“Subject to mechanical damage” is a phrase that gets used a lot in home inspection reports. While true of lots of things, like cars being able to run into furnaces and water heaters in the garage, it is especially common with electrical installations.
All wiring must be appropriately protected from damage and there are numerous clearance requirements to further protect wiring from damage. Whether it is NM (non-metallic-sheathed cable) wiring–commonly called “romex”–or single strand wiring sheathed in metal or plastic conduit, the conductors are protected for the use they are intended.
When not used as intended, additional protection may be required. For example NM wiring can be used in lots of places in the home and is generally protected by being installed in wall cavities or in attics where it isn’t really accessible. When it is used where it might get damaged it must be either given additional protected or is prohibited for use in those areas.
So now that we are all on the same page as far as the importance of the individual conductors being appropriately protected, we can discuss the installation in the following pictures.
This installation is clearly installed in a less than professional manner. It is single strand wiring run to the countertop receptacles of a kitchen island. As you can see the individual conductors are neither protected in cladding typical of NMC cable nor in metal conduit–flex or otherwise. This wiring is considered to be “subject to mechanical damage.”
While in the first picture, mechanical damage of the wiring “might” not happen, I think the second picture clearly shows that mechanical damage “will” happen and “is” happening.
Once again, it makes one wish that when wiring was wrong it would just not function. Unfortunately, electricity does not know the “rules.” But, it does continue to play by its own rules very well.
By Charles Buell, Real Estate Inspections in Seattle
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