Electrical contractor could not understand why tandems were not allowed

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. ](,)](,)

I agree with Mr. Sparky. Based on what you provided, I see nothing that prohibits the use of tandems or slim-line breakers. My own panel has some. As long as it is of the same manufacturer, I think it is OK. Keep in mind that you aren’t doing load calculations. (BTW, the Square-D breaker is prohibited in that panel I’m pretty sure.)

Well, that’s two that don’t know how to read a panel diagram.

Chris, send him this link to educate him.
How to know when tandem circuit breakers can be used (aka - cheater breakers) - StarTribune.com

C’mon Chris. Watch the spelling. It should be 20 year “Lektrishun”… :roll:

The wiring diagram clearly shows only a single breaker is allowed. Tandems are only allowed in certain panels according to their listings. The wiring diagram will show.if allowed. Also the model number will typically be something like 200m3040.

Interesting article. Learned something new.

What do you do when there is no panel label???

Pretty simple…panel label missing and couldn’t verify panel manufacturer requirements. It’s possible defects exist that could not be confirmed due to this. Have an electrician… blah, blah, blah.

Not all Electrical Contractors are created equal and being in the business for “20 years” doesn’t mean he did everything correctly for those “20 years” as well. The learning process is never ending and when I teach someone who refuses to listen then I smile, agree to disagree and move on.

Was not the case 10 years ago but I have mellowed in my old age and do not have time to stress those who do not care to learn or listen and I am always willing and ready to learn new things.

Paul, well said

Can There be tandem circuits on thi


s panel board?

There is a picture of the label. What does that tell you?

Not absolutely sure. I’m thinking no, but that’s why I posted it. I was hoping someone would confirm my thoughts instead of mess with them.

Nobody is messing with you. The information you seek is right on the label. Maybe this will help. Note the circuits at the bottom.

Compare the image from the OP to Stephens photo: