Radiator clang (with pic, recording)

J_L

Hi all,  I am having a problem with a loud banging hot water radiator.  It clangs several times a day and night but I'm not sure what the pattern is.  Often there is a loud noise then a softer one 10 minutes later.  When I feel the radiator after it clangs, it is sometimes just warming up but other times it seems to be at full heat.



The valve is completely open.  We attempted to bleed the one radiator today and only water came out, and it continues to bang.



Below is a recording of the sound it makes (sorry for the quality) and picture of the radiator:



<a href="http://www.youtube.com/watch?v=rsB8PWVQjoA">http://www.youtube.com/watch?v=rsB8PWVQjoA</a>



<img src="http://i39.tinypic.com/wswuw7.jpg" alt="" />

STEVEusaPA

I'm sure as you can imagine...

it's pretty hard to diagnose just based on that.  Need a lot more info about the system.  Could be many things, but if you bled the radiators and no air came out....it's probably not air.

Unfortunately, you really need someone to come out and take a look/listen.  It could be something as simple as pressure, to something more complicated.

J_L

Also

I didn't mention that it's the only radiator with a problem. But yes, it's not much to go on.  I guess I hoped that with a single rad affected and bleeding failed to fix it there might be some basis to make an intelligent guess, but I don't have a clue.

kcopp

sounds like expantion....

noise to me. what temps are they running at and it is just a bang on bang off set up? No boiler reset?

Alan (California Radiant) Forbes

Expansion

I second the notion that it's expansion.  It could be that the pipe is too tightly strapped to the joist below the floor or it might even be that the radiator is touching the wall and when it heats up, it moves slightly and makes that sound.

J_L

Follow up

Expansion makes a lot of sense the more I think about it.  I recently noticed when I walk in the room once in a while the slight flex in the wood floor will cause a minor version of the radiator bang.  And if I wiggle the rad I can also get a minor version of it.



Since the weather is not too cold here yet I turned off the valve temporarily the other day hoping it would stop the clanging during the night.  But that didn't work.  I should mention that with the valve knob completely turned off there still seems to be some warmth in the rad sometimes.



As for the boiler, it seems to be set at 89C/190F.  There is one thermostat in the hallway to set the target ambient temperature.  Sorry I don't know the answers to the other questions about the boiler set up but I can try to get them, but I think kcopp there is no boiler reset.



If it's expansion, what are the chances of a fix without tearing up the floor?

J_L

Also curious

Oh, I'm also curious about the boiler temp question.  Is the idea that a lower boiler temp might mean (slightly) less likelihood or degree of the expansion problem?