Burned Melted plug and receptacle--Help, please

[schwartzr33]

After 9 years of service, my homemade BIAB/HERMS control panel had a meltdown. The picture on the left is the plug that goes into the bottom of the control panel, which powers the heating elements (I move the other end of the cable between the mash/boil kettle and the HERMS). The picture on the right is the receptacle that the plug goes into. There are no other signs of anything burning in the control panel. This is a 240V, 30A system, built from Auber components. The two 5500W heating elements (one in the HERMS, one in the mash/boil) appear to be OK. I did not discover this until the brew day was complete.

Before I replace the melted plugs, can anyone offer any theories on what happened here? And how to prevent a recurrence? Thanks.

 

[Bobby_M]

It's more intuitive to expect poor connections to happen on the end that gets worn out from being plugged in and unplugged regularly but I think what happened is you accumulated some mild corrosion over time. If the plug had been cycled more, it would self clean the contacts.

I've been using this conductive assembly paste on my high current connections. Conductive Compound for Electrical Connections

The next best process would be to lightly sand the surfaces of the male plug with a mild abrasive occassionally.

 

[schwartzr33]

It's more intuitive to expect poor connections to happen on the end that gets worn out from being plugged in and unplugged regularly but I think what happened is you accumulated some mild corrosion over time. If the plug had been cycled more, it would self clean the contacts.

I've been using this conductive assembly paste on my high current connections. Conductive Compound for Electrical Connections

The next best process would be to lightly sand the surfaces of the male plug with a mild abrasive occassionally.

Bobby, thanks for your help. You built my HERMS and I'm using your elements.

 

[Ki-ri-n]

I just went through this myself. I "think" it may have been a loose connection. You may want to regularly check (1/year ?) all the screw terminal connections and make sure that they are tight.

Another thing would be to double check to make sure you're using the right sized gage wire for the maximum amount of amperage draw.

 

[doug293cz]

Definitely due to local overheating caused by high connection resistance. Either due to contact corrosion, as mentioned by @Bobby_M , plug blade that fits loosely in receptacle, or a loose screw connection in either the plug or receptacle. Based on the look of the blade that pulled out of the plug, my first thought is a loose screw connection to that blade. Heat would have been created at the screw terminal and conducted along the blade to damage both the plug and receptacle. I'd like to see some pics of the wire connections for both.

The fix is to replace both the plug and receptacle. Wires can be reused if you trim away any portion with discolored/damaged insulation (this may require new wire inside the control panel due to length issues.)

Brew on

 

[Broken Crow]

It's more intuitive to expect poor connections to happen on the end that gets worn out from being plugged in and unplugged regularly but I think what happened is you accumulated some mild corrosion over time. If the plug had been cycled more, it would self clean the contacts.

I've been using this conductive assembly paste on my high current connections. Conductive Compound for Electrical Connections

The next best process would be to lightly sand the surfaces of the male plug with a mild abrasive occassionally.

I've always kept a bit of sandpaper and emory-boards in my electonics tool-kit and in my studio I've always used Caig De-Oxit..(not sure about using it for high-current connections).. In my workbench supplies, I have a tube of GB Ox-Guard, but owing to injury, I have no recollection whatsoever of it or it's use.. Is it pretty much the same as the Compound you sell?

 

[Bobby_M]

I've always kept a bit of sandpaper and emory-boards in my electonics tool-kit and in my studio I've always used Caig De-Oxit..(not sure about using it for high-current connections).. In my workbench supplies, I have a tube of GB Ox-Guard, but owing to injury, I have no recollection whatsoever of it or it's use.. Is it pretty much the same as the Compound you sell?

It is similar. Zinc vs Carbon for enhancing conductivity. Just want to avoid dielectric grease because that would likely harm conductivity.

 

[Malticulous]

Stranded copper connections need to be torked and re-torked again. It's soft enough to flatten and become loose.