very hot circuit panel

Found this yesterday .one of the lines feeding the breaker was at 475 degrees and the meter was spinning like a top. All the breakers were 65 degrees any clue why?

The wire on the right appears to be loose and not properly inserted causing high amp draw.

All I see on the left is excess antioxidant paste. Not really an issue.

On the right it appears to be a loose connection which can cause arcing and subsequent overheating of the terminal.

The lug on the right appears very loose. Look at the threads outside the lug. The angle on the left makes it hard to see.

No offense Roy, but that is a common misconception. A loose connection, such as in the case of the photo above, actually causes a higher resistance. As such, the total current draw of the circuit is lowered, increasing the likelihood the OCPD will NOT trip to clear the fault.

This is the key reason loose/poor/improper connections are a critical hazard and always require repair.

Thanks for the correction
Would not connection as this cause a higher draw ?
Hence,why the meter was spinning as such?

No. Anytime resistance in a circuit increases, current flow will decrease. Theoretically speaking, resistance and current flow in a circuit are said to be inversely proportional. Therefore, a loose or poor connection will create increased resistance and actually reduce the current flowing in the circuit.

I cant really speculate on the meter without knowing current draw, system configuration, etc. Many factors can or will effect the meter, especially under abnormal or adverse conditions.

Makes very good sense.

This theory is true, but if loose enough to arc, it will certainly be hot as well.

Think of it like a water hose, if one area is pinched and smaller (like a loose connector only a small portion of the connection is making contact) water will flow faster through that area.

This is the increase in current that generates heat.

When arcing current density very high at the arc point.

When there is a good connection the current is spread throughout the wire to lug and is very low at any particular point.

No offense Mike, but a loose connection does not create additional current flow. It merely creates higher resistance, and the resistance reduces circuit current.

Think of it in this manner. If I have a 120 volt circuit and it is connected to a 10 ohm heater, the current flowing in the circuit is 12 amps. 120 divided by 10 =12 amps.

Now, if the connection to the heater is loose, the total resistance in the circuit increases. Let’s say the loose connection causes an increase of 2 ohms. 120 divided by 12 = 10 amps.

There is only one circumstance that an increase in resistance causes an increase in total circuit current flow. That is in the case of a 3 phase inductive motor load where one phase experiences an increase in connected resistance. The result of which will be a voltage drop in the single effected phase and an increase in current draw of the other 2 phases due to an imbalanced connected load.

I believe William.

He is correct but is not addressing the high current density at the arc points.

Could the heat and excess current flow be caused by a faulty breaker? Drawing more current at one leg?

Not really

A breaker can arc internally and cause heating of the breaker but that would not increase current flowing though the lug.

Lol, well, we can get more technical. If you notice in the photos by the OP, these are not just any type of cable. These are “compacted” strand cabling. Notice that in the photos, the outer edge of the conductor itself is nearly flat. That is a tell tell sign of compacted strand. Therefore, the current density in this type of cable differs from a cable comprised of a typical circular conductor anyways.

Current density not withstanding, this conductor is not failing under an arcing fault per say, rather more of a high resistance connection causing an increase in operating temperature above the design maximum permissible.

Note: Both compressed and compacted strand cables are manufactured to address conductor fill issues where aluminum cables are installed in conduit and raceways. These designs allow for a reduced overall outside cable diameter while still providing the same ampacity of the specific cables size.

I agree on the high resistance causing the heat.

There is minimal heat produced with a low resistance connection. :slight_smile:

Only utilization equipment can create a load on the panel or circuit.

Although you’re correct about an increase in resistance lowering the overall circuit current you didn’t mention about it creating the heat at the loose connection. In this case the overall current doesn’t matter as much as the heat generated by the bad connection point between the lug and the conductor.

Under normal conditions with a good connection there would be almost no resistance between the lug and the conductor therefore there would be no abnormal heating of the terminal.

Yea, I did mention heating. I agree totally as far as a properly connected electrical system providing a low impedance path for current flow, not just a low resistance path. There is no need to discuss proper connection points as that is not the topic of the OP.