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[New (to me), 110 year old home] Help with Grundfos UPS15-58FC Rattle (videos included)

blu_in_green Member Posts: 11
Hi everyone, I've been lurking for a while trying to learn enough about radiator systems, boilers, and circulating pumps to troubleshoot a persistent rattle. I have tenants moving in soon with a new baby and I'm hoping to get the nursery as quiet as possible.

Note on the system:
- 110 year old with a mix of Cast Iron fed by steel that looks like 1", a bit of copper to basement wall mounted rads (3/4 inch maybe), and a couple newer rads running pex (looks like 3/8").
- Circulator seems to run constantly (it doesn't cycle with the boiler). This is in Canada.
- Circulator is Grundfos UPS15-58FC
- There is a bad leak near the boiler which I plan to have fixed when it is warm enough to shut down the system for a couple weeks
- The system has been bled for the most part, but there is one upstairs rad that needs to be re-bled about once every week or two for 3-4 seconds (it makes a "tinkle" noise prior to being bled which, when bled, goes away).
- There does appear to be an air lock in one of the more recently added rads in a back room...I haven't figured out how to fix this yet, but it isn't annoying me like the rattle.

Are there any steps you can recommend to troubleshoot or mitigate the sounds?



  • Jamie Hall
    Jamie Hall Member Posts: 15,373
    I presume -- I hope! -- that there is an expansion tank and pressure gauge on this system? If so, what does the pressure gauge usually read? With the boiler on? With the boiler off? The combination of the leak and possibly low pressure may account for the air getting into the system and having to bleed that radiator.

    The pump noise -- there are others on here far more experienced than I, but I'm think that it sounds tired... bearings or seal.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • blu_in_green
    blu_in_green Member Posts: 11
    I'm not 100% sure what an expansion tank looks like, but there is a pressure gauge.

    Here are photos of the tank and gauge.

  • Jamie Hall
    Jamie Hall Member Posts: 15,373
    Thank you! Photos always help...

    First off, the pressure is slightly low. That 10 psi you are reading is only good for about 20 feet vertically, if that. If you could raise that pressure to 15 psi when the system is cold, you might well find that you won't have an air problem in that radiator any more.

    The expansion tank you are seeing is a perfectly good old-fashioned air tank, and they work splendidly well if they aren't "modernized" by someone who doesn't know what they are doing. Is there a gauge glass on one end? If so, can you see where the water level is in the tank? If not, not to worry, but it would help. Practically speaking, though, if the pressure in your system starts cold at about 15 psi and doesn't get much over 20 psi when the system is really hot and cranking, it's working the way it's supposed to.

    Do get that leak fixed, though. It's not helping you maintain pressure -- and it's not helping as a whole, because the less fresh water you have to put in the better.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • blu_in_green
    blu_in_green Member Posts: 11
    Thank you so much, Jamie! I’ll check for the glass gauge a little later.

    Any idea on whether the higher pressure would help my circulator rattle or will I have to keep searching for a solution to that?
  • Jamie Hall
    Jamie Hall Member Posts: 15,373
    I doubt that it will help the circulator rattle any... but one can always hope, eh?
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • dopey27177
    dopey27177 Member Posts: 433
    As you mentioned you have a water leak in the system. You have to bleed air out of radiators every couple of days.

    Your leak causes fresh water to re fill the system. The fresh water contains air in it. This what your bleeding out.

    Some system air will circulate and pass though the ppump. The air in the water causes the pump to cavitate. Cavitation creates some noise, sometimes sounds like marbles. Additionally, cavitation will damage the impellor of the pump.

  • Tim_D
    Tim_D Member Posts: 36
    That circulator rattle is common in Grundfoss circs when they are running to far to the right on the curve. In other words, there is no system head and it is free wheeling and killing itself. Could also possibly cause NSPH issues, also very bad.
    Alan (California Radiant) Forbes
  • blu_in_green
    blu_in_green Member Posts: 11
    > @Tim_D said:
    > That circulator rattle is common in Grundfoss circs when they are running to far to the right on the curve. In other words, there is no system head and it is free wheeling and killing itself. Could also possibly cause NSPH issues, also very bad.

    Hi Tim, could you explain what “running too far to the right on the curve” means?

    Is there a way to fix this free wheeling problem or is there another pump that would improve my situation?

    I’ve been googling Net Positive Suction Head, but nothing seems to give clear directing on how to solve for it? Do I need to adjust the pipe design at my boiler or can I fix this with settings?

