I get a call from a 20 plus year electrician wanting me to explain why tandem (or has he insisted calling them, twins) breakers were not allowed in this panel. And how I know this.
I tried to explain to him over and over that the diagram on the panel door illustrated that tandems were not allowed; and also 20 spaces/circuits was the maximum, and the installed tandems exceeded this. He kept asking how I could determine this. I told him it was on the diagram inside the panel door. He was not able to comprehend this. He said in older homes when panels are overloaded and there is no more room it is common practice to install twins.
He then said well there are a few other things to repair, such as 40 amp breaker with #10 conductor for the AC. I tried again explaining that it is often allowed to under size the conductor for the AC. It depends on the AC data plate. He never heard o that. ](,)](,)