NEC Questions Based on the 2008 NEC Code

March Part 1

 

Here is the follow up to yesterday’s newsletter. This includes all of the answers to the questions sent yesterday so you can see how you did.

 

By Mike Holt, for EC&M Magazine

 

Q1. Can a 2-pole snap switch be used to switch a 277V and 120V circuit?

     A1.  No, because there is no general-use snap switch listed for this purpose as required by 404.8(C).

 

Q2. Are you required to pre-twist conductors before installing a twist on wire connector?

A2. Maybe. All electrical products are required to be installed in accordance with equipment instructions as per 110.3(B), and according to the UL White book (product category ZMVV), “some connectors may specify that conductors are to be pre-twisted before assembly onto the connector.”

 

Q3. Does the NEC require a connection of a parking lot lighting pole to a ground rod?

A3. No, but metal poles used for the support of luminaires are required to be connected to an equipment grounding conductor of a type recognized in 250.118 [410.30(B)(5)].

 

Q4. Can the service disconnecting means for a building be located inside the building?

A4. The service disconnecting means must be placed at a readily accessible location either outside the building or structure, or inside nearest the point of service conductor entry [230.70(A)(1)]. 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.

 

Q5. What are the rules for overhead service conductors above a swimming pool?
A5. Permanently installed pools, storable pools, outdoor spas, outdoor hot tubs, fountains, diving structures, observation stands, towers, or platforms must not be placed within the clearances contained in Table 680.8. This rule doesn’t prohibit utility-owned overhead service-drop conductors from being installed over a permanently installed pool, storable pool, outdoor spa, outdoor hot tub, or fountain [90.2(B)(5)]. It does prohibit a permanently installed pool, storable pool, outdoor spa, outdoor hot tub, or fountain from being installed under an existing service drop that isn’t at least 22 1/2 ft above the water.

 

Q6. We have motors that are interlocked, preventing them from being on at the same time. Do we still have to add them up for our service and feeder calculations?

A6. No. Where the circuitry is interlocked to prevent operation of motors at the same time, only those motors that operate simultaneously (and result in the largest current) need to be counted [430.24 Ex No. 3].

 

Q7. I was told that a back-fed breaker needs to be bolted into the panel. Is this correct?

A7. Yes. Plug-in circuit breakers that are back-fed from field installed conductors must be secured in place by an additional fastener that requires other than a pull to release the breaker from the panelboard [408.36(D)].

 

Q8. Am I required to identify the raceways and enclosures in an emergency system?

A8. Only the boxes and enclosures (including transfer switches, generators, and power panels) for emergency circuits must be permanently marked as components of an emergency system [700.9(A)]. The Code doesn’t require raceways to be identified as a component of an emergency system..

 

Q9. Where must I install the disconnecting means for a remote building?

A9. The disconnecting means for a remote building must be installed at a readily accessible location at the building, either outside or inside nearest the point of entrance of the conductors [225.32].