Electrical Reliability: Remove Those Panel Covers!

A common mistake made by a number of thermography programs is skipping infrared inspections of panelboards (power and lighting panels) or failing to properly access the equipment by removing the front panel and the dead front.  Power and lighting panels now support critical equipment such as personal computers, PLCs, networks, communications, data backup and safety/warning systems.  Yet many facilities still seem to believe that these panels are non-essential equipment and do not need to be inspected with infrared.

While not covering up the actual face of the breaker, the dead front does hide from line of sight the line and load connections.  A warm breaker can mean a heavy load or a line, load or internal high-resistance connection.  And without removing the covers there is no way to know.  And a high-resistance connection with a light load may not even stand out as a possible problem without you actually inspecting the connection. With thermography it is crucial to remember that we see only surface temperatures.  And it is important to remember internal temperatures are usually significantly hotter than the surfaces we see with an infrared camera.

Once during an inspection of a 225-amp service panelboard, a technician of ours observed what appeared to be several heavily loaded breakers with the covers still in place.  This pre-inspection safety scan of the device with the cover in place revealed nothing that seemed alarming except for one 20-amp breaker that had an apparent surface temperature of approximately 130°F (54°C), slightly warmer than what one might expect to see with a normal or even heavy load circuit.

Upon removing the covers, the thermographer encountered what was actually a high-resistance connection on that breaker…measuring nearly 400°F (204°C) on the load side connection! The catastrophic failure of this component would probably have tripped the main and thus all power to the panel’s 42 circuits.

It never ceases to amaze clients of ours when they see large thermal gradients like this. What else can be hidden by those panels? Mains, neutrals, load balances, broken wires, burnt or discolored components, and of course the bus and load connections of the breakers themselves.

If you look at the visual image closely, you will see the discoloration that had occurred on the faulty connection due to overheating.  Good thermographers will not only know how to Think Thermally®, but must always remember to “Think Visually” as well.

In the case of this anomaly, merely tightening the connection is not enough. The breaker should also be replaced, and the conductor will need to be cut back or replaced and properly torqued.  Finally, reassessment of the repair and re-qualification of the asset will validate the success of the inspection and ultimately lead to a safer and more reliable environment.