Code Guide

Aug. 1, 2001
Answers to your most pressing National Electrical Code questions

Emergency lighting

Q. Recently an electrical inspector questioned the circuiting of the exit signs in a wastewater treatment facility. It has been our practice to provide a dedicated circuit from the local lighting panel to feed the exit signs. Each exit sign is equipped with an integral battery that provides power for emergency illumination upon failure of the normal source.

The inspector has indicated that the exit signs must be connected to the circuit serving the normal lighting in the area as is required for unit equipment.

My question is as follows: Does an exit sign with integral battery backup fall under the classification of “unit equipment” as defined under Article 700-12(e)?

A. Section 700-1 provides the information necessary to determine if Article 700 applies to your system. Article 700 will apply only if your local government legally requires a system classified as an emergency system.

My answer is based on the assumption that your installation is within the scope of Section 700-1. I have used the 1999 edition of the NEC.

Section 700-16 covers emergency illumination. This section requires egress and exit lighting to be part of a required emergency system. Since the exit signs are part of the emergency system, power must be supplied in accordance with Section 700-12.

You have indicated that the exit signs have integral-battery backup. Section 700-12(e) covers unit equipment as a source of emergency power. There are four conditions listed in this section. The exit signs must meet all four to be classed as unit equipment. I suspect your signs meet the criteria listed and are unit equipment.

Section 700-12(e) requires unit equipment to be connected to the branch circuit serving the normal lighting in the area. The unit equipment must also be connected ahead of any local switches. Due to the nature of unit equipment it is possible to insure the equipment will be operational even in the event of the failure of an individual branch circuit. With other power sources such an arrangement would not be practical.

If the backup system is a required emergency system, your inspector is correct. The unit equipment should be connected to the branch circuit that serves the area, ahead of any local switches. If an emergency system is not required by your local government, your signs may be classed as Legally Required (Article 701) or Optional Standby (Article 702). If you have a system covered by Section 701-1 as Legally Required, Section 701-11(f) will apply. This Section is the same as Section 700-12(e) so your inspector is also correct. If you are outside the scope of Section 700-1 or 701-1, your exit signs will then be within the scope of Section 702-1 as an Optional Standby System. Article 702 has no specific requirements for unit equipment. If you fit into Article 702, your installation should be acceptable and an individual branch circuit can be used.

In general, we tend to call anything connected to backup power “emergency.” In fact many systems of this type are not emergency systems. For example, backup power for computer systems is not normally required by law. Loss of computer power may be an emergency to the computer user but does not present a hazard to life. We tend to call such systems “emergency systems” when they are, in fact, Article 702 Optional Standby Systems.

In your case I suspect the emergency lighting is required and you are within the scope of Article 700.
Dann Strube

Pre-wiring lighting outlets

Q. The inspectors in my area feel that if you pre-wire a lighting outlet in a bedroom or habitable room in lieu of a switched receptacle, you have to put a keyless fixture and bulb for a final inspection. Article 210-70 states that you have to have either a switched controlled lighting outlet or receptacle. The definition of a lighting outlet is an outlet “intended” for the connection of a fixture. I feel that a finished blank cover meets the Code. They say a homeowner may hang his own fixture if I put a blank up.

Other inspectors have their own interpretation of the Code. I say they should not sell these basic wiring books at Home Depot and Lowe's. What is your interpretation of this section? Is a blank plate acceptable and meet the Code requirement?

A. You are correct that according to the definition of a lighting outlet, the outlet is complete without a fixture being connected. Since Section 210-70 only requires lighting outlets and not actual fixtures, the literal requirement of the NEC can be met without a fixture or lamp actually being installed. This is really not much different from using a switched receptacle to meet the lighting outlet requirement.

I should say that in my own experience, most inspectors insist on fixtures or lampholders of some sort, even temporary ones, being installed for a final inspection. I have never found that requirement to be unreasonable. In a case where a room has more than one lighting outlet, with separate switches, only one fixture needs to be installed to have “illumination.” Generally, the NEC does not require illumination except for equipment spaces, but building codes typically do require illumination, and rooms without windows would have to have fixtures or lampholders installed to meet this basic requirement.

Technically, the NEC does not require a lamp or fixture to be installed, but many AHJs interpret the requirement for a lighting outlet to include the intent for illumination as well. Arguing that no fixture is required is a bit like arguing that the lighting outlets don't have to be connected to a source of supply, since the definition of a lighting outlet doesn't mention a connection to a branch circuit. (This argument falls apart when the definition of an outlet is considered, however.)
Noel Williams

Knob-and-tube wiring

Q. When attaching wire to existing concealed knob-and-tube wiring, how should the splice be done? Case to resolve: In the ceiling of a kitchen during remodeling there is concealed knob-and tube wiring going to a porch light. We need to reconnect the porch light to a new switch and power source. How do we reattach the wires exiting the kitchen?

The Code in 324-12 doesn't say that the splice has to be in a box. Do we just use a Western Union splice and solder and tape a NM type wire to it? Is an “approved splicing device” a wire nut?

I think that the wiring techniques to be used are the same as was approved when knob-and-tube was Code approved, but I don't know those regulations since I wasn't around then.

A. Section 300-15 exempts knob-and-tube wiring from the usual requirement for boxes at splices. Section 324-12 requires the knob- and-tube splice to be soldered “unless approved splicing devices are used.”

I would consider listed pressure connectors such as “wire nuts” to be approved, but the AHJ may have to judge this on a case-by-case basis. Generally, with existing knob-and-tube wiring, there is no spare length of wire to use with such pressure connectors.

I usually recommend splicing to knob-and-tube wiring by baring the existing wire, wrapping a new wire around the bared conductor and soldering and taping, in the same manner as the existing splices.

Some inspectors permit the use of NM cable for this purpose so the NM sheath provides the equivalent of the flexible nonmetallic tubing that is required by Section 324-6. However, a strict reading would not permit this as the NM splice requires a box. Providing a flexible nonmetallic tube for the individual wires from the splices to a nearby box complies with the Code.

This tubing was originally the woven “loom” that can be seen in old installations, but many other forms of tubing are available now.
Noel Williams

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