Older panelboards may not permit mixing of Circuit Breakers. The following information was taken from one of my earlier posts on this Forum.
They.....I hear ya Joe.
I had a big issue with an electrician I hired to oversee the work being done at a resort since I could not be their all the time so he was like my forman. Anyway we was taking a Challenger 120A breaker and putting it in a SQ D Homeline...ok....I walked on the job and looked at the panel to give my stamp of approval so to speak.
Noticed he has taken a Black Marker and covered up the area that said Challenger...lol.....and ofcourse the local inspector ( CODE ) did not notice it was different...so then I popped it out and guess what....the back tap that would normally prevent it from working was dremeled away....just a small little plastic tab.....
Anyway......against CODE because the item was altered....and then for not being approved my the MANUF. for use in the actual panel.
His answer was...heck it has worked for years now and the Challenger breakers are 1/3rd the price of the Homelines 120A breakers....lol
I told him.....you know I can afford to have you buy the proper breakers you know.....lol