NJ HVAC Contractor cheat sheet

The refrigeration cycle: compression, condensation, expansion, evaporation. Heat is absorbed in the evaporator and rejected in the condenser.

Superheat = actual suction line temperature minus evaporating (saturation) temperature. Subcooling = condensing (saturation) temperature minus liquid line temperature.

Tonnage: 1 ton of refrigeration = 12,000 Btu/h = 200 Btu/min = 3.517 kW.

Coefficient of performance (COP) = net refrigeration effect / work input. Higher COP means more efficient.

Saturation: at a given pressure, refrigerant boils and condenses at the same temperature. Use a PT chart to convert.

Common refrigerants: R-410A (near-azeotropic blend, 50/50 R-32/R-125, higher pressure), R-134a (retrofit for R-12), R-407C, R-404A. R-22 is phased out for new equipment.

Components: compressor (raises pressure/temperature), condenser (rejects heat), metering device (TXV, fixed orifice, capillary tube), evaporator (absorbs heat).

TXV maintains constant superheat by modulating refrigerant flow; fixed orifice systems rely on charge and indoor/outdoor conditions.

Pressure-enthalpy diagram: useful for calculating mass flow, compressor work, and capacity.

Combustion requires fuel, oxygen, and ignition. Stoichiometric air for natural gas ≈ 10 ft³ air per ft³ gas (about 9.5:1 by volume).

Products of complete combustion: CO₂, H₂O, and heat. Incomplete combustion produces CO (carbon monoxide), a health hazard.

Furnace efficiency: AFUE (Annual Fuel Utilization Efficiency) is the standard measure. Minimum 80% for standard furnaces; 90%+ for condensing furnaces.

Condensing furnaces recover latent heat from flue gases; flue gas temperature is low enough for PVC venting. Non-condensing furnaces require metal vent.

Boiler types: hot water (hydronic) and steam. Hydronic systems use circulators, expansion tanks, air eliminators, and zone valves.

Steam boilers: use a low-water cutoff, pressuretrol, and Hartford loop. Steam moves through pipes by pressure; condensate returns by gravity.

Combustion air: must be provided per code (e.g., two permanent openings or direct vent). Insufficient air causes incomplete combustion and CO.

Gas piping: size per NFPA 54 and local code; use pipe sizing tables based on length, demand, and specific gravity.

Heat output: EDR (equivalent direct radiation) for steam; for hot water, use Btu/h based on flow and temperature difference (ΔT).

Heat pump: reversible refrigeration cycle. In heating mode, the outdoor coil is the evaporator and the indoor coil is the condenser.

Defrost cycle: when outdoor coil temperature drops below ~40°F, frost forms; defrost reverses the cycle or uses electric heat to melt frost.

Heat pump balance point: outdoor temperature where heat pump capacity equals building heat loss. Below it, auxiliary heat is needed.

Refrigerant lines: use proper size per manufacturer; insulate suction line; purge with nitrogen during brazing to prevent oxidation.

Evacuation: evacuate to 500 microns or less (with decay test) to remove moisture and non-condensables.

Charging: weigh in charge for fixed orifice systems; use subcooling for TXV systems (typically 8–12°F) and superheat for fixed orifice (typically 8–12°F).

Refrigerant safety: R-410A requires POE oil (hygroscopic); use dedicated gauges and recovery equipment. Do not mix refrigerants.

Leak detection: electronic detectors, soap bubbles, UV dye. Never use oxygen or air for pressure testing; use dry nitrogen.

Recovery: EPA Section 608 requires recovery of refrigerant before opening system; recovery cylinders must not be overfilled (80% rule).

Duct sizing methods: equal friction, static regain, velocity reduction. Use ACCA Manual D for residential duct design.

Available static pressure (ASP) = blower external static pressure minus pressure drops of filters, coils, grilles, and registers.

Friction rate: typically 0.1 in. w.c. per 100 ft of duct for residential. Use a duct calculator.

Equivalent length: add fitting allowances (e.g., 30 ft for a 90° elbow) to straight length to get total effective length.

Return air: size return grilles for 0.05–0.08 in. w.c. pressure drop; undersized returns cause high static and reduced airflow.

Duct sealing: seal all joints with mastic or UL 181 tape. Leakage wastes energy and can cause pressure imbalances.

Indoor air quality: control moisture (30–50% RH), provide ventilation per ASHRAE 62.2, use MERV 8–13 filters, and ensure proper combustion air.

Fresh air: use HRV/ERV for energy recovery. Bath fans: 50–100 cfm intermittent; kitchen hoods: 100–400 cfm.

