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A DIY upgrade QI have a question that concerns a knob-and-tube style installation in a residential home. Before my question, I'll provide some details of the house. This house is owned by my retired mother, and was owned by her parents before her. The house was built in the 1890s, without electrical wiring. In the early 1930s, knob-and-tube wiring was installed. During the next several decades, additions

A DIY upgrade

I have a question that concerns a knob-and-tube style installation in a residential home. Before my question, I'll provide some details of the house.

This house is owned by my retired mother, and was owned by her parents before her. The house was built in the 1890s, without electrical wiring. In the early 1930s, knob-and-tube wiring was installed. During the next several decades, additions were made to both the house and to the wiring.

I can't afford to hire a professional electrician, so I'd like to do the work myself. I have several years of wiring experience as an electrical maintenance technician at manufacturing plants in my area. I have worked at the apprentice level under a licensed journeyman. I have 20 years electronic/electrical/electromechanical experience, but have an associate's degree in electronics, not electrical technology. I am proficient with reading technical literature, with a high level of comprehension.

I want to first replace the existing premise wiring from the service entrance throughout the house. I am planning on using a combination of standard metallic conduit and PVC conduit. I plan to install spooled wire, including grounding, to outlet boxes. The second part of the plan is to increase the service level of the wiring. I want to install the outlets and the light outlets in accordance with the Code. More importantly, it must be a safe and sensible approach.

Am I able to perform the wiring from a NE Code point of view, although I do not possess a license? Since the first phase is repair of existing wiring, do the current codes apply? On the second phase of adding or increasing the service level, is this bound by the current codes? People have told me that because this is a repair job, regardless of how much is repaired, newer codes are not relevant. Since this is a large house of “nonstandard” construction, some areas may be very difficult to work with without causing significant damage to the walls that had been drywalled and are in well-maintained shape.

The NEC does not cover licensing issues. A new Article 80 in the 2002 NEC will cover some aspects of licensing and other Code enforcement and administration concerns, but the article is optional and has no effect until adopted by a legal jurisdiction.

The question of who can do the work is a local or state enforcement or licensing issue. Some areas have no such licensing and others have licensing rules that are very well defined and enforced. Most areas allow homeowners and some other property owners to do electrical work on their own property and take out any required permits on such property, but they are often also concerned with what happens to the new occupants of the house after you are finished with it and decide to sell it.

The question of how much work must be done is also a local issue. Some will require a house to be brought up to current code if some percentage of the house is being updated. Some jurisdictions will allow for variances for certain things if the nature of the construction makes rewiring difficult. However, many will require surface wiring for things such as wall switches and receptacles if the interior of the walls is inaccessible for wiring. Jurisdictions have varying interpretations of what is repair or maintenance and what is rewiring, but I doubt that many jurisdictions will take the position that “newer codes are not relevant.” You should check with your local jurisdiction. Whoever issues permits in your area may also be able to answer your questions on licensing requirements. You will probably have to get a permit to get the utility to come out and upgrade their part of a new service.
Noel Williams

Metric trade sizes

I just read your article on the 10 most important new Code changes (August cover story) and I have a comment about the format and editorial section. In the reference to using metric equivalents for listing conduit sizes, you state that ½, ¾ and 1 in. compare to 16, 21 and 27 mm as comparable units. I lived in England during the 1970s when they were converting to metric units for the entire society, and they kept their conversions as simple as possible. The conversion units they had for ½-, ¾- and 1-in. conduits were 15, 20 and 25 mm. By staying very close to the metric idea of multiples of 10, the average electrician was able to relate to the change more comfortably.

The problem with trade sizes is that they are not actual measurements, and neither are the metric designators. The metric designators chosen for the NEC are the actual dimensions of the interior diameter of a rigid metal conduit in millimeters rounded to the nearest whole number. This is not clear unless you can look at Table 4 for rigid metal conduit as it appears in the 2002 NEC or the preprinted versions.
Noel Williams

2002 motor changes

I have several questions regarding your article titled “The Top 10 Changes in the 2002 National Electrical Code” in the August issue of CEE News. The questions are in reference to the paragraph titled “New Safety Requirements for People Servicing Equipment.”

  1. Is it now a mandatory requirement that all motors have disconnects in sight of the motor?

  2. If only trained individuals are servicing motors and there are documented lockout/tagout procedures, will the lockable disconnect at the Motor Control Center (MCC) suffice for electrical isolation without the use of a local disconnect ?

