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100+ Free NM CID ES-3 Practice Questions

Prepare for the New Mexico CID ES-3 Low Voltage Special Systems (Under 50 Volts) Examination exam with instant access — no signup required.

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2026 Statistics

Key Facts: NM CID ES-3 Exam

75%

Passing Score

PSI NM Contractor Bulletin 4/3/2026

50 Q

Official Exam Questions

PSI NM Contractor Bulletin 4/3/2026

145 min

Time Allowed

PSI NM Contractor Bulletin 4/3/2026

USD 68.88

PSI Exam Fee

PSI NM Contractor Bulletin 4/3/2026

NM CID ES-3 is a 50-question PSI exam on low-voltage special systems under 50 volts, 75% pass, 145 minutes, USD 68.88 (bulletin 4/3/2026).

Sample NM CID ES-3 Practice Questions

Try these sample questions to test your NM CID ES-3 exam readiness. Each question includes a detailed explanation. Start the interactive quiz above for the full 100+ question experience with AI tutoring.

1Per NEC 2020 250.20(A), when must an alternating-current system of less than 50 volts be grounded?
A.Only when the Authority Having Jurisdiction writes a special condition
B.Whenever the secondary current can exceed 8 amperes
C.When supplied by a transformer whose primary exceeds 150 volts to ground, when the transformer supply is ungrounded, or when installed outdoors as overhead conductors
D.Never; systems under 50 volts are exempt from Article 250
Explanation: NEC 250.20(A) requires grounding of AC systems under 50 volts if the transformer supply exceeds 150 volts to ground, if that supply is ungrounded, or if the under-50-volt conductors are installed as overhead conductors outside buildings. A 24-volt transformer fed from a grounded 120-volt branch circuit is not automatically required to have its secondary grounded by 250.20(A). ES-3 work is defined as under 50 volts, so this section is a primary open-book stop.
2What is the minimum size of the copper bonding conductor or grounding electrode conductor for a communications primary protector under NEC 2020 800.100?
A.16 AWG copper
B.18 AWG copper
C.14 AWG copper
D.6 AWG copper
Explanation: NEC 800.100 requires the primary-protector bonding conductor or grounding electrode conductor to be copper or other corrosion-resistant conductive material and not smaller than 14 AWG. It must be run as straight and short as practicable and protected where subject to physical damage. Six AWG is the usual bonding jumper between a separate communications electrode and the power grounding-electrode system, not the minimum protector conductor size.
3In a one- or two-family dwelling, NEC 2020 800.100 limits the primary-protector bonding conductor or grounding electrode conductor to a maximum length of:
A.6 feet
B.10 feet
C.20 feet
D.50 feet
Explanation: NEC 800.100 requires that conductor to be as short as practicable. In one- and two-family dwellings it shall not exceed 20 feet (6.0 m). If 20 feet cannot be met, a separate communications grounding electrode is permitted and must then be bonded to the power grounding-electrode system.
4Where an intersystem bonding termination required by NEC 250.94 is present, the preferred connection for a communications primary-protector bonding conductor is:
A.The intersystem bonding termination at the service equipment
B.A driven rod that is intentionally isolated from the power grounding-electrode system
C.A cold-water hose bibb on the far side of the building
D.The nearest metallic sprinkler main, without bonding to the electrical service
Explanation: NEC 800.100 directs the protector bonding conductor to the intersystem bonding termination when one is provided. The IBT is bonded to the power grounding-electrode system so communications and power stay at the same potential during a surge. An isolated communications rod creates a dangerous potential difference between systems.
5If a separate communications grounding electrode is installed because the protector bonding conductor would exceed the dwelling length limit, how must that electrode be connected to the power grounding-electrode system?
A.Bond the two electrode systems together with a copper bonding jumper not smaller than 6 AWG
B.No connection is required if the rod measures 25 ohms or less
C.Connect them only through the equipment grounding conductor of a nearby receptacle
D.Keep them isolated so lightning current cannot enter the service
Explanation: NEC 800.100 requires a copper bonding jumper, generally not smaller than 6 AWG, between a separate communications electrode and the building power grounding-electrode system. The 25-ohm single-rod rule in 250.53 does not waive that bond. Isolating the electrodes leaves a high voltage between telephone, CATV, and power during a lightning event.
6Under NMAC 14.10.4.12, what grounding-electrode installation is required on new construction when a concrete-encased electrode is not present?
A.A single 4-foot rod driven inside the electrical room
B.At least 20 feet of 2 AWG bare copper in a continuous trench not less than 30 inches deep, with a minimum of two 8-foot ground rods, one at each end
C.Ten feet of 6 AWG insulated copper laid on grade and stapled to the foundation
D.No electrode is required if all branch circuits are GFCI-protected
Explanation: NMAC 14.10.4.12 amends NEC 250.50: a concrete-encased electrode is considered available on new construction. If one is not present, New Mexico requires at least 20 feet of 2 AWG bare copper in direct earth contact at not less than 30 inches depth, in a continuous trench at least 20 feet long, plus two 8-foot rods, one at each end. That state amendment is in the ES-3 allowed book and is stricter than a lone rod.
7Where an outdoor CATV drop enters a building, the outer conductive shield of the coaxial cable must be bonded or grounded:
A.As close as practicable to the point of entrance, typically with a listed grounding block connected per NEC 820.100
B.At the first TV set only, using the appliance equipment grounding conductor
C.Only if the drop is longer than 150 feet
D.To a dedicated isolated ground rod that is not bonded to the power system
Explanation: NEC 820.100 requires the coaxial shield to be bonded or grounded as close as practicable to the point of entrance. A listed grounding block tied to the intersystem bonding termination or another 820.100 electrode connection is the usual method. Length of the drop does not waive the entrance bond, and an isolated rod is not permitted.
8An ES-3 technician drives a new ground rod for a telephone protector 40 feet from the service and leaves it unbonded to the electrical grounding-electrode system. What is the principal hazard?
A.The telephone pair will carry too much DC loop current
B.A large potential difference can appear between communications equipment and grounded power equipment during a lightning or power-fault event
C.The Class 2 cable insulation voltage rating will be exceeded in normal operation
D.The protector will not pass a 25-ohm megohmmeter test
Explanation: Unbonded electrodes let communications and power rise to different potentials when lightning or a utility fault injects current. That voltage appears across handsets, network interfaces, and anyone touching both systems. NEC 800.100 requires the protector path to land on the same grounding-electrode system, using a 6 AWG copper jumper if a separate electrode is used.
9Which cable marking identifies a general-purpose Class 2 cable that is not listed for riser or plenum use?
A.CL2P
B.CL2R
C.CL2
D.FPLP
Explanation: NEC 725.179 marks general-purpose Class 2 cable as CL2. CL2R is the riser listing and CL2P is the plenum listing. FPLP is a power-limited fire-alarm plenum cable under Article 760, not a Class 2 marking. Using a general CL2 cable in a riser or plenum is not permitted.
10Class 2 cable installed exposed in a plenum or other space used for environmental air must be which listing?
A.CL2X
B.CL2
C.CL2R
D.CL2P
Explanation: NEC 725.135/725.154 require Type CL2P (or a permitted substitute such as CL3P or CMP) for exposed cables in ducts, plenums, and other environmental-air spaces. CL2R is only a riser listing. CL2X is a limited-use listing and is not a plenum cable. Chapter 3 raceways installed to 300.22 remain an alternative to exposed plenum cable.

