEC 694.22(B)
Per 694.22(B), which of the following is permitted on the wind turbine side of the disconnecting means?
- A The service disconnecting means
- B Output circuit isolating and shorting switches
- C The utility-interactive point of connection equipment
- D A readily accessible emergency shutdown control
Show answer & explanation
Correct: B — Output circuit isolating and shorting switches
694.22(B) permits rectifiers, controllers, output circuit isolating and shorting switches, and overcurrent devices on the wind turbine side of the disconnecting means. The other choices aren't part of that permitted list under this section.
Disabling a turbine safely during installation and service
NEC 694.28 Use open circuiting, short circuiting, or a mechanical brake to disable a wind turbine — but check the manufacturer's method first, since opening output conductors on some turbines is dangerous.
Q13 NEC 694.28
Per 694.28, which of the following is an approved method to disable a wind turbine for installation or service?
- A Reducing the inverter output to zero
- B Covering the blades with a tarp
- C Applying a mechanical brake
- D Disconnecting the anemometer wiring
Show answer & explanation
Correct: C — Applying a mechanical brake
694.28 lists open circuiting, short circuiting, or mechanical brakes as the approved ways to disable a turbine. Covering the blades, disconnecting the anemometer, or zeroing inverter output are not recognized disabling methods under this section.
GFCI-protected receptacles for wind turbine maintenance
NEC 694.7(E) Maintenance receptacles on a wind electric system must be sized to the overcurrent device rating and, if 125-volt 15- or 20-amp single-phase, must have GFCI protection.
Q14 NEC 694.7(E) Code lookup
A technician needs a 120-volt, 20-ampere receptacle at the base of a wind turbine tower for plugging in test equipment during scheduled maintenance. Which NEC section requires this receptacle to have GFCI protection for personnel?
- A 694.7(D)
- B 694.7(E)
- C 694.7(B)
- D 694.7(G)
Show answer & explanation
Correct: B — 694.7(E)
694.7(E) specifically addresses receptacles supplied from a wind electric system circuit and requires GFCI protection for 125-volt, 15- and 20-ampere receptacles used for turbine maintenance, in addition to 210.8. 694.7(B) covers general equipment listing/identification and 694.7(D) covers overvoltage protection — neither deals with receptacles or GFCI.
Overcurrent protection for wind circuits and equipment with multiple sources
NEC 694.15(A) When a wind circuit can be fed from more than one source, overcurrent devices must guard against every source, not just the main one.
Q15 NEC 694.15(A)
A wind turbine output circuit is connected to more than one electrical source. Per 694.15(A), how must overcurrent devices be arranged?
- A Omitted if the inverter has its own internal overcurrent trip
- B Located only at the source with the highest available fault current
- C Sized to 125% of the turbine's rated output current only
- D Located so overcurrent protection is provided from all sources
Show answer & explanation
Correct: D — Located so overcurrent protection is provided from all sources
694.15(A) requires overcurrent devices on multi-source circuits to be located so that protection is provided from all sources, since any source (including backfeed through an inverter) can drive current through the circuit. Protecting only the largest source, sizing to a single fixed percentage, or relying on an inverter's internal trip does not satisfy this all-sources requirement.