Michigan Mechanical License Classifications

Michigan doesn't hand out a one-size-fits-all HVAC license. Under MCL 339.5807 of the Skilled Trades Regulation Act (PA 407 of 2016), LARA issues Mechanical Contractor Licenses with specific classification letters that define exactly what type of work you're authorized to contract for. You can hold multiple classifications on a single license, but each one requires its own exam, experience documentation, and fees.

The Ten Classifications

Classification A — Hydronic Heating and Cooling and Process Piping. Covers closed and open-loop hydronic heating, hydronic cooling, process piping, and steam boilers under 15 p.s.i.g. This is the classification for radiant floor heating, boiler work, and expansion tank systems. Requires 6,000 hours of experience specifically in hydronic systems.

Classification B — HVAC Equipment. The core residential classification. Covers forced-air furnaces, central air conditioning, heat pumps, air handlers, and related gas piping and venting. If you're doing standard residential heating and cooling installs, this is your starting point. The exam is the most substantial — 150 questions over three hours, with a $100 fee.

Classification C — Ductwork. Covers design and installation of air distribution systems: sheet metal, flexible duct, and fibrous glass duct assemblies. If you're installing furnaces and AC units (Classification B), you'll almost certainly need this one too, since most residential jobs involve ductwork modifications.

Classification D — Refrigeration. Covers split systems, package cooling units, commercial walk-in coolers, and refrigerant lines. This is the classification for commercial refrigeration work. Note that you still need a federal EPA Section 608 certification for refrigerant handling — the state classification doesn't replace it.

Classification E — Limited Heating Service. Covers servicing, diagnostics, and repair of heating equipment up to specific capacity and pressure limits. Designed for contractors who focus on service and maintenance rather than full installations.

Classification F — Limited Refrigeration and AC Service. The cooling equivalent of Classification E — servicing and repair of cooling equipment up to specific tonnage and electrical limits. Covers light commercial applications.

Classification G — Unlimited Heating Service. Expands on Classification E with no capacity restrictions. Covers heating systems of any BTU rating, industrial burners, and commercial code compliance. Requires three years of active licensure in Classification E or equivalent experience.

Classification H — Unlimited Refrigeration and AC Service. Expands on Classification F with no capacity restrictions. Covers commercial refrigeration, chillers, heavy air conditioning, and industrial process cooling. Requires three years of active licensure in Classification F or equivalent.

Classification I — Fire Suppression. Covers wet and dry standpipes, sprinkler heads, NFPA 13/13D systems, and municipal water connections for fire extinguishing systems. A specialized classification that most HVAC-focused contractors won't need.

Classification J — Specialty. Covers LP piping, solar thermal systems, solid fuel appliances, and gas-fired decorative appliances. The catch-all for mechanical work that doesn't fit neatly into the other nine categories.

Which Classifications Do Most Contractors Need?

A typical residential HVAC contractor starts with B and C — HVAC Equipment and Ductwork. These two cover the vast majority of residential furnace, AC, and heat pump installations where ductwork is part of the job.

If you plan to handle refrigeration work (commercial coolers, split AC systems with refrigerant line sets), add Classification D. If your work includes boilers, in-floor radiant heat, or hydronic systems, add Classification A.

Service-only contractors who don't install new systems can start with E and F (limited service) and work toward G and H (unlimited) over time.

Experience and Exam Details per Classification

Classifications A–F and I–J require 6,000 hours (three years) of documented field experience under a licensed contractor. Classifications G and H instead require three years of active licensure in Class E or F, respectively, or an equivalent qualification. The experience must be specific to the classification — hours spent installing furnaces don't count toward a hydronic heating classification.

The HVAC Equipment exam (B) costs $100 and runs 150 questions in three hours. Every other classification exam costs $50, with 55 questions and a one-hour time limit. All exams are open-book — you bring your own bound reference materials (Michigan Mechanical Code, International Fuel Gas Code, etc.). Passing score ranges from 70% to 75%.

Adding Classifications to an Existing License

Already licensed? You can add classifications without getting a new license. Submit an application for the additional classification with your experience documentation and pay the state fee — which is pro-rated based on where you are in the three-year renewal cycle. Adding a classification in Year 1 costs the full $300, Year 2 costs $200, and Year 3 costs $100.

The Michigan HVAC License Guide walks through each classification's scope in detail and helps you identify which combination matches the work you plan to contract for.

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