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Hot Water Circulator Noise
Jerry Fountain
Member Posts: 7
I originally posted this on usenet (alt.hvac) but it was STRONGLY suggested that I post it here so here it is (with more quantitative measurements)
Upfront note: I'm not a HVAC pro, but I've got a fair bit of experience with piping and fluids (chemical engineer). I'm the homeowner & installer. I've lurked in the group long enough to have my Nomex jumpsuit on before posting :) (The last was for the usenet group, this area seems quite a bit more hospitable!!)
We've just replaced our old gravity based hot water boiler (very vintage, see http://pg.chem-eng.northwestern.edu/~gof/wood/Old%20Furnace.JPG for a
picture). This is part of a fairly major remodel. The new system is a Weil-Mclain CGs-6 with 3 zones, the first of which (the only one running right now) services the old large stand-up cast iron radiators (7 total ranging in size from about 2.5 feet long to one 10 feet long) of the existing first floor. All the piping was replaced for this zone from 3"-4" iron to 1" copper in a two-pipe direct-return arrangement. This is laid out with a backbone along the length of the basement (about 50 feet) with supply/return legs going to each of the radiators. The zone circulator is an Armstrong H-32 with 1-1/4" flange (1/6 HP, see http://www.armstrongpumps.com/present.asp?marketID=01&market_sectionID=01&classID=05&modelID=004&groupid=3 ) Piping in the boiler loop and trhough the circulator(s) is all 1-1/4" copper (other than into and out of the boiler itself), and is dropped down to 1" pipe after leaving the circulator.
The *boiler* is working fine. We're running into an interesting problem though that I have been trying to diagnose but have been unable to so far. The circulator is generating a LOT of noise ... at temperature. When the system starts up cold, there is little pump noise and little transmitted vibration to the rest of the system. The radiators have all been bled multiple times, and there is a spirovent just before the manifold to the circulators (on the supply side of the boiler). As the system heats up, at about 135-140degF the system starts giving off a fairly high frequency "sharp" noise. Around 150degF the noise settles a bit to a lower frequency "rumble" the continues as long as the temperature is above 150degF. Both noisy modes are quite loud and transmit though the system and to the first floor.
At first I thought the 135-140 noise was a problem with the circulator, so I swapped it out with the identical unit destined for the second floor. Same exact behavior. It doesn't seem like I should be getting cavitation at
such a low temperature, but as a test I opened to feed bypass and (slowly) raised the system pressure from 12-15 psi to 25 psi. No effect at all. If I block in the circulator by closing the blocking valves around it, the
sound does NOT change. That seems to eliminate the possibility of chatter from one of the check valves. We've got B&G circuit setters in the system so I used the test ports to check the operation. During normal operation the pump is showing a 3 psi (83" H2O or almost 7 feet) of developed head. Using the circuit setters, it looks like around 7-8 gpm of flow. Based upon the B&G Sizer program, this is about 3 feet/second flow rate for 1" pipe, 2 feet/second in the 1-1/4" pipe. Note: As the temperature of the water rises to the 160 degF point, the pressure head declines to about 2.5 psi.
So, does this spark any ideas from anyone? The two stage noise is really driving my a bit batty from a fundamentals standpoint, but hopefully someone with more field experience might have some idea of what the problem is. From the pump curve ( http://www.armstrongpumps.com/Data/performancecurves/Links/01_05_004/HSeriesCurve.pdf ) it would appear with a developed head of 7 feet I should be at close to 30 gpm!! From my (derived via circuit setter) flowrate, I should be in the 11 feet of head range (or 4.75 psi head). It's got me scratching my head.
A 'short term' solution that seems to be helping is I've throttled the circuit setter on the return leg of the zone to 40 (or 60% open). That seems to be the most open point where the severe shuddering noise at 150 degF has dropped out mostly, but there still seems to be the transitional noise at the 135-140 point.
Any and all help is greatly appreciated. I can provide pics of the layout if anyone thinks that would help.
Hopefully I won't run into this for the second zone. That will be an almost identical layout, but with Burnham cast iron baseboard radiators, 1" main feeder with 3/4" legs to each baseboard unit (8 total). The third zone with radiant for the bathroom will use a small wet circulator and a B&G S100 for an injection circulator to drive about 800 feet of tubing.
Upfront note: I'm not a HVAC pro, but I've got a fair bit of experience with piping and fluids (chemical engineer). I'm the homeowner & installer. I've lurked in the group long enough to have my Nomex jumpsuit on before posting :) (The last was for the usenet group, this area seems quite a bit more hospitable!!)
