Texas Electrician ExamTexas journeyman & master

Checked against primary sources 2026-08-24

The neutral-to-ground bond happens at exactly one place

Bonded at the service. Separated everywhere downstream. The reason is not tradition, and understanding it makes a whole family of exam questions automatic.

On this page
  1. The rule, in two sentences
  2. Why it matters, physically
  3. The general form of the prohibition
  4. The word unspliced is doing work
  5. The grounded conductor comes to the service even when nothing needs it
  6. A transformer resets the whole analysis
  7. A second building on the same property
  8. The range and dryer allowance people still quote
  9. How to spot these questions
  10. What this page cites

The rule, in two sentences

The neutral and the ground are joined at exactly one point and separated everywhere after it At the service, the grounded neutral conductor and the equipment grounding conductor are bonded together by the main bonding jumper. Downstream of that point, in every subpanel, the two are kept apart: the neutral floats on an insulated bar and the grounding conductors land on a bar bonded to the enclosure. If they are joined again in a subpanel, normal load current returns on the equipment grounding conductor and on any metal in its path, which is the fault this rule exists to prevent. SERVICE A B from the utility neutral bar grounding bar main bonding jumper the one legal connection feeder: ungrounded and grounded plus the grounding conductor SUBPANEL neutral bar, ISOLATED grounding bar, bonded to the can no jumper here joining them twice puts load current on metal that people touch to the electrode system one bond, one place. everything downstream stays apart.
Bond once, at the service. After that, separate. Joining them twice puts load current on metal people touch. Drawn against NEC 250.24(B), 250.28 and 250.142(B). In editions before 2026 the load-side rule was 250.24(A)(5).

At the service disconnect, an unspliced main bonding jumper connects the equipment grounding conductors and the enclosure to the grounded conductor (NEC 250.24(C)).

On the load side of the service disconnecting means, the grounded conductor is not connected to equipment grounding conductors, to metal parts, or reconnected to ground, except where this article says otherwise (NEC 250.24(B)).

Bonded once, at the service. Separated everywhere after it. That is why a subpanel has an isolated neutral bar and a separate ground bar, and why the bonding screw comes out.

Why it matters, physically

If the neutral and ground are bonded at a subpanel as well as at the service, the two conductors are in parallel between those points.

Normal neutral current now has two paths back. Some of it returns on the neutral and some returns on the equipment grounding conductor, and on the metal conduit, and on anything else bonded along the way.

That means current flowing on parts that are supposed to be at zero volts under normal conditions. Metal enclosures, appliance frames, water piping. Nothing has failed and nothing will trip. The system just quietly carries current on its safety path.

Then when a real fault happens, the path that was supposed to be clean is already loaded, and if the neutral ever opens the equipment grounding conductor becomes the only return for the entire load.

The general form of the prohibition

The section that states it for the whole system rather than for a service is 250.142. Its second half says the grounded circuit conductor may not be connected to non-current-carrying metal parts of equipment on the load side of the service disconnecting means, or on the load side of a separately derived system disconnecting means or its overcurrent devices (NEC 250.142(B)).

That sentence carries exactly two named ways out, 250.30(A)(1) and 250.32(B)(1) Exception No. 1. Everything else is closed.

Learn the section number as well as the rule. An item that asks where a grounded conductor may be used to ground equipment is quoting the first half of 250.142, and the answers on offer will be places that sound plausible.

The word unspliced is doing work

The main bonding jumper is specified as unspliced, and that word is on the exam.

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 is no longer referenced to the grounded conductor and the fault path is gone.

The section carries two exceptions, one for multiple disconnects in an assembly listed for use as service equipment, and one for impedance grounded systems. Read them in your own book rather than from this summary.

The grounded conductor comes to the service even when nothing needs it

On a grounded system of 1000 volts or less, the grounded conductor is routed with the ungrounded conductors to each service disconnecting means and connected to its terminal or bus (NEC 250.24(D)).

This catches people because it applies even where the load has no need for a neutral. A three-phase service feeding only three-wire loads still brings the grounded conductor to the service equipment.

The reason is that at the service, the grounded conductor is not a load conductor. It is the fault-current path back to the transformer. Without it there, a fault on the line side of the main has nothing to return through and the overcurrent device never sees enough current to open.

A transformer resets the whole analysis

A separately derived system gets its own bond, and the code does not fix where. The system bonding jumper is unspliced and the connection is made at any single point on the system from the source to the first system disconnecting means or overcurrent device (NEC 250.30(A)(1)).

A single point. Not the transformer, not the panel, whichever one the installer chose, and only one of them. Bond at both and you have built the same parallel path the subpanel rule exists to prevent.

Downstream of that single point the separation rule applies again, exactly as it does downstream of a service. So a panel fed from a transformer is separated, and a panel fed from that panel is separated too.

If an item puts a transformer anywhere between the service and the panel it is asking about, stop and work out which side of the system bonding jumper you are standing on before you answer.

A second building on the same property

Feed a detached building and the answer is not the subpanel answer and not the service answer. An equipment grounding conductor is run with the supply conductors, connected to the enclosure containing the building disconnecting means and to the grounding electrode conductor, and sized from 250.122 (NEC 250.32(B)(1)).

Then the sentence that decides the item: grounded conductors that are installed are not connected to the equipment grounding conductors or to the grounding electrodes at that building (NEC 250.32(B)(1)).

The building still needs a grounding electrode system of its own. What it does not get is a second neutral bond. That combination is what the item is testing, because the old practice of bonding at the outbuilding is still visible in the field and survives only under the exception for installations made before the current rule.

The range and dryer allowance people still quote

Frames of electric ranges, wall-mounted ovens, counter-mounted cooking units and clothes dryers, and the outlet or junction boxes in those circuits, are connected to the equipment grounding conductor (NEC 250.140). On anything new, that is the end of it, and the three-wire cord is not an option.

The old allowance survives as an exception and only as an exception. It reaches existing branch-circuit installations, and only where no equipment grounding conductor is present in the outlet or junction box (NEC 250.140).

Four conditions attach to it and all four have to be met. Two of them decide most items: the supply circuit has to be 120/240-volt single-phase three-wire, or 208Y/120-volt from a three-phase four-wire wye system, and the grounded conductor has to be 10 AWG copper or 8 AWG aluminum at minimum. Read the other two in your own code book.

The stale version of this fact says a three-wire range circuit is fine. It has not been fine for a new installation in a long time, and an item that describes new work and offers the grounded conductor as the grounding means is offering you the trap.

How to spot these questions

The one question underneath all five is where this panel gets its source. Utility service means you are at the bond. Another panel means you are downstream of it. A transformer means a new source and a new bond, once.

What this page cites

NEC and National Electrical Code are registered trademarks of the National Fire Protection Association.

Trojan Digital Marketing is an independent company. We are not affiliated with, endorsed by, or sponsored by NFPA, TDLR, PSI Services, or any licensing authority.

Bring your own current copy of the National Electrical Code. The Texas exam is open book.

All practice questions are original. They are not actual exam questions.

Built and maintained by Jeff Clerisier, Trojan Digital Marketing.

Every rule here is cited to the section it comes from, and corrections are logged in public with the date. This is study material rather than electrical advice, and it does not replace your own code book or your inspector.