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Taking a New Look At Old Residential Wiring

Safety and economic concerns lead the way for most electrical jobs on older buildings.

Existing wiring and materials in older structures need to be evaluated and replaced, as necessary.

This main breaker is fed by aluminum conductors, which need corrosion inhibitor and periodic retorquing. The output conductors on the right were done in copper, so corrosion is not an issue unless they were not tightened sufficiently or there was water in the box.

The equipment grounding system, including ground electrode conductor, must be bonded to any metallic water pipe within a building.

Electrical workers see many old residential buildings and are asked to evaluate the wiring in these aging structures. Such inspections are performed at varying levels of intensity.

Safety is the primary concern but efficiency and economy are also important. The National Electrical Code addresses hazards to life or property but not efficiency. It is best to begin with the Code and if a wiring installation is found to be compliant, only then is it appropriate to look at efficiency and economy.
NEC is revised every three years and each revision incorporates numerous changes. It is not expected that every building be immediately brought up to code. In order to be in compliance, an electrical installation must be in compliance at the time of the installation. Nevertheless, it is common to do certain types of optional upgrades.

For instance, if a house is being sold and subject to an inspection, the lending organization will want to see GFCIs installed in all currently required locations. GFCI and arc fault protection are great safety features and can be installed without running new branch circuits so these upgrades are highly appropriate.

Getting started

To evaluate a residential electrical installation, it is necessary to ascertain the scope of the inquiry. You have to look at the history of the electrical installation, the purpose of the inspection and the wishes of the owner, lending organization or insurance company.

If it is a routine sale, to check the status of the structure or a situation with no history of water inundation or fire, you will probably be asked to just look it over to see if it is safe. At the other extreme, if there has been prolonged flooding or other issues with the building, the interior finish probably will be removed in which case a total rewiring is in order.

A fundamental NEC requirement is that all wiring terminations be accessible. A junction box concealed behind building finish (a so-called "blind box") is not allowed. Therefore, it is possible to inspect all splices and terminations without tearing out finish walls or ceilings.

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