Electric Utilities Apps

Inspection Checklist for Rooftop Solar Systems

This Model Inspection Checklist for Rooftop PV Systems App can serve a variety of important functions. First, it can serve as a supplementary educational tool for new or experienced inspectors to ensure they are aware of the host of code requirements that must be verified on-site during the inspection. It can also increase the consistency of inspections, by both a single inspector, as well as different inspectors working for the jurisdiction. Consistent inspections ensure high-quality, safe installations and also reduce conflict with installers, who may complain when they perceive that different inspectors provide different results. The municipality can also use an inspection checklist as a tool for highlighting particular issues that seem to be repeatedly problematic for installers. For example, a checklist could contain a section for “common mistakes” which could highlight particular issues for both installers and inspectors to verify.

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Inspection Checklist for Rooftop Solar Systems

PV Array Configuration

Module manufacturer, make, model, and number of modules match the approved plans.

PV modules are listed to UL 1703.

DC modules are properly marked and labeled.

AC modules are properly marked and labeled.

Modules are attached to the mounting structure according to the manufacturer’s instructions and the approved plans.

Roof penetrations are flashed and counter-flashed.

PV modules are in good condition (i.e., no broken glass or cells, no discoloration, frames not damaged, etc.).

Residential one and two family dwelling limited to maximum PV system voltage of 600 volts.

Rooftop systems are designed in accordance with the IBC.

Roof access points, paths and clearances need to comply with the IFC.

Grounding

A complete grounding electrode system is installed.

Modules are grounded in accordance with manufacturer’s installation instructions using the supplied hardware or listed equipment specified in the instructions and identified for the environment, and using the grounding point identified on the module and in the manufacturer’s instructions.

Properly sized equipment grounding conductor is routed with the circuit conductors.

AC and DC grounding electrode conductors are properly connected. Separate electrodes, if used, are bonded together.`

Bonding fittings are used on concentric/eccentric knockouts with metal conduits for circuits over 250 volts.

Bonding fittings are used for ferrous metal conduits enclosing grounding electrode conductors.

Wire Management

Wires are secured by staples, cable ties, straps, hangers or similar fittings at intervals that do not exceed 4.5 feet.

Wires are secured within 12 inches of each box, cabinet, conduit body or other termination.

Cable closely follows the surface of the building finish or of the running boards.

Exposed single conductors, where subject to physical damage, are protected.`

Conductors

Exposed single conductor wiring is a 90C, wet rated and sunlight resistant type USE-2 or listed PV wire. (NEC 690.31(B)) If the wiring is in a conduit, it is 90C, wet rated type RHW-2, THWN-2, or XHHW-2.

Exposed single conductors used for ungrounded (transformerless) systems are listed and identified as "PV wire."

Conductor insulation is rated at 90C to allow for operation at 70C+ near modules.

Where conductors or cables are installed in conduits exposed to direct sunlight on or above rooftops, correction factors for ambient temperature adjustments are applied.

Grounded conductor is identified white or grey.

Open conductors are secured and protected.

Conductors are not in contact with the roof surface.

DC conductors inside a building are in a metal raceway or MC metal-clad cable that complies with 250.118(10), or metal enclosures.

If more than one nominal voltage system conductor is installed in the raceway, permanent identification and labeling is required.

For underground conductor installations, the burial depth is appropriate and warning tape is in place.

Aluminum is not placed in direct contact with concrete.

DC source circuit conductors are rated at 1.25 x 1.25 = 156% short-circuit (ISC) current from modules. NOTE: The module ISC x number of combined strings, if strings are combined. When DC source circuits (strings) are connected in parallel the short circuit current multiplies and PV output conductors from combined strings need to be sized appropriately.

PV circuit and premises wiring is separated.

PV system conductors shall be grouped and identified.

Overcurrent Protection

Overcurrent devices in the DC circuits are listed for DC operation.

DC source circuit overcurrent protection devices are rated at 1.25 x 1.25 = 156% short-circuit (ISC) current from modules. NOTE: The module ISC x number of combined strings, if strings are combined. When DC source circuits (strings) are connected in parallel the short circuit current multiplies DC over-current protective devices need to be sized appropriately.

Inverter output circuit overcurrent protection device (point of connection to AC system breaker) is sized based on the maximum inverter output current x 125%.

Overcurrent protection is required for the PV source circuit (modules and parallel connected modules), PV output circuit (conductors between source circuits and inverter), inverter output circuit, battery circuit conductors and equipment.

Where three or more strings are combined, a listed combiner box (UL1741) is used and fuses are required. When DC source circuits (strings) are connected in parallel, the current through a failed circuit can be the sum of the current connected from the other strings, therefore special consideration must be taken to ensure the sum of the total number of strings minus one does not exceed the module manufacturers series fuse rating, or conductor ampacity.

When a back-fed breaker is used as a utility interconnection means, the breaker does not read “line and load.”

PV interconnect breaker is located at the opposite end of the buss from the feeder connection, unless using 100% rated equipment.

