noisey baseboards

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Old 10-27-08, 12:18 PM
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noisey baseboards

Over the last 3 years I have been trying to solve the problem of my baseboards sounding as if I have a river running through them.
I have a simple 1 zone 3 loop system heating an apartment. This spring I replaced some of the baseboard units as I was remodeling a bathroom on one of the loops. There was some minor reconfiguring but nothing major. So after filling the system back up and bleeding the the loops again it appeared as if all the air had been purged.
Now that the temp has dropped in Chicago I have been paying attention to the sounds and hearing what sounds like a ton of air in the system.
It all started 3 years ago when the pump failed followed by the inlet water pressure valve failing causing my expansion tank to also fail. So i figured all of that out, replaced them and good to go right. No. Every since then I have not had a quiet heating system. Last year tried purging the system from the boiler (there is 0 bleeder valves on any of the baseboard units) and still never achieved a quiet system.
I was then convinced my float type air vent above the air scoop was faulty. I replaced it with and air disc vent. The HVAC guy assured me that this is what all the plumbers are using so I reluctantly took his word and used it. Again, never had a quiet system but spring had come and I was happy to give it a rest.
So here I am again needing heat and listening to the river flow through my pipes. Sorry for all the details I just like to get it all out there at once so i can get some good advice. Clearly there is something wrong or I am not bleeding the system correctly.
When purging I do the following. Turn off boiler, shut valve above pump, and purge 1 loop at a time until no more air bubbles are coming out. Close final loop then close bleed valve. Open everything back up and turn on the boiler. I DO NOT put the valve in fill mode.
I am think about replacing the float type vent above the boiler now. It doesn't leak but if I press the schrader valve I little air comes out then a little water.
Questions:
Should i not have used the air disc vent above the air scoop?
Does it sound like i need to replace the float vent above the boiler?
And finally, Am I bleeding the system incorrectly?
I truly appreciate everyone taking the time to read this novel. And Thank you for any advice.

-Benn
 
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Old 10-27-08, 01:12 PM
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adding pics

These pics were taken a while ago and have since removed all of the pipe insulation near the boiler.

http://s227.photobucket.com/albums/d...view=slideshow
 
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Old 10-27-08, 03:38 PM
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A-haa! It seems the noise started when you replaced the circulating pump? I think the water velocity in the piping is too high - anything approaching 4 ft/sec causes objectionable flow noise. Can you link us to the head-flow curve of the replacement pump?

Air in the system usually makes a gurgling noise AND stops flow past high points. If you bled the system properly, then there shouldn't be an air problem.
Doug
 
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Old 10-27-08, 04:18 PM
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Doug,

I have included pics of the pump. Is this what you were looking for?

http://s227.photobucket.com/albums/d...view=slideshow

Thanks,
Benn
 
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Old 10-27-08, 04:33 PM
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I think that gilmorrie has the right idea, that your noise (which may include air) is caused by overly high velocity. You may be able to confirm this by slowly closing the valve in the suction line of the pump. Understand that you may cause the pump to cavitate with this action so it isn't a cure.

The pictures show a float type vent on the air eliminator fitting. If you changed this to a hygroscopic disc vent you went backwards. The float vent is (in my opinion) far superior to the hygroscopic disc type.

You also have the pump in the wrong place in relation to the expansion tank and this alone could be the cause of your noise. You could try removing the expansion tank from the air eliminator and connecting it at the purge fitting. This arrangement is known as "pumping away" and is the preferred piping arrangement. The (relatively) small piping and minimal straight distances before and after the air eliminator are not conducive to proper air elimination.

When you did your "reconfiguring" just what exactly did you do? By all things holy every time the water flow turns downward an air vent should be fitted. I don't know why installers don't do this as it is a relatively minor cost item at the time of installation.
 
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Old 10-27-08, 05:19 PM
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Furd,
Thanks for the insight. I remodeled a bathroom and basically took out the old baseboard unit and replaced it with a new one after moving some of the pipes into the new wall.
As you noticed i did replace the float vent above the expansion tank with an air disc and never felt good about it. Now you have confirmed my suspicions I will replace it with a new float type airvent.
So the main problem could be the pump is to big?
 
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Old 10-27-08, 05:26 PM
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Big is a subjective term. Your current pump may be pumping a greater flow than the system requires. Being a single-stage centrifugal pump this is not a difficult thing to correct but it could take some experimenting. The easiest would be to re-pipe the pump with a ball valve on the discharge side and then close the ball valve partially to decrease the flow.
 
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Old 10-27-08, 08:21 PM
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I seriously doubt that NRF22 is too big ... isn't that more or less equivalent to the Taco 007 ?

Benn, I don't think you mentioned, so I'm gonna ask ...

What does the pressure gauge read cold? _________ and hot? _______

How many stories tall is the building ? (or better yet, what's the elevation difference from the bottom of the boiler to the top of the highest point in the system ?)
 
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Old 10-27-08, 08:31 PM
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NRF-22 may be part of the problem. What was the pump it replaced? Between not pumping away and now having a fairly substantial circulator, you may be pulling down the pressure enough to cause the air problems you describe.

