FL HVAC flashcards
FL HVAC · Build recall with a focused review session.
32 cards. Read the term and the definition here. The deck at the top of this page is optional.
- Gross margin formula
- Gross margin equals sales minus direct job costs, divided by sales. It excludes overhead and measures how much each job contributes to covering fixed expenses.
- Break-even sales
- Break-even sales equal annual overhead divided by gross margin percentage; at that sales level the company covers all fixed costs with zero net profit.
- Notice to Owner deadline
- In Florida, a Notice to Owner must be served before first furnishing or within 45 days after first furnishing to preserve the supplier's or subcontractor's lien rights.
- Markup versus margin
- Markup is a percentage of cost, while margin is a percentage of selling price. A 25% markup equals a 20% margin on the same job.
- State-certified contractor
- A state-certified contractor holds a Florida license and may practice anywhere in the state; a registered contractor may work only in jurisdictions where locally registered.
- Florida Product Approval
- A system or method of construction approved by the Florida Building Commission for statewide use; Miami-Dade Notice of Acceptance applies in the high-velocity hurricane zone.
- Notice of Commencement
- A document the owner records before work begins that identifies the property, contractor, and lender; it protects the owner and lender against certain lien claims.
- Final inspection
- The building department inspection after completion that verifies code compliance before a certificate of occupancy or completion is issued.
- Manual J
- ACCA's room-by-room residential load calculation method; it accounts for envelope, infiltration, internal, and latent loads using design conditions.
- Sensible heat ratio
- The sensible load divided by the total load. It indicates how much of the cooling capacity removes heat versus moisture and guides coil selection.
- Sensible airflow formula
- CFM equals sensible BTU per hour divided by 1.08 times the temperature difference in degrees Fahrenheit for standard sea-level air.
- Latent airflow formula
- CFM equals latent BTU per hour divided by 0.68 times the humidity ratio difference in grains of moisture per pound of dry air.
- Subcooling charging method
- Measured as condensing saturation temperature minus liquid-line temperature; used to charge TXV systems to the manufacturer's target, typically 8–12°F.
- Superheat charging method
- Measured as suction-line temperature minus evaporating saturation temperature; used to charge fixed-orifice systems to the manufacturer's target.
- Evacuation target
- A vacuum of 500 microns or lower held for 15 minutes confirms that moisture and non-condensables have been removed from the refrigerant circuit.
- Condensate trap purpose
- The trap holds a water seal that offsets cabinet static pressure so condensate drains; without it, air is pulled in or blown out.
- Manual D
- ACCA's duct design method that uses available static pressure and total effective length to determine friction rate and size each duct run.
- Equivalent length
- The total effective length of a duct run including straight duct plus fitting allowances, expressed in feet, used to calculate friction rate.
- Flex duct bend radius
- Flex duct should be fully extended and bends kept at least 1.5 times the duct diameter to avoid excessive pressure drop.
- Transfer grille
- A grille or jumper duct that provides a return air path between a closed room and the return system, preventing room pressurization.
- Superheat definition
- Suction-line temperature minus the evaporating saturation temperature; it confirms that all liquid refrigerant has boiled off before the compressor.
- Subcooling definition
- Condensing saturation temperature minus liquid-line temperature; it confirms that liquid refrigerant fills the last part of the condenser.
- Compression ratio
- Discharge pressure in psia divided by suction pressure in psia; high ratios increase compressor heat and reduce capacity.
- R-410A charging
- R-410A is a near-azeotropic blend and must be charged as a liquid from the cylinder to prevent fractionation and incorrect composition.
- Ohm's law
- Voltage equals current times resistance (V = I × R); power in a resistive circuit equals voltage times current.
- Capacitor discharge
- Before testing, short the capacitor terminals through a resistor to remove stored voltage; capacitors can hold a lethal charge after power is removed.
- Thermostat C wire
- The common wire provides 24V power to the thermostat; without it, smart thermostats may need batteries or a power-stealing device.
- MCA and MOP
- Minimum circuit ampacity sizes the conductors; maximum overcurrent protection sizes the breaker, both taken from the equipment nameplate.
- Recovery cylinder fill limit
- A refrigerant recovery cylinder may be filled to no more than 80% of its water capacity by weight, leaving room for liquid expansion.
- Lockout tagout
- A procedure that isolates and locks electrical or other energy sources before service, with a tag identifying the worker and reason.
- Fall protection threshold
- OSHA requires fall protection when working at heights of 6 feet or more, including roofs, ladders, and elevated platforms.
- Refrigerant frostbite protection
- Liquid refrigerant boils at very low temperature and can freeze skin on contact; gloves and goggles are required when handling it.