I apologize in advance, because all of you have helped me immensely on my whole house generator installation, and you are waaayy smarter than I will ever hope to be.
However, that duct seal putty is awful! They used it on the outside of my SER cable coming into my basement electrical panel. I just happen to check that area the other day and sure enough, I saw daylight peaking through. I personally do not trust that product. It totally pulls away from the outside penetrations. Prior to these wall penetrations with the SER cables I had a perfect air sealed basement rim joists. I studied this for 6 months before I took the task myself. Now I have to figure out how to get it back to its original nirvana! So that is either going to be caulk or fire block spray foam or both! I just have to decide which one will not interfere as a chemical reaction with the SER cable sheathing. Just my 2 cents.