The four bonding jumpers, and why sorting them by name loses the item

Four jumpers carry the name

The word jumper gets attached to conductors doing quite different jobs in Article 250, and an exam item will hand you one name and three plausible descriptions of the others. Learn the four by where each one lives.

Three more conductors carry the word and belong on the electrode side of the house. NEC 250.66 sizes the bonding jumpers that connect electrodes to each other, 250.64(E)(3) sizes a jumper from a ferrous raceway to the grounding electrode conductor inside it, and 250.53(D)(1) puts a jumper around a water meter so the electrode path survives a plumbing call.

Sort on the job the jumper does

Sorting on the word bonding fails, and it fails in the direction that costs you the answer.

NEC 250.66 sizes bonding jumpers used to connect grounding electrodes. NEC 250.64(E)(3) sizes a bonding jumper from the raceway that encloses a grounding electrode conductor. Both are called bonding jumpers and both size on the electrode side. A candidate who sorts on the word reaches for Table 250.122 and produces a number that appears nowhere in the four choices.

Run it the other way and the same rule holds. A supply-side bonding jumper has bonding in its name and sizes on the fault-path side from Table 250.102(C)(1). A bonding bushing at a service raceway sizes on the fault-path side as well. Two names pointing one way and four items sorting the other way, which is why the useful question is what the conductor does.

How the exam asks it

Our bank of 500 original Texas practice items puts 66 in the grounding and bonding area. The phrase bonding jumper appears in 17 of the 500, and all 17 of them sit inside that one area, which makes this the densest vocabulary in the subject.

The forms repeat.

• Define the term. You are asked what a main bonding jumper is, and the three wrong answers are accurate descriptions of other conductors: the run from the service enclosure out to the ground rod, the jumper installed around a water meter, and a bond between two subpanels fed from the same service. Each one is a real thing with a real name, which is what makes the item work.
• Sort two conductors. One conductor runs with the circuit conductors from a panel to a load and another runs from the service out to a rod, and you name each. The distractor that takes people sorts the two by where they land, since both end on a bar.
• Judge an installation. A jumper goes in at a place the code permits and a second goes in at another place the code also permits, and you say what results.

That last form is worth sitting with, because the wrong answer is the installer's own reasoning: either location is allowed, so both must be allowed. The item exists because that sentence gets said out loud on jobs.

The jumper at a receptacle

NEC 250.146 asks for a jumper from the receptacle grounding terminal to a grounded box, and then names the situations where the connection is reliable without one. Among those named conditions are a surface-mounted box in direct metal to metal contact with the device yoke, a device listed and identified for the purpose, and a listed floor box.

What the section doubts is a yoke held by mounting screws through a plaster ring or into a painted surface, which leaves the grounding contact of the receptacle hanging on paint and a screw thread. So both extreme answers on this item fail. Relying on the mounting screws is the practice the section declines to accept, and claiming the jumper is always required misses the named conditions that release it.

A metal box fed by nonmetallic sheathed cable is the companion item. The cable connector clamps a nonmetallic sheath and brings no metal path with it, so the box gets a grounding screw in the tapped hole or a listed clip joining it to the equipment grounding conductors inside (NEC 250.148(C), with the methods named at 250.8).

Ahead of the service disconnect

The bonding ahead of the service disconnecting means is written to a higher standard than the bonding used elsewhere, and the reason is worth carrying into the room.

Ahead of that disconnect there's no equipment grounding conductor and no overcurrent device on the premises. A fault between an ungrounded service conductor and the metal service raceway returns on the bonded raceway and the grounded service conductor, all the way back to the source on the utility side, and it keeps flowing until the utility protection reacts. That's why NEC 250.92 names specific methods and goes past the locknut used elsewhere.

The same thinking reaches past services in one place. For circuits over 250 volts to ground, boxes with oversized, concentric or eccentric knockouts call for the methods otherwise reserved for services, which includes bonding jumpers and bonding bushings. The rule carries an exception where no such knockouts are encountered or the enclosure is listed for a reliable bonding connection, and even the ordinary case specifies two locknuts, inside and out, in place of the single locknut used on smaller work.

A ferrous raceway sleeved over a grounding electrode conductor sits in the same family. Left unbonded, the steel acts as a choke, because the changing field induces an opposing current in it and raises the impedance of the path it was installed to protect. Bonding at each end puts the sleeve in parallel with the conductor, and one end is too few.

What it costs on the job

Two of these turn up in inspection reports more than the rest.

The first is a system bonding jumper at the source and a second one at the first disconnecting means. Both locations are permitted individually, so the installer defends it as redundancy, and what it produces is a closed loop with derived neutral current coming back partly on the metal between the two enclosures. The fix is removing one of them, and the argument about which one is the only real decision. The single-point rule behind that sits on separately derived systems.

The second is a jumper around the water meter treated as the whole water piping requirement. NEC 250.53(D)(1) puts that jumper around the meter and any other removable item so the electrode path survives a service call on the plumbing. NEC 250.104(A) is a separate duty that bonds the interior metal water piping system to the service, sized under 250.102(C). One protects a path that already exists and the other creates a path for a fault that energizes the piping, so a short jumper at the meter answers half of it.

