Photovoltaic systems, NEC 690.12 rapid shutdown, and the three cheapest items on a Texas paper

Three items, and why they are cheap

Renewable Energy Technologies is 2 of the 56 scored items on the journeyman NEC Knowledge portion and 1 of the 24 scored on Calculations, which makes it the second smallest area on the knowledge outline, ahead only of control devices and disconnecting means at one item.

Three items across the sitting, from a subject with one central idea, in articles most candidates walk past. Seventy percent passes the knowledge portion, leaving room for about sixteen wrong answers across 56 scored items, so handing over three of them spends most of a fifth of that margin before you sit down.

The bank carries four items here and they cover the whole shape of the subject: what rapid shutdown acts on, which article governs a load side connection, what wiring method a direct current run inside a building takes, and what Article 705 wants of a busbar fed from two ends.

The fact everything else follows from

A photovoltaic module makes power whenever light lands on it, and the sun stays where it is. Every other source in the book can be interrupted at its origin, and an array runs on one that keeps supplying it.

So the article is built around limiting how much energized conductor is left once somebody opens a disconnect, and around telling everyone who might touch the building what stays live. Hold that sentence and much of Article 690 becomes predictable.

Direct current makes it harder in two ways, and both explain rules that look fussy on first reading. An alternating current arc crosses zero twice a cycle, and a great deal of switchgear design quietly depends on that moment to put it out. A direct current arc keeps burning until something separates far enough, which is why the disconnects here are rated the way they are. And an array is a current limited source: short a module and it delivers only modestly more current than at its operating point, which is why NEC 690.8 sizes circuits off a multiple of short circuit current. A fault can sit on a PV circuit all day while drawing too little to open an overcurrent device, so the article leans on detection and on marking what stays live.

What rapid shutdown actually does

It shrinks the energized footprint to a small region around the array. An answer choice claiming it de-energizes the array is wrong on its face, because the thing keeping those modules live is daylight.

Three ideas carry the function, and an item is usually testing which one is which.

• Controlled conductors: the PV system conductors running away from the array toward the rest of the building. Those are what the function acts on.
• The array boundary: a defined region one foot from the array in every direction. Conductors running more than three feet inside a building from their point of entry count as outside it.
• The clock: every limit in the section is stated as a voltage reached within a period after the function is initiated, so nothing here is instantaneous.

The reason for all of it is a firefighter with an axe, cutting a ventilation hole or throwing a ladder against a wall, who needs to know what the conductors running past their hands will be doing a minute after the switch outside was hit. Killing the service does nothing about them, because the service disconnect sits on the utility side and leaves everything coming off the roof energized.

Two limits, one on each side

Outside the boundary the limit is tighter, because that is where people stand. NEC 690.12(B)(1) holds controlled conductors outside the array boundary to no more than 30 volts within 30 seconds of initiation, a level chosen around what a person can be near.

Inside the boundary NEC 690.12(B)(2) offers a choice, and this is the part that moved most across recent editions. One option is a listed PV hazard control system installed to the instructions that come with its listing, with the same initiation device telling it to go to its controlled state where it needs telling. The other is a voltage limit: the highest voltage inside equipment, between any two conductors of a circuit, or between any conductor and ground inside the boundary, held to no more than 80 volts within 30 seconds.

So the shape is one clock and two voltages. The tighter number sits outside where the people are, and the looser number applies inside the array where a listed system may be doing the work.

NEC 690.12(C) holds the initiation device requirements in three numbered paragraphs covering what the device is, where it goes and how it is marked. Read them twice in your own book.

Article 690 or Article 705

Two bank items turn on this. Article 690 covers the photovoltaic system up to the point where it meets another source. Article 705 covers interconnected electric power production sources, so the load side connection rules and the busbar limits live there. A system connected to the load side of a dwelling service disconnect is an Article 705 question, and a full answer usually needs both articles open at once, which is what makes these items slow.

The busbar item is the harder of the two. A bar fed from both ends can carry more current in the middle than either supply device by itself suggests, so Article 705 limits the total of the supply device ratings against the busbar rating and pushes the two sources to opposite ends, so no length of bar sees both. A label records the arrangement for the next person to add a breaker. Answers that rebuild the panel or remove the main are there for candidates reaching for hardware ahead of the calculation.

Article 706 covers energy storage systems, where a battery question belongs, and Article 710 covers stand alone systems. NEC 690.1 draws one more line, giving large scale photovoltaic electric supply stations to Article 691. Deciding which article you are in comes first, the same reflex disconnecting means items reward.

Direct current circuits inside a building

One bank item runs direct current circuits from a roof array to an inverter in the garage and asks what Article 690 requires of that run. The answer is metal raceway or metal clad cable, all the way to the first readily accessible disconnect inside the building, with the wiring method marked so that anybody cutting into a wall knows what is behind it.

The metal is there to contain an arc, which is why the choice offering nonmetallic raceway on the theory that no metal part can then become energized reads the requirement backward. Cable tray with the conductors marked at both ends is a method the section leaves out for this part of the run. And the choice saying ordinary wiring method rules are enough treats a source that keeps supplying power as an ordinary circuit.

This is where PV crosses into everyday work, which is why wiring methods reading pays twice here.

Maximum voltage and the three methods

Cold is the worst case. A module's open circuit voltage rises as it gets colder, so a string sitting comfortably under an equipment rating on a July afternoon can climb past it on a clear January morning, and the calculation is done at the lowest expected ambient temperature for the site.

