OR HVAC Contractor cheat sheet

Oregon CCB license types: residential general contractor, residential specialty contractor, commercial general contractor, and commercial specialty contractor; each carries a separate endorsement scope.

A residential specialty contractor may not take a project whose combined structural and non-structural work exceeds the specialty threshold; exceeding scope is an unlicensed-activity violation.

CCB license renewal runs on a two-year cycle; the licensee must show continuing education and a current surety bond before renewal is granted.

Oregon requires a surety bond filed with the CCB; a residential general contractor bond is $20,000 and a residential specialty contractor bond is $10,000, with commercial bonds higher.

A written contract is required for residential work above $2,000; it must state the contractor's CCB number, the work scope, price, and payment schedule.

Oregon's right-to-cure notice process: the owner must give written notice and allow the contractor a chance to inspect and offer to repair before filing suit on a defect.

The Construction Contractors Board handles consumer complaints and can order arbitration or mediation; unpaid CCB civil penalties can suspend the license.

Lien rights: a construction lien must be perfected by recording within 75 days after the claimant stops providing labor, materials, or equipment.

A HVAC contractor performing work on a structure must carry workers' compensation coverage or hold a valid exemption on file with the CCB.

Oregon adopts the statewide specialty codes through the Building Codes Division; local jurisdictions may amend only where the state authorizes, so the state code edition controls.

The Oregon Residential Specialty Code (ORSC) governs one- and two-family dwellings and townhouses; commercial and multi-family work falls under the Oregon Structural Specialty Code (OSSC).

A permit is required before installing, altering, or replacing a HVAC appliance, duct system, or fuel gas piping; permit fees are set by the jurisdiction's adopted fee schedule.

Inspection sequence for HVAC: rough-in (ductwork, refrigerant lines, gas piping, venting) before concealment, then final inspection after equipment startup and controls are complete.

Oregon Mechanical Code clearance requirements: appliances must maintain the manufacturer's listed clearances to combustibles, and vent terminations must meet the code's minimum distances from openings and intakes.

The Oregon Energy Efficiency Specialty Code sets duct insulation R-values, duct sealing, and equipment efficiency minimums for new and altered systems.

A code change or field modification that deviates from the approved plans requires a revised permit application and re-review before the work is covered.

Stop-work orders may be issued for work without a permit or work that creates an imminent hazard; the contractor must obtain approval before resuming.

Sensible heat formula: Btu/h = 1.08 x CFM x delta-T (dry air at standard conditions); latent heat: Btu/h = 0.68 x CFM x delta-grains.

Total heat = 4.5 x CFM x delta-enthalpy (Btu/h), useful when comparing coil loads on a psychrometric chart.

Equipment sizing follows ACCA Manual J for load, Manual S for equipment selection, and Manual D for duct design; oversized equipment causes short cycling and poor latent removal.

Static pressure budget: typical residential supply static 0.1-0.2 in. w.c., return 0.05-0.1 in. w.c., and total external static pressure must stay within the air handler's rated limit.

Duct sizing by equal friction or velocity method; supply trunk velocities commonly 600-900 fpm residential, branch runs 400-700 fpm, and return ducts lower to limit noise.

Refrigerant superheat at the evaporator outlet is typically 8-12 degrees F in fixed-orifice systems; subcooling at the condenser outlet is typically 8-12 degrees F in TXV systems.

A heat pump's balance point is where building load equals capacity; below it, supplemental electric resistance or fossil fuel heat stages in.

Combustion air: a confined space needs two permanent openings sized at 1 square inch per 1,000 Btu/h of input when both openings communicate with the outdoors.

The refrigeration cycle: compressor raises pressure and temperature, condenser rejects heat and subcools, metering device drops pressure, evaporator absorbs heat and superheats.

Superheat = actual evaporator outlet temperature minus the saturated suction temperature at that pressure; low superheat risks liquid floodback to the compressor.

Subcooling = saturated condensing temperature minus liquid line temperature; low subcooling suggests undercharge, high subcooling suggests overcharge or a restricted liquid line.

