Pump Noise in a Gravity Conversion

Brian Macdonald_4

I have a Gravity Hot Water System that was converted to forced flow three years ago. The problem is that I can clearly hear the circulator running in almost every room in the house, except the boiler room (basement). The pump is almost silent when one in standing next to it. The sound seems to resonate from the radiators. The original pump was a Bell and Gosset (100 series, I think) and the current one is a Taco 007 (the B & G got a leak, as did the second and third B & G's). The Taco is somewhat quieter than the B & G's were but still noisier than I would like. The near boiler piping is 1 1/4" feeding two 3" supply and two 3" returns. Any ideas on what could be done (easily, if possible) to reduce the resonant noise? According to the information in posts here on the Wall and in Dan's books the pump is sized correctly. Thanks in advance! Brian Macdonald.

Steamhead

First question

How many square feet of radiation does this system have? Second- are you Pumping Away? Third- is the water quality questionable?

If you've gone thru three B&G 100 circs in three years something is definitely wrong. Post a photo if you can.

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Mike T., Swampeast MO

Resonance

Make certain the new pump is securely mounted and that all piping is very well supported.

Ensure that all of the pipe hangers are tight and that there are a sufficient number. If they're the easily adjustably type, experiment with tightening and loosening (not so loose as to lose support of course).

Brian Macdonald_4

803 Sq. Ft. of EDR to the best of my ability to calculate. Yes, pumping away from expansion tank. I think the water quality is OK. I drained a little last month to put the system into a vacuum to change a bleeder valve and the water that came out was slightly blackish and pretty smelly but no slime or goobers or other "boiler snot". I am attempting to attach pictures. Oh, the pumps. All the B & G's were replaced in the first five weeks. First one had a flange bolt overtightened which broke the flange causing the leak, the second was installed with the gasket wound up in the impeller (that one was REALLY noisy)causing leak, third leaked oil from the motor bearing area and may have just been over oiled but at this point I suggested to the installer that maybe a different make of circ would be worth a try...

Mark Hunt

The boiler


needs to have a by-pass installed at the very least, primary/secondary piping would be preferred.

The system is a high volume/high mass system with a relatively small content boiler attached.

Get the manufacturers instructions and look up piping arrangements for the type of system you have. You will find that they recommend a by-pass to protect the boiler from low return water temps.

Mark H

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Brian Macdonald_4

Yes, I know but....

Thanks, Mark, Mike, and Steamhead. I understand that P/S or at least a bypass would be good, but unfortunately I didn't learn that until after the installers 1 year warrenty on workmanship ran out. Besides which they can't fit pipe that doesn't leak, or install a circ properly, or figure out why the boiler sometimes wouldnt light, or check for gas leaks before they leave, or... In a nutshell that particular company will never enter my house again. Nor do I currently have the money to hire another company to repipe, or the time to do it myself right now. Just looking for ideas on the noise so when the time comes to get it fixed I'll know what to do or ask for.

I really had no intention of getting into a rant or anyting like that, it's just that with the level of knowledge I had when I purchased this system it was hard to tell who was good and who wasn't. Looking back I don't think any of the bidding contractors would have done the job right. Everyone can talk the talk. I have just chalked it up to experience and moved on.

Now, any more ideas on the noise, which could be a factor in any piping arrangement? I would hate to repipe only to have the same noise problem, although obviously the possible condensing issue would be resolved.

Thanks,

Brian Macdonald

ernie_3

you may have.....

done an EDR but did you calculat how much water you are moving and how much head you need? The 3" pipe is the giveaway. On first glance I would try the Taco 008. Also, how do you figure you're pumping away? The X-tank should be on the inlet side of the pump. Yours is tapped off of the boiler.

Mark Hunt

Velocity noise


Yopu could try throttling the flow and see if that reduces the noise.


Mark H

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Brian Macdonald_4

pumping away

The circ is on the supply side of the boiler just about 10 inches away. The expansion tank is all of 2 or 3 feet from the circ inlet. Is that not close enough to be "pumping away"? Why not?

Thanks.

Brian Macdonald.

Brian Macdonald_4

velocity noise

I will! Let's try the simple easy things first.

Thanks.

Brian Macdoanld

tim smith

pump noise

My guess is it's vibration through the piping from the pump, try when you are able to get some diaphragm style Safe Flexes. These have a double bellows in the flex to absorb vibration, worked great on some jobs I have done. I have used the 1" and the 3" sizes for residential and commercial jobs with vibration problems. Good luck, Tim.

Dale

Looking at the picture

I think the velocity is too high, a taco 005 or the smallest pump you can find would be all you need with 3" mains. Since your picture shows valves on both of the returns and the supply after the pump I would close both return valves off slowly and then the pump outlet. I know this sounds weird since it's a loop circuit but ball valves don't throttle very well and you'll need to get them pretty near closed to affect flow. The other posts are correct as to pipe supports and isolation dampers. You could put on a thick glove and hold the outlet pipe and see if a person up stairs notices any change in noise.
Also, most gravity systems were designed to top out at 190 or 200 degrees so if the high limit is set at 200 or so you may want to try raising the pressure in the boiler to 18 or so cold from 12psi to lessen the chance of spot boiling.

jerry scharf_2

expansion tank

Brian,

I doubt this has anything to do wit the noise, but is that expansion tank big enough? Just wondering if someone did the calcs for the water volume and temps involved.

jerry

Steamhead

Brian, that setup will only work for Pumping Away

if the boiler is designed to act as its own air separator. I think that boiler might have actually been made by Dunkirk, though it says Lennox on it. In the Dunkirk literature that I have, the tapping at the left rear is only for the safety valve, not the expansion tank or to act as an air vent.

