Notable Changes in the Mechanical Codes July 2004 The following are some of the changes between the 1997 Uniform Mechanical Code and the 2003 International Mechanical Code(M) and the 2003 International Fuel Gas Code (F). This list is not meant to be all-inclusive, but represents some of the most notable changes I have found (to date) which would affect the greatest percentage of contractors and designers. This is not a full text of the changes, but only a brief description. See the codes for more information. The City of Missoula has absolutely no choice over code adoption in terms of content or date. The City is mandated to adopt these codes, without change, by the Building Codes Bureau, of the State of Montana. Note: Make sure that you obtain the Errata (list of corrections) to the code books. This can be found on the ICC web site: (www.iccsafe.org/cs/codes/errata.html) M202 Definition of Hoods: Backshelf, Double Island Canopy, Eyebrow, Passover, Single Island Canopy, Wall Canopy. Definition of types of cooking appliances: Extra Heavy, Heavy, Medium, Light. F303.3; M303.3 No fuel fired appliances in toilet rooms,or obtain combustion air from toilet rooms. (except direct-vent, and other exceptions) Note: These exceptions do not apply to water heaters, which are regulated by the Uniform Plumbing Code. F304.2; M304.2 Listings vs. codes: most restrictive applies. F303.3 Unvented heaters now allowed with many restrictions. It is strongly advised that you contact the inspector before installing these appliances to avoid as many problems as possible. F302; M302 Boring/ Notching/ Cutting requirements explained in mechanical codes. (No change from building codes) F304 Combustion air requirements are basically the same for fuel-gas appliances. We will still basically consider homes built after 1980 as unusually tight construction. Allowances and formulas are provided if engineering is desired. Note that there is a reduction for grills and louvers of 25% or more. F305.2 Mechanical rooms opening into garages are considered part of the garage, not part of the dwelling. Minimum 18 off floor for parts that spark, glow or have flame.
F308; M308 Commonly used clearance reduction method now requires 24 gauge sheet metal. Change from 2 to 3 clearance when combustible material is above vent. F404.7 Exterior exposed gas piping now 3-1/2 above roof or grade. F404.9 Burial depth of 12 for steel OR plastic gas piping, exception for lights or BBQ s. F406.4 Gas line air tests: defines types of gauges. Allows for tests of less than 10 psi, however anyone wishing to test at less than 10 psi should have reason and make arrangements with inspector beforehand. Inspector will continue to assume that a 10 psi test will be performed on all low pressure systems. F409.1.2 Shutoff valves prohibited in concealed locations. F410.2 T-fittings required downstream of medium pressure regulators. F408.4 Specific details about sediment traps and drip traps. F409.5 Shutoff valves now required within 6 of appliance. F621.1 Allows unvented room heaters with many restrictions. It is advised that you contact the inspector before installing these appliances to avoid as many problems as possible. F503.5.10 Space around vent in chimney not allowed for combustion air. F503.6.6 Vent termination now 2 above wall within 10 -OR- 8 away. F503.6.9.1 Vent maximum now 7 times draft hood outlet size of smallest appliance. (example: 3 diameter water heater = 7.07 sq inches, x 7 = 49.5 sq inches; so, 8 diameter vent would be too large) F 504.2.11 Vent connector maximum size no more than 2 sizes larger than appliance outlet. F503.6.6.1 Decorative shrouds not allowed at vent termination unless listed.
F504.3.6 and 7 Elbows in connectors and vents. Reduction in vent capacity in excess of two elbows. F614.5; M504.5 Clothes dryers exhausting excess of 200 cfm must have make-up air. 100 square inches required in closets. F621 Allows unvented room heaters with many restrictions. It is advised that you contact the inspector before installing these appliances to avoid as many problems as possible. M301.3 Refers to the International Fuel Gas Code for gas-fired appliances, piping, equipment and venting. Note that the most restrictive would apply if there are any conflicts. M301.7.2.3 Specifications for drain pans under equipment. M309.1 All interior spaces designed for human occupancy must be designed for 68 degrees F. M312.1 ASHRAE Handbook of Fundamentals and ASHRAE Handbook - HVAC Systems and Equipment adopted by reference. M401.5 All exhaust and intake air minimum 10 feet from lot lines OR buildings on the same lot. M401.5.1 Air intakes must be 10 feet from vents, chimneys, plumbing vents, streets, alleys, parking lots, or loading docks. M401.5.2 Exhaust cannot be directed onto walkways. M403.2.1 Ventilation air shall not be recirculated from one dwelling unit to another OR to dissimilar occupancies. M403.3 New outdoor air and ventilation air requirements for occupancies, some in locations not previously required. M504.6 Directional fittings required on clothes dryers. M504.6.1 Maximum length for clothes dryer ducts of 25 feet, less 5 feet for each 90 degree elbow. Exception for dryers listed for longer lengths.
M504.7 Commercial clothes dryer duct clearance of 6 to combustibles. M505.1 Domestic range hoods: smooth interior walls and air-tight. M506.3.1.2 Make-up air ducts for Type I hoods must be metal within 18 of hoods, insulation noncombustible. M506.3.5 Separate grease ducts for each hood unless in the same room and story and other limitations. M506.3.8-9 Details for location of grease duct access doors. M306.3.10 Grease duct enclosure clearance now 6 from duct. M506.3.11 Requirements for access doors in grease duct shafts. M506.3.12.1 Exhaust outlet termination now 40 inches above roof. M506.3.12.2 Termination through wall allowable in some situations. Consult with inspector first. M506.5.3 Upblast fans must be hinged and include weatherproof electrical cable to permit inspection and cleaning. M506.2.2 Under counter dishwashers specifically excluded from hood requirement. M506.2.3 Domestic cooking appliances used for commercial purposes require commercial hoods. M507.7.1 Type I hoods specifically required to be welded or brazed (with exceptions). M507.13 All airflow requirements for hoods have changed. Check definitions (chapter 2) for type of appliances. Note that airflow is measured AFTER subtracting any make-up air supplied into hood. This eliminates the advantages of a compensating hood. M507.14 Performance test now mandated by code.
M507.16.1 New Capture and containment test : field observation with all appliances operating. Be sure to allow extra time for modifications to be made, if needed, before opening of business, or granting of certificate of occupancy. M508.1.1 Make-up air must now be tempered (heated) to within 10 degrees F of air in the conditioned space. M601.2 Special requirements for exit corridors and plenums above exit corridors. M605.1 Air filters must be in a convenient location. This would suggest that attics and crawl spaces would not be allowed if there were better options such as filter grills M606.2.1 Smoke detectors for unit shutdown now requires on return side instead of supply side. M606.2.2 Smoke detector shutdown specifically not required in fan-terminal units (with exceptions). M602.3 Stud wall cavities for return air shall not convey air from more than one floor level. Stud wall and joist R/A isolated with approved fireblocking. M607.3.2.1 Smoke dampers must close when fans are off if detectors require a minimum velocity to operate. M(chapter 7) and M(chapter 8) Combustion air and venting chapters apply only to NON-fuel gas appliances. M917.2 Commercial cooking appliances not allowed in dwellings. M(chapter 10) Boiler chapter deleted by State of Montana. Questions? Should something bed to the list? Contact me. Office hours are normally 7:30 AM to 9:00 AM and again at 3:30 PM to 4:00 PM. -Doug Anderson Sr. Mechanical Inspector 258-4721