Whine in hydronic system

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Old 12-08-07, 04:30 PM
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Whine in hydronic system

Here's the scoop!
I had a call to look at a hot boiler that making a squeal or whine and bothering the people that slept on the other side of the wall. The people told me it had been doing it since last year.
The boiler room, when I arrived, was neat and well constructed. It was a little super hot 105,000btu's. It serviced 4 zones on Honeywell ZV's. There were 2 Tasco pumps on the system. One for supply and one return. The supply side left the boiler, into a 15ltr extol tank, into air separator, up to the supply pump and off to the zones. When the system has a call for heat it satisfies ok. When the bioler water temp gets to a certain temp, usually 180 f. just prior to the boiler going off at it's 180 set, a whine starts. It is high pitched and quits when the boiler goes down. I put my trusty ear against a screwdriver and it seems like its around the air seperator (impossible). I traced the noise back to the pump. I thought the return pump was the problem. I changed it. No go. if i throttle the supply valve out of the boiler the noise gets worse. Any thoughts??
trout lake
 
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Old 12-08-07, 05:23 PM
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What's the pressure reading?
 

Last edited by Grady; 12-09-07 at 10:34 AM.
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Old 12-08-07, 05:29 PM
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Sounds like a flow issure or a mineral build-up in the boiler.
 
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Old 12-08-07, 05:47 PM
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Why would there be a pump on the supply AND the return?
 
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Old 12-08-07, 06:39 PM
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re;whine

Originally Posted by rbeck View Post
Sounds like a flow issure or a mineral build-up in the boiler.
I thought the harmonic sound could possibly come from sludge build up on the exchanger. Whats the best way to eliminate?
 
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Old 12-08-07, 06:43 PM
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Originally Posted by NJ Trooper View Post
Why would there be a pump on the supply AND the return?
Thamks for comments NJ
Lots of systems in these parts use a 2 pump system. I don't agree it's required but so,e genius thought it would make the system more efficient I suppose. it would in theory reduce the load on the single pump system and theoretically be easier for flow.....dahhhh
tl
 
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Old 12-08-07, 06:46 PM
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whine

The exchanger build up makes sence. Would you guys recommend a flush or load exchanger with an additive, let it sit then flush?
tl
 
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Old 12-08-07, 06:54 PM
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Originally Posted by Who View Post
What's the pressure reading?
around 20psi cold or hot
was about 5 when I arrived and I jacked it up to something more appropriate
tl
 

Last edited by Grady; 12-09-07 at 10:36 AM.
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Old 12-08-07, 06:55 PM
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Is there a bypass line on the boiler ? no real point in my asking, just curious... I did read a raypak install lately that talked about the bypass valve and 'harmonics' . I do wonder if it has something to do with the '2 pump' system... maybe somehow there is interaction between the two? What happens if you cut power to one or the other pump ?
 
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Old 12-08-07, 07:01 PM
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Originally Posted by NJ Trooper View Post
Is there a bypass line on the boiler ? no real point in my asking, just curious... I did read a raypak install lately that talked about the bypass valve and 'harmonics' . I do wonder if it has something to do with the '2 pump' system... maybe somehow there is interaction between the two? What happens if you cut power to one or the other pump ?
NJ
interesting! what was the connection?
there is (1) mixing valve on the system, (1)
backflow on the supply downstream of prv, (1) backflow at enterance or return manifold.
I asked a buddy few hrs ago and he mentioned dirty exchanger also. Puzzled!!!
tl
 
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Old 12-08-07, 07:10 PM
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Try calling the mfg and see what they have to say

604.929.1214 Allied Engineering Co.

There is a blurb in one of their manuals that says audible noise can be a result of mineral scaling in the heat exchanger.
 
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Old 12-08-07, 07:29 PM
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Originally Posted by trout lake View Post
NJ
interesting! what was the connection?
Not sure really... and I don't recall exactly what the manual said about it... it is in one of the posts here, as I read it in response to someone posting with a question about Raypack.

Originally Posted by trout lake View Post
there is (1) mixing valve on the system, (1)
backflow on the supply downstream of prv, (1) backflow at enterance or return manifold.
I asked a buddy few hrs ago and he mentioned dirty exchanger also. Puzzled!!!
tl
I'm puzzled too...

Is the mixing valve there to run cooler water to radiant loop ?

By 'backflow' I assume you are talking about flow-chek valves ?

Here's the manf website:

Allied Boilers

If you click LITERATURE you get a page with downloadable PDF files. I could not open the install manual for the MG series, Adobe said it was broken file. But in the user manual is where I read about the 'noises' ... check it out.

By the way, it looks like the AAE series install manual works, and there doesn't seem to be much difference between the two other than size.

The heat exchanger in them is some kinda steel "SPIRAL TUBE" design...
 
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Old 12-08-07, 08:51 PM
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Originally Posted by NJ Trooper View Post
Not sure really... and I don't recall exactly what the manual said about it... it is in one of the posts here, as I read it in response to someone posting with a question about Raypack.



