NEC Separately Derived Systems Exam 2026/2027

Separately Derived Systems Exam Prep
2026/2027 – 100 NEC-Based Questions with
Answers – Master System Bonding
Jumpers, Grounding Electrode Conductors
& Generator Transfer Switches

Description:

Pass your 2026/2027 electrical licensing exam with 100 NEC-aligned questions on
separately derived systems. Covers system bonding jumpers, grounding electrodes,
generators, transformers, and DC systems. Includes answers and explanations.




Download the complete 2026/2027 exam prep guide now.

, NEC Separately Derived Systems Exam 2026/2027
Course Code: ELEC 402 / CODE-302
Subject: Grounding and Bonding of Separately Derived Systems
Time Allowed: Varies by instructor
Academic Level: Advanced / Professional Certification


Part 1: Core Concepts and Definitions

Question 1
A premises wiring system where power is derived from a source of electric energy or
equipment other than a service, and which has no direct electrical connection between circuit
conductors of one system and another except through bonding or grounding connections, is
defined as a(n) ______.

 A. Auxiliary system
 B. Isolated power supply
 C. Separately derived system
 D. Emergency system

Answer: C
Explanation: The definition of a separately derived system is explicitly provided in Article
100 of the NEC. It emphasizes the absence of a direct conductive path between conductor
systems, other than bonding or grounding connections.

Question 2
Which of the following is typically not considered a separately derived system?

 A. A generator with a transfer switch that does not switch the grounded neutral
conductor
 B. A transformer with a primary and secondary that are electrically isolated
 C. An autotransformer with a grounded conductor common to both the primary and
secondary
 D. A solar photovoltaic system with an inverter that creates a new AC source

,Answer: C
Explanation: An autotransformer does not provide electrical isolation between the primary
and secondary circuits because the grounded conductor is shared. Therefore, it does not meet
the definition of a separately derived system.

Question 3
What is the term for the connection between the grounded circuit conductor and the supply-
side bonding jumper or the equipment grounding conductor, or both, at a separately derived
system?

 A. Main bonding jumper
 B. System bonding jumper
 C. Grounding electrode conductor
 D. Supply-side bonding jumper

Answer: B
Explanation: Section 250.2 defines the system bonding jumper as the connection at a
separately derived system that ensures electrical continuity between the grounded conductor
and the equipment grounding conductors or supply-side bonding jumpers.


Part 2: System Bonding Jumper Sizing and Location

Question 4
When a system bonding jumper for a separately derived system is of the wire type, it must be
sized using Table 250.102(C)(1) or the 12.5% rule based on the largest derived ungrounded
phase conductor(s) or the total circular mil area of all conductors connected to any one
ungrounded phase at the source.

 A. True
 B. False

Answer: A
Explanation: NEC 250.30(A)(1) and 250.102(C)(1) permit sizing wire-type system bonding
jumpers based on the ungrounded conductor area, including the 12.5% rule for conductors
connected in parallel.

, Question 5
Which of the following locations is permitted for installing the system bonding jumper for a
transformer-type separately derived system?

 A. The source enclosure only
 B. The first system disconnecting means enclosure only
 C. Both the source enclosure and the first disconnecting means enclosure for the same
system by exception
 D. The service equipment enclosure

Answer: C
Explanation: NEC 250.30(A)(1) allows the system bonding jumper to be installed at either
the source or the first disconnecting means. An exception permits it to be located at both ends
under specific engineering supervision.

Question 6
If a separately derived system has 600 kcmil copper secondary ungrounded phase conductors,
what is the minimum size required for a copper, wire-type system bonding jumper?

 A. 2/0 AWG
 B. 1/0 AWG
 C. 3/0 AWG
 D. 4/0 AWG

Answer: B
Explanation: Based on NEC Table 250.102(C)(1), a 600 kcmil copper ungrounded
conductor requires a minimum copper system bonding jumper of 1/0 AWG.

Question 7
The system bonding jumper for a separately derived system is permitted to extend beyond the
enclosure where it originates.

 A. True
 B. False

Answer: B
Explanation: NEC 250.30(A)(1) requires the system bonding jumper to be installed within