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jsurpless
Knocking Noise In Baseboard Heating Zone
jsurpless

There's a baseboard heating zone in my 2-year old house that makes a knocking noise when the thermostat initially calls for heat; as it eventually stops, I assume that it's the result of the pipes expanding as the water temperature increases. In addition, the knocking lasts longer if the heat has been off for a longer period of time (i.e, first thing in the morning)

I've seen the TOH segment on noise that baseboard systems make but I'm not sure how to address mine since the sound seems to be coming from inside the floor and differs from the normal creaking that aluminum fins make (it's quite pronounced as I can hear it on the other side of the house downstairs)

Also, not sure if this is relevant but I don't think that knocking has always been present; I think that it started last winter and wasn't present the first year that we were in the house

Any thoughts or suggestions?

Thanks

johnjh2o
Re: Knocking Noise In Baseboard Heating Zone
johnjh2o

The hole in the flooring isn't large enough to allow the pipe to move freely when it expands from being heated.

brewster
Re: Knocking Noise In Baseboard Heating Zone
brewster

John nailed it!

If you can locate the particular pipe hole that's making the noise, take a caulking gun & squirt a good glob of butyl caulking compound, silicone cmpd, urethane cmpd, or go to Home Depot/Lowes & buy a tube of "high heat" caulking cmpd, (usually has bright red printing on the tube & is dark red in color) especially made for heating system applications---these tubes are designed to work with a CAULKING GUN, which costs extra; however, for just a single application, you can try cutting the tube tip with a razor or knife & squeezing the plastic tube into the hole to complete the job.

Another fix if you have access & know the location is to cut lengthwise a 3" piece of thin-walled plastic tubing, or garden hose, grease it & work it into the offending pipe hole.

If the tubing or caulking doesn't work, go down to the boiler & REDUCE by 5 or 10 degrees the HIGH LIMIT control on the hot water gauge or Aquastat---this will make the boiler run a little longer at the slightly lower temp, but MAY make a difference.

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