Mod-con forced hot water system that squeals
My plumber recently replaced the boiler in my small 3-zone Colonial with a Lochinvar WHN-85 boiler with a Lochinvar SIT 40 indirect water heater. Seems to work well, but I’ve been having trouble with noise.
First, the boiler occasionally emitted what I called a foghorn noise out of the exhaust pipe (the plumber opined it was a French horn). The solution was to tune the mixture to the rich side of the specified range (i.e. more gas per air, and more CO2 in the exhaust), which made it go away.
Now, however, I have this squeal. It’s at about 8300 Hz, which is pretty close to the top of my hearing range and extremely annoying. It’s very hard to localize because of the pitch, but I did some snooping and playing around with the circulator speed switches, and found that changing the speed on the main circulator (the one going between the boiler and the zones) changed the sound. My plumber replaced that circulator, but the squeal remains. I found I even can hear the squeal coming out of the first floor radiators.
Here’s a video I posted to Youtube. I found that this time changing the zone 3 (first floor) circulator changes the sound, and even reliably makes it go away and come back.
So, do I ask the plumber to replace this circulator, too? Have you heard of (or just heard) this kind of sound before? Other possible causes?
Thanks,
Dan
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Replies
go to heatinghelp.com betcha they know the answer
wonder if the circulator is pushing water too fast....
Try using the ball valves to throttle back the flow a bit, see if that affects it.
Your flows may be on the high side, or just right. Measure the delta-Ts on those loops and report back. If the water coming back is less than 10F cooler you can just reduce the flow.
In any heating-system sculpture like that it's work putting at least R4 pipe insulation on all of the exposed distribution plumbing, which may kill the resonance all by itself. If the water temps in those loops are never going to exceed 150F it's fine to insulate it with 5/8" wall closed cell foam of the type used for potable plumbing. (Don't cheap out with the 3/8" wall R2 stuff found at box-stores- order the stuff online if you don't have a plumbing supply place that handles it.) For higher temp stuff you may need to pull the operating temp specs for whatever you insulate it with. With mod-cons you probably won't have to resort to the 1" fiberglass stuff used on steam heating systems, but even the 1" stuff is available online for a lot cheaper than the box stores are asking for the half-inch goods. (This supplier will sells reasonably priced higher-temp goods in small lots, won't make you buy a case of it: http://www.statesupply.com/catalogsearch/result )/?q=Pipe+insulation#p=2 , but there are others.)
The fix for the foghorn issue may not be the best one, and it probably won't fix it long term, and may have only fooled you into thinking that fixed it. The air intake and vent pipe lengths have a tuned resonance, and both the modulation rate & burner blower's speed will affect whether it's singing bass notes or not. It may only do it's thing at just the lowest firing rate or some other firing rate, and not at others, as was the case with this guy's mod-con fog horn:
http://terrylove.com/forums/index.php?threads/utica-ssc-modcon-boiler-intake-moan-noise.59021/#post-436915
post a still pic of your piping and label the pipe sizes. First glance it looks like pipe sizes are different than I do.
Water velocity could be the problem. Also need to see the set up and draw it out for myself.
Please tell us what model pumps those are , all 4 of them and what pipe sizes you have there . It appears that you have some velocity noise and probably very poor heat transfer . [email protected] if you would like to PM me .
Well, the squeal seems to have been banished. As Dana suggested, I tried closing each ball valve on the input/output of the suspect circulator. Results: the squeal continued, albeit with a slightly different sound. This seemed to be a durable result, and to me strongly implied that it was the circulator itself.
My plumber came and pulled out the circulator and housing. He found what he described as a "tiny" ding on one of the impeller blades (I didn't see it). He replaced the whole assembly, and the squeal seems to be gone (no sign of it in two days).
I'll let you know if it returns, and thanks for the help.
Dan