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Monday, October 28, 2019
Question:
Re: CQD answer published Monday, October 14, 2019 - Working Space
In regards to the question below, I would like to offer my observation on this issue of "work space" requirements. In the NEC article covering it, it has a foot note under the table where it states this applies to equipment having "EXPOSED" live parts. The term "EXPOSED" is defined in Art. 100, thus that must be used to determine applicability. It states: Exposed (as applied to live parts). Capable of being inadvertently touched or approached nearer than a safe distance by a person. It is applied to parts that are not suitably guarded, isolated, or insulated.
All of the panels now on the market do NOT have EXPOSED live parts when the definition is applied. Even though live parts of terminals can be viewed, they are generally recessed or otherwise arranged (suitably guarded) so that "inadvertent" contact is highly unlikely. Buss bars are covered, screws are recessed, etc. The only way to contact live conductive parts is to "deliberately" do it. This is also true of "safety" type disconnect switches. The hinged cover is interlocked with the handle and the cover can only be opened with the switch in the "OFF" position. When the cover is then opened, the only thing energized is the incoming termination, which is guarded and recessed to avoid "inadvertent" contact. Yes, if the interlock is defeated, then a hazard exists, but this is "deliberate". Here's the Working Space requirement: 110.26 Spaces About Electrical Equipment.
Each condition applies to the "Exposed" live parts as defined in Art. 100. If this working space requirement was applied without this caveat, almost every installation would be in violation. Some equipment complies to IEC regulations and quantifies levels of exposure using the Ingress Protection (IP) rating. IP 3, or greater, is generally regarded as "finger safe". IP1 indicates "back of hand" safe, which is also protection against inadvertent contact.
Nick Abbatiello
A
Answer:
Hey Nick thanks for your thoughts. We removed all the NEC copied text in your question (comment) to shorten it and because readers can see that by looking it up in their NEC or online.
It is understandable how you have that opinion but it is not necessarily the same one AHJ's have. The need for working space with specific dimensions is based on whether the equipment is likely to be examined, adjusted, serviced or maintained while energized as stated in 110.26(A).
The Informational Note for the definition of Exposed in Article 100 uses the word "suitably " but that word is not specifically defined or described in this rule. Components that are intended for protection from contact with a finger (12.5 mm) are described as IP 2X (Ingress Protection (IP 20 is common)). Informational Note 2 to Table 110.28 states that IP ratings are not a substitute for enclosure Type ratings. Using IP 20 rated components can reduce risk but during troubleshooting it is very likely that test instruments with probes will be used and finger safe components do not provide suitable protection from those. There can also be other concerns besides the device or equipment construction.
By comparison NFPA 79, the Electrical Standard for Industrial Machinery, in 11.5.1.1 Exception 4 allows reduced working space under certain conditions and limitations including the live parts needing to be guarded such that contact with a 12.5 mm (0.5 inch) rod will not occur. Notice that it does not eliminate the working space requirement
If you believe that working space is not necessary if specific components are used submit a Public Input for the 2023 NEC. Until there is an exception or clear direction in 110.26 that enclosures containing finger safe components do not need working space it seems providing it is necessary.