Stumped on banging pipe..

[LiQuId]

I live in a 12 unit apt building and since ive lived here I and the landlord have been attempting to diagnose this random banging sound.

mechanical room is located on main floor.

banging is most evident on second floor but I can hear it also benieth me on the third in the same similar location as the tenants below me.

I have tried switching on and off pumps in the mech room to cause this banging to reveal itself to no avail ( never does when im hunting for it )

this sound is most present on the side of the building that the mechanical room is on.

Sound has gotten louder following replacement of an old pump on the heating loop leading me to believe this probblem is related to the heating ( hydronic baseboard )

any ideas? I am wondering if the baseboard in the units below is shifting when the zone valves open to feed the loop but I cannot simulate any conditions that cause this. this sound may not happen for a day or two and then out of the blue "BANG".....

thanks for the insight guys

 

[havasu]

The TV show "Ask This Old House" just did a segment on loud noised from baseboard heating. They advised the copper pipe will expand up to 3/4" in a 10 foot segment of baseboard and the only remedy is to cut some length and aluminum fins to allow for expansion. I hope this helps because being from So Cal, I only know of them via TV shows!

 

[LiQuId]

thanks for the responsed havasu. I am leaning towards expansion as the problem though its hard to be sure of the location since this sound is completelly random and often disapears for days before returning. I will be talking with the building manager to try to better pin down location.

 

[ddocfletcher]

Has this problem been resolved?

 

[LiQuId]

not as of yet, we have given tenents 24 hours notice and will be investigating to first see if there isnt a zone valve installed backwards somewhere in one of the units that would explain the randomness of these sounds. at this time it seems more plausablle that this is the case and not expansion, I will post the results when I have them.

 

[ddocfletcher]

I was just about to suggest a zone valve as the cause. But, I see now that your already onto it. An upside down zone valve will make a bang noise every time the the thermostat stops calling for heat.

 

[LiQuId]

2 of em in this building, and a reverse acting thermostat installed with a NC valve... problem solved though. some other issues to adress at a future time found as well.