    Thanks for the input, Tim!
  • Jamie Hall
    Jamie Hall Member Posts: 15,373
    Technical terms... "running too far to the right on the curve". What @Tim McElwain is referring to is what is called the characteristic curve of a pump -- the relationship between the pressure which it is developing and the rate of flow through it. "Running too far to the right" means that the flow rate is towards the high end and the pressure developed is towards the low end of the pump's capability. In some pumps under those conditions the impeller -- the moving part -- can move slightly along its axle and that can make a rattle. The way to fix the problem is to increase the pressure the pump is working against, such as by slightly closing a valve in the circuit. Wasteful of energy, but it might help.

    Net Positive Suction Head is the term for the absolute pressure at the inlet of the pump. Absolute pressure is the pressure related to a pure vacuum, rather than to the atmosphere (that's called gauge pressure) and if it's too low the water (or whatever) will boil, then the bubbles collapse in the pump and make a racket -- or worse. The way to help that is to increase that pressure. Increasing your overall system pressure -- as I suggested earlier -- will help. In hot water heating systems, it also helps -- sometimes a great deal -- to have the expansion tank and water feed very near the inlet to the pump.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • blu_in_green
    blu_in_green Member Posts: 11
    Thanks for all this guidance Jamie, Jake, and Tim.

    Re:too far to the right - I will try to close my outlet side valve

    Re: NPSH - I'm not entirely sure how to adjust my system pressure. The pressure gauge seem to be passive (reading the system) rather than letting me dial in the system.

    Re: Airlock/no flow in the rad in my back room, is there any way to troubleshoot this by forcing air one way through the system until it comes out? The bleeder doesn't seem to be working; the pressure on both sides of the rad seem to be equivalent.

    I'm trying to find enough basic information to guide myself through the problems.

    I saw recommendations for Dan's books, but some of the reviews suggested they weren't prescriptive enough.

    What guides or resources might I purchase or view to guide me through the troubleshooting? The Modern Hydronic textbook looks a bit daunting when I'm just looking for prescriptive next steps.
  • Jamie Hall
    Jamie Hall Member Posts: 15,373
    On the system pressure -- somewhere there should be a pipe connecting the system and your domestic water. Somewhere on that line there should be a valve. To increase the system pressure, keep an eye on the pressure gauge and open that valve a bit. Stop when the gauge reads 15 psi.

    Now... there is always a chance that the valve may open. And not close. So you will want to stay there, or come back soon, and check that the pressure is still what you want it to be!
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • blu_in_green
    blu_in_green Member Posts: 11
    edited April 2020
    Ah okay; thanks for dumbing this down for me :-)....So I tried a couple things:

    - the domestic supply has a valve that says “set 12-15 maintain 10-25” I lifted the lever a bit and it hissed a bit but it’s sitting between 12-15 cold on the pressure gauge.
    - I went around the house to bleed all the rads except my “problem” airlocked one at the back of the house that is getting no flow at all. The upstairs rads had considerable air to bleed so that felt useful.
    - I did notice when the boiler was running today that the pressure gauge read about 25 psi. This is the highest I’ve noticed, but I will keep checking to see if that is common every time the system runs (with warmer weather my boiler is running much less.
    - my old expansion tank doesn’t have a gauge. The valve connecting it to the boiler return line seems to be closed (turned all the way to the right). I’m not sure what use it is with the valve closed. Maybe this needs adjustment?
    - I turned the outlet side valve right after the circulator maybe 10-15% closed, in an attempt to stay off the “right of the curve”....

    So far, same rattle behavior....I will try to bleed the upstairs rads again tomorrow to see if they refilled with air.

    Thanks again for all the tips and help. This is really chewing me up. I’ve looked for local expertise, but not finding anyone who doesn’t want to replace the whole system...

    Couple more photos
  • HomerJSmith
    HomerJSmith Member Posts: 1,196
    edited April 2020
    It appears to me that the pump is installed backward, but whata I know. The motor body could have been rotated at the time of installation. I can't see the volute very well in your video. If it is the newer 15-58 FC with the internal flow check, maybe that is malfunctioning.

    The tridicator seems to me in the wrong place.

    You could always pull the four allen head screws and remove the motor body from the volute. I have found solder balls and wood sticks in a volute once. Check for the smooth rotation of the rotor while you're at it.
  • Jamie Hall
    Jamie Hall Member Posts: 15,373
    Is that the only pipe that connects the expansion tank to the rest of the system? If so, try opening it... and see what happens.

    I can't honestly say I'm too surprised that people you talk to want to replace things. This is a very old system -- and while they can be made to work, and work well (one of the houses I maintain has one not unlike it), they are a bit pesky -- and well beyond the experience of most of the younger generation.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • dopey27177
    dopey27177 Member Posts: 433
    As far as the air and pressure situation goes you should not have pressure greater than 15 psi in the system. That pressure setting is based on having enough system pressure to get water up to the highest heating element plus 2 Psi.

