Mike Holt

Articles by Mike Holt
Grounding and Bonding of Separately Derived Systems
Separately derived systems (SDSs) include most transformers as well as any generator or UPS supplying a transfer switch that opens the neutral conductor.
Code Q&A
Q. What are the NEC requirements for the installation of smoke detectors in dwelling units?
Code Q&A 1
Q. What are the Code requirements for bonding bushings on 277V or 480V branch and feeder and circuits?
Stumped by the Code?
Q. What are the rules on spacing receptacles in a dwelling unit?
Transformer Secondary Conductors 3
Similar to feeder taps, covered in the last issue, transformer secondary conductors can be every bit as confusing. Let's take a closer look at 240.21(C)
Code Q&A
Q. When PVC conduit is used, does the Code require an equipment grounding conductor between the meter enclosure and the service disconnect?
Code Q&A
Q. Section 110.14(C) requires the use of the 60°C column for 100A or less and the 75°C column for above 100A for conductor sizing. What is the value of THHN rated 90°C if the ampacity cannot be used for conductor sizing?
Feeder Taps 2
Sometimes, it makes sense to tap into a feeder conductor to power another conductor. From Art. 100, we know that a feeder conductor runs between service
Code Q&A
Q. Is there any allowance in the NEC to locate receptacles in dwelling units where it is convenient for furniture layout or the designer’s wishes, if the required number of receptacles is installed?
Code Q&A
Q. Is it permissible to run heating/air-conditioning duct 4 feet above a panelboard if the ductwork services the room where the panelboard is located?
Code Quandaries
Q. If structural steel is used as a grounding electrode for the electrical service, is it also necessary to supplement the steel electrode with an additional electrode such as a ground rod?
Code Q&A
Q. A single main breaker is installed, then taps supply individual meters with disconnecting means for individual tenants. Should a main bonding jumper be installed at the single main breaker or at each separate disconnect?
Code Q&A
Q. When a conduit leaves a Class I, Division 1 classified paint spray room and goes under the concrete floor into a cabinet in the motor control room that is non-classified, is one sealing fitting in the paint mix room sufficient, or is an additional sealing fitting required in the non-classified area as well?
Code Changes 2008
It's hard to believe it's that time again, but the 2008 NEC is upon us. In this latest Code cycle, the Code Making Panels (CMPs) sifted through 3,688
Code Quandaries
Q. What is the minimum depth for placing Schedule 40 PVC conduit below a concrete slab?
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