Alternating Current. Electrical current which periodically reverses Inverters convert DC current to AC current, which travels back to the point of interconnection
AFCI
Arc-Fault Circuit Interrupter. A device intended to provide protection from the effects of arc faults by recognizing characteristics unique to arcing and by functioning to de-energize the circuit when an arc fault is detected.
AHJ
Authority Having Jurisdiction. an organization, office, or individual responsible for enforcing the requirements of a code or standard, or for approving equipment, materials, an installation, or a procedure.
Ampacity
The maximum current, in amperes, that a conductor can carry continuously under the conditions of use without exceeding its temperature rating.
ASCE
American Society of Civil Engineers. The professional society for the designers and builders of society's infrastructure, devoted to the protection of the public's health, safety and welfare, and instrumental in shaping a sustainable world.
AWG
American Wire Gauge. A measure of wire thickness which also dictates cross-sectional area, and for a given material, ampacity.
Backfeed
Flow of electric power in the direction reverse to that of the generally understood or typical flow of power. Typically referring to backfeeding of power generated from solar panels back to the main panel.
Backsheet
A film on the back side of a module that protects the solar cell(s) from severe environmental conditions.
Busbar
Metal bars that distribute power within electrical panels. The rating of the busbar determines the rating of the electrical equipment.
CEC
California Energy Commission, the primary energy policy and planning agency for California or California Electrical Code, the California version of the National Electrical Code (NEC).
Combiner Box
Combiner boxes are commonly used to combine several solar panels (or strings/branches of panels) into a common bus.
CT
Current Transformer. A device that measures the current in a conductor by generating a smaller output current proportionate to that measured.
Datasheet
Specifications providing valuable information regarding the technical aspects of particular equipment.
DC
Direct Current. Electrical current which flows consistently in one direction. This is what solar panels produce and what batteries hold in storage.
DC-to-DC converter
A device that can provide an output DC voltage and current at a higher or lower value than the input DC voltage and current. Per module, it maximizes solar energy generated per system by performing Maximum Power Point Tracking (MPPT).
Derate
To lower the rated capability of something such as an electrical main breaker.
EGC
Grounding Conductor, Equipment. A conductive path(s) that is part of an effective ground-fault current path and connects normally non-current-carrying metal parts of equipment together and to the system grounded conductor or to the grounding electrode conductor, or both.
GEC
Grounding electrode conductor. Connects the system grounded conductor or the equipment to a grounding electrode or to a point on the grounding electrode system.
ISC
Short-circuit current, the current through the solar cell when the voltage across the solar cell is zero
kW
Kilowatt. Unit of measurement, one thousand Watts.
lbs
Pounds. Imperial unit of measurement for weight
m
Meter. SI base unit for distance
mm
Millimeter. One thousandth of a meter
Microgrid
A small network of electricity users with a local source of supply that is usually attached to a centralized national grid but is able to function independently.
Microinverter
A device used with a solar panel to convert the energy that is generated (Direct Current) to usable electricity for a home (Alternating Current).
MSP
Main Service Panel. The central panel where all branch circuits originate and service and various electrical loads throughout a building.
Multiconductor
A wire or cable composed of multiple electrical conductors.
NFPA
National Fire Protection Association, international nonprofit organization devoted to eliminating death, injury, property, and economic loss due to fire, electrical and related hazards.
NM
Nonmetallic sheathed, the cable consists of a factory assembly of two or more insulated conductors within an overall nonmetallic jacket.
NRTL
Nationally Recognized Testing Laboratory. A term used by OSHA to identify third-party organizations that have the necessary qualifications to perform safety testing and certification of products covered within OSHA and each organization's scopes.
OCPD
Overcurrent Protection Device. A device capable of providing protection for service, feeder, and branch circuits and equipment over the full range of overcurrent between its rated current and its interrupting rating, e.g. a breaker or fuse.
Ohms
SI base unit for electrical resistance, expressing the resistance in a circuit transmitting a current of one ampere when subjected to a potential difference of one volt
Overcurrent
Any current in excess of the rated current of equipment or the ampacity of the conductor. It may result from overload, short circuit, or ground fault.
Panelboard
A single panel or ground of panel units designed for assembly in the form of a single panel, including buses and automatic overcurrent devices, and equipped with or without switches for the control of light, heat, or power circuits; designed to be placed in a cabinet or cutout box placed in or against a wall, partition, or other support; an accessible only from the front.
PCS
Power Control System. Systems or devices which electronically limit or control the steady state AC currents, or DC currents, to a programmable limit or level.
PV
Photovoltaic System. The total components, circuits, and equipment up to and including the PV system disconnecting means that, in combination, convert solar energy into electric energy.
PVHCS
PV Hazard Control System. System defined by the UL3741 standard to ensure safety for fire fighting operations.
PVRSA
PV Rapid Shutdown Array. An array that complies with the electrical safety requirements set for solar panel systems by the National Electric Code.
PVRSE
PV Rapid Shutdown Equipment. Equipment intended to be used in a PVRSS to initiate, disconnect, isolate, or attenuate the controlled conductors of a PV system.
PVRSS
PV Rapid Shutdown System. System consisting of PVRSE intended to initiate, in addition to disconnect, isolate or attenuate the controlled conductors of a PV system.
RSD
Rapid Shutdown Device. A system that is designated to provide compliance with To comply with Section 690.12 of the National Electric Code by opening the photovoltaic circuits, disconnecting them from the inverter, and removing all residual voltage and current on the conductors.
VOC
Open circuit voltage, the maximum voltage that the solar panel can produce with no load on it.
Sheathing
Board or panel material used in floor, wall, and roof assemblies.
Sq.
Square. Combined with a unit of measurement for area, such as Sq.Ft. square feet.
Subpanel
A smaller service panel that distributes power to a specific area of the home or other buildings on the property. It is essentially a satellite circuit breaker panel that has its own breakers.
THWN, THWN-2
Thermoplastic Heat and Water-resistant Nylon-coated. A cable which is suitable for use in both dry and wet locations with a maximum temperature rating of 75ºC. THWN-2 cable is rated to 90ºC.
Underlayment
What lies between the shingles and the roof sheathing, or roof deck, which is typically either plywood or OSP.
Upsize
To increase in size. Typically refers to the sizing of inverters, breakers, and related equipment of a solar panel system.
V
Volt. SI derived unit of measurement to express a difference in electrical potential.
W
Watt. The SI derived unit for energy transfer. The rate of electrical work when current of one ampere flows across a potential difference of one volt. Alternatively expressed as one joule per second.
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