What should I use to seal the hole where my central air enters the house?

Question

Wood foundation house with vinyl siding. The hole that was made to allow the lines for my central air conditioner to enter the house is basically wide open - the silicone/caulking that was around the hole has eroded or something, and when I look at the hole from inside the house (in my furnace room) I can see clear through to the outside - I can see daylight. I was thinking of spraying some expanding foam into the hole, then using caulk to seal around the hole, but I'm wondering if that's the correct approach. Has anyone on here ever done this before?

thanks!

Answer 1

Duct seal, or similar product, is a common solution.

Knead it until malleable, then mold it in and around the hole like clay. It is nontoxic, paintable, and will stay flexible.