POLARIS CORROSION
- Thread starter Zee
- Start date
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ptonsparky
Tom
- Occupation
- EC - retired
Environment, excessive moisture, improper torque.
petersonra
Senior Member
- Location
- Northern illinois
- Occupation
- engineer
I would bet someone over torqued it.
ptonsparky
Tom
- Occupation
- EC - retired
Agree.
electrofelon
Senior Member
- Location
- Cherry Valley NY, Seattle, WA
How does excessive torque cause corrosion?
Fred B
Senior Member
- Location
- Upstate, NY
- Occupation
- Electrician
Likely not the corrosion directly with the over torque but in combination with the over torque compromising the conductors then a little more heating of conductors than would be expected because of the compromised conductors, it would accelerate corrosive effects leading to additional heating and further compromising it becoming a viscous cycle and eventually leading to the conductor total failure. All depending on loads applied to the conductors and initial damage by how over torqued the connection was made.
Over torqued is just about as bad or maybe worse as under torqued. Seen torque so extreme that when loosening the connector multiple strands were actually cut through.
synchro
Senior Member
- Location
- Chicago, IL
- Occupation
- EE
Was this a solar installation, and if so were the conductors carrying AC or DC?
If it is DC and the connection was sufficiently poor to cause at least a few volts drop, then that might greatly accelerate corrosion because of electrolysis. This is assuming that at least some moisture was present. And as the corrosion proceeds the voltage drop would increase, which then increases the rate of the corrosion, further increasing the voltage drop, etc., ...
electrofelon
Senior Member
- Location
- Cherry Valley NY, Seattle, WA
That is what everyone says, however I don't think in my 24 years doing this I have ever seen a connection fail from excessive torque. Just because I have not seen it, doesn't mean it doesn't exist of course, but it must be extremely rare.
ptonsparky
Tom
- Occupation
- EC - retired
Interesting. Hadn't thought of that aspect at all.
electrofelon
Senior Member
- Location
- Cherry Valley NY, Seattle, WA
I was kind of thinking the same thing, but wouldn't that require water/electrolyte for that to happen? Maybe the box leaks or does not drain properly?
Maybe the conductors we're contaminated with foreign material. For example there was water or some other substance trapped between the strands and the gel in the Polaris fitting prevented it from evaporating.
Some compounds such as flux are highly corrosive, someone may have wanted to tin the ends with solder and after they applied the flux something prevented them from following through. Anything is possible.
I would think under torquing would cause more problems than over torquing.
The only thing I would bet money on, however, is I bet this was directly caused by a violation of 110.3(B).
Some compounds such as flux are highly corrosive, someone may have wanted to tin the ends with solder and after they applied the flux something prevented them from following through. Anything is possible.
I would think under torquing would cause more problems than over torquing.
The only thing I would bet money on, however, is I bet this was directly caused by a violation of 110.3(B).
zbang
Senior Member
- Location
- Roughly 5346 miles from Earls Court
I'd like to see some research about over-torquing before accepting it as the problem. For instance, how are solid copper strands "compromised" by it? They're already being crushed by the clamping action. It's possible that the lug is compromised with microcracks, but that would cause the lug to break apart, not the wire to corrode.
ggunn
PE (Electrical), NABCEP certified
- Location
- Austin, TX, USA
- Occupation
- Electrical Engineer - Photovoltaic Systems
It's hard to say; were the Polaris blocks' lugs the right size for the conductors? Overtorqueing, undertorqueing, wrong size lugs, anything that introduces resistance generates heat, and heat accelerates chemical reactions. Also, heat damage and corrosion are difficult to tell apart, and often there are both. Sometimes heat will melt strands, which increases resistance, which generates more heat, which melts more strands, which runs away until the conductors are completely severed. The common denominator is resistance heat.
zbang
Senior Member
- Location
- Roughly 5346 miles from Earls Court
Not saying it doesn't, but how does over-torqueing an otherwise correct connection increase resistance? Seems like it should lower the resistance.
ptonsparky
Tom
- Occupation
- EC - retired
It cuts the strands.
scrypps
Member
- Location
- United States
Exact same thing happened to me. It was a can in the sun. The connector basically melted due to a loose connection. I made the connection myself, and when I picked it apart and found the conductor, it was over-torqued. Some conductors were a little flat.
It’s hard to think a connection too tight would eventually become too lose, but it’s because the conductors where compromised. It probably might not have happened if it wasn’t in the sun in triple digits. But it most likely would never have happened if it had been torqued properly.
ggunn
PE (Electrical), NABCEP certified
- Location
- Austin, TX, USA
- Occupation
- Electrical Engineer - Photovoltaic Systems
Which adds resistance, which adds heat, which compromises more strands, which adds more resistance, which adds more heat...
MD Automation
Senior Member
- Location
- Maryland
- Occupation
- Engineer
Just throwing this thought out there...
Was the Polaris connector oriented such that it could "collect" condensation in the wire ports? You say it was a rooftop JBox, so you know there will be water condensing in it. If the Polaris connector was put in the box so that water draining down the wire ran into the port, then maybe enough collects there to promote / accelerate corrosion? That big insulated contraption would sure hold water nicely if it was upside down.
Full disclosure - I am not a real electrician, but did get shocked at Holiday Inn once
Was the Polaris connector oriented such that it could "collect" condensation in the wire ports? You say it was a rooftop JBox, so you know there will be water condensing in it. If the Polaris connector was put in the box so that water draining down the wire ran into the port, then maybe enough collects there to promote / accelerate corrosion? That big insulated contraption would sure hold water nicely if it was upside down.
Full disclosure - I am not a real electrician, but did get shocked at Holiday Inn once
zbang
Senior Member
- Location
- Roughly 5346 miles from Earls Court
Ah, that's not simply over-torqued and I wouldn't call it such; that's flat out strand damage. For a spec of 400 inch-pounds (33.3 ft-pounds), cranking to 500 is 25% over but probably isn't going to break any strands. OTOH double-torque might well damage the strands.
Or, there's over-torque and there's gorilla-arm massive over-torque damage.
ggunn
PE (Electrical), NABCEP certified
- Location
- Austin, TX, USA
- Occupation
- Electrical Engineer - Photovoltaic Systems
One thing that overtorqueing can do, especially if the wire is near or below the range of gauges the lug is made for, is to spread out the strands so that some of them do not participate in the connection. Resistance, heat... off to the races.
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