Code, Safety, Installation Practices and Business/Licensing Requirements
Code, Safety, and Regulatory Requirements
Which code governs
Mechanical installations fall under the International Mechanical Code and the International Residential Code. Gas piping follows the International Fuel Gas Code. Refrigerant safety follows ASHRAE 15 and 34. The EPA Section 608 program governs refrigerant handling: technicians must be certified, venting refrigerant is prohibited, recovery equipment is required, and appliances above certain charge sizes need leak inspections and recordkeeping.
Safety groups and combustion air
Refrigerants are classified by toxicity and flammability - A1 such as R-410A, and A2L mildly flammable refrigerants that bring charge limits and ignition-source rules. Confined-space combustion air is a favorite question: two permanent openings, each sized at 1 sq in per 1,000 BTUH of total input, one near the top and one near the bottom; openings drawing from indoor air follow similar sizing with a minimum area.
Field safety
Lockout/tagout, PPE, and a CO monitor belong on every job. Gas piping needs a sediment trap, a shutoff valve, and a union. Vent connectors have slope and clearance requirements. A disconnecting means must be within sight of the equipment.
Traps
Applying commercial refrigerant rules to a residence, forgetting that a permit and inspection are required, sizing gas pipe by diameter alone instead of longest length plus total load, and assuming A2L refrigerants can be handled exactly like A1.
Worked example
A 100,000 BTUH furnace in a confined space needs two openings of 100 sq in each, one high and one low.
Installation Practices and Business/Licensing Requirements
Doing it right the first time
Quality installation starts with a load calculation (Manual J), equipment selection (Manual S), and duct design (Manual D). Line sizes come from the manufacturer's table, not habit. Evacuation to 500 microns with a standing decay test, a nitrogen pressure test at the specified pressure, and brazing with flowing nitrogen prevent the callbacks that exam questions disguise as diagnostic puzzles. Charge by weight whenever the nameplate permits it. Document static pressure, temperature split, superheat or subcooling, and combustion analysis at startup.
Running the business
Licensing is a state matter; certification such as EPA 608 or NATE is separate. Most jurisdictions require permits and inspections, and the contract should state scope, price, payment schedule, exclusions, and warranty terms in writing. Change orders belong in writing before the extra work happens.
Estimating
Know the difference between markup and margin. Markup is a percentage of cost; margin is a percentage of price. Labor burden - payroll taxes, insurance, truck, tools, non-billable time - must be recovered in the hourly rate rather than treated as profit.
Traps
Charging by superheat on a system that calls for weighing in the charge, skipping the nitrogen purge during brazing, failing to pull a permit, and confusing margin with markup. Another common trap is quoting a price based on the bare part cost and forgetting overhead.
Worked example
A part costs $100. At a 30 percent markup the price is $130. At a 30 percent margin the price is $100 / (1 - 0.30) = $142.86. The margin figure is always the higher number.