Thermal expansion

Brad White_203

What if anything was done to the system since the last time it worked well?

I mean, iron expanded and contracted before, it has not been that cold outside. If you have outdoor reset, the expansion over any given hour should be minimal.

What is the operating water temperature?

ED_45

converted gravity system

My converted gravity to forced hot water system had run perfectly for 18 years until last year. For no known reason the column radiators and piping started banging almost like a steam system. Hi limits working, not flashing. The only explanation anyone can come up with is the cast iron is expanding and contracting now that the heat is calling. The noise lessens as the heat is on more regularly. Any other ideas out there?

ED_45

The only change was a failed htx60 expansion tank which was replaced. Operating water temp 140. the banging continued after the change. It's not air, the radiators bleed perfectly.

Brad White_203

Was the tank replacement

volume for volume, model for model? And what is the operating pressure range, cold to hot?

ED_45

exact replacement- gauge about 12-15 cold- 20 when hot

ED_45

As an example, tonight my thermastat was satisfied approx 6pm, not calling for heat. On 3 separate occasions a different radiator in my house would make a noise equal to the sound of someone hitting it once with a hammer.