We've just replaced our old gravity based hot water boiler (very vintage, see http://pg.chem-eng.northwestern.edu/~gof/wood/Old%20Furnace.JPG for a
picture). This is part of a fairly major remodel. The new system is a Weil-Mclain CGs-6 with 3 zones, the first of which (the only one running right now) services the old large stand-up cast iron radiators (7 total ranging in size from about 2.5 feet long to one 10 feet long) of the existing first floor. All the piping was replaced for this zone from 3"-4" iron to 1" copper in a two-pipe direct-return arrangement. This is laid out with a backbone along the length of the basement (about 50 feet) with supply/return legs going to each of the radiators. The zone circulator is an Armstrong H-32 with 1-1/4" flange (1/6 HP, see http://www.armstrongpumps.com/present.asp?marketID=01&market_sectionID=01&classID=05&modelID=004&groupid=3 ) Piping in the boiler loop and trhough the circulator(s) is all 1-1/4" copper (other than into and out of the boiler itself), and is dropped down to 1" pipe after leaving the circulator.
The *boiler* is working fine. We're running into an interesting problem though that I have been trying to diagnose but have been unable to so far. The circulator is generating a LOT of noise ... at temperature. When the system starts up cold, there is little pump noise and little transmitted vibration to the rest of the system. The radiators have all been bled multiple times, and there is a spirovent just before the manifold to the circulators (on the supply side of the boiler). As the system heats up, at about 135-140degF the system starts giving off a fairly high frequency "sharp" noise. Around 150degF the noise settles a bit to a lower frequency "rumble" the continues as long as the temperature is above 150degF. Both noisy modes are quite loud and transmit though the system and to the first floor.
At first I thought the 135-140 noise was a problem with the circulator, so I swapped it out with the identical unit destined for the second floor. Same exact behavior. It doesn't seem like I should be getting cavitation at
such a low temperature, but as a test I opened to feed bypass and (slowly) raised the system pressure from 12-15 psi to 25 psi. No effect at all. If I block in the circulator by closing the blocking valves around it, the
sound does NOT change. That seems to eliminate the possibility of chatter from one of the check valves. We've got B&G circuit setters in the system so I used the test ports to check the operation. During normal operation the pump is showing a 3 psi (83" H2O or almost 7 feet) of developed head. Using the circuit setters, it looks like around 7-8 gpm of flow. Based upon the B&G Sizer program, this is about 3 feet/second flow rate for 1" pipe, 2 feet/second in the 1-1/4" pipe. Note: As the temperature of the water rises to the 160 degF point, the pressure head declines to about 2.5 psi.
So, does this spark any ideas from anyone? The two stage noise is really driving my a bit batty from a fundamentals standpoint, but hopefully someone with more field experience might have some idea of what the problem is. From the pump curve ( http://www.armstrongpumps.com/Data/performancecurves/Links/01_05_004/HSeriesCurve.pdf ) it would appear with a developed head of 7 feet I should be at close to 30 gpm!! From my (derived via circuit setter) flowrate, I should be in the 11 feet of head range (or 4.75 psi head). It's got me scratching my head.
A 'short term' solution that seems to be helping is I've throttled the circuit setter on the return leg of the zone to 40 (or 60% open). That seems to be the most open point where the severe shuddering noise at 150 degF has dropped out mostly, but there still seems to be the transitional noise at the 135-140 point.
Any and all help is greatly appreciated. I can provide pics of the layout if anyone thinks that would help.
Hopefully I won't run into this for the second zone. That will be an almost identical layout, but with Burnham cast iron baseboard radiators, 1" main feeder with 3/4" legs to each baseboard unit (8 total). The third zone with radiant for the bathroom will use a small wet circulator and a B&G S100 for an injection circulator to drive about 800 feet of tubing.
0
Comments
-
Just a guess
from a guy w/o an engineer's degree.
That 10' long old style radiator holds a lot of H2O; not to mention the other 2.5 footers. You reduced the supply and returns to 1". Could be your noise is starting when that 130+ water hits those cool, large water volume radiators. That's a lot of water to move w/ the H-32 connected to a 1" supply and return.
Why don't you turn off the valve on that large radiator and see if the noise subsides? We normally run 1" tubing on systems w/ about 80K of installed radiation. And. That is w/ midget radiators or baseboard. Matching old radiation to new piping is sometimes more art, than science.
Just a thought. Good luck.0 -
Sure sounds like caviatation
to me. Hard to hear from here
Got it purged well? Lossen the flange bolts and make sure the pump is not trapping an air pocket. Any flow restricting devices on the inlet side of the circ? Where are the flow setters located? Where are the flow checks located? Do you have a gauge on the inlet side right at the circ? Expansion tank location in regards to the circulator? Get one that reads vacumn, you may need it:)
When water drops below it's vapor pressure, boiling occurs. Vapor pressure is tied to temperature. At 130 degrees water will boil at around 2psia. 0 gauge pressure = 14.7 psia at sea level.
