Baseboard clunk

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Ok, so first time in my life I'm a homeowner, and also first time I have baseboard heat. The problem is the noise that the baseboard makes when the thermostat turns the heat off.
The noise is like a big bang or clunk. And when more than one heaters do it same time, it can scare you. Not to mention the neighbors. Not all heaters do it though. And it doesn't happen every time.
This seemed to come up every once in a while, but still I couldn't find any answers with Google that seemed to apply to this case. I live in a condo, and I don't have my own boiler, so that limits some things that I can do or check.
Here's a sound file too, that I recorded, maybe that will help: http://mikkopel.dyndns.org:1000/misc/clunk.mp3
How do I stop the sounds? Thanks!
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Not having any idea of the type of system you have, the only thing that I can think of that may clunk when you turn it off, would be a solenoid valve. Is there anything on or near the baseboard units? Are they hot water or steam?

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RBM wrote:

There is one of these doohickeys at the end. Or beginning rather, I believe.
http://mikkopel.dyndns.org:1000/misc/baseboard1.jpg
I haven't seen any movement, or anything when the noise happens, but then again, I haven't watched it that closely. I just tried to watch carefully, but this time it didn't bang. And it doesn't bang every time.
But a lot of times. And not just one baseboard. But some are still quieter than others. I can't really seem to find any pattern.
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Take the cover off that "doohickey" -- which is probably a zone valve. I'll bet you see something amiss inside it that coincides with the noise.
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Doug Miller (alphageek at milmac dot com)
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The picture isn't quite clear enough to verify it as a zone valve as opposed to a solenoid valve. I've never seen one built right into a baseboard heater. If it is a zone valve, it'll have a couple of springs inside the cover that force it closed when the thermostat is down. Possibly they are catching on a piece of sheet metal of one of the heaters? Zone valves close fairly slowly, at least compared to solenoid valves, so they usually don't cause a water hammer

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RBM wrote:

I opened it up:
http://mikkopel.dyndns.org:1000/misc/baseboard2.jpg
I had my wife turn the heat off, while I was looking at it, and I can see the motor action when it happens. But now it's not making the noise. I'm not sure if it's because the cover is off, but then again it didn't make the noise every time anyway.
There also seems to be a lever of some sort on the left of the picture. What's that for?
Doesn't look like it's ever been cleaned under there either... ;)
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That's a bypass lever, it allows you to open the valve, and latch it open manually. There are generally three or four wires attached to the valve, when it is electrically opened, it has a built in switch that closes a circuit which would turn on a circulator pump to push the hot water through the valve. This switch however is not activated when the valve is opened manually

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Another possibility: This is clearly a sort of Rube Goldberg system. It's entirely possible that each zone valve is controlling a master valve located out of sight, which could be the source of the noise

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I just heard the sound which wouldn't open on my pc. It sounds just like a garden variety Honeywell hot water zone valve de-energizing and closing under spring tension, but I have no clue what the bang could be. If I were you I'd find the valve and watch it to see that the pipes aren't loose and possibly banging against something when it closes

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Mikko Peltoniemi wrote:

I have had two homes in Alaska with hot-water baseboard heat. In both of them there were an assortment of creaking, groaning, banging noises and every one of them seemed to be traceable to the way the hot water pipes were run between the units. What was happening was when the pipes heated and cooled they were expanding and contracting and rubbing against the nice pitch-laden framing lumber. This movement was not gradual but grab-and-release causing occasional noises. I found out that later that new code required that low-friction plastic inserts be used in the holes in the studs to eliminate the pipe-on-wood rubbing and that noise was no longer a problem.
I really doubt that any noises could come directly from the zone valves opening and closing. There are two commonly-used zone valve types in home heating: one uses a wax capsule heated by the control voltage which moves the valve and the other uses a small motor. In both cases the opening and closing is very slow (on the order of 5 - 10 seconds) and cannot cause the sort of pipe banging that is sometimes experienced with the quick solenoid valves in dishwashers and ice makers.
As for what you can do about it, short of actually digging into your walls, you can simply wait a while. After a few years I hardly noticed it any more...
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John McGaw
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John McGaw wrote:

Hmmm... Not the sort of zone-valve setup I was expecting.
Looking at your picture I will have to say that you definitely have a valve type I'm not familiar with and it certainly could be a fast-moving solenoid type after all. If so, your banging might be totally different that what I experienced. But if so, since it is right out in the open it may be a lot easier to trace and repair. Can you work with someone to test the action of one of the offending valves by cycling the thermostat on and off? If you are right next to the valve you can place your hand on it or on the pipe next to it and actually feel if there is any sudden motion which might explain the bang. If the pipe is moving back and forth under the influence of the water you might be able to tell if it is hitting against anything (sheet metal, edge of a hole, bracket, etc). If so, a bit of foam insulation of the sort used on water pipes stuffed into the gap may dampen the vibrations.
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John McGaw
[Knoxville, TN, USA]
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John McGaw wrote:

It's not that fast. When I look at it, it takes a few seconds to reach from one end to another. Also, I can definitely understand clicking and small noises like that when the heat is on. But since it's a loud, one-time, bang, when the heat goes out, it doesn't seem normal to me.
I wonder if the people who listened to the clip agree, that the sound is not normal?
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I've not seen a valve like that. The Synchron motor on the top usually turns very slow, 1 or 2 rpm, but the sound seems to be something that slams shut. Possible that the insides are worn and a seal or gasket is no longer in place to soften the sound. My guess is the noise is in the valve body, not the top motorized portion.
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Clark wrote:

The problem is that there's only so much I can do, since it's a condo. But I have tried to look for a bleed valve or something, in case there's air. And since it's the top floor of the building, I thought there might be.
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Have the building check the lave soliniod and the pipes this is more than you should do and if it is a condo are oblgated to do least you bugger everyones heat it is a feed promblem
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Ahhh, ok, the zone valve on the radiator makes sense now. I haven't been around these types of systems but as I understand it the system provides a continuous (24/7) supply of hot water to a main supply loop and then the local zones pull hot water off as needed. Since the noise isn't always repeatable I'd suspect it depends on how many other zones are pulling hot water from the system.
I think you're going to have to work with the condo maintenance folks on this one. If the maintenance folks & condo governance folks are unresponsive then you'll have to get a heating tech in to diagnose the problem and force the issue. All in all, it doesn't sound like much fun...
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Naaah. It's a perfectly normal zone valve, low-speed motor to open it, spring to close it. My system has half a dozen almost exactly like it.

Oh, absolutely, that's not normal. It sounded like a sheet-metal sort of sound to me, or a spring. Open and close it manually a time or two. Does it operate smoothly, or does it feel like something's binding?
I kinda wonder if perhaps the noise might have been just the cover rattling. Leave the cover off for a couple days, and see if the noise appears.
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Doug Miller (alphageek at milmac dot com)
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Wow, you could play that on your computer to terrify children. Just loop the playback.
Got me puzzled. Likely a loose pipe some where. Banging on a wall, maybe. I'd suggest to touch the various pipes when the noise happpens, and see if you can isolate the source. Shim wtih cadboard behind the pipe might help.
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Mikko Peltoniemi wrote:

The heating system is not part of the condo, and therefore not your responsibility. Whoever maintains the building itself is responsible for maintenance and repair of the heating system. It would be a different story if each condo had its own furnace, but here, there's a central boiler.
You should call building maintenance and have them look at it. If you start messing with things you could take out the heat for everyone in the building, and put yourself in the hospital with severe steam burns. You don't have control over the supply of hot water/steam, and can't shut it off.
I find it hard to believe that yours is the only condo in the building with this problem.
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