New Mexico Low Voltage Practice flashcards
New Mexico Low Voltage Practice · Build recall with a focused review session.
33 cards. Read the term and the definition here. The deck at the top of this page is optional.
- Ohm's Law
- Current equals voltage divided by resistance (I = E/R). Used to solve for unknown voltage, current, or resistance in any DC or resistive AC circuit.
- Three-Phase Power Formula
- True power equals the square root of three times line voltage times line current times power factor. Applies to balanced three-phase loads.
- Circular Mil
- A unit of conductor cross-sectional area equal to the area of a circle one mil in diameter. For a solid round conductor, CM equals the diameter in mils squared.
- Voltage Drop Formula
- Single-phase drop equals two times K times current times length divided by circular mils. The factor of two accounts for the outgoing and return conductors.
- Ampacity Correction Factors
- Table ampacity is multiplied by an ambient temperature correction factor and by a conductor bundling adjustment factor. Both apply when conditions require.
- Power Factor
- The ratio of true power in watts to apparent power in volt-amperes. A value below one indicates reactive load, typically from motors or transformers.
- Transformer Turns Ratio
- Primary voltage divided by secondary voltage equals primary turns divided by secondary turns. Current ratio is the inverse of the voltage ratio.
- Class 2 Circuit
- A power-limited circuit classified by NEC Table 725.4 based on source and load. Its limited energy reduces fire and shock hazard.
- Class 3 Circuit
- A power-limited remote-control or signaling circuit with limits above Class 2 but still energy-limited. Class 3 cable may be substituted where Class 2 is required.
- Plenum Rated Cable
- Cable listed for installation in environmental air spaces such as return air plenums. Marked CL2P, CL3P, or FPLP depending on circuit class.
- Low Voltage Drop Impact
- On a 24-volt circuit, a two-volt drop is over eight percent. Low voltage systems require conductor sizing based on distance, not habit.
- Power over Ethernet
- IEEE 802.3 standards delivering DC power over data cable. 802.3af supplies 15.4 watts, 802.3at 30 watts, and 802.3bt up to 90 watts.
- Conduit Fill Rules
- NEC Chapter 9 Table 1 limits fill to 53 percent for one conductor, 31 percent for two, and 40 percent for three or more.
- Box Fill Calculation
- NEC 314.16 assigns volume per conductor: 2.0 cubic inches for 14 AWG, 2.25 for 12 AWG, and 2.5 for 10 AWG, plus device and clamp allowances.
- EMT Support Interval
- Electrical metallic tubing must be supported at intervals not exceeding 10 feet and within 3 feet of every box or termination fitting.
- Communications Cable Support
- Category and communications cable must be supported at intervals not exceeding 4.5 feet and within 12 inches of a box or termination.
- Working Clearance Depth
- NEC 110.26 requires 3 feet of depth for equipment up to 150 volts and 4 feet for 151 to 600 volts, with 30-inch width and 6-foot-6-inch height.
- New Mexico Electrical Code
- New Mexico adopts the NEC through the Construction Industries Division and publishes it with state amendments as 14.10.4 NMAC.
- Authority Having Jurisdiction
- The official who enforces the code, interprets its provisions, and may grant written exceptions for alternate methods or materials under NEC 90.4.
- NEC 110.3(B) Requirement
- Listed and labeled equipment must be installed and used in accordance with the listing and any instructions included in the listing or labeling.
- Local Amendment Precedence
- Where a locally adopted amendment is stricter than the state or national code, the stricter amendment governs the installation and inspection.
- Arc Flash Boundary
- The distance at which incident energy equals 1.2 calories per square centimeter. Inside this boundary, arc-rated PPE is required per NFPA 70E.
- Test Before Touch
- Verify the meter on a known live source, test the target circuit, then re-verify on the known source before trusting a zero reading.
- Megohmmeter Test
- An insulation resistance test applied at 250, 500, or 1000 volts DC. A reading below one megohm on low voltage wiring indicates damage or moisture.
- Lockout Tagout
- An energy control procedure requiring a lock, a tag, and verification of zero energy state by the person performing the work before contact.
- Certifying Cable Tester
- A tester that reports wire map, length, insertion loss, and near-end crosstalk, verifying that a link meets a named category performance standard.
- Burdened Labor Rate
- The base hourly wage plus payroll taxes, insurance, and benefits, typically 25 to 40 percent above base. Used to price labor in estimates.
- Retainage
- A percentage of each payment withheld until substantial completion. Commonly 5 to 10 percent on private New Mexico construction projects.
- Written Change Order
- A signed, priced document authorizing a scope change before work proceeds. Verbal direction should be confirmed in writing within 24 hours.
- Smoke Detector Spacing
- NFPA 72 permits 30-foot spacing on smooth ceilings, covering about 900 square feet per detector. Spacing is reduced for joisted or sloped ceilings.
- Notification Appliance Circuit
- A 24-volt DC circuit powering horns and strobes. Voltage drop must be calculated so the end device receives its minimum operating voltage.
- T568A and T568B
- Two pinout standards for eight-position modular jacks. They differ in pairs two and three, and the same standard must be used at both link ends.
- Fail-Safe Versus Fail-Secure
- A fail-safe lock releases when power is lost, supporting life safety egress. A fail-secure lock remains locked on power loss and is used where egress is not required.