Originally Posted by David Bell

Originally Posted by

CCF10162010_00000.jpg This is what I see out there for the most part.
From the IRC:
-

M1305.1 Appliance access for inspection service, repair and replacement.

Appliances shall be accessible for inspection, service, repair and replacement without removing permanent construction, other appliances, or any other piping or ducts not connected to the appliance being inspected, serviced, repaired or replaced. A level working space at least 30 inches deep and 30 inches wide (762 mm by 762 mm) shall be provided in front of the control side to service an appliance. Installation of room heaters shall be permitted with at least an 18-inch (457 mm) working space. A platform shall not be required for room heaters.



From the NEC:


- 110.26 Spaces About Electrical Equipment.
- - Sufficient access and working space shall be provided and maintained about all electrical equipment to permit ready and safe operation and maintenance of such equipment.
- - - (A) Working Space. Working space for equipment operating at 600 volts, nominal, or less to ground and likely to require examination, adjustment, servicing, or maintenance while energized shall comply with the dimensions of 110.26(A)(1), (A)(2), and (A)(3) or as required or permitted elsewhere in this Code.
- - - - (1) Depth of Working Space. The depth of the working space in the direction of live parts shall not be less than that specified in Table 110.26(A)(1) unless the requirements of 110.26(A)(1)(a), (A)(1)(b), or (A)(1)(c) are met. Distances shall be measured from the exposed live parts or from the enclosure or opening if the live parts are enclosed.


- - - - - Table 110.26(A)(1) Working Spaces specifies the minimum clearance in front of the equipment to be 36 inches, and the clearance goes up for some conditions where the voltage to ground is 151-600 volts to ground (not seen in the typical residence).



So now you have:


a) Manufacturer's installation instructions which state 24 inches.


b) IRC which states 30 inches in the mechanical section.


c) NEC (and its equivalent in the IRC requires the same thing) which states 36 inches.



Q. So which *are you supposed to* go by?


A. (from the IRC):

R102.1 General.

Where, in any specific case, different sections of this code specify different materials, methods of construction or other requirements, the most restrictive shall govern. Where there is a conflict between a general requirement and a specific requirement, the specific requirement shall be applicable.



Note that manufacturer's installation instructions are 'code by reference' and therefore fall under "the most restrictive shall govern", i.e., *IF* the manufacturer's installation instructions specified 42 inches clearance, that would be the requirement as it would be "the most restrictive", however, lacking that, "the most restrictive" applies - the NEC working space requirements.