|
Figure 01
|
For EC&M Magazine
By Mike Holt, NEC® Consultant
Here's the follow-up to yesterday's newsletter.
This includes the answers to the questions sent, so you can see how you did.
Note: The answers to these questions are based on the 2017 NEC.
Underlined text indicates a change in the rule for the 2017 NEC.
Q4. Does the NEC allow service equipment to be mounted on trees or other vegetation?
A4. Trees or other vegetation aren’t permitted to be used for the support of overhead service conductor spans or service equipment [230.10].
Author’s Comment:
• Service drop conductors installed by the electric utility must comply with the National Electrical Safety Code (NESC), not the National Electrical Code [90.2(B)(5)]. Overhead service conductors that aren’t under the exclusive control of the electric utility must be installed in accordance with the NEC.
Q5. What wiring methods are allowed by the Code for service-entrance conductors?
A5. Service-entrance conductors can be installed with any of the following wiring methods [230.43]:
(1) Open wiring on insulators
(3) Rigid metal conduit
(4) Intermediate metal conduit
(5) Electrical metallic tubing
(6) Electrical nonmetallic tubing (ENT)
(7) Service-entrance cables
(8) Wireways
(9) Busways
(11) PVC conduit
(13) Type MC cable
(15) Flexible metal conduit (FMC) or liquidtight flexible metal conduit (LFMC) in lengths not longer than 6 ft
(16) Liquidtight flexible nonmetallic conduit (LFNC)
(17) High-density polyethylene conduit (HDPE)
(18) Nonmetallic underground conduit with conductors (NUCC)
(19) Reinforced thermosetting resin conduit (RTRC)
Q6. What are the NEC requirements for service disconnects?
A6. The service disconnect must open all ungrounded service-entrance conductors from the building premises wiring [230.70].
(A) Location.
(1) Readily Accessible. The service disconnecting means must be placed at a readily accessible location either outside the building, or inside nearest the point of service conductor entry. Figure 01
WARNING: Because service-entrance conductors don’t have short-circuit or ground-fault protection, they must be limited in length when installed inside a building. Some local jurisdictions have a specific requirement as to the maximum length permitted within a building.
(2) Bathrooms. The service disconnect isn’t permitted to be installed in a bathroom. (3) Remote Control. If a remote-control device (such as a pushbutton for a shunt-trip breaker) is used to actuate the service disconnect, the service disconnect must be located at a readily accessible location either outside the building, or nearest the point of entrance of the service conductors as required by 230.70(A)(1).
Author’s Comment:
• See the definition of “Remote Control” in Article 100.
• The service disconnect must consist of a manually operated switch, a power-operated switch, or a circuit breaker that’s also capable of being operated manually [230.76].
(B) Disconnect Identification. Each service disconnecting means must be permanently marked to identify it as part of the service disconnecting means.
(C) Suitable for Use. Each service disconnect must be suitable for the prevailing conditions.
Q7. When does the Code require ground-fault protection of equipment on service disconnects?
A7. Ground-fault protection of equipment is required for 277/480V service disconnects rated 1,000A or more. The rating of the service disconnect is based on the rating of the largest fuse that can be installed or the circuit breaker’s highest continuous current trip setting [230.95].
Q8. What is the Code definition of a “Tap Conductor”?
A8. Tap Conductors. A conductor, other than a service conductor, that has overcurrent protection rated more than the ampacity of a conductor. See 240.21(A) and 240.21(B) for details [240.2].
|