If this information is correct, you need to add an air separator to the supply line between the boiler and the circulator, and move the tank and air vent to the separator. I believe Spirovent makes a vertical separator that should fit your situation well.

I've attached the Dunkirk piping diagram that I have. For Pumping Away, the circ would go about where the diagram is labeled "Supply Main", after the air separator ("purger" in the diagram).

The Taco 007 is the right size circ for your system, if the EDR is at or near the 803 square feet you gave us.

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Brian Macdonald_4

expansion tank

Yes, I think it is big enough although the one installed with the new boiler was not - at hight temps the pressure would get high enough to blow the pressure valve. With the current expansion tank (twice the size of the old one) the pressure rise from cold to high limit is about 5 - 6 lbs. Tank is charged to 16 lbs. by the way - it's a three storey house.

Thanks.

Brian Macdonald

Brian Macdonald_4

air separator

Steamhead, the position of the expansion tank is as installed by the original contractor. There was no air separator installed at all. I added the current one (on the pipe to the expansion tank) because I could never bleed all the air from the radiators and was hearing bubbles gurgling through the system. Air seemed to be getting trapped somwhere and making it's way around later. The air separator as installed has actually helped tremendously. Part of the reason I put it there is it seemed a likely place for air to get trapped and also I could put it in without draining the whole system. I have bled the rads several times since installing the separator and have got no air at all.

Thanks.

Brian Macdonald

Steamhead

Air separators work best

when installed in the supply line leaving the boiler. This way they catch the air as it flows out of the boiler with the water.

I suspect your separator, as installed, is simply serving as a place to mount an air vent. The water velocity inside the boiler is fairly low, which will allow some air to separate and be vented.

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Brian Macdonald_4

air vent

Steamhead,

Yes, I'm sure you are right. When this thing gets piped properly (maybe next summer) that's how we'll do it. I believe I said the wrong thing in my earlier post - there is still no "air separator" per se. What I installed was an automatic air vent, hoping the relatively wide space of the boiler would slow the flow in that spot enough to allow some of the air to go up the pipe to the auto vent.

Thanks to you and everyone else for your input. It is greatly appreciated.

Brian Macdoanld

Brian Macdonald_4

Safe Flex

Tim,

Would you tell me where I can find literature on this product? Has anyone else out here used them and how long do they (should they) last? I browsed the web for a little bit but couldn't come up with any information.

Thanks.

Brian Macdonald

Brian Macdonald_4

Update

Hi. I have tried adjusting pipe hangers and throttling back the isolation valves. I was unable to affect the noise by adjusting hangers. Throttling the valves did help some when done as Dale suggested. Interestingly the noise was only reduced when both the supply and return valves were closed more than halfway. Just closing supply or return alone did not affect the sound much. However I am worried about slowing the flow enough to create too large a delta T for the (improperly piped) boiler to handle. I am leaving them open for the moment.

Questions. Am I right that slowing the flow will increase Delta T? What would be the "right" delta T for a gravity conversion in general? Should this be measured on a "near design temp" day? I seems in this shoulder season weather I am seeing a delta T of 6 - 7 degrees before the boiler shuts off on outdoor reset.

Are some makes of circs noticed to be quieter than others by you folks who hear a lot of them? Are there any other suggestons for making a quiet system in general? This is all about gathering information for a possible future repipe.

Thanks again.

Brian Macdonald

Mike T., Swampeast MO

The gravity conversion conondrum

Yes, slowing the flow will increase the delta-t. Gravity systems typically operated with a 30° delta-t.

Problem is that if you try to reduce flow to the level that will result in such a delta-t you probably won't get full flow through the system!

The only way I know of to reduce the flow and increase delta-t while ensuring complete circulation and balanced delivery of heat is to install TRVs on the radiators.

Then you get DEEP into the potential for condensation when you start running the generally very low temperatures required because of the typically oversized radiation.

Dale

Even the blind hog

Finds the acorn once in a while. Since you have ball valves remember that you get alot of flow quickly when they are just partially open the flow is most certainly not linear to the handle position. The old gravity system was made for really low flow at a pretty high temp and delta tee. I would get a digital thermometer and check the actual temps, I still think your flow may be too high. You may need to add a boiler bypass to make sure you don't condense. If you want to do some piping flow meters and circuit setters can be installed.

Brian Macdonald_4

blind hog

When I get cool enough weather to get a long enough burn cycle to get a stable delta T (I have thermometers on the supply and return now) I may try throttling back until some reasonable Delta T is reached. I'm thinking 15 - 20 degrees. Opinions, anyone?

Thanks.

Brian Macdonald

Dick Charland

Pump noise at radiators

I'm not sure how long this has been converted from gravity to a closed system with a circulator or if this has been a problem all along. There were some gravity systems that controlled the flow through the radiators by installing restrictors in each radiator return. These should have been removed when the system was converted and could account for what I think you may be hearing.

Brian Macdonald_4

restrictor plates

****, thanks for the interesting idea. This will be the conversion's third season, and the noise has been there since the install. I have had two of fifteen radiators out since I have lived here. Both were on the second of three stories and neither had restrictor plates. There may possibly be plates on the third floor rads but i have the hand valves closed on those. We use the third floor for a guest area and don't heat it if we don't have guests. When the valves are open the third floor heats very well (too well - I usually just open one of three rads). I suppose there could be plates on the other second floor rads, although I seem to get pretty good flow through them. I have all second floor rads throttled back pretty far with the hand valves (except for the stuck one)to balance the first floor with the second. Does it still sound to you like it could be restrictor plates? The installing contractor certainly didn't check for them.

Thanks.

Brian Macdonald