Texas puts the duty on named people. 16 TAC 73.53 requires electrical work to be performed in compliance with applicable codes and ordinances, and 16 TAC 73.51(g) places supervision and regulatory compliance on the contractor and the master electrician together.

The Texas layer on top

Two things sit on top of Article 250 for anyone working or testing in this state.

Texas adopts the 2026 National Electrical Code on 1 September 2026 under 16 TAC 73.100, and the examinations reference that edition from the same day. Article 250 kept its number this cycle while other parts of the book moved, so a tab set built for a 2023 copy still sends your hand to the wrong page elsewhere. The dates are worked through on which code edition applies.

Then the cities. Tex. Occ. Code 1305.201(c) lets a municipality adopt procedures for local amendments to the National Electrical Code and for administering it, and 1305.201(d) requires electrical work inside the corporate limits to be installed in accordance with all applicable local ordinances. So the governing text on any given job is the state-adopted edition plus that city's amendments, and asking which edition and which amendments before you price work somewhere unfamiliar is ordinary practice here. Our page on what a city can still require sets out where that power starts and stops.

The four hours of continuing education you owe at each renewal point at the code as adopted under the Occupations Code, and the rule names no year at all (16 TAC 73.25(b)(1)), which is why a national update course can be entirely correct everywhere else and wrong on a Texas amendment. The rule itself is set out on the four hours, as the rule is written.

What to do before test day

Three drills, and the first one is the whole topic.

1. Write the four jumpers on one card with the section beside each and the thing that sizes it. Main at 250.28, system at 250.30(A)(1), supply-side from Table 250.102(C)(1), equipment jumper at 250.146 and 250.102. Add the electrode-side three underneath, because those are the ones that get sized from the wrong table.
2. Take any grounding item you meet and answer one question before you read the choices: is this conductor headed for the earth, or headed back to the source? Nearly every rule in Article 250 answers one of those two, and the ones answering back to the source are the ones that matter when something goes wrong. The same sort is worked through on grounding and bonding as two jobs.
3. Answer thirty mixed items under a clock. Our free timed practice set prints the section behind every answer, so a miss teaches you the section number as well as the rule.

Where you want the sizing worked line by line, with the tables traced and the figures set out, that lives in the practice exam. This page is the Texas candidate's view of the same vocabulary: which jumper the item is about, and what a missing one costs once an inspector opens the can.

Questions people ask

What is a main bonding jumper?

It's the connection between the grounded conductor and the equipment grounding terminal or bus at the service, made inside the enclosure that holds the service disconnecting means (NEC 250.24(C)). It's the one deliberate connection between the two systems on a service-supplied installation, and 250.28 sets its material, construction, attachment and size. The conductor running from that enclosure out to the ground rod is the grounding electrode conductor, which is a different conductor with a different sizing rule, and an exam item on this will offer you that description as a wrong answer.

How does a system bonding jumper differ from a main bonding jumper?

They do the same job at different sources. The main bonding jumper makes the connection at a service. The system bonding jumper makes it on a separately derived system, at any single point from the source to the first system disconnecting means or overcurrent protective device (NEC 250.30(A)(1)). The location is fixed for one and chosen by the installer for the other, and both are unspliced and sized under 250.28. Where a step-down unit sits between the service and the panel in a question, find the system bonding jumper before you answer anything else.

When does a receptacle need a bonding jumper to the box?

As a rule, unless the installation meets one of the conditions NEC 250.146 names. Those conditions cover situations where the connection between yoke and box is reliable on its own, among them a surface-mounted box in direct metal to metal contact with the yoke, a device listed and identified for the purpose, and a listed floor box. What the section declines to rely on is a yoke held by mounting screws through a plaster ring or into a painted surface, which is exactly the arrangement most people assume is sufficient.

Which table sizes a bonding jumper?

That depends on which jumper. A main or system bonding jumper is sized under 250.28. A supply-side bonding jumper is sized from Table 250.102(C)(1), and so is the conductor bonding interior metal water piping to the service under 250.104(A). An equipment bonding jumper on the load side of an overcurrent device is sized from 250.122. A jumper connecting grounding electrodes to each other is sized under 250.66 with the ceilings that attach to the electrode type. Sorting by the word bonding puts you in the wrong table about half the time.

Is a jumper around the water meter the whole water piping requirement?

It answers one of two duties. NEC 250.53(D)(1) puts a bonding jumper around a water meter and any other removable item so the electrode path survives a plumbing service call. NEC 250.104(A) separately bonds the interior metal water piping system to the service, with that conductor sized under 250.102(C). One protects a path that already exists and the other creates a path for a fault that energizes the piping. An installer who fits the meter jumper and stops has satisfied the first duty and left the second one open.

Why must the main bonding jumper be unspliced?

Because a splice is a point of failure in a conductor whose entire job is to be there when something goes wrong. If the main bonding jumper opens, the service enclosure loses its reference to the grounded conductor and the fault path back to the source goes with it, so every equipment grounding conductor on the premises ends at a dead end. NEC 250.24(C) states it, and the section carries two exceptions, one for multiple disconnects in an assembly listed for use as service equipment and one for impedance grounded systems.