Q1. Does the Code allow the electrical room to be used for storage?

A1.The working space required by 110.26(B) must be clear at all times. Therefore, this space isn’t permitted for storage.

When normally enclosed live parts are exposed for inspection or servicing, the working space, if in a passageway or open space, must be suitably guarded.

Author’s Comment:
• When working in a passageway, the working space should be guarded from occupants using it. When working on electrical equipment in a passageway one must be mindful of a fire alarm evacuation with numerous occupants congregated and moving through the area.

CAUTION: It’s very dangerous to service energized parts in the first place, and it’s unacceptable to be subjected to additional dangers by working around bicycles, boxes, crates, appliances, and other impediments.

Author’s Comment:
• Signaling and communications equipment aren’t permitted to be installed in a manner that encroaches on the working space of the electrical equipment.

Q2. What are the Code requirements for sizing the grounding electrode conductor at a service to a rod type electrode and concrete-encased electrodes?

A2. Metal underground water pipe electrodes and metal in-ground support structures must be sized in accordance with Table 250.66. Other electrodes such as ground rods, concrete-encased electrodes, ground rings can be sized using 250.66(A) through (C).

(A) Rod-Type Grounding Electrode. If the grounding electrode conductor or bonding jumper connects to one or more ground rods [250.52(A)(5)] and doesn’t connect to another type of electrode that requires a larger conductor, the grounding electrode conductor isn’t required to be larger than 6 AWG copper.

(B) Concrete‑Encased Grounding Electrode. If the grounding electrode conductor or bonding jumper is connected to one or more concrete‑encased electrodes [250.52(A)(3)] and doesn’t connect to another type of electrode that requires a larger size conductor, the grounding electrode conductor isn’t required to be larger than 4 AWG copper.

Q3. What does the Code require in regard to installing a grounding electrode using ground rods?

A3. Rod Electrodes [250.53(A)] .
(1) Below Permanent Moisture Level. If practicable, pipe electrodes must be embedded below the permanent moisture level and be free from nonconductive coatings such as paint or enamel.

(2) Supplemental Electrode. A rod electrode must be supplemented by an additional electrode that’s bonded to:
(1) Another rod electrode
(2) The grounding electrode conductor
(3) The service neutral conductor
(4) A nonflexible metal service raceway
(5) The service disconnect

Ex: A single rod electrode having a contact resistance to the earth of 25 ohms or less isn’t required to have a supplemental electrode.

Author's Comment:
• Generally, a single ground rod won't have a contact resistance of 25 ohms or less. In many cases, a ground rod with a supplemental (two rod electrodes) won't have a contact resistance of 25 ohms or less. The maximum number or rod electrodes required by the NEC is two, even if the 25 ohm requirement isn't met.

(3) Spacing. The supplemental electrode for a rod electrode must be installed not less than 6 ft from the rod electrode.

(B) Electrode Spacing. Electrodes for premises systems must be located no closer than 6 ft from lightning protection system grounding electrodes. Two or more grounding electrodes that are bonded together are considered a single grounding electrode system.

(C) Grounding Electrode Bonding Jumper. Grounding electrode bonding jumpers must be copper when within 18 in. of the earth [250.64(A)], be securely fastened to the surface, and be protected from physical damage [250.64(B)]. The bonding jumper to each electrode must be sized in accordance with 250.66.

Author's Comment:
The grounding electrode bonding jumpers must terminate by any of the following means in accordance with 250.8(A):
• Listed pressure connectors
• Terminal bars
• Pressure connectors listed as grounding and bonding equipment
• Exothermic welding
• Machine screw‑type fasteners that engage not less than two threads or are secured with a nut
• Thread‑forming machine screws that engage not less than two threads in the enclosure
• Connections that are part of a listed assembly
• Other listed means

When the termination is encased in concrete or buried, the termination fittings must be listed for this purpose [250.70].

Q4. When does the Code allow the building metal structure to serve as a grounding electrode?

A4. Metal In‑Ground Support Structure(s). Only metal in-ground support structure(s) in direct contact with the earth vertically for 10 ft or more can serve as a grounding electrode. [250.52(A)(2)]

Note: Metal in‑ground support structures include, but aren’t limited to, pilings, casings, and other structural metal.

Q5. If more than one electrode is available, what does the Code allow for connecting one grounding electrode to another electrode?

A5. Grounding Electrode Conductor Connections. Grounding electrode conductors and bonding jumpers are permitted to terminate and use the following to extend the connection to another electrode(s) [250.68(C)]:

(1) Interior metal water piping that’s electrically continuous with a metal underground water pipe electrode and is located not more than 5 ft from the point of entrance to the building can be used to extend the connection to electrodes. Interior metal water piping located more than 5 ft from the point of entrance to the building isn’t permitted to be used as a conductor to interconnect electrodes of the grounding electrode system.

(2) The metal structural frame of a building can be used as a conductor to interconnect electrodes that are part of the grounding electrode system, or as a grounding electrode conductor. Hold‑down bolts securing the structural steel column to a concrete‑encased electrode [250.52(A)(3)] can connect the metal structural frame of a building to the concrete‑encased grounding electrode. The hold‑down bolts must be connected to the concrete‑encased electrode by welding, exothermic welding, the usual steel tie wires, or other approved means.

(3) A rebar‑type concrete‑encased electrode [250.52(A)(3)] with an additional rebar section to an accessible location above the concrete, where not in contact with the earth or subject to corrosion, can be used for the connection of the grounding electrode conductors and bonding jumpers.