Duct insulation: R-8 for supply ducts in unconditioned spaces; R-6 for return. Vapor barrier on the outside.

Ohm's law: V = I × R. Power: P = V × I × PF for AC. Use for troubleshooting motors and controls.

Motor types: PSC (permanent split capacitor), ECM (electronically commutated motor), shaded pole. ECM is more efficient and programmable.

Contactors and relays: use a coil to control higher-voltage circuits. Contacts may be normally open (NO) or normally closed (NC).

Thermostats: low-voltage (24V) control. Typical terminals: R (power), W (heat), Y (cool), G (fan), C (common).

Defrost control: time-temperature or demand defrost. Check sensor and board.

Capacitors: start and run capacitors. Test with a capacitance meter; bulging or leaking indicates failure.

Lockout/tagout: follow OSHA and NFPA 70E. Verify power off with a meter.

Wire sizing: use NEC Table 310.16 for ampacity; derate for temperature and conduit fill. Use copper conductors for most HVAC.

Grounding: equipment grounding conductor required. GFCI protection for outdoor receptacles and near water.

Residential load calculation: ACCA Manual J. Commercial: Manual N or ASHRAE methods.

Heating load: sum of transmission losses (U × A × ΔT) plus infiltration. Cooling load: solar gain, internal gains, conduction.

Design conditions: use ASHRAE 0.4% cooling and 99% heating design temperatures for the location.

Equipment sizing: do not oversize. Oversized AC short cycles, poor dehumidification. Use Manual S.

Duct sizing: Manual D. Airflow: 400 cfm per ton nominal for cooling.

Energy code: New Jersey adopts IECC with amendments. Key requirements: insulation R-values, window U-factors, duct insulation, and air sealing.

Manual J8 (8th edition) is current for residential. Requires accurate envelope details.

Blower door test: measures air leakage (ACH50). Required by some energy codes.

Ventilation: ASHRAE 62.2 requires mechanical ventilation in tight homes.

NJ Uniform Construction Code (UCC) is N.J.A.C. 5:23. It adopts the International Codes with NJ amendments.

HVAC contractor license: issued by NJ Division of Consumer Affairs. Must have a licensed master HVACR contractor to perform work.

Permits: required for new installation, replacement, and alterations. Apply to local construction official.

Inspections: required at rough-in and final. Work must be inspected before covering.

Continuing education: 5 hours per year for master HVACR license renewal (varies).

Insurance: general liability and workers' comp required for licensure.

Code enforcement: local construction official interprets code; appeals go to the Construction Board of Appeals.

Refrigerant handling: EPA Section 608 certification required for refrigerant purchase and handling.

Contract requirements: written contract required for home improvement projects over $500; must include 3-day right to cancel.

Fuel gas piping: use NFPA 54 and NJ fuel gas code. Pipe sizing based on length, demand, and specific gravity. Use black iron, copper (with limits), or CSST.

Gas leak detection: use soap bubbles or electronic detector. Never use flame.

Combustion air: provide per code. For confined spaces, use two openings sized 1 in² per 1,000 Btu/h input (each).

Venting: follow manufacturer's instructions and code. Category I (natural draft), Category III (power vent), Category IV (condensing).

CO safety: install CO alarms per NFPA 720. Symptoms of CO poisoning: headache, dizziness, nausea.

Refrigerant safety: ASHRAE 15 and 34. Use proper PPE (gloves, goggles). Avoid inhalation; ensure ventilation.

Recovery: EPA Section 608. Recover refrigerant to 0 psig for low-pressure systems, 10 in. Hg vacuum for high-pressure, or per equipment manufacturer.

Refrigerant cylinders: never fill over 80% liquid capacity. Store upright and secured.

Lockout/tagout: follow OSHA 1910.147. Verify zero energy.

Estimating: use manual J load, equipment cost, labor hours, overhead, and profit. Add contingency (5–10%).

Contract types: fixed price, time and materials, cost-plus. Include scope, payment terms, schedule, and change order process.

Lien rights: file preliminary notice and mechanics lien if unpaid. NJ requires notice within 90 days for residential.

Change orders: must be written and signed before work. Include cost and schedule impact.

Project management: schedule, coordinate trades, track submittals, and maintain as-builts.

Warranty: typically 1 year labor, 5–10 years parts (manufacturer). Clarify in contract.

Insurance: general liability, workers' comp, and auto. Keep certificates current.

Permits and inspections: include in project schedule. Final inspection required before final payment.

Billing: progress billing based on milestones. Retainage typically 5–10% until final acceptance.