Home › Forums › Public Forums › General Plumbing › Circulator pump in hot water central heating causes hum throughout hou
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9 Sep 2000 at 11:14 am #273474MasterPlumbersKeymaster
I’ve just purchased a 90+ year old house with gas-fired, central heating using hot water radiators.
As an aside, the previous owner told me that he had a lot of problems with the circulator pumps dying, and his repair person told him the cause was the circulator pumps starting up and shutting down all the time. So now it is wired to always be on. The owner would shut the circulating pump off for the summer.
After having some cool nights last week, I decided to make sure the heating system was working. Everything seems to work, but the circulating pump seems to cause a noticeable hum in the pipes that can be heard throughout the house (including my 2nd floor bedroom).
The pump itself doesn’t seem to be that noisy when you are standing next to it. It seems to be vibrations in the pipe elsewhere that resonate and cause the hum.
Does anyone have any suggestions for quieting things down?
9 Sep 2000 at 5:12 pm #287770Harold KestenholzParticipant
There is not one clear answer to solve this problem. It would help to know the manufacturer and model number to analyze the system conditions. I heard this sound from many different brands of circulators and heard a similar sound from air conditioning coils.
The impeller, the circular part that spins to paddle the water, can move forward and back in the circulator body. As the circulator wears the bearing, or sediment builds on the body, flow conditions change. An impeller has several blades, the flow over it is not the same at all points around the circumference. As an impeller blade passes part of the pump head wall, the pressure at that point changes. The spinning impeller makes a rhythmic pressure wave in the water.
This hydraulic resonance is carried throughout the column of water instantly in all directions (Pascal’s Law,) as water is a non-compressible (it doesn’t take up shock like a gas.) A tube or pipe of the right size or diameter will act like a string in a guitar and vibrate sympathetically with the pulsations, so one possible solution is to fasten the vibrating section differently.
The pressure waves can become louder or go away as the impeller moves in the pump body (changing the vibration cavity or reed of a wind instrument changes the sound.) The sound might be reduced or made louder by changing the pressure conditions on the pump impeller. This might be done by changing the system pressure or changing the pressure against the impeller by shutting a valve slightly a few feet up the outlet pipe of the circulator (like blowing too soft or too hard on a clarinet.)
This is all really iffy. A quick fix might occur if you change the circulator. An experienced technician who will follow through this procedure until the noise disappears is your best solution.
9 Sep 2000 at 5:22 pm #287771Harold KestenholzParticipant
In another view, your house was built 90+ years ago. At that time, a water heated system often was a gravity system, designed to work without a circulator. If that was the original intent and the system is the same, the water moved around the system for decades by the different weights of hot and cold water. A circulator would be spinning freely doing little necessary work. An unloaded circulator can make noise.
A circulator doesn’t make noise when it is still in the box on the shelf. I wonder if your system can run well without the circulator running at all. A method of controlling the temperature would be an outdoor reset controller. There are still some living people who can understand a gravity system.
10 Sep 2000 at 3:07 am #287772SylvanLMPParticipant
Harold, give the guy a break QUIT talking engineering and pump curves and horse power Vs head pressures or cavitation etc.
OK Michael, check the circulator for the proper mounting as per manufactures directions (get the name of the circulator) send a post card to the manufacturer and hopefully they will explain the proper way to take the load off the motor mounts.
A lot of stumble bums have no idea how to properly support these motors and only have the motor hanging off the piping and this sets up a strain on the impeller and housing and thus causes weird sounds to travel.
FORGET the “Gravity SYSTEM” as it is very inefficient and what it is nature going slowly heating this house.
The gravity way is simple, hot water rises cold being heaver sinks this causes a natural circulation VERY TIME CONSUMING to say the least.
Want to fine tune this old system really to make it work fantastic USE NON ELECTRIC ZONE VALVES at each radiator.
Do NOT call a “heating GUY” or a tech or other fancy name for an unlicensed person.
Call a Licensed plumber and heavens forbid NO engineer as they will only confuse you with facts
Believe it or not an old two pipe system is so much better then that unground CRAP folks are pushing today.
Do not be concerned about redesigning this great kind of system JUST concentrate getting it Quiet like it supposed to be.
Have you LMP try holding this circulator when your calling for heat and SEE if it gets quit OUT of balance impellers will cause sound waves to travel
Also try to get the HP and RPM 1750 on up You may have a high head
(HV) circulator in lieu of a little red B&G (GREAT PRODUCT)
Hey feel free to E mail me privately anytime if you need advice AND ILL Discuss more options with Harold when I get him alone again.
