COMMENT 1-118 draft -- UPSs feeding fixed wiring.
I'm looking for constructive criticism on the following, and if you think it is merited, support in the form of comments from you on 1-118. Thanks, Jim Williams
100 I Fixed Wiring. Conductors, raceways, etc. installed under chapter 3 methods.
110.27 Uninterrupted Power Supply (UPS) Connected to Fixed Wiring.
(1) When a UPS supplies fixed wiring, each place the UPS supplied circuit(s) is accessible shall have a clearly legible marking in letters not less than 6 mm (¼ in.) high reading “UPS Supplied”. The label shall comply with 110.21(B).
(2) When a control panel contains a UPS which supplies current to fixed wiring external to the control panel, the control panel shall have a clearly legible sign in letters not less than 6 mm (¼ in.) high reading “Caution this panel contains a UPS”. The sign shall comply with 110.21(B).
(B) Disconnecting Means. A disconnect meeting the requirements of 110.25 shall be installed for all output circuits from the UPS.
Exception: Meeting the requirements 110.27 is not required in areas meeting all the requirements of 645 Information Technology Equipment. Or 646 Modular Data Centers.
5. Statement of Problem and Substantiation
90.1(A) Practical Safeguarding. The purpose of this Code is the practical safeguarding of persons and property from hazards arising from the use of electricity.
The recent introduction of fixed wiring in buildings fed from UPSs in other than Information Technology Equipment areas has introduced a new hazard. Until recently when you opened the main service disconnect for a building you would be able to assume that fixed wiring was no longer energized. APC and other manufacturers are selling UPS accessories for their products to facilitate connection to fixed wiring. (For example see http://www.apcmedia.com/salestools/A...8L95_R0_EN.pdf). This installation guide does not require an output disconnect.
The recent introduction of UPSs embedded in control panels which feed external fixed wiring presents a similar hazard. I have directly experienced a case of this sort. I was tasked to replace a shunt-trip 3-pole circuit breaker with trip alarm contacts. I opened all the circuits serving the control cabinet. I measured the voltages on the circuit breaker power connections, the shunt-trip, and the trip alarm contacts. I found that the shunt-trip circuit was de-energerized, but that the trip alarm contact was still energized. I opened the control cabinet (not something I normally would do, because the cabinet and associated equipment were maintained under contract by a third-party). I found that a standalone style UPS like one might buy in a big box store was inside and its output was energizing the trip alarm contacts. I also confirmed that all external power to the control panel was indeed turned off.
I am proposing the addition of 110.27 and the associated 100 I Fixed Wiring additions to the NEC to warn electricians of these new hazards. I am suggesting the use of “UPS supplied” as labeling for receptacle outlet covers (and other covers) because it also serves as useful label for non-electrician users.
The exception is proposed because those qualified personnel working in 645/646 areas are already expecting UPS supplied receptacles.
Terms Terms akin to Fixed Wiring are used in:
(fixed (fixed wiring system) 250.34(C)(3)<info>, 511.16(B)(2);
(fixed[-(fixed[-type] wiring method(s)) 393.6(B)(4), 411.2(B)(5), 501.104(A)(2), 505.17(A), 518.4(A), 520.5(A), 550.19(A), 550.32(D);
(fixed wiring) 400.8(1), 500.8(B)(1)<info>, 511.7(A)(1), 513.7(A), 513.10(C)(1), 513.10(D)(1), 513.16(D)(2), 515.7(A), 516.7(A), 517.61(A)(3), 530.31, 620.21(A)(2)(b)
The response from CMP-1 limited itself to the original example (an elevator control panel, and not to the general cases supplied above).
Panel Statement: The problem identified by the submitter relates to product
design and marking rather than installation. In addition, the submitter is
proposing specific requirements in the general section of the code which may
be more appropriate in other sections of the code. In sections such as
620.52(B), the submitter’s concerns are addressed.