NM HVAC Contractor flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Qualifying party

The licensed individual who passes the trade exam and is actively in charge of the contractor's HVAC work in New Mexico; loss of this person requires notice to CID and replacement within the rule's timeframe.

CID license classification

New Mexico Construction Industries Division issues licenses by classification and scope; HVAC work falls under mechanical classifications, and bidding outside that scope is a violation.

License number display

New Mexico contractors must show their license number on advertising, bids, and contracts, and may not contract for work beyond the classification held.

Unlicensed contracting penalty

Contracting without a New Mexico license is a misdemeanor and subject to CID citations and civil penalties; the contractor also loses lien and collection rights.

Gross receipts tax

New Mexico imposes gross receipts tax on the seller of services and goods; HVAC contractors pay it on receipts and must not treat it as a sales tax.

Break-even revenue

Break-even revenue equals fixed overhead divided by gross margin percentage; it shows the sales volume needed before the business earns any net profit.

Labor burden

Labor burden includes payroll taxes, workers' compensation, liability insurance, and benefits added to base wage to compute the true hourly cost used in estimates.

Retainage

A percentage, commonly 5-10%, withheld from progress payments until final acceptance; it is tracked as accounts receivable and affects cash flow planning.

Bid bond

A bid bond guarantees the contractor will enter the contract at the bid price if awarded; failure can result in forfeiture up to the bond amount.

Waste factor

A percentage added to takeoff quantities to cover cutting and scrap; typical values are 10-15% for sheet metal and 5-10% for pipe and fittings.

Critical path float

Float is the time an activity can slip without delaying project completion; activities on the critical path have zero float and must be managed closely.

Substantial completion

The stage when the work is sufficiently complete for the owner to use it for its intended purpose; it triggers warranty start, retainage release, and occupancy.

Fall protection threshold

OSHA 29 CFR 1926 requires fall protection at 6 feet in construction; New Mexico enforces through its state Occupational Health and Safety Bureau plan.

Extension ladder ratio

Extension ladders are set at a 4:1 slope, extend 3 feet above the landing, and are secured at the top; the top two rungs are not to be used.

Confined space oxygen range

Entry requires atmospheric testing with oxygen between 19.5% and 23.5%, a permit, an attendant outside, and a rescue plan before entry.

Lockout/tagout

Before servicing HVAC motors or controls, the disconnect must be locked and tagged, and zero energy verified, per OSHA 1910.147 requirements.

Manual J

Manual J calculates room-by-room heating and cooling loads from envelope, orientation, infiltration, and internal gains, and is the basis for equipment selection.

Manual S

Manual S selects equipment using manufacturer expanded performance data matched to the Manual J load, rather than nominal capacity alone.

Sensible heat equation

Sensible heat equals 1.08 times CFM times the temperature difference at sea level; at 5,000 feet the factor drops to about 0.83 because air density is lower.

Total heat equation

Total heat equals 4.5 times CFM times the enthalpy difference in Btu per pound; it combines sensible and latent loads in one calculation.

Category IV furnace

A condensing furnace operates with positive vent pressure and flue gas below the dew point; it vents in PVC or CPVC and produces acidic condensate requiring a trap.

Combustion air openings

Two permanent openings are required, one within 12 inches of the top and one within 12 inches of the bottom, each sized per the applicable code table.

Boiler low-water cutoff

A low-water cutoff shuts off the burner when water level drops below a safe point; it is required along with a relief valve and expansion tank.

Superheat and subcooling

Superheat is measured at the evaporator outlet and sets TXV or orifice charge; subcooling is measured at the condenser outlet and confirms liquid seal.

EPA Section 608 venting ban

Refrigerant may not be knowingly vented; recovery is required before opening a system, and technicians must hold the certification type matching the equipment.

Recovery cylinder limit

A DOT-approved recovery cylinder must not be filled above 80% of capacity by weight and must be labeled with the refrigerant type and amount.

Fan laws

CFM varies directly with RPM, static pressure with RPM squared, and horsepower with RPM cubed; these laws predict performance when fan speed changes.

Friction rate

Friction rate equals available static pressure divided by total effective length; residential duct design commonly targets 0.1 inch w.c. per 100 feet.

Motor full-load amps

Full-load amps are read from NEC Table 430.248 for single-phase and 430.250 for three-phase motors; branch conductors are sized at 125% of that value.

Thermostat wire convention

Standard thermostat colors are R for power, W for heat, Y for cooling, G for fan, and C for common; mismatched wiring causes staging and control faults.

Nitrogen purge brazing

A nitrogen purge prevents internal oxidation during brazing of copper refrigerant lines; 15% silver phos-copper is used for copper-to-copper joints.

Rough-in inspection

A rough-in inspection verifies framing, duct, piping, and electrical before concealment; it must be scheduled and passed before drywall or insulation covers the work.