I recently had some disappointing work done by an electrician who is not responding to my phone calls. I need to move forward on my project, and I think that if I am careful, read a lot, and enlist help, I can do a better job myself.
The electrician installed an outdoor sub panel that has 2 remaining knockouts in the back. I'd like to use these knockouts to wire my addition. One of the knockouts is quite big. It is my understanding that you are only allowed to run one NM wire through a connector clamp (one of these):
I have also read that some connector clamps are approved for 2 NM wires. Since I only have 2 knockouts, if I could find this type of clamp, I could run 4 circuits in my addition.
I've scoured the internet, and have been unable to find anything that says it is approved for 2. In my main panel (which was installed in 1980, and presumably approved), I have 3 Romex cables in a 3/4" clamp. I'm not sure how this came to be, and if it is legal.
Does anyone know where I could find such a clamp that specifically states it is approved for 2 NM cables? Also, do I need to use anything special - the panel is a surface mount, but there is a small gap behind it where I can see light coming in from outside. I think it would be possible for water to get in there. Is there such a thing as a gasket that seals between a panel and the inside of the wall?