29 CFR 1926.404: Wiring design and protection
The official text is on the eCFR. Below: how the section is organized, the paragraphs our ASP, CHST questions are built on, and free questions to try.
Quoted from the eCFR, current as of 2026-10-14; last amended 2021-09-17.
How 29 CFR 1926.404 is organized
- (a)3 paragraphs
- (b) Branch circuits—(1) Ground-fault protection—(i) General27 paragraphs
- (c) Outside conductors and lamps—(1) 600 volts, nominal, or less17 paragraphs
- (d) Services—(1) Disconnecting means—(i) General5 paragraphs
- (e) Overcurrent protection—(1) 600 volts, nominal, or less10 paragraphs
- (f) Grounding69 paragraphs
Paragraphs our practice questions cite most
Counted across the 21 live PassCited questions on this section: our bank, not the real exam.
“(5) Grounding connections—(i) Grounded system. For a grounded system, a grounding electrode conductor shall be used to connect both the equipment grounding conductor and the grounded circuit conductor to the grounding electrode. Both the equipment grounding conductor and the grounding electrode conductor shall be connected to the grounded circuit conductor on the supply side of the service disconnecting means, or on the supply side of the system disconnecting means or overcurrent devices if the system is separately derived.”
“(3) Before equipment is used after any incident which can be reasonably suspected to have caused damage (for example, when a cord set is run over); and”
“(10) Made electrodes. If made electrodes are used, they shall be free from nonconductive coatings, such as paint or enamel; and, if practicable, they shall be embedded below permanent moisture level. A single electrode consisting of a rod, pipe or plate which has a resistance to ground greater than 25 ohms shall be augmented by one additional electrode installed no closer than 6 feet (1.83 m) to the first electrode.”
“(6) Tools likely to be used in wet and/or conductive locations need not be grounded if supplied through an isolating transformer with an ungrounded secondary of not over 50 volts. Listed or labeled portable tools and appliances protected by a system of double insulation, or its equivalent, need not be grounded. If such a system is employed, the equipment shall be distinctively marked to indicate that the tool or appliance utilizes a system of double insulation.”
“(2) Polarity of connections. No grounded conductor shall be attached to any terminal or lead so as to reverse designated polarity.”
Free practice questions on 29 CFR 1926.404
Question 1
On a construction site, a portable diesel generator feeds a distribution panel through a transformer-based separately derived system. The system is grounded, and the electrician is deciding where to make the connections to the grounding electrode. A coworker proposes landing the equipment grounding conductor and the grounding electrode conductor on the grounded circuit conductor at a terminal on the load side of the system's overcurrent devices, since the loads are located there. Which response is correct under the standard?
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Answer: A. Not acceptable; the connections must be made to the grounded circuit conductor on the supply side of the system disconnecting means or overcurrent devices
OSHA's construction wiring rule, 29 CFR 1926.404(f)(5)(i), requires a grounded separately derived system to connect the equipment grounding conductor and grounding electrode conductor to the grounded circuit conductor on the supply side of the system disconnecting means or overcurrent devices. A load-side terminal fails. A continuous ground path is required but does not move this point. The rule sets no last-receptacle bonding, and neutral-to-frame bonding does not replace the electrode connection.
Answer A rests on
29 CFR 1926.404(f)(5)(i)(opens ecfr.gov in a new tab)“Both the equipment grounding conductor and the grounding electrode conductor shall be connected to the grounded circuit conductor on the supply side of the service disconnecting means, or on the supply side of the system disconnecting means or overcurrent devices if the system is separately derived.”
Question 2
A contractor installs fixed equipment on a direct-current (DC) circuit. The equipment grounding conductor is sized to carry any fault current, but it runs in a separate conduit from the circuit conductors. A reviewer asks whether this routing meets OSHA's rule on grounding methods. What is the correct answer?
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Answer: B. It is compliant, because for DC circuits only, the equipment grounding conductor may be run separately from the circuit conductors
OSHA's grounding-methods rule normally requires the equipment grounding conductor to be in the same raceway, cable or cord, or to run with or enclose the circuit conductors. For DC circuits only, it may be run separately. The rule does not extend this to AC, and it does not limit DC grounding conductors to flexible cords.
Answer B rests on
29 CFR 1926.404(f)(8)(i)(opens ecfr.gov in a new tab)“Noncurrent-carrying metal parts of fixed equipment, if required to be grounded by this subpart, shall be grounded by an equipment grounding conductor which is contained within the same raceway, cable, or cord, or runs with or encloses the circuit conductors. For DC circuits only, the equipment grounding conductor may be run separately from the circuit conductors.”
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A study aid, not legal advice or an official interpretation. Always check the current eCFR text.