I am a heating and air conditioning contractor in the Philadelphia area. Been doing this stuff a long time, but I've run into something that I'm struggling with. I recently purchased a house with oil hot water baseboard heat. I added (2) radiant loops to the bathrooms when we renovated them this summer. They are off their own secondary loop with their own circ.
I have (4) zones of heat not including the radiant, zoned with zone valves ( a mix of taco and honeywell 4 wire valves). A single Taco 007 circ pump (located on the return close to the boiler, pumping towards the expansion tank on the supply side).
I'd never heard it hammer before the radiant loops went in, but now it happens almost every time another zone completes its call. It's bad too. The finned element sounds like it wants to jump out of the cabinet it's so violent. I figured it was being caused by the radiant circ somehow so I turned off the radiant, but that didn't stop it. It continues to happen, so now I'm assuming it is being caused by where the secondary loops for the radiant were tied in.
Anyone have any experience with this? I'm stumped. Luckily it's in my own home, so I can just benefit from what I learn.