Common refrigerants: R-410A operates at roughly 60% higher pressure than R-22; R-134a is a medium-pressure refrigerant used in chillers and medium-temperature refrigeration.

A receiver stores liquid on the high side in systems with a thermostatic expansion valve; a suction accumulator protects the compressor from liquid slugging.

A TEV maintains constant superheat by modulating refrigerant flow; a capillary tube is a fixed restriction whose flow varies with pressure difference.

Refrigerant oil miscibility matters: mineral oil suits CFC/HCFC systems, while POE oil is required with HFC refrigerants and absorbs moisture readily.

Recovery cylinders must not be filled above 80% of capacity by weight; DOT cylinders require hydrostatic testing on a defined interval.

Ohm's law: E = I x R; power in a resistive circuit: P = E x I; for single-phase motors, brake horsepower relates to watts by 746 W per hp.

Locked-rotor amps (LRA) exceed running-load amps (RLA); a start capacitor and potential relay or PTC device provide the extra starting torque.

A run capacitor wired in series with the start winding shifts phase; a failed run capacitor causes high current, low torque, and motor overheating.

Control transformer sizing: VA rating must exceed the sum of connected control loads; a 24 V secondary at 40 VA supplies about 1.67 A.

Thermostat wiring conventions: R power, W heat, Y compressor, G fan, O/B reversing valve, C common; a missing C wire prevents smart thermostats from powering.

Defrost controls on heat pumps use time-temperature or demand-defrost boards; a stuck defrost termination can leave the unit in defrost and cause cold blow indoors.

Electrical safety: lockout/tagout before servicing, verify with a meter rated for the circuit's category, and discharge capacitors before touching terminals.

NEC requires a disconnecting means within sight of the HVAC equipment and a dedicated branch circuit sized to the nameplate minimum circuit ampacity.

Gas piping sizing uses the longest-run method with tables keyed to inlet pressure, specific gravity, and pressure drop; natural gas is typically 0.60 specific gravity.

A manifold or drip leg is required at the appliance connection, and a sediment trap must be installed downstream of the shutoff valve ahead of the controls.

Combustion air for a confined space: openings sized at 1 square inch per 1,000 Btu/h of total input when both communicate with outdoors; 1 per 2,000 Btu/h if one opening is high and one low.

Venting categories: Category I natural draft (negative pressure, non-condensing), Category III positive pressure non-condensing, Category IV positive pressure condensing.

A B-vent is a listed double-wall natural-draft vent; single-wall connectors require clearance to combustibles and must slope upward toward the vent.

Combustion analysis targets: natural gas flue CO2 roughly 8-9% at steady state, and CO in flue gas should stay well under 100 ppm air-free; ambient CO must be near zero.

A manifold gas pressure check confirms the appliance's rated input; natural gas appliances commonly require 3.5 in. w.c. manifold pressure, LP appliances 10-11 in. w.c.

Leak testing: a new gas piping system is pressure-tested with air or inert gas per the code's test pressure and duration before the gas is turned on.

Refrigerant safety: ASHRAE classifications A1 (low toxicity, no flame propagation) through B3; A2L refrigerants are mildly flammable and require ignition-source controls and ventilation.

Oxygen-acetylene torch setup: open the acetylene valve no more than 1.5 turns, use a flashback arrestor, and never use acetylene above 15 psig.

Brazing requires nitrogen purge through the tubing to prevent internal oxidation (scale) that can clog metering devices and damage compressors.

Personal protective equipment for HVAC work: safety glasses, gloves, hearing protection near compressors, and fall protection above six feet.

Refrigerant exposure limits: use a calibrated leak detector and monitor oxygen levels before entering a confined equipment room; refrigerant displaces oxygen.

Electrical lockout/tagout: isolate the disconnect, apply a lock, verify zero voltage with a meter, and tag the equipment before service.

Ladder and scaffold safety: maintain a 4:1 ladder angle, three points of contact, and secure access to rooftops with a guardrail or tie-off point.

Jobsite documentation: record refrigerant added and recovered by weight, equipment model and serial numbers, and readings taken at startup for warranty and code compliance.