Mechanical Systems

Access must be maintained to unions, valves, equipment in the ceilings walls and floor, such as, water valves, unions in gas piping, sump pump pits, etc. Provide an identified readily accessible opening with enough clearance to maintain and inspect the devices.

Clearances for Furnaces and Water Heaters

Clearances around appliances to elements of permanent construction including other installed equipment and appliances, shall be sufficient to allow inspection, service, and repair or replacement without removing such elements or appliance. Clearances shall be provided on the sides and rear of each appliance to comply with the manufacturer’s installation instructions or a minimum of 3 inches whichever is greater.

Combustion Air

If walls are to be placed around the furnace and hot water heater areas, adequate combustion air must be maintained to the appliance for proper operation. Access and clearance must also be maintained to access and replace and service the equipment without the removal of other equipment. Comply with the manufacturer’s installation instructions for minimum clearance. Generally at least 30 inches of clearance is required in front of a furnace or water heater unless more is required by the manufacturer.

For air from inside the building the room occupied by a gas appliance must have a total volume of 50 cubic feet for each 1000BTU/h combined input rating of the appliances. An adjacent room may be included in the minimum volume if openings between the room are provided as noted below for inside air (see diagram).

  • Outside air - the opening area depends on the method • used. Contact the City if you have specific questions regarding this method.
  • Inside air - inside air may also be provided from an • adjoining room through openings located within 12 inches of the floor and ceiling. Each opening shall equal 1 square inch for each 1,000 BTU/hr of total input rating of all appliances and a total minimum of 100 square inches. The adjoining room must have a volume equal to at least 50 cubic feet for each 1,000 BTU/hr of aggregate input rating of the appliances.

Bathroom Exhaust Fans

Each room containing a water-closet, bathtub or shower shall be provided with a mechanical ventilation system with an intermittent capacity of not less than 50 cfm. Ventilation air from the space shall discharge directly to the outside.

Return Air Vents

The code prohibits return air vents in kitchens, bathrooms, and closets.

Common Mechanical Requirements that get Overlooked:

  • Vent bathroom exhaust fans to the exterior.
  • Maintain minimum working clearances (as listed on the equipment or the installation instructions) around furnace and water heater, and be sure to provide adequate width for future replacement.
  • Provide adequate combustion air to the furnace/hot water heater room.
  • New duct joints should be made airtight by using tapes or mastics.
  • ALWAYS follow the manufacturers’ installation instructions.