Pinging in hydronic pipes

Old 03-13-10, 08:35 AM
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Pinging in hydronic pipes

Dear NJ Trooper, [or anyone else who has suggestions! - edit: NJT]

I just saw a post about a guy who was having problems with pinging in his hydronic baseboard heating. It seems to happen when the system is cool and worse when cold. so most likely thermal expansion in the copper piping. I have a customer with this problem in one zone and I do not know how to stop it. any advice would be greatly appreciated.

Thank you

Last edited by NJT; 03-13-10 at 12:58 PM.
Old 03-13-10, 01:08 PM
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You are probably correct that it's expansion noises... why only in one zone though I wonder? Tough part about troubleshooting this kind of thing when you can't 'babysit' the system is that it's unlikely that you will be there when it makes the noises!

Or, have you already heard the noises yourself?

If not, ask the customer to shut the system off so it cools down before you get there... then fire it up and go around and see if you can localize the sounds...

Then start looking around for tight fitting pipes, clearance holes not big enough for the pipe, bent and distorted fins, bent brackets, etc... if you can localize the noises, sometimes cutting plastic 'shims' from milk bottles can be used as 'insulators'... sometimes these can be placed between the brackets that hold the elements inside the baseboard, and the elements themselves.

Check the aquastat on the boiler also... see what the settings are on the high limit control... maybe it's too high...

Adding an 'outdoor reset' to the boiler system can help also, but care must be taken that the boiler isn't allowed to run too cool, as this will damage the boiler. Outdoor reset will allow cooler water to run through the pipes when the weather is warmer and the water doesn't NEED to be as hot...
Old 03-13-10, 04:15 PM
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Here is a theory I've read somewhere: "pinging" is caused by non-uniform thermal expansion or contraction within the pipe wall itself. When you park a car with a hot engine, you may hear pinging as the hot exhaust manifold or exhaust pipe cools off, right? That's perhaps easier to understand than a hot-water pipe, since the geometry of the car's exhaust system isn't symmetrical like a piece of pipe.

But even with a run of circular pipe, there may be hangers, bends, joints, or other points that cause the pipe's cross-section to expand/contract non-uniformly. Maybe causing the pipe walls or the joints to "ping."

If this theory applies to your situation, I can't think of much to do. Maybe jury-rig rubber snubbers on the pipe to prevent or muffle the pinging? You could grab the offending pipe with your hand, and see if it makes a difference.

The more common noise with hot-water piping, as Trooper explained, is more of a repeated knocking or banging - when an expanding pipe ratchets across a wooden joist.

I don't think either pinging or knocking is particularly hazardous - just annoying. We get some pipe knocking in our master bedroom. I usually hear it only sub-consciously, and it seems reassuring to realize that the heat is coming on. (Maybe like rain on the roof - I'll sleep like a baby). Forced-air furnaces also make noise: when the fan comes on, the metal ductwork may give an abrupt "pop" or "boom," and the fan noise is often noticeable (more so than a circulating pump in the basement).

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