Noise related to expansion of copper in Radiant / Hydronic / Baseboard heating

[Derek Wetzel]

Hi,

I'm curious if there are any experiences/insight beyond standard troubleshooting for this issue. The most practical resolutions i've seen so far are to straighten the fins (which i've done) and to ensure the return pipe is not resting on any metal hooks which could create noise... I do not have a return pipe that I can see in the entirety of the system, which I suppose means it's one long loop? I don't see visually that the pipe is impaired from expansion by any wall or opening and yet we still hear loud repeated knocking in various locations every time the pipes expand. It is different from the lighter popping of the fins expanding, which i'm relatively fine with since they are not as jarring as the knocking sound of these pipes... I've tried flushing the system but have realized that isn't the solution to this problem. I fear the problem areas are in the wall and unreachable unless I start tearing down the house to follow the entirety of the line... What are my options here?

 

[Dana]

What water temperatures are you running (and do they need to be that high?). If you're blasting 180F-190F water at the system that could heat the place with 130F- 140F water (all too common) the amount of expansion/contraction would be less using a more moderate water temp.

If you have last winter's fuel bills, first run a fuel-use heat load calculation, then measure up the lengths of all the baseboards to the nearest foot, and divide heat load by baseboard length. The resulting BTU per foot ratio will tell you what the average water temperature needs to be.

With the lower temperatures it the run times will be longer before the thermostat gets satisfied, and if the boiler is oversized for the radiation it may cycle a bit. The ratio of the BTU output of the boiler to the total baseboard length matters too.