I redid my pool in 1993, including a new pool light. I used brass conduit from the light niche to a junction box and it is fed by a 20A GFI breaker, Siemens QF120, type QPF. It gets very low usage but several months ago the lamp burned out. I pulled the unit out, replaced the lamp and reinstalled. Was fine for a month or so then started shutting off, at first every hour or so, then more and more often. Took the entire unit out and noticed that the cord seal was brittle and cracked but no moisture was inside the lamp assembly. Even though the seal is only protecting an area that is completely filled with potting resin, I dug out the old rubber, and replaced it with special silicone designed for pools. Made no difference. I bought a brand new light assembly and installed that, same thing. Yesterday I replaced the breaker with a new one but still, after 10-15 minutes, it trips. There are absolutely no nicks, cuts etc in the cord, the end was sealed before pulling the cord to the J-Box and a foot or two was removed anyway. Any ideas would be appreciated. I was so sure that it was the breaker. . .