NEC 690.7(A) gives three permitted methods and an item lives in the difference between them. The general method sums the modules' rated open circuit voltage for the series string and corrects it for the lowest expected ambient temperature using that module's own temperature coefficients, which works for any module because the coefficients come off its listing. The table method corrects the same sum using the factors in Table 690.7(A), and the first four words of that method restrict it to crystalline and multicrystalline silicon modules. The third is a documented and stamped design by a licensed professional electrical engineer.

So when a maximum voltage question appears, find the module technology in the stem before you find the numbers. Crystalline and multicrystalline silicon give you the table, and anything else sends you to the coefficients, so a choice reaching for the table anyway is wrong however the arithmetic comes out. Leave the table itself in your book.

The worked voltage arithmetic, method by method, lives in the question set. This page stays with what a Texas candidate settles before the arithmetic starts.

What actually moved in 2026

Less than you have been told, and the useful news is that your section addresses still work. The 2026 edition ran a template through the book putting listing requirements at the .2 position of an article and reconditioned equipment at .3. Article 690 picked up a listing requirement at NEC 690.2, a vacant position, so nothing behind it moved.

The addresses hold. Maximum voltage is at 690.7, rapid shutdown at 690.12, the system disconnecting means at 690.13, the equipment disconnecting means at 690.15, wiring methods in the 690.31 area, and equipment grounding through 690.43 and 690.45.

The lesson generalizes the other way. Some articles in Chapters 5 and 6 were reorganized wholesale and some were barely touched, so check the article you are in before applying one rule to the whole book. The substantive 2026 work here went into 690.12(B)(2), where the listed hazard control system option was tightened. Texas moves to the 2026 edition on 1 September 2026 under 16 TAC 73.100, and the examinations follow that day.

What Texas did to residential backup work

One Texas change belongs here because it reaches the equipment most often sold alongside an array. Senate Bill 1252 of the 89th Legislature added Tex. Loc. Gov't Code 229.102, barring a municipality from adopting or enforcing an ordinance, rule or other measure that regulates the installation or inspection of a residential energy backup system. A companion amendment at Tex. Loc. Gov't Code 214.214 closes the route through a local amendment to the code, and the definition the bar turns on was added at Tex. Loc. Gov't Code 214.211(6).

That definition reaches a backup energy system at a residential property capable of supplying no more than 50 kilowatts to the residence, or storing no more than 100 kilowatt hours. Home battery storage lands inside those figures in most installations.

Two limits sit on the limit. A municipally owned utility keeps its authority inside its own service area, and Chapter 1305 licensing reaches a backup system exactly as it reaches a panel change, so who may do the work is untouched. The act applies to work initiated on or after 1 September 2025, leaving a job already under way on the old footing. It is easy to miss because it lives in the Local Government Code.

Questions people ask

How many photovoltaic questions are on the Texas journeyman exam?

Three across the sitting. Renewable Energy Technologies carries 2 of the 56 scored items on the journeyman NEC Knowledge portion and 1 of the 24 scored items on Calculations, which makes it the second smallest area on the knowledge outline, ahead only of control devices and disconnecting means. Because the subject has one central idea and sits in articles most candidates skip, the effort per item is lower here than almost anywhere else on the paper. Seventy percent passes, so those three items are most of a fifth of your whole margin.

What does rapid shutdown under NEC 690.12 act on?

The controlled conductors outside the array boundary, which it brings down to a low voltage within a stated time after somebody initiates the function. It works on conductors because daylight keeps the modules producing, so the array itself stays live. Opening the service disconnect does nothing here, since that device sits on the utility side and leaves everything coming off the roof energized. Stopping the inverter leaves the direct current conductors between the array and the inverter live. Read 690.12(B) and 690.12(C) end to end in a 2026 book.

What are the two voltage limits in 690.12(B)?

Outside the array boundary, NEC 690.12(B)(1) holds controlled conductors to no more than 30 volts within 30 seconds of initiation, which is the number that matters to a person on a roof or on a ladder. Inside the boundary, NEC 690.12(B)(2) offers either a listed PV hazard control system installed to its listing instructions, or a limit of no more than 80 volts within 30 seconds. Same clock, two voltages, tighter on the outside where people stand. Three distractor families come out of this one section.

Which article covers connecting a PV system to an existing service?

Article 705, which covers interconnected electric power production sources. Article 690 covers the photovoltaic system up to the point where it meets another source, so a connection to the load side of a dwelling service disconnect belongs to 705, along with the busbar limits. Article 230 covers services, and a load side connection sits downstream of the service disconnect. Article 250 sets no rules about the point of connection. Most solar questions need both 690 and 705 open at once, which is what makes them slow on the clock.

Did the section numbers in Article 690 change for 2026?

Barely. The 2026 edition ran a template through the book that puts listing requirements at the .2 position of an article, and Article 690 picked up a listing requirement at NEC 690.2. That position was vacant, so nothing behind it moved. Maximum voltage stays at 690.7, rapid shutdown at 690.12, the system disconnect at 690.13 and the equipment disconnect at 690.15. Other articles in Chapters 5 and 6 were reorganized wholesale, so check the article you are in before applying any one rule about renumbering.

Can a Texas city write its own rules for home battery storage?

Since 1 September 2025 its room to do so is narrow. Tex. Loc. Gov't Code 229.102 bars a municipality from adopting or enforcing a measure regulating the installation or inspection of a residential energy backup system, and Tex. Loc. Gov't Code 214.214 closes the route through a local amendment to the code. The definition at Tex. Loc. Gov't Code 214.211(6) reaches a system capable of supplying no more than 50 kilowatts to the residence or storing no more than 100 kilowatt hours. A municipally owned utility keeps authority inside its own service area, and Chapter 1305 licensing still governs who does the work.