The eye of the tiger, I mean eye of the impeller is a prime location for this type of pressure to be present. And a good place for cavatation to be occuring. You could have a restriction coaxing this condition.
Is that a high head pump? Is it the correct pump for the application? Could it have been switched? Zone valves added?
hot rod
Bob "hot rod" Rohr
trainer for Caleffi NA
Living the hydronic dream0 -
> from a guy w/o an engineer's degree.
>
> That 10'
> long old style radiator holds a lot of H2O; not
> to mention the other 2.5 footers. You reduced
> the supply and returns to 1". Could be your
> noise is starting when that 130+ water hits those
> cool, large water volume radiators. That's a lot
> of water to move w/ the H-32 connected to a 1"
> supply and return.
The sound occurs whether or not the loop is open. Even if the pump is blocked in the noise continues.
>
> Why don't you turn off
> the valve on that large radiator and see if the
> noise subsides? We normally run 1" tubing on
> systems w/ about 80K of installed radiation.
The boiler is good for 140k, but that is serving the entire house (first and second floor). It is also a bit oversized based upon the room-by-room heat calcs we did for the entire project. So we're less than 80k for the first floor loop.
> And. That is w/ midget radiators or baseboard.
> Matching old radiation to new piping is sometimes
> more art, than science.
The system does respond a lot faster than the old gravity based system, so I don't think rate of water flow is an issue. We can actually get the house pretty hot fast.
Thanks for the ideas.
Jerry
0 -
> to me. Hard to hear from here Got it purged
> well? Lossen the flange bolts and make sure the
> pump is not trapping an air pocket. Any flow
> restricting devices on the inlet side of the
> circ? Where are the flow setters located? Where
> are the flow checks located? Do you have a gauge
> on the inlet side right at the circ? Expansion
> tank location in regards to the circulator? Get
> one that reads vacumn, you may need it:)
>
> When
> water drops below it's vapor pressure, boiling
> occurs. Vapor pressure is tied to temperature.
> At 130 degrees water will boil at around 2psia. 0
> gauge pressure = 14.7 psia at sea level.
>
> The
> eye of the tiger, I mean eye of the impeller is a
> prime location for this type of pressure to be
> present. And a good place for cavatation to be
> occuring. You could have a restriction coaxing
> this condition.
>
> Is that a high head pump? Is
> it the correct pump for the application? Could it
> have been switched? Zone valves added?
> hot rod
0 -
Think mirco-bubbles? When you said system was purged how long? Sprio-vent working? When ever I do a job like yours I purge for at least 1 hour full force,run system for a week and return to purge some more,air is a great thing but not in a heating system to many places to hide.P.S. My own house which we built 2 years ago with 7 zones and was purged forever still has alittle air in it.John@Reliable0 -
Retired and loving it.0 -
Air in System
Just a DOP but you need to isolate all the zones and purge them one at a time, this requires a lot of valves that most people do not install, also put the discharge hose in a 5 gal bucket and run untill no bubbles show up plus 5 to 10 more min,Keep all the zones closed untill the purging is finished, the micro bubblers, air scoops, auto and manual bleeds are for the removal free o2 that is disolved in the h20 and gets traped in the system once the water is flat ie no free o2 unless you have a leak the system should not make a sound , ALL SPELLING ERRORS ARE COPYWRIGHTED0 -
I ran into something similar
turned out to be a harmonic vibration in the pipes. Switching from a B&G 100 (similar to the H-32 I believe) to a Taco 0010 solved the problem.
To Learn More About This Contractor, Click Here to Visit Their Ad in "Find A Contractor"All Steamed Up, Inc.
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Steam, Vapor & Hot-Water Heating Specialists
Oil & Gas Burner Service
Consulting0 -
NOISE ON HOT WATER HEATING SYSTEM
I just finished a project last season and I am experiencing a problem that once the heat goes on there is a lot of noise and loud banging. It seams to be due to an expansion in the heating lines.
the following is the Building information:
Cellar and six (6) stories
Each story has two (2) apartments
Each apartment has two (2) zones
Each zone has a 1¼supply and 1¼ return
Each floor height is 11 ft.
Radiators are Cast Iron Sunred Radaitors and connections are from under floor
Risers has on each floor one (1) kindoff rod with kindoff clips to hold all pipes firm, and not shaking
Pipes hang under each floor under the kindoff not ontop
All boilers are in the cellar
Please try to help me with the above banging problem. i hope someone out there will be able to shed some light on this matter.
Best Regards, Abe
0
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