Code Quandaries

Jan 1, 2004 12:00 PM, By Mike Holt, NEC Consultant

Q.

Can I install a reducing fitting at an explosionproof seal located just outside the boundary of a Class 1 Division I area?

A.

Yes, if it's a listed explosionproof reducer fitting. However, if the reducer is located after the seal, then the reducing fitting isn't required to be explosionproof listed [501.5(A)(4)] (Fig. 1).

Q. Is it permissible to wrap a stranded wire around the screw terminal of a receptacle?

A.

According to the UL White Book under the RTRT category, stranded wire is permitted to terminate to a screw terminal of a receptacle [110.3(B)].

Q.

Is it permissible to use a galvanized ground rod for a grounding electrode? If yes, must it be listed?

A.

You may use a galvanized ground of 8 feet in length and not less than 0.625 inches in diameter as an electrode. The rod isn't required to be listed [250.52(A)(5)(b)].

Q.

If I installed a listed breaker from one manufacturer in a listed panel from another manufacturer, does this void the panel listing?

A.

Depends on whom you ask. I'm sure equipment manufacturers only warranty their panelboards when used with their circuit breakers. However, UL certifies circuit breakers by independent manufacturers to be suitable for installation in different manufacturers' panelboards. This is an issue equipment manufacturers constantly battle, and it will be resolved by the AHJ [90.4 and 110.3(B)] or by a judge in the courtroom.

Q.

Our township requires a sprinkler system in electrical equipment rooms. The sprinkler system in our building is located 2 feet in front of and just above the main switchboard. Several sprinklers are located along this run, and no protection is provided to the switchboard in case of a leak or a sprinkler goes off. Is this a violation of the NEC?

A.

No. Section 110.26(F)(1)(c) permits sprinkler protection of electrical equipment as long as the piping isn't located above the switchboard.

Q.

I have a situation where our electrical engineer has designed something I believe may not be Code-compliant. He wants to supply three separate single-phase 480V transformers from a 3-phase breaker. The first transformer is connected to Line 1 and Line 2, the second to Line 2 and Line 3, and the third to Line 1 and Line 3. The overcurrent protection device for each of the transformers is sized in accordance with Table 450.3(B). Is it Code compliant to supply single-phase loads from a 3-phase breaker?

A.

Sure. A 3-phase breaker may supply three single-phase line-to-line loads, but no more than one conductor can be placed on the circuit breaker terminal, unless the terminal is identified for two conductors.

Q.

Can I plug a power-strip into another power-strip (daisy-chain)?

A.

No. According to the UL White Book (category XBYS), “Relocatable power taps are not intended to be series connected (daisy-chained) to other relocatable power taps or to extension cords.”

Q.

Can a 30kVA transformer be suspended above a suspended ceiling used for environmental air? If yes, does it need to be plenum-rated? The ceiling is accessible by removing any 2-foot by 4-foot ceiling tile, and the clearances around and above the transformer comply with code and manufacturer specifications.

A. Yes, as long as it's a dry-type transformer rated 600V, nominal, or less and doesn't exceed 50kVA [450.13(B)] (Fig. 2). If the transformer case is metal, it isn't required to be listed as having adequate fire-resistant or low-smoke-producing characteristics [300.22(C)].

Q.

Can a 277V circuit supply a wall-mounted compact fluorescent night light in a homeless shelter?

A.

Maybe, maybe not. According to 210.6(A) the maximum nominal voltage between conductors for luminaires in dwelling units and guest rooms of hotels, motels, and similar occupancies shall not exceed 120V. Because a room of a homeless shelter would be considered a “similar occupancy,” the maximum nominal circuit voltage for luminaires would be 120V. However, this only applies to the guest rooms of the homeless shelter, not the common area.

Q.

Can communications cable be installed within supply and return air ducts?

A.

Yes. Communications cables can be installed in ducts, plenums, and other spaces used for environmental air, as long as the cable is Type CMP [800.53(A)].

Correction: In the October 2003 Code Quandaries column, the answer to the following question included additional text that didn't apply. The question and answer should read as follows:

Q.

I think that a 120V outdoor receptacle for sump pump equipment in an industrial plant should be plugged into a GFCI receptacle for personnel safety. Is there an NEC article that addresses it directly or indirectly?

Also, are there any Code rules that require a receptacle for drinking fountains in commercial/industrial settings to be GFCI-protected?

A.

Sorry, but the NEC doesn't require GFCI protection for any of these applications.

Need some help with an installation? E-mail Mike at mike@mikeholt.com with a description of the situation and your question may show up in a future column.