Solar PV Systems practice questions

Correct: B — Yes, up to six switches or sets of circuit breakers may combine into one disconnecting means

Per 690.13(C), a PV system disconnecting means can consist of up to six switches or sets of circuit breakers, mounted in a single enclosure or a group of enclosures, and a single disconnecting means is permitted for the combined ac output of one or more inverters or ac modules. There's no rule limiting it to one breaker, no requirement to separate ac modules and inverters, and no requirement about enclosures being on different walls.

Correct: C — Sum the parallel module short-circuit current ratings and multiply by 125 percent

690.8(A)(1)(a)(1) requires summing the short-circuit current ratings of parallel-connected PV modules and applying a 125% multiplier. The inverter continuous output rating is the method for inverter output circuits, not source circuits, under 690.8(A)(1)(c). Omitting the multiplier or substituting a 70% factor doesn't match the required calculation.

Correct: B — An isolating device without an interrupting rating, marked "Do Not Disconnect Under Load"

690.15(A)(3) permits an isolating device per 690.15(B) only where the maximum circuit current is 30 amperes or less; at 25 A this is available, but at 40 A only an equipment disconnecting means under 690.15(C) qualifies. The equipment disconnecting means, simultaneous-disconnect, and lockable-disconnect options all describe 690.15(C) equipment disconnects, which remain valid at any current level, so they aren't the answer that's uniquely unlocked by the lower current.

Correct: D — Electrical metallic tubing (metal raceway)

Since this circuit exceeds 30 volts and 8 amperes, 690.31(D)(1) requires metal raceway, metal enclosures, or Type MC cable meeting 250.118(A)(10)(b) or (c). Metallic tubing qualifies as metal raceway. Type NM cable and plain PVC or nonmetallic cable trays don't provide the required metal containment, and being exposed doesn't exempt a circuit from this requirement.

Correct: B — No, because it meets the solidly grounded, two-module, not-on-a-building exception

690.41(B) permits solidly grounded PV source circuits with not more than two modules in parallel and not on or in buildings to skip GFDI protection. The other options misstate the exception — GFDI is otherwise required above 30 V or 8 A, and being off a building alone (without solid grounding and the two-module limit) doesn't create the exception.

Correct: D — 600 volts

Per 690.7(2), PV system dc circuits on or in one- and two-family dwellings shall not exceed 600 volts. The 1000-volt figure applies to arrays on other building types or dc circuits inside buildings generally, not one- and two-family dwellings.

Correct: A — A tool for opening the connector

690.33(C) sets the tool-to-open threshold at over 30 volts dc (or 15 volts ac) for readily accessible connectors, not 50 volts. At 40 Vdc and readily accessible, a tool is required for opening, independent of the connector's current-interrupting rating. Intermatability listing is only required when connectors are not identical type and brand.

Correct: D — They must be listed for use in PV systems

690.9(B) requires overcurrent devices used in PV source circuits to be listed for use in PV systems. There's no exact-100%-with-no-rounding rule, no breaker-only restriction, and no outdoor-location requirement in this section.

Correct: A — The conductors have sufficient ampacity for the maximum circuit current, and combined source currents do not exceed the max OCPD rating for the module or converter

690.9(A)(1) requires both conditions: sufficient conductor ampacity for maximum circuit current, and combined source current not exceeding the maximum OCPD rating specified for the PV module or electronic power converter. The raceway and one-end options are conditions from 690.9(A)(3)'s exceptions, not the no-OCPD-needed path, and neither is sufficient by itself.

Correct: A — Installation on or in a one- and two-family dwelling

690.31(G)(1) flatly bans this equipment on or in one- and two-family dwellings. A detached industrial building and a ground-mounted array aren't dwellings or habitable-room buildings, so they aren't banned outright, and 9 ft above grade actually satisfies the 'less than 10 ft' exterior placement rule rather than violating it.

Correct: D — 600 mm (24 in.)

Per 690.31(C)(1)(b), exposed cables sized 8 AWG or smaller must be supported and secured at intervals not exceeding 600 mm (24 in.). The 1400 mm (54 in.) spacing applies only to exposed cables larger than 8 AWG under 690.31(C)(1)(c), and 300 mm (12 in.) is the cable tray support interval under 690.31(C)(2), not the exposed-cable interval.

Correct: B — Open-circuit voltage increases as temperature drops, so cold weather produces the highest system voltage

Per 690.7(A), PV open-circuit voltage rises as ambient temperature falls, so the coldest expected temperature at the site produces the maximum system voltage — that's why the correction is required. The claim that voltage decreases in cold weather has it backwards, and temperature does affect voltage (not just current), so those distractors misstate the underlying physics behind 690.7(A).

Correct: C — The cover must be locked or require a tool to open

Per 690.13(A)(2), when a disconnecting means for circuits above 30 V is readily accessible to unqualified persons, any enclosure door or hinged cover exposing energized parts when open must be locked or require a tool to open. The 48 V system is above the 30 V threshold, so the locked-or-tool-required cover option applies; there's no exemption at 50 V, and welding shut or relocating away from readily accessible are not what the rule calls for.

Correct: C — A readily accessible outdoor location

690.12(C) specifically requires that for one- and two-family dwellings, the initiation device be located at a readily accessible outdoor location — not merely somewhere labeled or indoors near equipment.

Correct: B — A ground-mounted PV system whose circuits enter a building used solely to house PV equipment

690.12 exempts ground-mounted PV system circuits that enter buildings whose sole purpose is to house PV system equipment. Rooftop arrays on occupied or general-use buildings, including a storage garage, still fall under the general rapid shutdown requirement since that exemption applies only to nonenclosed detached structures like carports and trellises, not enclosed storage buildings.

