Michigan Compiled Laws, Chapter 339. Occupational Code § 339.5803

(a) “Limited heating service” means the servicing of gas-designed sectional boilers that have inputs of not more than 1 million British thermal units, utilizing a combustion safeguard designed to shut off the main gas supply 10 or more seconds after pilot flame failure, and all other gas-fired or solid-fuel equipment and systems limited to input ratings of less than 400,000 British thermal units per unit; or oil-fired equipment and systems designed for the use of number 1 or number 2 fuel oil, that has a maximum firing rate of less than 5 gallons per hour per unit; or electrical furnaces and electric boilers that use the same kilowatts that are equivalent to the fossil fuel British thermal units generated.

(b) “Limited refrigeration and air conditioning service” means the servicing of refrigeration equipment and systems and air conditioning equipment and systems employing the refrigeration cycle of unlimited capacity utilizing group 1 refrigerants as listed in the Michigan mechanical code or an equivalent nationally recognized model mechanical code.

(c) “Process piping” means any piping which is not part of a system designed to provide air conditioning or of a refrigeration system. Process piping includes, but is not limited to, pipes that transfer chemicals and other fluids, gases, or vapors for systems other than air conditioning systems as covered by the Michigan mechanical code or an equivalent nationally recognized model mechanical code.

(d) “Refrigeration” means the use of equipment and systems, including, but not limited to, refrigeration piping, employing the refrigeration cycle to generate low temperatures for other than air conditioning equipment and systems. Refrigeration includes, but is not limited to, equipment and systems such as supermarket refrigeration, industrial refrigeration, the preservation of biological materials, and food storage facilities. Refrigeration does not include the installation of portable self-contained units such as refrigerators, dehumidifiers, and other similar equipment of not more than 1.5 horsepower or other equipment exempted from the Michigan mechanical code.

(e) “Servicing” means the maintenance, repair, and servicing of previously installed equipment and systems.

(f) “Specialty license” means a license issued under this article that allows the licensee to perform work within limits established by the board in 1 or more of the work classifications described in section 807(2). 1

(g) “Unlimited heating service” means the servicing of heating equipment and systems without restrictions concerning thermal capacity or grade of fuel oil or type of fuel.

(h) “Unlimited refrigeration and air conditioning service” means the servicing of refrigeration equipment and systems and air conditioning equipment and systems employing the refrigeration cycle unlimited as to thermal capacity or type of refrigerant.