By Frank G. Ross  

Over 300 years ago, on 17 January 1706, Benjamin Franklin was born in Boston.  He had little formal education, but his life became the model rags to riches story.  A self-made man, Franklin loved reading and expanding his knowledge through discussion and scientific inquiry.

The best known of all Franklin’s scientific accomplishments is his lightning rod.  In the 18^th century many beliefs about nature were based on superstition and folklore.  Electricity was some mysterious force while lightning was evidence of the wrath of God.  Franklin’s studies challenged these ideas.  He conducted many experiments to determine the nature of electricity.  Much of what he discovered is still with us today including many terms he coined such as charge, discharge, conductor, battery and electric shock.

Using his understanding of electricity he correctly inferred the nature of lightning in 1750. His famous kite and key experiment in 1752 confirmed that lightning is a form of electricity and can be directed to the earth through conductive materials preventing damage to buildings.  Passive lightning protection systems are referred to as “Franklin” systems to this day.  Fortunately, Franklin had such a system installed at his own home since it was subsequently struck by lightning and saved by his invention.

Living in this electrical age it is difficult for us to fully appreciate how important lightning rods were to the 18th century. The discovery that thunderclouds contain electricity and that lightning is an electrical discharge greatly changed the way people perceived this aspect of the natural world.  The invention of conducting rods to protect buildings from damage due to lightning was a clear example of how curiosity-driven research can lead to significant practical benefits.  The principles of “grounding” and the subsequent developments in electrical safety all date back to Franklin’s research.

A century and a half after Franklin’s discovery the same technology was applied in developing electrical distribution systems.  Transformers, which were especially vulnerable to the enormously high voltages of lightning, were grounded to help protect them.

Then as now, the primary function of the grounding system is safety for the property and its inhabitants.  In homes, it provides an alternative path around the electrical system in the event of a lightning strike, line surge or unintentional contact with a higher voltage. 

The first electrical codes arose in the 1880s.  However it wasn’t until 1928 that the familiar three prong plug was invented by Philip F. Labore, an engineering student.  As the story goes his landlady had a cat that would frequently knock a portable fan off its table.  When the landlady plugged the fan back in she would get a shock.  Philip thought that by adding the third prong to the plug that the shock would be directed back into the plug instead of his landlady.  As it turned out he was right.  As the need for increased safety became apparent grounded three prong systems were made mandatory.

Knob and Tube (K&T) wiring is the oldest standardized wiring method found in American homes.  This system uses ceramic knobs and tubes to carry the wring. It has proven to be reliable and safe when left in its original state because safety was inherent in its design.  With this method, the wires were run in uninsulated floor and wall spaces which protected them from damage and provided air circulation.  The knobs of K&T ensure one inch clearance to wood framing and tubes isolate the current-carrying wires from nearby wood members.  Unfortunately, when modifications are made by unqualified persons, the inherent safety of K&T may be diminished.

The current accepted method for protecting home electrical systems is with breakers in a panel.  They operate by “tripping” to the ‘off’ position when the circuit is overloaded.  Prior to breakers, a fuse panel was commonly used and may still be found in many homes.  Fuses, when sized properly and installed correctly, provide excellent protection.  Unfortunately, they are often sized incorrectly, allowing the wiring to be overloaded.  I have also seen shunted fuses (a penny behind the fuse) which are obviously very unsafe.  Older ceramic fuse panels, and panels with cartridge fuses, also pose a risk of electric shock since the components are exposed.  Lengths of copper tubing replacing the cartridge fuses such as those I saw in one home I inspected increase the risk by eliminating the intended protection of the entire system. 

Benjamin Franklin considered the lightning rod one of his most important accomplishments.  Considering the longevity of the idea, I would have to agree.

Frank Ross is a Certified Utah Home Inspector for Pillar to Post Professional Home Inspection and a full member of the National Association of Certified Home Inspectors and a member in good standing with the Utah Better Business Bureau.  Readers may contact Mr. Ross at (435) 867-6400 or frank.ross@pillartopost.com