I'm puzzled too...

Is the mixing valve there to run cooler water to radiant loop ?

By 'backflow' I assume you are talking about flow-chek valves ?

Here's the manf website:

Allied Boilers

If you click LITERATURE you get a page with downloadable PDF files. I could not open the install manual for the MG series, Adobe said it was broken file. But in the user manual is where I read about the 'noises' ... check it out.

By the way, it looks like the AAE series install manual works, and there doesn't seem to be much difference between the two other than size.

The heat exchanger in them is some kinda steel "SPIRAL TUBE" design...
Thanks for info....i'll check
 
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Old 12-09-07, 08:04 AM
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TL, are the circulators both mounted with the motors in the horizontal position ? Why do I ask ?

If the motors are mounted vertically above the pump, there is a greater tendency for the pump to cavitate.

Reading up on circs in series (Modern Hydronic Heating, Siegenthaler) we find that this is a viable way to increase flow in a higher head (more restrictive) system, but that there is a greater tendency for pumps to cavitate. Especially if they are 'flange to flange'. Your system has the heat exchanger separating them, so the tendency to cavitate is less, but still exists.

I wonder if the noise you are hearing is one or both of the pumps beginning to cavitate ? OR, maybe the two pumps are creating TOO MUCH FLOW through the heat exchanger ? Looking at Allied's info (boiler manf) they talk about 'noises' possibly being due to either scale, or IMPROPER FLOW.

That SPIRAL design of the HX really makes me wonder about these things...

Why doesn't it make the noise at lower water temps ? Because the water is denser. Higher temp water has less density, and would be easier to cavitate in a marginal situation.
 
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Old 12-09-07, 03:08 PM
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Originally Posted by NJ Trooper View Post
TL, are the circulators both mounted with the motors in the horizontal position ? Why do I ask ?

If the motors are mounted vertically above the pump, there is a greater tendency for the pump to cavitate.

Reading up on circs in series (Modern Hydronic Heating, Siegenthaler) we find that this is a viable way to increase flow in a higher head (more restrictive) system, but that there is a greater tendency for pumps to cavitate. Especially if they are 'flange to flange'. Your system has the heat exchanger separating them, so the tendency to cavitate is less, but still exists.

I wonder if the noise you are hearing is one or both of the pumps beginning to cavitate ? OR, maybe the two pumps are creating TOO MUCH FLOW through the heat exchanger ? Looking at Allied's info (boiler manf) they talk about 'noises' possibly being due to either scale, or IMPROPER FLOW.

That SPIRAL design of the HX really makes me wonder about these things...

Why doesn't it make the noise at lower water temps ? Because the water is denser. Higher temp water has less density, and would be easier to cavitate in a marginal situation.
Thanks for your input NJ
Cavitation is not the problem, guaranteed.
Pumps are spaced adequately and this is not the issue.
I'm leaning towards the harmonic noise from a dirty coated exchanger and am not sure the best remedy!!!
tl
 
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Old 12-09-07, 05:10 PM
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Originally Posted by trout lake View Post
Cavitation is not the problem, guaranteed
How you know that ?

By the way, you don't have to quote the entire message you are replying each time... FYI ...
 
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Old 12-09-07, 08:37 PM
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Cause..
Caviatation is a specific sound and this ain't it.
If it were the pumps cavitating, they would do it through the entire heat cycle. In this case, the harmonics start at the high end of the temp rise just before the boiler goes off as it nears it's temp set.
I heard somewhere (i hope it wasn't in a bar) that if srud buils on the exchanger, the harmonic vibration can happen as the water super-heats. The crud layer acts as a baffel between the exchanger and the water and all sorts of wierd things happen.
Not sure......for sure can't dispell the exchanger theory.
thanks fer yer input....it's appreciated
tl
 
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Old 12-09-07, 09:04 PM
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I think you can have cavitation at higher temps and not at lower temps becuz of the lower density of the water at the higher temp...

Honestly... I would try powering down each circ in turn and see what happens. Even the new one you just installed. I wouldn't rule anything out at this point, you might start chasing ghosts.

I'm kinda down with the scaling myself, but keeping an open mind. Just glad it's YOU that's working on it and not ME !

Call Allied too... they might say 'oh yeah, it's _________... and here's how ya fix it' !
 
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Old 12-10-07, 05:58 PM
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whine

i picked a good heading...."whining"...that be me.......wine at this point is more appropriate.
I'll revisit the problem this coming Saturday.
I'm going to flush the system and try an additive(don't know which one) and watch results. A pal in the trade told me to introduce detergent to the boiler and if harmonics are coming from there it will stop them. At that point circulate it through the boiled and re-flush. Should end problem if in fact it waz the prob.
Sounds just bazzar enough to be the problem. Id call allied and I can just here it "sir.....you need a new hi-efficency boiler and we've got just the puppy 4 u
tl
 
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Old 12-10-07, 09:29 PM
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Originally Posted by trout lake View Post
Cause..
Caviatation is a specific sound and this ain't it.
If it were the pumps cavitating, they would do it through the entire heat cycle. In this case, the harmonics start at the high end of the temp rise just before the boiler goes off as it nears it's temp set.
Why not try shutting the supply end pump off when the system gets near the end of the heating cycle?

