AZ HVAC flashcards

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

Arizona Registrar of Contractors

State agency that licenses and regulates Arizona contractors, investigates complaints against licensees, and can suspend or revoke a license or order restitution to a harmed homeowner.

R-39 Classification

Arizona residential license limited to air conditioning and refrigeration work on residential structures; the commercial counterpart is C-39 and the dual license is L-39.

$1,000 Licensing Threshold

In Arizona a contractor's license is required for any project of $1,000 or more in labor and materials; unlicensed contracting carries criminal penalties.

Eight-Year Statute of Repose

A.R.S. § 12-552 generally bars construction defect lawsuits more than eight years after substantial completion, even when the defect was hidden for years.

Superheat

The number of degrees a refrigerant vapor is above its saturation temperature at the same pressure; measured at the evaporator outlet to verify metering-device performance and charge.

Subcooling

The number of degrees a liquid refrigerant is below its saturation temperature at the same pressure; measured at the condenser outlet and used to verify charge on TXV systems.

Thermostatic Expansion Valve

Metering device that modulates refrigerant flow to hold a constant superheat at the evaporator outlet as the load and outdoor conditions change.

One Ton of Refrigeration

A heat absorption rate equal to 12,000 Btu per hour, or 200 Btu per minute, roughly the heat needed to melt one ton of ice in 24 hours.

AFUE

Annual Fuel Utilization Efficiency: the percentage of fuel energy delivered to the space over a heating season, about 80% for standard furnaces and 90% or more for condensing furnaces.

Balance Point

The outdoor temperature at which heat pump capacity exactly equals the building heat loss; below that temperature supplemental electric resistance or gas heat must operate.

Condensing Furnace

Furnace with a secondary heat exchanger that condenses water vapor in the flue gas, reaching 90%+ AFUE, vented in PVC and draining acidic condensate through a trap.

Manifold Pressure

Gas pressure measured at the burner manifold with a manometer, typically 3.5 in. w.c. for natural gas and 10 to 11 in. w.c. for propane.

Ohm's Law

Voltage equals current multiplied by resistance, V = I × R; combined with P = V × I it lets a technician solve for any circuit value from two known quantities.

Motor Branch 125% Rule

Branch-circuit conductors, disconnects, and controllers must be sized at not less than 125% of the motor's nameplate full-load current, per the National Electrical Code.

PSC Motor

Permanent split capacitor motor: a run capacitor in series with the start winding produces moderate starting torque with no centrifugal switch and no start capacitor.

Equipment Disconnect

A means to disconnect power that must be installed within sight of the HVAC equipment and generally within 50 feet of it.

External Static Pressure

The sum of supply and return static pressures the air handler must overcome, measured with a manometer; residential units are typically rated at 0.5 in. w.c.

Equal Friction Method

Duct sizing method that holds pressure drop constant, commonly 0.1 in. w.c. per 100 feet of effective length, beginning at the longest run.

Return Grille Velocity

Return grilles are commonly sized for 300 to 500 feet per minute face velocity so that noise and pressure drop stay acceptable.

Nitrogen Purge

A low flow of dry nitrogen through the tubing while brazing displaces oxygen, preventing internal copper oxide scale that would later contaminate valves and the compressor.

500 Micron Vacuum

Evacuation standard for a new system; the micron gauge is isolated from the pump and the vacuum must hold without rising, confirming no leaks or moisture remain.

15% Silver Solder

Higher-silver brazing filler used on high-vibration joints and copper-to-steel connections; copper-to-copper joints normally use 5% silver-phosphorus without flux.

Manual J

ACCA method for room-by-room heating and cooling load calculation using envelope construction, window data, infiltration, and internal heat gains.

Sensible Heat Equation

Q in Btu/h = 1.08 × CFM × temperature difference between entering and leaving air; the constant assumes sea-level standard air density.

Total Heat Equation

Q in Btu/h = 4.5 × CFM × enthalpy difference, used to determine total coil capacity when entering and leaving air enthalpies are known.

Sensible Heat Ratio

Sensible load divided by total load; the selected equipment's sensible heat ratio must match the calculated value or the space will run humid.

Recovery Cylinder Fill

A refrigerant recovery cylinder may never be filled above 80% of its water capacity, controlled by weight on a scale to leave room for liquid expansion.

OSHA Fall Protection

Fall protection is required at six feet in construction and four feet in general industry, provided by guardrails, personal fall arrest systems, or nets.

Section 608 Certification

Federal EPA credential required for technicians who service, repair, or dispose of refrigerant-containing appliances; categories are Type I, II, III, and Universal.

Gross Margin

Margin percent equals price minus cost, divided by price, times 100; a 25% gross margin corresponds to a 33.3% markup on cost.

Preliminary 20-Day Notice

Arizona notice given by a subcontractor or supplier within 20 days of first furnishing labor or materials, preserving mechanics' lien rights on the project.

Change Order

A written, signed modification to the contract scope, price, or schedule; work performed without a signed change order is often uncompensated.