National Electrical Installation Standards

Good morning, First, thank you for continuing this forum. I was recently called on to connect a radon blower. The installer left a switch kit provided from the blower manufacturer. I don’t know if the kit comes with the blower or if it is a separate item purchased by the radon mitigation contractor. The kit contained a weatherproof box, switch, weatherproof cover, two liquid- tight cord connectors and a 30 inch piece of SJOW cord. An image of the kit can be seen here: https://www.radonaway.com/products/radon-system-accessories/outdoor-fan-covers-accessories/kit-sf180-elec-out-switch-kit.php. It is billed as an exterior switch kit. 400.12(1) states that cord cannot be used as a substitute for fixed wiring unless specifically permitted in 400.10. This installation does not seem to fit any of the uses permitted in 400.10(A). The blower is connected to the rigid 3” piping with flexible couplings and pipe clamps to allow replacement without cutting into the fixed piping. But it should not need frequent repair or changing. I think it might be a stretch saying it complies with 400.10(A)(8). There is nothing in the instructions supplied with the blower that mentions the switch kit, only that the installation must be done according to the NEC. There were no instructions supplied with the switch kit. Do you think installing the blower using the cord in this kit is acceptable? Bob
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What is the maximum allowable height that a panel box can be installed from the floor? Philip Muldoon
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Re: CQD answer published Wednesday, September 5, 2018 - Load Calculations Load calculations per 220.83 existing building. I'm curious how additional loads should added? I have been told by chief electrical inspectors at least 3 different ways. 1. Additional loads at 40% 2. Additional loads at 100% 3. Additional loads at 125% I understand the misunderstanding. I've been told to use the 40% rule because that's what we'll be used the next time then additional loan is added.. makes sense. So I understanding the two other additional load calculations are extrapolated from other parts of the code book to make it more difficult to add additional loads to the existing structure? Are any of these methods correct or following the code as it is written? I am aware of how the rest of the calculation is done the first 10000 volt amps at 100% and the remainder at 40%. But the NEC does not specifically say additional loads at 40% or what percentage it should be added in at? Any help in this matter would be greatly appreciated. And as always Charlie thank you for the code question of the day and all of your great work answering our questions! Thanks, Oliver Allen
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I need the code # for Lighting in Machine work space Francis Scarnati
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Charlie, I enjoy reading your questions and answers every weekday. I am currently in a debate with a co-worker over 410.36(B) regarding lay in fixtures in suspended ceilings. My position is that as long as the fixture is secured to the grid via listed clips, screws, bolts, rivets, etc, there is nothing I can fail the installation on as an electrical inspector. He contends that the light must be secured to the building structure by at least 2 support wires stating that we do not know whether or not the ceiling is rated to support the fixture. I argue that that would be a building code issue and therefore fall on the building inspector to enforce an not the electrical inspector. Who is correct or are we both partially correct in some aspects? Regards, Jeff
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Re: CQD answer published Monday, September 3, 2018 -Swimming Pool Lighting Charlie, here is some additional information about pools and hot tubs. The Model Aquatic Health Code (MAHC) https://www.cdc.gov/mahc/editions/current.html Tammy
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Love the service you provide. While it’s clear in 250.64 that a grounding electrode conductor metal conduit requires bonding at both ends, does this rule apply to IT equipment bonding with a bonding conductor sleeved in a metal conduit? Ed Sim
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Re: CQD answers published August 9, 21, 29, & 30, 2018 -Service Equipment 5 One more response to the Wednesday, August 29, 2018 Q&A if you want to continue this discussion. It is interesting to note that the installation of an electric utility's meter does not service equipment make. The meter location normally constitutes the service point and if it located remote from the service, the meter installation may be looked upon as a "wide place in the conduit." In other words, a service disconnecting means and overcurrent protection is not required so three wires are all that is required to the service in the case of a 120/240V, 1Ø installation. Take care, Charlie Eldridge | Consultant
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Hi Charlie, what are your thoughts on residential grade devices installed at other than a dwelling? Another example: A Home Version load center at a commercial installation? Let's say 110.10, 110.28, etc have been met. I think the answer might lie in 110.3 and it's about researching all components. Thanks for your great forum! Norm Feck
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Hello can a 3/0 feeder be connected to a 400 amp OCPD in a series rated system? Here is the situation, there is a separate 3/0 feeder run 75 feet to a 200 amp commercial unit sub panel with a 200 amp main breaker installed within it. The distribution board only has a 400 amp OCPD available to supply the tenant space. The full load on the 3/0 will never (overload) exceed 200 amps with the installed 200 amp sub panel main breaker. If somehow there is a ground fault or short circuit (not overload) somewhere between the unit 200 amp OCPD and the distribution 400 amp OPCD that high fault current should open the 400 or even the 2000 amp building main. It would seem that the 3/0 would have overload, short circuit, and ground fault protection as required by the NEC? The 3/0 would not be considered tap conductors because they originate and end up at an OCPD. Your thoughts? Thanks Vince
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There are 2 sections I'd like to be clarified 1. Load calculations per 220.40 2. Grounding per 250 service grounding. - 2 Bob Gregg
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There are 2 sections I'd like to be clarified 1. Load calculations per 220.40 2. Grounding per 250 service grounding. - 1 Bob Gregg
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I have adjoining restaurants with separate meters, disconnects and service locations. They want to use power from one tenant for a led tape light in a window blocked by a 1hr shared fire wall in the other tenants' space. I know 400.7, 400.8 for the cord reasons Can they really share power by code? You would have to disconnect 2 different locations. Ben Miller
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What are the requirements for lighting pools to be able to swim at night? Sean Hogan
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Re: CQD answer published August 13 & August 23, 2018-Grounded Conductor Terminations 3 I agree with your answer on this but would like to append it with the need to consider impedance-grounded system. They can have a neutral wire (although mostly delta), but it's not intentionally grounded. So, not all neutrals are necessarily solidly grounded. Since most applications of impedance grounding is industrial and vast majority of electricians are not, but residential and commercial, their in lies the issue of lack of familiarity. Since most NEC classes are geared to residential and commercial, it makes the less covered impedance-grounded system even more mysterious. Lastly, when I used to attend NEC classes and update sessions (now happily retired since 2004, but like to keep an oar in the water), the thing that was always impressed by instructors is that: "The NEC is not an instruction manual"! Electricians need to continuously learn new things as well as keep up with changes. Submitting change proposals to the NEC is always a great way to learn about an issue. Even if your idea is not adopted, the CMP will give you an explanation of why it was rejected, and that is often very valuable since it's almost like getting an interpretation. It's great you encourage that. Best Regards, Nick Abbatiello
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