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Home > Home Wiring USA > Definitions and Calculations > Existing Panel or Wiring (NEC 2002)

The Definition of Existing Panel or Wiring (NEC 2002)

By Warren Goodrich
The Definition of Existing Panel or Wiring (NEC 2002)

If you are planning to upgrade, or add on to, the existing panel or sub-panel of an existing dwelling, the inspector's office may, upon inspection of the project, check the following (life threatening) conditions of the existing structure. They commonly will check the entire structure on a spot check basis for unsafe conditions.

Upgrading a Service or Adding to a Service in an Existing Structure

The following are examples of corrections that may be required for existing wiring conditions; open junctions (may or may not including knob and tube style wiring, properly installed), bare wires or damaged conductors (they can bend the existing wiring on a spot check basis looking for over-worked or over-heated conductors), (if, for example, these conductors are bent between the fingers, and the insulation crumbles in your hand then they have been damaged) making them unsafe. Broken devices or fixtures in unsafe condition.

Improper wiring installations created in the past which would be unsafe such as conductors not approved in the manner they are being used (wiring designed to be in conduit and is not, triplex designed to be used as outside wiring and being used as building wiring, over-current devices installed that are too heavy to protect the conductors they are to protect. (Example: 30 amp fuses on 15 amp wire) etc. Wiring that is too small or improper such as 20 amp wiring to a dryer, range cables cut with smaller wire used to extend the range cable, etc.

If you are upgrading a service, and the existing sub-panels are being utilized as existing from the old main service, then the existing sub-panels are a part of the new installation, and can be checked for conditions of safety, and proper loading. If upon inspection they find a feeder to an existing sub-panel overloaded by its rating of the overcurrent protection device, or an unsafe conditions pertaining to the sub-panels, or its feeders exist, then the existing condition may be addressed for safety, and brought to current code standards. If the sub-panel is in safe and proper condition, and no new load is being added to the existing sub-panel then it may be allowed stay to as existing as long as it is in a safe, and proper condition, as it was originally designed.

Rewiring an existing dwelling

If you are partially rewiring an existing structure, the life threatening conditions, the same as mentioned above in the service upgrade section, can be checked as described above. If you do not change the integrity of the existing wiring, and it is still in a safe and proper condition, then commonly inspectors my consider that existing wiring as an often used terminology of forever it be in that condition, unless the existing wiring is changed or load is being added. You usually may change the devices as long as they are changed according to code requirements.

[Two prong receptacle, changed to tree prong receptacles are allowed if they are protected by a gfi control or other proper wiring is applied as per the nec requirements].

Any new installations in an existing home must meet the current code requirements. The principle of the above text is, if it is existing and in a safe condition then commonly inspectors rule that for ever it be considered as existing, and unchanged. If that wiring is ruled as unsafe, or changed or added to, then it is no longer existing, and must meet current code requirements. If you change the beginning of a system segment, the entire system segment may be ordered by the ahj to be brought up to the current code. [example a main service will change the conditions of the sub panels and therefore the change may involve it's sub service relatives, if the new change affects them, in the opinion of the ahj.] [ if a system is existing without grounding, and you do not change the integrity of the system [with grounding devices] then it is commonly allowed by the ahj to remain existing and without grounding.

If you have any situation that is questionable, please feel free to call your local code enforcement division to clarify your position before starting the project, they are there to help you not hurt you.

This document is based on the 2002 national electrical code and is designed to give you an option, as a self - help, that should pass minimum code requirements. While extensive research has been implemented in the preparation of this self - help document, the author and / or provider of this document assumes no responsibility for errors or omissions, nor is any liability assumed from the use of the information contained within this document by the author or provider.

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