The new general rule in 430.102 is that all motors must have a disconnect in sight of the motor. The exception to this new rule applies where there is an individual, permanently installed locking means on a disconnect that is in sight of the controller, such as a disconnect that is part of a motor control center combination starter and disconnect. However, under the new rule, in order to use this exception you must also comply with one of the conditions listed in the exception:

  1. Locating a disconnect within sight of the motor is impracticable or would introduce additional hazards, or

  2. The location is in an industrial installation and you have written safety procedures and only qualified persons will work on the equipment.

If you have a lock-out/tag-out program that complies with OSHA (or NFPA 70E) and you are in an industrial environment, the same rules apply as before. Qualified persons are part of the OSHA.70E requirements.

A new Fine-Print Note explains what is meant by additional hazards.

“Impracticable” is subject to the interpretation of the AHJ(s).
Noel Williams

Motor disconnect switches

Please answer the following questions about an expansion project in California:

  1. Is it necessary to install a motor disconnect switch close to each LV motor? The MCCs in our electrical rooms have combination starters (circuit breaker and contactors).

  2. Is it allowable to install a motor-disconnect switch for DC motors? How about for AC motors with VFD?

I believe that most electrical work in California is currently covered by the 1996 NEC. The answers to your questions would be the same under the 1999 NEC, but could be different under the 2002 NEC.

Section 430-102(b), Exception, permits a lockable disconnect at a motor controller to be used in lieu of a local disconnect at a motor. Since the circuit breakers in MCCs are usually capable of being individually locked in the off position, another disconnect at the motor is not required under the 1996 or 1999 NEC.

The NEC does not distinguish between AC motors, DC motors and AC motors with VFDs with regard to the location of disconnecting means. A VFD is the controller for the motor it drives. A lockable disconnect at a DC motor controller or a VFD satisfies the requirements for disconnecting means for both the motor and controller. Another disconnect within sight of the motor is not required by the NEC, but may be a good idea in some cases.
Noel Williams

200A transfer switch

I am looking for some preliminary info on the installation of a Cutler-Hammer 200A transfer switch. I don't know the specific model number, but it is a non-fused, knife-blade-type mechanical device that has three positions: on-off-on. The three positions stipulate a neutral or non-current carrying position. My question is this: Is this switch, which will interrupt the normal current flow from the power company's load side of the meter, take the place of the load center panel existing as the main/principal? Will I treat the existing load center as a subpanel after installation? The transfer switch has a definite bonding terminal along with the neutral terminal feed thru connection. I would appreciate your input but will also ask the local Code authority.

Because your transfer switch is manually operated, I will assume that you are supplying an optional standby system as covered by Article 702. Emergency system and legally required standby systems are covered by Articles 700 and 701 respectively, and both require automatic transfer switches.

Section 230-82 lists a very limited number of things that are permitted to be connected ahead of the service disconnect. If the transfer switch is marked as suitable for use as service equipment as required by Section 230-66, then it could take the place of your current main disconnect. (The NEC says “marked,” but many inspectors take this to mean “listed,” and at any rate it must be “approved.”) However, the service overcurrent device is required by Section 230-91 to be integral to or immediately adjacent to the service disconnect. Since your transfer switch is non-fused, the main overcurrent device, whether it is a new device or the existing main service overcurrent device, would have to be located immediately adjacent to the transfer switch.

Although Section 230-82 (4) does allow taps for standby systems to be located ahead of the service disconnect, it still requires proper protection of the service conductors. A proposal to allow the connection of transfer switches ahead of the service disconnect was made but not accepted for the 2002 NEC. The main concern was that such transfer switches might not be properly rated for the use and the fault current.

In short, the transfer switch can be located between the meter and the main service overcurrent device only if the switch is rated as service equipment, has adequate short circuit ratings and is located immediately next to the service overcurrent device. Unless there's an overcurrent device ahead of the main breaker in your panel, the panel must remain as the service overcurrent device. If the main panel is remote from the meter and transfer switch location, another overcurrent device would have to be added adjacent to the transfer switch to serve as the service overcurrent device. Some inspectors may allow the transfer switch to be treated as the “tap” device allowed by 230-82(4), but the service conductors still require overcurrent protection, and this interpretation is not the accepted practice in all jurisdictions. My own interpretation and practice has been to install the main service disconnect and overcurrent device ahead of the transfer switch.
Noel Williams

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