424.66(B) Duct Heaters. Limited Access.
Code Change Summary: New rules require working space for duct heaters with limited access.
Sometimes it takes a magician to figure out how all of the things required above a suspended ceiling in a building are going to fit. Getting them to fit is one thing but making them fit and observing all required rules and regulations for the applicable code at the same time is another story.
Section 110 in the NEC® has requirements on working space for equipment that is likely to be examined while energized while section 306 in the International Mechanical Code requires specific access for HVAC equipment that requires maintenance.
The changes to section 424.66 include new subsection (B) which contains similar language as the working space requirements in section 110.26:
Here are some of the highlights:
All of the following apply to duct heaters above a ceiling:
- The enclosure must be accessible through a lay-in type ceiling or an access panel.
- The width of the working space shall be the width of the enclosure or 30 in., whichever is greater.
- All doors or hinged panels must open to at least 90 degrees.
- The space in front of the enclosure must comply with the depth requirements of Table 110.26(A)(1).
- Horizontal ceiling T-bar is permitted in this space.
Below is a preview of the NEC®. See the actual NEC® text at NFPA.ORG for the complete code section. Once there, click on the “free access” tab and select the applicable year of NFPA 70 (National Electrical code).
2011 Code Language:
424.66 Installation. Duct heaters shall be installed in accordance with the manufacturer’s instructions in such a manner that operation does not create a hazard to persons or property. Furthermore, duct heaters shall be located with respect to building construction and other equipment so as to permit access to the heater. Sufficient clearance shall be maintained to permit replacement of controls and heating elements and for adjusting and cleaning of controls and other parts requiring such attention. See 110.26.
2014 Code Language:
424.66 Installation.
(A) General. Duct heaters shall be installed in accordance with the manufacturer’s instructions in such a manner that operation does not create a hazard to persons or property. Furthermore, duct heaters shall be located with respect to building construction and other equipment so as to permit access to the heater. Sufficient clearance shall be maintained to permit replacement of controls and heating elements and for adjusting and cleaning of controls and other parts requiring such attention. See 110.26. Working space about electrical enclosures for resistance heating element–type duct heaters that are mounted on duct systems and contain equipment that requires examination, adjustment, servicing, or maintenance while energized shall comply with 424.66(B).
(B) Limited Access. Where the enclosure is located in a space above a ceiling, all of the following shall apply:
(1) The enclosure shall be accessible through a lay-in type ceiling or an access panel(s).
(2) The width of the working space shall be the width of the enclosure or a minimum of 762 mm (30 in.), whichever is greater.
(3) All doors or hinged panels shall open to at least 90 degrees.
(4) The space in front of the enclosure shall comply with the depth requirements of Table 110.26(A)(1). A horizontal ceiling T-bar shall be permitted in this space.