FL HVAC cheat sheet

Gross profit = sales − direct job costs; net profit = gross profit − overhead expenses.

Selling price for a target margin = cost ÷ (1 − target margin %); markup % is calculated on cost, margin % on selling price.

Break-even sales = annual overhead ÷ gross margin percentage.

In Florida, a Notice to Owner must be served before first furnishing or within 45 days after first furnishing to preserve lien rights.

A claim of lien in Florida must be recorded within 90 days after final furnishing of labor, services, or materials.

Labor burden = base wage + payroll taxes + workers' compensation + insurance + benefits; it must be added to the base labor rate before pricing.

Written, signed change orders before extra work is performed protect the contractor's right to payment for changes.

The Florida Building Code is enforced by local building departments; a permit is required before HVAC installation and a final inspection is required before occupancy.

A state-certified contractor may work anywhere in Florida; a state-registered contractor may work only in the jurisdictions where registered.

The Florida Construction Industry Licensing Board (CILB) under DBPR licenses HVAC contractors and investigates complaints.

The Florida Energy Code sets minimum SEER2, EER2, and HSPF2 efficiencies by equipment type and climate zone.

HVAC equipment in the wind-borne debris region requires Florida Product Approval or a Miami-Dade County Notice of Acceptance.

A Notice of Commencement is recorded by the owner before work begins and preserves the owner's and lender's lien defenses.

Section 489.113, Florida Statutes, defines the scope of work licensed contractors may perform; unlicensed contracting is a criminal offense.

Manual J is the ACCA room-by-room load calculation procedure; square-foot rules of thumb are not acceptable for sizing.

Total cooling load = envelope conduction + infiltration + internal gains + latent load.

Sensible airflow: CFM = sensible BTU/h ÷ (1.08 × temperature difference °F).

Latent airflow: CFM = latent BTU/h ÷ (0.68 × humidity ratio difference in grains).

One ton of refrigeration = 12,000 BTU/h; nominal cooling airflow is 400 CFM per ton.

Sensible heat ratio (SHR) = sensible load ÷ total load; it determines the required apparatus dew point.

Florida summer design conditions are roughly 92–95°F dry bulb and 75–77°F wet bulb with indoor design of 75°F and 50% RH.

The duct load factor and ventilation load must be added to the room load before equipment selection.

Manual S is used to select equipment whose capacity meets the Manual J load at design conditions, not at nominal rating conditions.

Match indoor and outdoor units per the AHRI directory; mismatched coils void rated capacity and efficiency.

Charge a TXV system by subcooling and a fixed-orifice system by superheat, following the manufacturer's chart.

Evacuate refrigerant lines to 500 microns and hold the vacuum to confirm no moisture or leaks remain.

Purge with dry nitrogen while brazing and never braze with refrigerant in the lines.

A condensate trap must offset the fan static pressure; a secondary drain pan with a float switch is required where damage may occur.

Steady-state temperature split is typically 16–22°F between return and supply air at 350–450 CFM per ton.

Start-up checks include electrical voltage and amp draw, refrigerant charge, airflow, condensate drainage, and control operation.

Manual D sizes ducts using the available static pressure and total effective length to establish the friction rate.

Typical duct velocities are 600–900 FPM in supply trunks, 500–700 FPM in returns, and 400–700 FPM in branches.

Flex duct must be fully extended, supported every 4–5 feet, and bent no tighter than 1.5 times its diameter.

Seal all duct joints and seams with mastic or approved tape; the Florida Energy Code requires duct leakage testing.

Duct insulation in Florida is typically R-6 minimum, with R-8 used in attics and exposed locations.

Each room needs a return path via a transfer grille or jumper duct; closed doors otherwise pressurize the room.

ASHRAE 62.2 requires mechanical ventilation; intermittent bath exhaust is 50 CFM and kitchen exhaust is 100 CFM.

A typical residential blower static pressure budget is 0.5 in. w.c. total external static.

Superheat = suction line temperature − evaporating saturation temperature.

Subcooling = condensing saturation temperature − liquid line temperature.

Compression ratio = discharge pressure (psia) ÷ suction pressure (psia).

R-410A is a near-azeotropic blend and must be charged as a liquid to avoid fractionation.

EPA Section 608 certification is required to handle refrigerants; intentional venting is prohibited.

Pressure-test with dry nitrogen, then evacuate to 500 microns; never use refrigerant to leak-test.

High superheat indicates undercharge or a restriction; high subcooling indicates overcharge or a liquid-line restriction.

POE oil is hygroscopic and absorbs moisture quickly, so lines must remain sealed until evacuation.

Ohm's law: V = I × R; power: P = V × I for resistive loads.

Discharge capacitors before testing and use a meter rated for the voltage present.

RLA is running load amps and LRA is locked rotor amps; LRA is the starting current surge.

Standard 24V thermostat terminals: R = power, W = heat, Y = cool, G = fan, C = common.

A disconnect must be within sight of the equipment and lockout/tagout must be applied before service.

Size conductors per ampacity and the breaker per the nameplate MCA and MOP.

To reverse a three-phase motor, swap any two of the three supply leads.

GFCI protection is required in wet and outdoor locations.

Fall protection is required at 6 feet or more; ladders are set at a 4:1 slope.

Recovery cylinders must not be filled beyond 80% of their water capacity by weight.

Never vent refrigerant; recover, recycle, or reclaim it per EPA Section 608.

Wear gloves and goggles when handling liquid refrigerant; it causes frostbite at −50°F or below.

Combustion appliances require CO testing and proper flue draft to prevent carbon monoxide poisoning.

Lockout/tagout isolates electrical energy before service or repair.

Heat stress prevention includes hydration, shade, and scheduled rest breaks.

Used oil, filters, and refrigerant cylinders are regulated wastes and must be disposed of properly.