10 Sep 2000 at 4:56 pm #287773Harold KestenholzParticipant
Unfortunately, Sylvan is only marginally able to understand the written word, so he gets half the meaning of this question. Evidence:
1. The circulator makes no noise while you are standing next to it; therefore the couplings are not making noise at the circulator. As he suggests, check the alignment. If the circulator does have a coupling, that is a way to move the impeller forward and back if it has some play in the bearing, but it is not a fix. It is a clue to change the circulator. That was my first answer.
2. Gravity systems circulate water on their own, even when you don’t want them to, if you have nothing to stop their flow. Sylvan’s suggestion to put valves on the radiators would stop and start flow. This would help the situation by controlling heat in the rooms, but more important to your question, it would slow down the natural flow of water in your system to help your circulators.
What most young plumbers don’t know today is that a pump should not be driven by water coming into the inlet or be totally unloaded. In other words, if the pump does not have a back pressure against it, the impeller bearing gets a varying load, accelerating wear and making noise. Clue: your statement about frequent pump failure.
Manufacturer experience with this problem recommends the smallest circulator that will move enough water and a balancing valve 10 pipe diameters from the circulator outlet to set up a constant head pressure against the impeller.
10 Sep 2000 at 5:44 pm #287774GuestParticipant
The pump you have on there now has too high of a flow rate, the faster the flow rate, the faster water moves through the lines, this causing friction, making noise no matter where your at in the house.
Solution…. Install a low flow rate circulating pump.
10 Sep 2000 at 10:39 pm #287775SylvanLMPParticipant
Hey My good Friend and Mentor Harold,
If this gentleman goes through several pumps because of short cycling Why cant they install a weighted flow control valve to prevent the hot water from flowing when the circulator is off thus having the impeller moving with the stratification of the hot water molecules and causing a possible reverse impeller condition?
2nd thought is If they did use NON electric zone valves and put the circulator on constant run this system would balance out with the heat going exactly where need via valve build in controller / actuator pre set for each radiator
Another problem associated with premature pump failures especially on hydronics is the use of ferrous body/internal parts which cannot take fresh water and this system should be checked out for possible leaks allowing make up water to go undetected.
3rd Thought. Harold as we both know a lot of these older GREAT systems relied on a balancing valve for each zone sort of like a gas cock valve to control volume and suppose the balancing cocks are closed partially closed causing a high head (restriction) wouldn’t this also cause noise (velocity moving through this valve) AND premature pump failure?
Considering these pipes are well over sized do to the natural circulation of hot being lighter moves up and cold being heavier moves down. A balancing valve would have to have been adjusted to prevent over heating in some zones and under heating in others.
If this system was installed properly there should be a thermometer on the RETURN manifold for each zone (riser) just above the balancing valve and this set the volume / temperature for each section of the house
Another option would be to relocate the circulator to the discharge line rather then on the return where it was common practice to do years ago.
Hey Harold this is FUN dealing with a professional, thank you
11 Sep 2000 at 12:45 am #287776Harold KestenholzParticipant
Good points Sylvan.
I suspect circulator failure in this probable gravity system is partly from being driven by the water after the heating cycle and partly by running without a back pressure.
A quality flow control valve more like a pressure reducer, or a large zone valve can also stop the water from moving after the heating cycle. Some of these old systems would keep a flow control valves in the open position from their own gravity power.
An injection system into a joined supply/return will also make the circulator controllable.
I agree that the system should be treated as a sealed system to prevent unneeded corrosion from frequent addition of fresh water. The old tank-in-the-attic hand filling technique told the owner that there was a leak by more frequent refilling fequirements. Automatic does not always mean good.
The balancing cocks may be there. If so, then balancing the system will be a great help toward comfort. On the downside, the plumber-engineers who supervised the older systems balanced the system by tricks in pipe sizes and joining the main above, to the side, and below the main, the cocks might not be there.
90 years ago, 1910, thermometers were a valuable device not to be left on the job, so the taps for them might not be there; but it is simple enough to introduce them.
Sylvan, I hope there is someone nearby this owner with your knowledge to help correct these problems. This is fun.
11 Sep 2000 at 4:26 am #287777GuestParticipant
Thanks for the considered replies, folks. They are appreciated.
To answer a couple of your questions, the circulator pump is an “Armstrong” model Astro 50. The date code is “1298”. The sticker on it says 1.0 Amps, 110 W, 3000 RPM, and it says it has a working pressure of 140 PSIG. There is also a rating on it of Class F – 10 mu F (?).
The furnace itself is a Slant/Fin model “Galaxy”.
I don’t believe the furnace and the heating system are as old as the house — there are areas in the basement where it is apparent that there used to be a hot air “gravity flow” furnace stove in the basement kind of setup.
Parts of the house are still served by older, heavier radiators with older, heavier pipe, while newer additions to the house are served by very modern, German-looking thin radiators.
I do not see separate temperature/control valves going off to separate parts of the house.
