Galvanic Action

[Steve.Peel]

The AHJ has required me to isolate my uninsulated equipment grounding conductor (bare aluminum ground in SER AL cable) from contact with bare copper grounds from NM cable where they could or do come in contact before being lugged at the ground bar. Upon request for code references, the following were provided:

Code Ref: 110.14 - 250.70 - 342.14 - 344.14 etc. etc.

Galvanic action (NEC 342.14 and NEC 344.14) being the main reason for the requirement.

Can anyone shed some light on this for me? I believe that the potential for galvanic action (if there is any) rests in the fact that the two dissimilar metals are bonded together (as required) at the ground bar. Can contact between wire of differing metals outside of termination points cause or increase likelihood of galvanic action?

 

[mcclary's electrical]

the two metals being bonded to the same potential does nothing to stop the reaction that occurs when aluminum is touching air along with copper.

However, I think this is picking too much. If they're touching together in the panel, I don't see anything wrong with that.

 

[Steve.Peel]

the two metals being bonded to the same potential does nothing to stop the reaction that occurs when aluminum is touching air along with copper.

However, I think this is picking too much. If they're touching together in the panel, I don't see anything wrong with that.

So are you saying that a seperate reaction can occur at the point of contact between the copper wire and the aluminum wire?

 

[mcclary's electrical]

the two metals being bonded to the same potential does nothing to stop the reaction that occurs when aluminum is touching air along with copper.

However, I think this is picking too much. If they're touching together in the panel, I don't see anything wrong with that.

So are you saying that a seperate reaction can occur at the point of contact between the copper wire and the aluminum wire?

absolutely

 

[flashlight]

the two metals being bonded to the same potential does nothing to stop the reaction that occurs when aluminum is touching air along with copper.

However, I think this is picking too much. If they're touching together in the panel, I don't see anything wrong with that.

In that case, wouldn't they constitute a (very weak) battery ? We could use them to power our cell phones.

 

[R Schick]

Ul 60950

Ul 60950

Table J.1, Electrochemical Potentials, in UL 60950 indicates that aluminum in contact with copper or copper alloys produces a potential of 0.65 volts. The standard recommends against any combination of metals which result in a potential above 0.6 volts.

The request by the AHJ had some legitimacy.