Correct: D — 305 mm (1 ft) from the array in all directions

690.12(B) defines the array boundary as 305 mm (1 ft) from the array in all directions. The 1 m (3 ft) distance is a separate measurement used in 690.12(B)(1) for conductors inside a building, not the array boundary itself.

Correct: D — As internal components of the ac module, exempt from Article 690's PV source circuit requirements

690.6(A) states that Article 690's PV source circuit requirements do not apply to ac modules — the source circuit, conductors, and inverter are internal components of the module. The inverter output circuit classification and standard PV source-circuit treatment both describe wiring outside this exemption.

Correct: C — 80 volts dc or greater

690.11 sets the threshold at 80 volts dc or greater between any two conductors. The 50 V, 100 V, and 150 V thresholds are all voltage levels used elsewhere in Article 690 (such as rapid shutdown or grounding rules), not the arc-fault protection trigger, so they are plausible but incorrect here.

Correct: D — The larger of the 125%-of-max-current value or the max current with adjustment and correction factors applied

690.8(B) requires the ampacity to be not less than the larger of 690.8(B)(1) (max current × 125%) or 690.8(B)(2) (max current with adjustment and correction factors). Using only the 125% value or only the adjustment/correction value ignores the rule's 'larger of' comparison, and picking the smaller value would undersize the conductor.

Correct: B — A 3-wire circuit with both outer conductors solidly grounded

690.41(A) lists six configurations: functionally grounded 2-wire, bipolar with a center-tap reference, circuits not isolated from a grounded inverter output, ungrounded circuits, solidly grounded circuits (as permitted in 690.41(B), not with both outer conductors grounded), and circuits protected by listed and identified equipment. Grounding both outer conductors of a 3-wire circuit isn't one of the recognized schemes.

Correct: A — All conductors in the box have an insulation rating at least equal to the maximum circuit voltage present, and identification/grouping rules are met

690.31(B)(1) allows PV dc circuits and inverter output circuits to share a junction box, pull box, or wireway without a barrier as long as all conductors carry an insulation rating equal to at least the highest circuit voltage present, and the dc conductors are identified and grouped per 690.31(B)(2) and (B)(3). A barrier is only one of the two permitted paths, not an absolute requirement, and current rating of the inverter circuit isn't the deciding factor.

Correct: D — Hard service cord rated extra-hard usage, listed for outdoor use, water resistant, and sunlight resistant

690.31(C)(4) requires flexible cords on moving parts of tracking arrays to be a hard service cord or portable power cable suitable for extra-hard usage, listed for outdoor use, water resistant, and sunlight resistant. Junior hard service cord and lamp cord fall short of the extra-hard-usage rating, and building wire in flexible metal conduit is not a flexible cord/cable assembly covered by this rule.

Correct: D — 690.47(A)

690.47(A) requires PV array equipment grounding conductors to connect to a grounding electrode system per Part VII of Article 250, in addition to any equipment grounding conductor requirements of 690.43(C). 690.47(B) instead specifies which electrodes and GEC sizing are permitted, and 690.45 only covers EGC sizing, not the grounding electrode connection itself.

Correct: C — 690.47(B)

690.47(B) is the Grounding Electrodes and Grounding Electrode Conductors section, and it specifically states a ground-mount support structure can serve as the grounding electrode if it meets 250.52. 690.47(A) covers buildings/structures supporting a PV system, a different scenario, and 690.45 sizes equipment grounding conductors, not the grounding electrode conductor.

Correct: A — No, mounting devices used for bonding must be listed, labeled, and identified for bonding PV modules

690.43(A) requires that devices and systems used both for mounting and for bonding module frames be listed, labeled, and identified for bonding PV modules (per UL 2703). A generic conductive rail with non-listed clamps doesn't satisfy this, voltage is irrelevant under 690.43, and mounting hardware CAN serve as the bonding path when properly listed — so the 'never' option is also wrong.

Correct: A — 690.31(C)(3)

690.31(C)(3) is the multiconductor jacketed cable rule and lists the 1.8 m (6 ft) securing interval for cable run outside a raceway, closely following support structures. 690.31(C)(1) governs single-conductor cable and 690.31(C)(4) governs flexible cords/cables to tracking arrays, neither of which fits jacketed multiconductor cable on fixed racking; 690.31(C)(2) covers cable tray installations, not exposed surface-mounted runs.

Correct: C — Type MC cable

Per 690.31(A)(2), PV dc circuit conductors over 30 volts that are readily accessible to unqualified persons and not guarded must be installed in Type MC cable, multiconductor jacketed cable, or raceway. Unjacketed single-conductor cable and open conductors don't meet this, and the 30-volt threshold — not 100 volts — is what triggers the requirement.

Correct: A — 690.12(D)

690.12(D) sets the label content, roof diagram, and 3/8 in. capitalized lettering for the label at the service equipment location. 690.12(D)(1) only adds a detailed roof plan view for buildings with more than one rapid shutdown type or none, and 690.13(B) covers disconnect marking, not rapid shutdown labeling.

Correct: D — The maximum rated voltage output of the dc-to-dc converter

Under 690.7(B)(1), when the listing instructions don't specify a method, the maximum voltage defaults to the converter's maximum rated voltage output. Summing outputs applies only to series-connected converters under 690.7(B)(2), not a single unit. Temperature-adjusted open-circuit voltage is a PV source circuit calculation under a different part of 690.7, not the dc-to-dc converter output calculation.