Or does it require 5 foot clearance with the doors to the generator open?
The requirements in the 2018 Edition of NFPA 37, Section 4,1,4 are the following:
4.1.4 Engines Located Outdoors.
N 220.127.116.11 Engines and, if provided, their weatherproof housingsthat are installed outdoors shall be located at least 1.5 m (5 ft)from openings in walls and at least 1.5 m (5 ft) from structureshaving combustible walls except as provided in 18.104.22.168.1 or22.214.171.124.2.
N 126.96.36.199.1 A clearance less than 1.5 m (5 ft) shall be permittedwhere all portions of structures that are closer than 1.5 m (5 ft)from the engine enclosure have a fire resistance rating of atleast 1 hour.
N 188.8.131.52.2* A clearance less than 1.5 m (5 ft) shall be permittedwhere it has been demonstrated through methods acceptableto the authority having jurisdiction that a fire within the enclosurewill not ignite combustible structures.
The 5 foot minimum separation from openings in a structure is measured from any point of the generator weatherproof enclosure to any opening in the adjacent wall of a structure. I always tell installers to picture placing a dome over the generator than extends 5 feet past the generator on all sides, and to verify that there are no openings to the structure within that imaginary dome.
These clearances are in addition to the working space requirements in NEC Article 110.26 for electrical equipment, generators included. Also watch out for gravity or mechanical air-intakes for make-up air systems, as the ICC Mechanical Code requires a minimum of a 10 foot separation from any source of noxious contamination (generator exhaust).
Thank you very much for the info Brian!
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