Howdy y’all,

Who is the smartest dude you’ve never heard of?  Let me give you a hint…  He had a sweet mustache and his name is the same one being used by an electric car company.  Any idea?  You got it – Nikola Tesla!  Tesla was one of the smartest dudes ever.  He was the one responsible for figuring out a way to incorporate alternating current into our electrical supply system.  In doing so, he not only put Thomas Edison and his direct current out of business, but he was able to change the way electricity was distributed to the masses.  If not for Nikola Tesla, we would all be living in very different times.

As a home inspector, I have inspected so many different electrical panel boxes over the years.  I have come up with a list of five problems that I see time and time again during my inspections.  I want to go through each of these issues, explain why they’re problems, and address why they need to be corrected by a licensed electrician.


Problem 1 – Openings in the Panel Box

Open knockouts and missing strain relief clamps are two of the biggest deficiencies I find when inspecting panel boxes.  All panel boxes are designed with perforated “knock outs” that are used as entry and exit points for the electrical wires and access points for the breakers or fuses.  If the perforated plates are “knocked out” and no breakers are installed in the corresponding location within the box, a permanent opening remains in the front cover.  This allows access to the interior of the panel, which can be dangerous.  Openings like this need to be corrected by an approved method, and unlike every other repair on earth, Duct Tape is not considered acceptable.

Strain Relief Clamps are clamps that electrical wires run through when entering and exiting a panel box.  These strain relief clamps serve several purposes.  First, they fill any gaps between the wiring and the panel openings of the box.  Secondly, they act to protect the wiring from damage against the sharp metal edges of the panel openings by holding the wires securely in place.

Problem 2 – “Double Taps”

One wire per hole!  Double taps are some of the most common deficiencies found in panel boxes and luckily they are one of the easiest to correct.  “Double taps” are when multiple conductors (hot or neutral wires) are inserted into a single opening, on either a breaker or a buss bar THAT WAS NOT DESIGNED FOR MULTIPLE WIRES.  Some breakers and buss bars are designed to accept multiple wires so “double taps” are totally acceptable in these situations.

The only two breakers that I’m aware of, that allow for “double taps” are Cutler Hammer and Square D.  There are two major problems with double taps.  First, double taps generally indicate that there is no more room left in a panel box and the double tap has been added to squeeze more amperage out of a particular circuit. In this situation an upgrade to a larger panel or a new sub-panel is needed.

The second reason why double taps are dangerous is if a breaker or bar isn’t designed to hold multiple conductors, there is a greater chance of the conductors coming loose.  Loose wires can cause arcing and overheating, both of which are dangerous conditions in any electrical system

Problem 3 – Over-fusing 

Electrical wires are designed to carry certain amounts of electricity.  The larger the wire, the more current it can carry.  If a wire gets too much current flowing through it, it can overheat and cause a fire.  Breakers and fuses limit the amount of current an electrical wire has to handle.  When the amount of current is greater than what an electrical wire can handle, the breaker or fuse is designed to cut the power to that wire, preventing it from overheating.  In order for this to happen, the amperage size of the breakers and fuses must match with appropriately sized wires.  When a breaker or fuse is rated for higher amperage than what a wire is designed to handle, the circuit is considered over-fused.

The best analogy I can think of to explain the relationship between current and wire size is fishing and fishing line.  If you’re fishing for goldfish, a small fishing line will do just fine.  Similarly, if a circuit only has a few lights drawing power through it, a small 14AWG electrical wire will work just fine.  14 AWG is the smallest gauge wire allowed in residential construction.

If however, you decide to give up on the goldfish and start fishing for a much larger fish, like a shark, the small goldfish line won’t be large enough to handle that bigger fish.  Sharks need a much larger fishing line to prevent it from snapping.  It’s the same with electricity.  If we’re running something that draws more amperage, we need a larger wire to prevent it from overheating.  We need to make sure that the amperage of all breakers and fuses are properly sized for the corresponding wire.  If they’re too large for the wire then it’s considered “over-fused”.  Over-fusing is a VERY serious problem that needs to be corrected to prevent the overheating of wires that can potentially burn a house down or even worse, kill a family.  It’s scary how often I see over-fused circuits, but it is a serious problem that needs to be corrected by a qualified professional.  

Problem 4 – Water Intrusion and Metallic Corrosion

Obviously water and electricity make for extremely dangerous conditions.  Any signs of moisture in a panel box is a serious red flag.  Water can enter a panel box many different ways.  Service entry’s that lack a proper drip leg is one of the more common ways I see water entering a panel box.  Anytime a panel box is exposed to moisture, either as liquid water or water vapor, corrosion is likely to occur. Corrosion in a panel box requires repairs by a qualified electrician.  

Problem 5 – Zinsco, Federal Pacific and S Type Fuses

I’ve seen hundreds of different panel boxes over the years, but there are two panel boxes that I recommend be evaluated by a licensed electrician EVERY time I see them.  These are Zinsco and Federal Pacific “Stab-Lok” panels.  These two panels are so dangerous I will not even remove their covers during an inspection.  In the Zinsco panels, the main buss bar can energize the panel cover when removed.  You can identify these Zinsco panels by the color of their breaker handles, which are red, blue, pale green and off white.  The problem with Federal Pacific “Stab-Lok” panels is that the breakers can become loose and even pull out from the breaker busses resulting in a dangerous electrical hazard.  Both Zinsco and Federal Pacific “Stab-Lok” panels are dangerous and need to be evaluated and replaced by a qualified and licensed electrician.

S Type fuses are safety fuses that replaced T Type Edison-Base fuses.  S Type fuses have adapters designed to fit Edison-Base fuse holders.  Once these adapters are installed they cannot be removed.  The problem I often encounter is when the base of the metal adapters extend beyond the insulating housing.  This makes it almost impossible to remove the metal door of the panel box without touching the metal fuse adapter.  For this reason, I always check to see how far each fuse extends from the box before I remove the cover.  If I see one that has the adapter, I refer it to a qualified electrician because it’s too dangerous for me to inspect

While I often encounter many other issues when inspecting main panels and sub-panels during my home inspections, these are just five of the most common. Problems that can arise from faulty wiring are some of the most dangerous and devastating to you and your family. If you suspect that your home has any of these deficiencies that I’ve talked about, I strongly suggest you hire a qualified electrical contractor.  He can do a thorough evaluation of your entire electrical system and make sure that it safe and operable for you and your family for years to come.

Be Happy and Be Kind,

T.J. Thorne