From what I have read, the hotter the temperature of the water, the more likely cavitation can occur.

What happens if you only use one pump? Do you still get flow everywhere? Two pumps seems wasteful, especially zoned with with ZVs and probably not having a differential bypass.
 
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Old 12-11-07, 10:57 PM
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I think something needs a good flush! hehehehehe (couldn't resist).

Just out of curiousity, is the noise there if the pressure is increased to say 25 psi.? How about when you put it back to 5 psi? Are you getting real good flow through ALL zones? Is it possible the noise is coming from one of the zone valves?

I once had a strange 'whistle' come from an oil line, but only after the boiler ran for a couple of minutes. I blew it out, no fix. I ended up changing it and the noise disappeared.

Do you have enough thrust clearance on the drive coupling? Sometimes once the unit heats up and there is no clearance you can get a noise from the pump because of lack of clearance. I check this out after a customer tells me that a 'tech' changed the coupling and their boiler makes a humming noise before it starts up. Sure, the motor is being restricted. Loosen the 2 mounting bolts on the pump 1 turn and see if it still happens.

I also came upon a rattle with an occasional minute whistling sound in the boiler once that ended up being a loose piece of solder in the copper piping near the circulator, but you would only hear it rattling when the circulator started or stopped.

Sometimes the problem is too simple and we are looking too deep.

Good luck, Charlie
 
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Old 12-12-07, 03:49 PM
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whining solved(i think)

Hey guys
FYI
Spoke to a design guy at Allied yesterday (super hot and Raypac boiler systems)
I explained to him from the beginning the diagnosis. He stopped me half way through and said "I know exactly". And, I think he did.
He said it was a dirty exchanger, he runs in to it all the time. He said the guys troubleshooting this problem usually end up on a fu8nny farm after replacing pumps and loosening flange couplings.
It's basically a resonance between the dirty fins in the exchanger and the water. Said it usually starts around 140f and ceases at shut-down. (my delima ). Solution........pour a half a cup of liquid detergent in the boiler and leave it in (don't flush). Problem......disappears.
Ya know the funny thing...........a young guy in the trade, whom I have a tonne of respect for, told me the same thing and I discounted him for a fruit cake. Goes to show you......
I'll add the soap an Saturday and let ya all know...
jeezzz....this thing grew legs and turned into a real "soap opera"
tl
 
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Old 12-12-07, 03:56 PM
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Let me ask you this: After you add the detergent will you please take some of this laundry off my hands?
Sorry, Couldn't resist. Well, I just learned something. Amaxing! Thanks proffessor!
 
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Old 12-13-07, 05:32 PM
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Originally Posted by boilersrus View Post
Let me ask you this: After you add the detergent will you please take some of this laundry off my hands?
Sorry, Couldn't resist. Well, I just learned something. Amaxing! Thanks proffessor!
THERE'S ONE IN EVERY CROWD!!
 
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Old 12-13-07, 07:08 PM
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Make that two... I thought of it too, but Charlie beat me to the SUBMIT.

But, please do let us know how it works out for ya...

I'm still not sure you need two pumps though !
 
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Old 12-13-07, 07:58 PM
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NJ
ya....I hear you about the 2 pump thing, and partially agree.
For the price of the pump tho, (less than $100), I like the set up......here's y
As you know boiler manufactures, 90% of the time, put the pump on the wrong side of the boiler. I've taken the engineers to task on it and they admit it isn't the most appropriate side but do it for "shipping reasons". With the pump on the return, pump head suffers about a 2 lb loss of efficiency. You cant pick the pressure fluctuation on the boiler because it happen between the expansion tank set and the pump on the boiler return. In other words, between the rise and fall. So what's the big deal with that type of loss? Not much in a perfect world. My god, it wasn't to many years ago when gravity feed was all we knew(for us old timers anyway). That head loss creates one minor problem. What is it u say? Air entrapment in water relies on pressure. Reduce the pressure even slightly off of delta p and you allow for the potential of minor amounts of oxygen molecules releasing. It requires certain other factors in the equation for this to happen like rapid firing of the boiler and large temperature swings on the system, but trust me, it happens. Consequently....pumps on the wrong side are one of the biggest mitigating factors for air in systems...............I know what your saying....all this from a guy that can't figure out a winery boiler..
tl
 
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Old 12-13-07, 08:25 PM
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Yep... pumping away from PONPC ... not only for shipping reasons do they mount the pump on the return, but older pumps couldn't handle the hot water temps as well, so they started mounting them on the cooler return side in an attempt to provide longer life. Then I guess it just sorta became 'habit' as the manufacturers forgot why they were mounted there in the first place, even after new materials were developed that would handle the temps...
 
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