Not so Silent Hydronics - Need Help

larry

Thank you Gary. If I can't figure it out, I will give you a call. The boiler is a Vitodens. I was planning on contacting you anyways to provide yearly service checkups down the road. The setup has mechanically stabilized the pipes without question. It was just really bothering me to have these two pipes that would swing and jiggle if bumped or even lightly touched. Maybe I was wrong but it seemed like undue stresses were being placed on pipe joints.

larry

After our new heating system was installed I noticed that the supply and return pipes going to the hydronic air handler in the basement were not so well supported. I was more than a little disappointed that my contractor's workmen left these pipes just swinging in the wind. The pipes go up the side of the air handler, and then over the top of the supply and adjacent return plenums before emerging and heading towards the manifold. I understand why they didn't support the pipes; it was because there really wasn't any "easy" way to do after the air handler was in place.

I felt like I could solve the problem better than the folks who left it like that in the first place. Below is a picture of what I came up with (used Mupro clamps and bracket and also rubber washers between the pipe nipples and joist and at the end of the screw holding the strut to the joist). It certainly works, but my previously silent system now has a vibration coming up through the floor joists and creating an annoying low level hum in our dining room (only when the AHer is in heat mode, not in fan only).

I probed around with a mechanics stethoscope and much to my suprise the vibration isn't coming from the joists that my support rig is attached to. It's coming from a joist two away from the support, and nothing related to the hydronics is even attached to this joist.

I'm a bit at a loss to understand this one. Any suggestions on how to approach this.

Mike T., Swampeast MO

Nice heavy stuff that looks very well installed but you're still relying on those small diameter but relatively very long threaded rods to do the support. Sorry to say this, but that's a great way to magnify harmonic vibrations.

It might not be as pretty, but since you're certainly accurate, why not cut some nice fitted blocks to cradle the tubing on top of that beam I see to the right?

larry

Mike,

What you see to the right isn't a beam, it's the top of the insulated supply plenum. I guess your idea would still work all the same. I could also mount plates to the side of the plenum and use real short pieces of threaded rod to support the pipes. I was trying to stay away from supporting the pipes by the plenum/ducting thinking that might induce some vibration into the duct work and sound could travel all through the first floor. Likewise, a longer piece of strut could be used and slightly cantilevered beyond the joist closest to the pipes. That way the threaded rods could be very short as well. But why am I hearing the resonation in the other joist which isn't even part of the deal?

I've also considered another approach where this could be re-piped so it's attached to the concrete wall to the rear and run over to the manifold. I originally didn't understand why they chose to run the pipes as they did when the basement wall was available. I'll have to bring this up with the contractor.

Unknown

Look further into the source. Where is it comming from?

Larry,

Those really nice Mupro hangers aren't doing a darned thing where you have them placed. It would probably have been ok to have left these two pipes "swinging in the wind.'

I suggest that you do a bit more probing with your mechanics stethoscope. Is this an oil fired boiler? If so, what type of burner? Is it set up right? If the vibration is coming from the joist bays "two joists away," look at where and why. Hydronic heat is silent if done properly. Remove the hangers you put in and listen and feel around. Harmonic resonance can be a real hard to solve problem sometimes but, it can always be isolated. I know of a company in Cambridge MA that specializes in sound and vibration isolation. If it gets too bad give us a call.

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Mike T., Swampeast MO

Not sure that I'd make attachments to ductwork--probably strong enough, but they're great vibration transmitters.

As to why you hear the sound in a completely different joist, can only say that resonances happen where something is exactly in "tune" with the vibration.

A couple months ago, mother-in-law called me in a panic that her house sounded like it was "coming apart". Got there and glassware in a bank of kitchen wall-cabinets was making an unearthly buzz. Her husband is on an oxygen concentrator that uses a small compressor. It was in a room at least 40' away. Moved it a couple inches and the noise stopped.

Unknown

Sound proof,,,

There is a whole industry dedicated to sound proofing and vibration. As a nuclear pipe fitter on the 688 class subs I CAN SAY I KNOW A THING OR THREE ABOUT SOUND AND VIBRATION liberation.

As far as your Vitodens goes, why not have the installer do the service? No way the vibration is comming from the WB2.

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