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Home Inspection Checklist and Electrical Safety

Electrical System – Early Detection of Heat Build-up

In terms of Home Maintenance, electrical safety is one area that is paramount.  The following discussion should be an item on your ‘Home Inspection Checklist’ to be addressed at least every six months.  What follows is a simple and effective means for early detection of a potential electrical problem that is not uncommon.

Heat build-up in your house or home wiring (we will call it the electrical distribution system) may be indicative of a couple of things that warrant scrutiny in the name of electrical safety.  If you detect heat at your electrical panel or meter enclosure, it should be questioned.

First, let’s define what I mean by heat -or, heat build-up.  If your meter enclosure is sitting in the hot sun it will naturally be hot to touch.  If that’s the case, you should check it in the morning or later at night when the sun is not a factor.  Place the back of your hand against the meter enclosure (meter can).  If the enclosure is hot to touch, it needs to be checked.

Loose Connections

Loose connections inside your electrical equipment (meter enclosure or electrical panel) will cause, over time, a build-up of heat -slight at first, but becoming warmer going forward.  It is not uncommon for copper and aluminum conductors to become slightly loose due to

Heat Damaged Loose Connection
Heat Damaged (Loose) Connection

corrosion between dissimilar metals (galvanic corrosion) in the case of aluminum wiring, or the physical properties of copper conductors under compression.  When a loose connection is under a significant electrical load, it may heat up, ever so slightly, at first.  The thermal cycling (heating up and subsequent cooling down) will cause the connection (again, over time) to become more loose.  Put another way, thermal expansion and contraction cause connections to loosen.  The thermal expansion occurs as electrical loads cycle between high and low demand.  There is a point, if a connection becomes loose enough, that arching occurs, causing small carbon deposits to build-up and pitting of the metal -increasing the resistance of the connection.  As time advances, you can see how the problem gets progressively worse.  The more the connection deteriorates, the less the connection is able to conduct current due to the increased resistance -which causes heat.

circuit breaker heat damage from loose connection
Circuit Breaker Heat Damage From Loose Connection

The resulting build-up of heat at the connection, increased arching, carbon deposits, pitting, and increased heating is the snowball rolling down the hill effect.  Hence, the recommendation to place your hand on a meter enclosure and the back of your fingers against the Main breaker (especially) and the branch breakers, as well.

I was involved with the replacement of a meter enclosure that came very close to burning down the structure to which it was attached.  The root cause was overheated bolted mechanical power connections inside the meter enclosure that went unnoticed until visual signs were manifested.  The connection to one phase was lost (half the panel was dead) and the employees who worked there wondered why the lights wouldn’t come on.  The electrical repairs to that building (a former house being used for a seasonal office) consisted of an entire new electrical service including the lateral feeder from the street, service drop, meter equipment, and panel inside the building.  In dismantling the existing electrical equipment it was apparent the the wooden structure had suffered heat damage and was close to igniting.

Since that day, I am in the habit of touching the meter enclosure on my house on a regular basis -usually when I happen to be walking by.  The long-term reliability of electrical power connections -whether compression or bolted (mechanical) type, cannot be taken for granted.

It should be noted that warm to touch does not necessarily indicate a problem.  Very warm or hot to the touch should be scrutinized by a qualified licensed journeyman electrician who can first measure the load on the system, and investigate further as necessary.

Infrared Thermography (thermal imaging) is useful in detecting ‘hot spots’ before they become a problem.

Infrared Detection of Heat Build Up from Loose Connection
Infrared Detection: Bright yellow is indication of higher heat from Loose Connection

The intent here is not to alarm anyone. The conditions described above took a long time to get that bad.  My purpose is to raise awareness of possible problems that can be easily and effectively monitored and detected early -before the situation becomes a life-safety issue.

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Additional Resources for Information:

Should You Be Doing Electrical Preventive Maintenance?

Electrical Connections for Power Circuits

Performance of Utility Power Connectors

Corrosion and Current Testing of Copper and Aluminum Power Connectors

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