The pump appears to be very solidly mounted in a run of pipe. It has the words “Do not install with motor above or below pump body” and in this respect it does appear to be mounted properly.
As an aside, I did notice a leak at one of the radiator valves today.
11 Sep 2000 at 1:11 pm #287778Harold KestenholzParticipant
The present Armstrong Astro line starts with higher model numbers. Someone might have the old catalog. The present models are cartridge types like TACO 007. I have heard many plumbers describe this noise problem with 007’s. I have heard this transmitted noise through my own home system from my TACO 007 when The non-electric zone valves are open to provide little resistance.
There were older Armstong circulators that used a magnetic drive and that impeller made noise when it was running under light load. Armstrong and TACO are very long-lasting circulators, it is not lack of quality. The circulators require a steady back pressure on the impeller to run quietly. Put a balancing valve at least 10 pipe diameters away from the circulator outlet. Adjust the balancing valve until there is a 20 degree temperature difference from supply to return after running the burner and system until the return water gets to 120 F (when the weather gets cooler.)
Other suggestions from Sylvan to provide even comfort levels are worthwhile when investment permits.
11 Sep 2000 at 11:44 pm #287779SylvanLMPParticipant
Hey Harold, I love hot water heating as it is not only very forgiving but you can play all sorts of great games with it.
Indoor out door set backs, non electric zone valves with and without remote bulb applications, the sizing is not that critical as compared to steam systems.
You can make a system as simple as a one pipe loop Or as complicated as a circulator for each zone with all kinds of by passes
The flow control valve I was talking about would require minimum HP to open as it would only be closed to the normal stratification of hot to cold movement.
The Solco and B&G types for example do not require much in the way of power to lift the weight up YET in time of circulator you can manually set them to open for gravitational flowing.
The problem with using a circulator supplied by a boiler manufacturer is Price. The manufacturers main concern is bottom line and “AVERAGE” demand
For example an automatic feeder is factory set 12-15 PSI so this would handle buildings up to 34.65 feet high above the boiler BUT in reality you must take off the positive pressure required to make sure air is not in the system “positive” pressure of 4 PSI which is I am correct would be almost 9 1/4 feet Then you have the friction losses to take into consideration and other restrictions.
I personally like B&G and am now trying Armstrong as per supply house recommendations SAME Price but a better warrantee IM told.
By using a circulator on constant run with the non electric thermostatically controlled valves the system would have a constant thermo setting with little coefficient of expansion per inch per degree taking place THUS no creeping sounds and less possibility of thermo shock
The supply and return (DELTA) temperature would indicate the exact BTU demand in velocity of this system once it was balanced out.
Another strong point about these older systems is the temperature of the heated water could be raised much higher with the same velocity with little concern as the newer copper systems should never be run at any temperature above 180 degrees with more then 2-3 FPS
1. Water at high velocity. High water velocity may be caused by an
undersized piping system or an oversized pump. One of the interesting myths
here is the notion that a return line failed because Type M copper was used,
so the repair is to install Type L copper. Since Type L copper has a smaller
ID than Type M copper, the velocity in the system is actually increased,
raising both the likelihood and rate of erosion that may take place. The
real solution is to lower the water velocity. Installation of a smaller
capacity pump or a throttling bypass on the existing pump should help in
lowering the velocity of the water in the system. The relationship is as
follows: Reduce pipe size, increase velocity; increase pipe size, reduce
velocity. Recommended velocity for hot water in a copper tube system is 4 –
5 feet per second (fps). If systems are designed to respect these velocities
the return lines will last as long as the rest of the system. The practice
of reducing tube diameter for the return line run is counterproductive and
is the main cause of high velocity in these systems. Since there is no
sizing guide in the Model Codes for return lines, there is little guidance
for the plumber on how to size this portion of the system. In the course of
installing or replacing circulating lines, some contractors have been
increasing the size of the return loop piping to 1″ or at least the same
diameter as the hot water supply out of the water heater.
2. Numerous, abrupt changes in direction in the piping system. Where
structural conditions cause numerous directional changes, long radius (1.5
Diameter) fittings should be used to minimize the interruption of laminar
flow. ( Hazen Williams) Pump manufacturers also have recommendations that limit the number of
changes in direction near the pump and the minimum distances these can be
installed from the pump. This is to protect the pump from these same
erosion/corrosion processes (cavitation). This is the main reason why you
would not use a corrugated connector on these pump installations. Flow
characteristics, the number and severity of the bends that could be made in
these connectors may be detrimental to the pump. < explains PUMP Burn out HUH?
Ah the joys of knowing ones job
Harold isn’t it fun talking professionally? LOL
12 Sep 2000 at 6:57 am #287780GuestParticipant
Congratulations. There might be hope for you after all…
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