'Wind' noise in water pipes. What is it?

[ghirschi]

We recently had a plumber replace the priority switch (the rectangular silver piece) in this Navien Heating Box (model #KD-HB0100) and now we have a ghost that lives in the pipes. Any ideas on what is causing the 'wind' noise even when no water is running? Even the plumber is stumped.

https://youtu.be/N9sGwBovxFY

It stops when I turn off the water supply into the box.

Thanks for any suggestions!

 

[plumb_bob_square_pants]

Pictures please. I can't do the videos on my phone. Is there a mixing valve or bypass valve on the inlet or outlet? Sounds like you might there might be a leak bypassing the valve. Does this system have a recirculation pump?

 

[ghirschi]

This unit does have a mixing valve and a recirculation pump. The pump only comes on when the thermostat makes a call for hot water for the auxillary heat. However, it wouldn't come on when it should have when I was testing things last night. This leads me to further suspect the priority switch / check valve in the unit which was recently replaced due to a leak. The switch gives the domestic hot water priority over the space heating side. If that switch isn't opening or closing properly, it may not allow the pump to come on and it might be restricting water flow causing the noise? Just a guess at this point.

Here's a link to the manual.
http://www.rural-energy.net/docs/om_nHeatbox.pdf

 

[frodo]

does the priorty switch have an arrow for direction on it ?

which way is it pointed ?


pipe diagram shows 2 models ?

and shows a priorty switch with ck valve. ck flow direction

 

[ghirschi]

Yes, the priority switch has an arrow on it's face and it was installed pointing up. I'm pretty sure that's the direction of the water flow but I'll have it double checked when the plumber comes back tomorrow.

Yes, the manual shows two models. Mine is the simpler one (with one circulating pump).

 

[frodo]

if the arrow is correct, next i would ck is air in the heat side lines

if air gets into the boiler it makes a hell of a thumping racket, you think it is trying to get up and run out the door

 

[plumb_bob_square_pants]

Thumping yes but the relaxing sound of wind? Maybe it just wants to help you sleep at night. If it's pulling air this could be a culprit but it just seems unlikely. Could the pump be coming on and not pulling water? This started after the repair? Or maybe was coming on and now it's not. I'm going to get a bald spot if I don't stop scratching my head on this one.

 

[ghirschi]

There are really two issues: the pump not coming on and the soothing wind sound. I'm hoping that getting the pump problem diagnosed and fixed will resolve the noise issue as well. I'll do some more tinkering tonight.

 

[plumb_bob_square_pants]

Careful.. you don't want your tinkering to turn the pleasant wind into a raging gail.

 

[frodo]

if the pump was run at a long period of time full of air , it is burned up.

not saying yours is, but if a pump cavitates long enough it will burn up

your proplem to me sounds like the tech that installed the priorty switch. did not bleed the system completly

and you are experiencing air hammer and pump cavitation

to purge

close retur valves, open supply valves. bypass auto fill and manual fill system

after, you have flow on the return side, WITH NO BUBBLES

open return, manually circ system. and listen for woosh. woosh is air

silence is no air.

I have, in the past, hooked a hose to a system and let it circ all night with make up water on pump on and a return drain purging

 

[ghirschi]

We've made some progress.

The pump still works (yea!) and the priority switch correctly disengaged the pump when the domestic hot water was turned on. There is a switch on the circuit panel that needs to be in the "off" position or the pump won't come on. I have no idea why but that was the fix.

However, the "wind" noise is still there. I believe it is simply water flowing through the pipes in the heating box. The same sound occurs for a second or two after running water is turned off. If so, the question is then where the water is flowing when nothing is turned on?

I checked everywhere for leaks and didn't find any. (Of course, there could be a leak behind a wall or in the ceiling but I would expect to eventually see that water manifest itself somewhere). I watched the leak detector on the meter with no water running and strangely, I could see it move in the reverse direction. It wasn't much, a very small amount (maybe 20 degrees) after 5 minutes.

So here are my current ideas/questions about what's going on:
- Could the water be backflowing through the main? Do houses have a check valve or backflow preventer of some kind that might not be working?
- The priority switch in the heating box has a built-in check valve. Perhaps it's faulty?
- Would air in the pipes cause water to flow back and forth if no water is running?

Thanks for all your help.
Greg

 

[frodo]

look at your manual for settings for the mixing valve