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Disconnect requirements for fixed electrical space heating equipment


Aug. 22, 1997

It has come to the attention of the department that some installations of fixed electric space heating equipment may not be in compliance with the disconnect requirements of NEC Section 424-19.

The particular installations in question are load management systems utilizing storage heat units that are supplied by more than one branch circuit. Typically these units will be supplied by a branch circuit for the heat storage section and a separate circuit connection for the blower section. The blower section branch circuit(s) are not controlled by the utility as part of its load management program while the heat storage branch circuit(s) are controlled through this program. Many of these units incorporate blower motors that are not rated over one-eighth horsepower and do not include supplemental overcurrent protection for the heating load. These units, unless they incorporate unit switches for all connected circuits, are required to have disconnects installed in accordance with Section 424-19 and as allowed by part (b)(1). Disconnects for equipment without motors or with motors of less than one-eighth horsepower may be located out of sight from the equipment where lockable in the off position. Locking accessories available from panelboard manufacturers are acceptable where they are of the type that is retained by the panelboard enclosure.

The requirement for grouping of disconnect means for equipment supplied by more than one circuit is found in the main part of Section 424-19 and requires the disconnecting means to be located adjacent to each other or, where branch-circuit switches or circuit breakers are utilized, located in the same panelboard or in panelboards that are immediately adjacent to each other. Multiple disconnects for the same unit are required to be marked to identify other branch-circuit disconnecting devices that serve the same unit. Alternatively, marking at the equipment identifying the location of the grouped disconnects is acceptable.

Refer to part (a) of Section 424-19 where supplementary overcurrent protection is provided or where motor horsepower is one-eighth or greater.

Particular attention to different installations and types of equipment must be made to ensure compliance with these requirements.

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