Electrical Connections

Crimp on terminals are listed and installed using a listed tool specified for use in crimping those specific crimps.

Pressure terminals are listed for the environment and tightened to manufacturer recommended torque specifications.

Connectors are listed for the voltage of the system and have appropriate temperature and ampere ratings.

Twist on wire connectors are listed for the environment (i.e. wet, damp, direct burial, etc.) and installed per manufacturer’s instructions.

Power distribution blocks are listed.

Terminals containing more than one conductor are listed for multiple conductors.

Connectors and terminals used for fine strand conductors are listed for use with such conductors.

Connectors that are readily accessible and operating at over 30 volts require a tool for opening.

Module connectors are tight and secure.

Wiring and connections of inverters, PV source circuits, battery connections, etc., and all interconnections are performed by qualified personnel.

Charge Controllers

Charge controller is listed to UL Standard 1741.

Exposed energized terminals are not readily accessible.

Diversion charge controllers that are used as the sole means of regulating charging of batteries have a second independent means of control to prevent overcharging.

Disconnects

Disconnects used in DC circuits are listed for DC operation.

Disconnects are installed for all current carrying conductors of the PV source.

Disconnects are installed for the PV equipment. NOTE: For inverters and other equipment that are energized from more than one source, the disconnecting means must be grouped and identified.

Disconnects and overcurrent protection are installed for all ungrounded conductors in ungrounded (transformerless) PV power systems.

Inverters

Inverters are listed to UL 1741.

Point of connection is at a dedicated breaker or disconnect.

Total rating of the overcurrent devices supplying equipment does not exceed 120% of the equipment rating.

Listed AC and DC disconnects and overcurrent protection are grouped and identified.

No multi-wire branch circuits are installed where single 120-volt inverters are connected to 120/240-volt load centers.

The plastic barrier is re-installed between the AC, DC wiring and communication wires.

Batteries

Storage batteries for dwellings have the cells connected to operate at less than 50 volts.

Live parts of battery systems for dwellings are guarded to prevent accidental contact by persons or objects.

Flexible battery cables are listed RHW or THW, 2/0 minimum for battery cell connections. (NEC 690.74) NOTE: welding cables, marine, locomotive (DLO), and automotive cables do not meet the current Electrical Code requirements.

Flexible, fine strand cables are only be used with terminals, lugs, devices, and connectors that are listed and marked for such use.

High interrupt, listed, DC rated fuses or circuit breakers are used in battery circuits. The AIC is at least 20,000 amps.

Cables to inverters, DC load centers, and/or charge controllers are in a conduit.

Conduits enter the battery enclosure below the tops of the batteries. NOTE: this is to avoid accidental ventilation of gases into electrical equipment where sparks may occur. Follow battery enclosure manufacturer's instructions for venting and conduit locations.

A disconnect means is provided for all ungrounded conductors derived from a stationary battery system over 30 volts.

Area is well ventilated and the batteries are not installed in living areas.

Signs and Labels

All interior and exterior DC conduit, enclosures, raceways, cable assemblies, junction boxes, combiner boxes, and disconnects are marked.

The markings on the conduits, raceways and cable assemblies are every 10 feet, within one foot of all turns or bends and within one foot above and below all penetrations of roof/ceiling assemblies, walls and barriers.

Marking is placed adjacent to the main service disconnect in a location clearly visible from where the disconnect is operated.

The markings say “WARNING: PHOTOVOLTAIC POWER SOURCE” and have 3/8 inch (9.5 mm) minimum-sized white letters on a red background. The signs are made of reflective weather resistant material. Self-adhesive signs are available from suppliers.

Where PV circuits are embedded in built-up, laminate, or membrane roofing materials in roof areas not covered by PV modules and associated equipment, the location of circuits shall be clearly marked.

Labels are phenolic where exposed to sunlight. Labels required on conduit are permanent, weather resistant and suitable for the environment. Labels have a red background with white lettering.

Fire Safety

Rooftop mounted PV panels and modules have the proper fire classification rating.

Rooftop DC Conduits are located as close as possible to the ridge or hip or valley and from the hip or valley as directly as possible to an outside wall to reduce trip hazards and maximize ventilation opportunities.

Conduit runs between sub arrays and to DC combiner boxes are installed in a manner that minimizes total amount of conduit on the roof by taking the shortest path from the array to the DC combiner box.

DC Combiner Boxes are located so that conduit runs are minimized in the pathways between arrays.

DC wiring in enclosed spaces in buildings is installed in metallic conduit or raceways. Conduit runs along the bottom of load bearing members.

DC wiring methods shall not be installed within 25cm (10”) of the roof decking or sheathing except where directly below the roof surface covered by the PV modules and associated equipment.

All roofs have an access point that does not place ground ladders over openings such as windows or doors, are located at strong points of building construction, and in locations where the access point does not conflict with overhead obstructions such as tree limbs, wires, or signs.

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