About the NM CID ES-3 Exam

The New Mexico CID ES-3 examination covers low-voltage special systems under 50 volts. The official open-book PSI exam has 50 scored questions, a 75% passing standard (38 points), and 145 minutes allowed. Allowed references are NEC 2020, NFPA 72 (2010), and New Mexico Electrical Code NMAC 14.10.4 (2020). This official ES-3 identity is distinct from the older generic nm-low-voltage-contractor practice route. PSI lists the fee at USD 68.88 (bulletin updated 4/3/2026). This English-language MCQ bank is a study aid, not an official PSI form.

Questions

50 scored questions

Time Limit

145 minutes

Passing Score

75% (38 of 50 points)

Exam Fee

USD 68.88 (PSI Services LLC (for New Mexico Construction Industries Division))

NM CID ES-3 Exam Content Outline

8%

Grounding and Bonding

Low-voltage grounding (4 items)

8%

Conductors

Low-voltage conductors (4 items)

4%

Electrical Power Conditioning

Power conditioning (2 items)

12%

Electrical and Electronic Knowledge

Electronics fundamentals (6 items)

6%

General Low Voltage

General under-50-volt rules (3 items)

10%

Sound and Video Systems

Sound and video (5 items)

8%

Intrusion Detection and Alarms

Intrusion alarms (4 items)

14%

Fire Detection and Alarms

Fire alarm systems (7 items)

10%

Computer and Data Systems

Data systems (5 items)

4%

CCTV Systems

CCTV (2 items)

4%

Testing Equipment

Testing equipment (2 items)

4%

CATV and MATV Systems

CATV/MATV (2 items)

8%

Applied Systems Design

Applied design (4 items)

How to Pass the NM CID ES-3 Exam

What You Need to Know

  • Passing score: 75% (38 of 50 points)
  • Exam length: 50 questions
  • Time limit: 145 minutes
  • Exam fee: USD 68.88

Keys to Passing

  • Work through all 100 available questions
  • Review every answer and explanation
  • Track weak areas and revisit them
  • Use our AI tutor for tough concepts

NM CID ES-3 Study Tips from Top Performers

1Fire detection is the largest specialty slice (7 of 50); study NFPA 72-2010 with NEC Chapter 8 and Article 760/725 concepts
2This official ES-3 bank is not the generic nm-low-voltage-contractor route
3This bank is an English-language MCQ study aid, not an official PSI form

Frequently Asked Questions

How many questions are on the NM ES-3 exam?

The official PSI examination has 50 scored questions. Passing is 75% (38 points) within 145 minutes (bulletin updated 4/3/2026).