Single zone with 3 loops? How many feet of piping total are we talking? Approximately how many elbows?
 
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Old 10-27-08, 09:42 PM
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I didn't look at the curves on the 22... so I ain't sure ... but, in itself, if the water is moving too fast, you will hear noises similar to what you hear from your domestic pipes when you open a tap; the sound of water moving through the system.

Whether or not the pump is too big, you should NOT hear any air moving in the system.

Key point in pumping AWAY from the expansion tank is the fact that the circulator will ADD dynamic pressure to the system, causing any air bubbles to shrink in size and be more easily moved to the air collection device and expelled.

When you pump TOWARD the expansion tank, the circulator SUBTRACTS dynamic pressure from the system and any bubbles will GROW LARGER and become more difficult to remove.

The bigger the pump, the more profound this effect becomes, so if the pump is too big, it could be a contributing factor, but not the sole reason...

I still wanna know what the pressures in the system actually are though, and the height of the system.
 
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Old 10-28-08, 10:10 AM
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The psi ranges between 12 - 16 cold and hot respectively. The baseboards are all on the 2nd floor so in theory they are all at the same elevation which is aprox. 18' above the boiler.
The following are all estimates but should be pretty close as i did use a tape and actually count all the elbows but some stuff is in walls ect.
Loop 1 16 elbows 130'
Loop 2 25 elbows 140'
Loop 3 14 elbows 6 45's 160'
The length of pipe includes the return pipe.
When pumping towards the expansion tank as is in this case, does it make a difference the tank is at the end of the line? That is how this one was installed, just before it returns to the boiler.
Thanks,
Benn
 
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Old 10-28-08, 06:22 PM
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OK, by my 'ROT' (Rule Of Thumb) which ppl don't like ... I'm going with something like less than 10 ft of head for loop 3 ... that's your worst case.

NRF-22 pump curve shows around 7.5 GPM at 10 Ft... but I'm thinking the head might be a little higher than 10 ... probly more like 12 ... at 12 ft, yer down around 5 GPM ... so, yeah, it's probly slightly too large. You might be able to choke it a little bit with a valve as furd suggested ... I've never tried that ... I would use a globe valve though, not a ball valve.

OR, what about a differential pressure valve ?

I forget... these are 3 ZONES ? or are you running all three in parallel, with one t'stat ?
 
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Old 10-28-08, 08:04 PM
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One zone with three branches and one NRF-22 should be something like this:

branch1 4.5 gpm
branch2 4.2 gpm
branch3 4.1 gpm

System flow is 12.9 gpm at 6.4 ft of head. Pressure diff across the circ is 2.7 psi. Because the circulator is pumping toward, rather than away from, the expansion tank, the 2.7 psi is being achieved by developing negative pressure on the suction side. In a 15 psi system, the pressure up top is going to be pretty low. [Hey Troop, how low? ]

In the absence of evidence for other potential causes (e.g., leaks causing more air-laden water to be added), guessing here that the perpetual air problem is due to low pressure at the top of the loops. Changing connection point of the expansion tank may cure it.
 
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Old 10-28-08, 09:21 PM
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[Hey Troop, how low? ]
Ummmm... well, assuming that there is 4 PSI up top to start with ... and you measure pretty much at the center of the loop ... and that the pressure change across the loop is linear ... I'm gonna say approximately 2.65 PSI ...

If you were to pump away, I think it would be 5.35 in this example.
 
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Old 10-28-08, 09:39 PM
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Just as an aside to calculating head...

is it true that for two parallel piped loops, the total head of the two loops in parallel can be gotten from:

(Hd1 X Hd2) / (Hd1 + Hd2) = HdTotal ?

and that for more than two parallel loops you can use this equation:

1 / (1/Hd1 + 1/Hd2 + 1/Hd3 + 1/Hdx ) = HdTotal ?
 
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Old 10-28-08, 09:51 PM
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So according to your numbers Xiph, it appears that the 22 is almost perfect for the job ? If not just a wee widdle bit uberpumped ? Ja ?

I actually came up with a bit higher numbers... 17 GPM total, but I'm goin' with the Swordfish ...
 
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Old 10-29-08, 07:13 AM
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Trooper, I will admit to having cheated for this one and used Siggyware. Also did it quick and didn't save my work. Might try to back out the numbers to see how your eqns above work out. Sometime....

But yeah, the difference in the pressure at the top of the loops is pretty significant, so furd and you called this one, it appears.

Bennhamm, the folks here can walk you through how to move the expansion tank connection if you want. That should cure it.
 
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Old 10-29-08, 03:48 PM
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Benn, by the way, that pressure range you mentioned earlier is fine... my thinking was that perhaps your pressure was low ... cuz that'll cause air noises too ...

I need to look at the pics again to get an idea of what might be involved in moving the tank connection point.

I also want to see where the automatic air vent is going to be in relation to the pump... it's not a good place for it if it ends up on the suction side of the pump. It _could_ take a gulp of air every time the pump starts...

You still with us ?
 
