Attic furnace installation must comply with you local mechanical code or IMC (International Mechanical Code) if such was adopted in your area. The following are attic furnace installation requirements based on 2009 IRC and 2009 IMC (The codes refer to it as “Appliances in attics”).
- Attic furnace access / passageway and platform
- Attic furnace passageway and service area electrical requirement
- Appliance in the attic / Attic furnace access / passageway and platform
Access opening and an unobstructed passage way to the appliance / furnace in attic area must be provided and be adequate in size to allow removal of the largest appliance installed.
Attic furnace / appliance clear access opening dimensions are:
- 20 inches (508 mm) by 30 inches (762 mm) minimum
but it must be large enough to permit removal of the largest appliance installed in the attic area.
Attic furnace passageway minimum dimensions requirements:
- 30 inches high (762 mm)
- 22 inches wide (559 mm)
- 20 feet max length (6096 mm)
measured along the center-line between the attic access opening and the attic furnace.
This 20’ limitation applies to the minimum 30” height only )low clearance attics). If there are no obstructions on the passageway to the attic furnace, and it has a minimum 6 feet (1829 mm) height and 22 inches (559 mm) width along its entire run, the walkway length limit goes up to 50 feet (15250 mm) in IRC (International Residential Code) and has no limit in UMC (Universal Mechanical Code)
The attic furnace passageway flooring
The passageway requires continuous, solid flooring which is minimum 24” wide (material has not been specified but it must be able to support the installer and the appliance’s weight).
Attic furnace service platform
A minimum 30 inches (762 mm) by 30 inches (762 mm) level service platform / space is required in front of the attic furnace’s / attic appliance service access panel. The attic furnace passage way and level service area are not required if you have your attic furnace / appliance installed in such way that it is serviceable through the attic access opening and it can be removed through that opening
Attic furnace / appliance passageway and service area electrical requirement
There should be a light fixture installed at or near the appliance area and controlled by a switch located by the attic passageway access opening. Also, an electrical outlet receptacle must be provided at or near the attic furnace / appliance for servicing purposes.
If you are installing an attic furnace, air handler or combination of both please visit attic drip pan installation