Tandem breaker usage

Does anyone have a good explanation of tandem breakers and WHERE they are authorized for use.

I seem to have this problem OVER AND OVER that licensed ELECTRICIANS have no idea what I am talking about and I try and explain it and they say its OK with the NEC and then I try to tell them its not the NEC its the panel manufacture that dictates where and IF they can be installed and it goes on and on…

I take pictures of the legend on the panel, pictures of the tandem breakers and where they are and ARE not to be installed according to the legend and they STILL seem dazed and confused.

All help would be appreciated.

Russell, you are correct that the label determines if tandems can be used. The NEC rules would be 110.3(B) that items must be used as listed and labeled.

Often times the part number will also show that tandems can be used. For example a Square D part number like QO200M3040 would allow up to ten tandems whereas the QO200M40 would not.

I understand this…the electricians don’t. Thats the problem! Now I have to find a way to educate them. Thanks for the response

Good luck with that. :wink:
I sit through 32 hours of CEU classes every new code cycle and I’m frequently amazed at some of the questions that licensed electrical contractors ask.

Most of my panels are so old, there is no label left to dictate where or if they go. Im just happy they are the same make.