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Old 10-29-08, 03:57 PM
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Waitaminnit guyz, I just looked at the pics again, and it appears to my tired old eyes that he already IS pumping away ...

The pump is on the return, pumping toward the boiler, yes ?

And isn't the airscoop and tank just upstream of the circ ?

Looks like 3 zones on the supply mani in the foreground, and two? (maybe 3rd is hidden ?) returns on the manifold behind that one.

So now what ?
 
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Old 10-29-08, 08:10 PM
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Tired eyes... the AS and the ET are on the supply. It comes up and elbows over. The pic of the return manifold with array of globe valves goes down to the return. It looks like....
 
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Old 10-30-08, 01:52 AM
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Yup... I see it now ... all I needed was a few hours sleep!

I agree that it looks like it would be pretty easy to move the tank to the return manifold where the drain hose is hooked up now.

Benn, it sounds like you are purging correctly, closing the valve in the common return above the pump, closing all the return valves except the one you want to purge, open the drain hose valve...

At this point, you can use the fast fill to move the water faster through the zone, and would probably get more air out ...

And, it might could be that moving the tank connection would help, if not solve, your air problems. You could remove and plug the tap in the bottom of the air scoop. Remove the drain valve. Make up an 'adapter' that threads in where the valve was... threaded male adapter, ball valve, tee with drain, threaded female adapter ... then the tank on the bottom ...

The ball valve with the drain below would let you easily service the expansion tank in the future.
 
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Old 10-30-08, 08:28 AM
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You could even just test this out by using a braided dishwasher hose (get a long one; I think they are rated sufficiently for this temp and pressure) and adapt it to the drain where the green hose is. Connect exp tank to dishwasher hose, connect other end to drain. Not ideal, but probably close enough. Set the exp tank on the floor in a 'wok ring' made from a pail, cut-off 3gal bucket or whatever.
 
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Old 10-30-08, 10:16 AM
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ok, thanks for the help so far guys.
I wanted to clarify that the pump is pulling the water from the boiler then pushing it through the supply mani. After the water completes the loops it comes back together then through the air scoop/expansion tank before returning to the boiler.

To test the placement of the ET, is it possible to flip the circ. pump over? If this solves the rushing water sound I could then put it back and move the ET. Thoughts?

I also updated the photos.
Image hosting, free photo sharing & video sharing at Photobucket
 
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Old 10-30-08, 03:57 PM
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Benn, I think you have the flow backward in your mind...

It appears to me that your circulator is pumping DOWN, and INTO the boiler on the RETURN. The manifold with the three red valves is the RETURN manifold.

The SUPPLY is the one toward the rear, and comes off the top of the boiler, then to the air scoop, then splits into three and goes UP to each of the loops.

No, you can't just turn the pump around. Hot SUPPLY water comes off the TOP of the boiler, and cool RETURN water goes in the bottom. I don't think your system would be none too happy about you reversing the flow.

I think it's probably the same work, or perhaps easier, to change the tank location.

If you don't have the pipe soldering skills, you could make that adapter I mentioned with all threaded fittings. Put it together with some teflon tape, some pipe dope, and a couple wrenches. Lemmee know if yer up for it and I'll sketch something for ya ...
 
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Old 10-30-08, 04:12 PM
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NJ Trooper,
You nailed that one. I was thinking it ran the other way. Very obvious now I think about it.
I am very comfortable sweating pipe and willing to give it a shot. If you could tell me how to rearrange the expansion tank I would be grateful.
Thanks,
Benn
 
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Old 10-30-08, 07:04 PM
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Benn, here's how I'm connected with mine. Keep in mind that you don't need to have the pressure gauge, and you don't need to use a high pressure steam valve (I just happened to have those things in my 'junque' box, so I used them).

At that top of that piece, above the ball valve is my air scoop... just barely visible... what you see is the pipe coming down to a ball valve, a tee fitting, then the connection to the tank. Off the tee used to be just the valve (it's got a threaded side port), but my pressure gauge crapped out so I added this one. Like I said though, you can just put the drain directly into the tee.

What this does for you is makes it possible to check and adjust the air charge in the expansion tank without having to drain anything from the boiler, and if you had to, makes it very easy to change the tank without getting wet.

If you built something like this, you would remove the drain valve that your hose is connected to. Screw this adapter in to the pipe, and hang your tank right there. You could re-use the drain you took off if you wish... if it's in good shape...

In retrospect, I would have used threaded black pipe instead of the copper just for the extra strength... this setup is kinda 'wobbly'. But this is the general idea...

OH, WEBSTONE makes a ball valve with a hose drain built right in. If I did this again, that's what I would use. I think you can get that valve with a male thread on one end, and a female thread on the other... I'll look ... if you got one of them, you could just put that valve in, and screw the tank right on...

 
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Old 10-30-08, 07:25 PM
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No, looks like only female pipe thread ends, so if you use this, the tank would thread into one end, then a short nipple screwed in where the old drain valve was.

Webstone Ball Drain

Less than $10 here...

Then, use a 1/2" threaded plug to close the hole in the bottom of the air scoop.
 
 

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