Maximum Temperature Rise for Fused Disconnect

[haze10]

We started doing infrared testing of our Allen Bradley 2100 MCC buckets. There appears to be common hot spots where fused disconnect switches are employed. The hot spots are typically where the disconnect blade is hinged, where the blade meets its corresponding stab, and at the line side of the fuse clips. Ambient temperature is around 80F maximum. Temp rise on the hot spots can be a relatively low 15C to a high of 70C. My question is at what temperature rise do we need to replace the switch. I am seeing literature that says max rise should be limited to 30C or 50C. Does anyone have a threshold that they recommend.

Also, is it recommended to apply a conductive grease to the blades or fuse ends such as Penetrox, or MG Chemicals Carbon Grease?

Thanks,
gary

 

[waross]

I would hesitate to use Penetrox on moving parts.
Penetrox is not a lubricant, it is a joint compound.
From the Penetrox data sheet:

Non-Petroleum Base Vehicle With Zinc Particles Suspended

The zinc particles help penetrate the ubiquitous oxide film on aluminum, but may lead to accelerated wear on switch blades.
For an application where the switch is seldom operated I may use Penetrox.
For an operation where the switch is used often, such as for saw sharpening or changing or tool changing I would look for another product rather than chance accelerated wear of the switch blades.
For frequently operated switches I would look for a graphite based automotive lubricant.