I am soliciting opinions on article 250.92(B)(2). I am curious as to the code compliance of "myers hubs" under this article.
It seems to me that even though myers hubs are threaded, they provide no better bonding than a typical locknut on any other fitting (for the panel/equipment side of the fitting). As noted by the last part of 250.92(B), "Standard locknuts are not to be the sole means of bonding for this section".
It makes sense to me that the threaded portion of the hub is a quality connection. But just like the weak link in a chain, the locknut side of the hub is no better than a standard EMT fitting for bonding purposes.
This situation brings two questions to mind;
1) If the myers hub is acceptable for service bonding, why are EMT fittings not? They both have that common weak link of the locknut, and neither are specifically listed (nor required to be) for service bonding.
2) If only threaded bosses are allowed (such as in weatherproof boxes), why have the thousands of myers hubs that I have seen in service bonding use not caused some sort of failure? Granted I have not seen every installation to know if any have failed, nor do I posses any failure rate data of myers hubs in service bonding situations, but I would think that I would have seen or heard of such issues in my fourteen year career.
I think that something is rotten in Denmark, to coin a phrase, and am curious what others think.
Enjoy your day!
It seems to me that even though myers hubs are threaded, they provide no better bonding than a typical locknut on any other fitting (for the panel/equipment side of the fitting). As noted by the last part of 250.92(B), "Standard locknuts are not to be the sole means of bonding for this section".
It makes sense to me that the threaded portion of the hub is a quality connection. But just like the weak link in a chain, the locknut side of the hub is no better than a standard EMT fitting for bonding purposes.
This situation brings two questions to mind;
1) If the myers hub is acceptable for service bonding, why are EMT fittings not? They both have that common weak link of the locknut, and neither are specifically listed (nor required to be) for service bonding.
2) If only threaded bosses are allowed (such as in weatherproof boxes), why have the thousands of myers hubs that I have seen in service bonding use not caused some sort of failure? Granted I have not seen every installation to know if any have failed, nor do I posses any failure rate data of myers hubs in service bonding situations, but I would think that I would have seen or heard of such issues in my fourteen year career.
I think that something is rotten in Denmark, to coin a phrase, and am curious what others think.
Enjoy your day!