    1 pound of pressure will raise water 27 1/2" or 2.33 feet. Some times the expansion tank does not have enough air space in it and air removal problems can occur. The system air is supposed to go into the the expansion tank when the water is hot and the pump is pumping. When the system is not in operation some of the air and water from the expansion tank goes back into the system. You would need to drain some water out of the expansion tank, unfortunately I do not see a way to break the vacuum to allow water to be drained from the tank.

    Looking at the pictures and seeing all the leaks and pipe replacement needed I recommend that you spend some more money than just fixing a system piping disaster (poorly designed and installed piping).

    The design recommendations I am sending you is called pumping away, it is part of Dan's book on water heating systems.

    There will be two enclosures. Dan's simple drawing and a drawing from Bell and Gossett that is more complex. The B&G drawing shows measurements and lists parts by name.

    The only thing you need to disregard in the B&G drawings are the bypasses and flow control valves if you are using one pump.

    If you are using one pump and have two zones you need to leave the check valves on the return near the boiler.

    What makes this installation ideal is it sets up a differential in pressure. Primary benefit is it sucks the water out of the boiler and causes any system air to flow to the lower pressure, the outlet piping of the boiler.

    The location of the pump in outlet piping causes an increase in water pressure to the heating system and will force any entrapped air back to the boiler.

    If you look at the new install you will see an air eliminator fitting that will send air to the vent valve.

    This system is self bleeding after the initial fill, you will never have to manually vent the system unless you get a real big leak or drain the system for service.

  • blu_in_green
    blu_in_green Member Posts: 11
    Thank you! The diagram is very helpful to guide me through the redesign.

    I traced the pipes and I’m wondering what you guys think about whether I need balancing valves to correct some of the strange pipe sizing.

    I watched a YouTube video about modern hydronic designs, and all I can seem to tell is that my system shouldn’t work at all based on the randomness of the pipe sizing.

    Right now my first out is my first on the return.

    - 3/4 inch copper short run out and back in the basement to a bedroom.
    - Next I have 1/2 copper converting to 1/2 or 3/8 pex feeding the rest of the basement.
    - next is 3/4 cast iron switching after about 20 inches to 1 inch cast iron that runs the length of the house, up one level, then converts to 1/2 or 3/8 pex to a Rad that doesn’t seem to get any flow (the one that seems air locked)
    - then next is 2 inch cast iron going two levels up

    Believe it or not, everything in the house actually seems pretty balanced with open valves except the mystery rad that gets zero flow off the 1 inch cast iron (even when disconnected it seems to get nothing flowing through the pipes).

    Based on this, I’m wondering if during the leak repair and resign of the boiler stack whether it’s worth adding some balancing valves and if so what you’d recommend.
  • dopey27177
    dopey27177 Member Posts: 433
    It is hard to figure out what needs to be done. A diagnosis on flow due to the pipe sizing at this time cannot be offered. Typically pipe size to the heating elements is 3/4" and in some cases 1/2". It all depends on how much water needs to flow thru the heating elements based on a 180 degree inlet hot water.

    As far as balance valves go the most economical valve to use is a ball valve that can adjust the flow rate. This valve typically is installed on the discharge side of the heating element. the install should be done on the 3/4" piping or the largest heating elements in the building. The 3/4" pipe can flow 4 GPM per minute usually this amount of flow is not needed in the average heating element.

    I do not recommend doing this until you do pumping away.

    The relocation of the circ pump will change the entire flow of water as the pressure to the system when heat is needed becomes greater than when the pump is on the return side of the boiler.

    Again with pumping away if done in accordance to the drawings will cause the system to purge itself of air while in the heating operation mode.

    Do what is most important first then follow up with balancing valves if needed.

  • SuperTech
    SuperTech Member Posts: 1,579
    I don't think there's a simple solution to this problem, such as adding balancing valves. Pumping away and adding a micro bubble air eliminator should help with the air issues, but the distribution piping sounds like a nightmare.
    If it was my house I would probably rip out the all the piping, correct the boiler piping by moving the expansion tank, air eliminator and circulator so it is pumping away on the supply side. I would home run PEX to all the emitters and back to manifolds on the boiler, piped reverse return with flow setters to each emitter.
  • Steve Thompson (Taco)
    Steve Thompson (Taco) Member Posts: 190
    Based on what I've read I believe the only issue is the noise. Assuming that's accurate, my guess is something is bad in the rotating assembly of the circ, although a rattling check valve external of the pump could be the cause as well (doubtful).

    Try touching something like a screwdriver to your ear and various locations on the circ (creating a stethoscope). You'll be able to get a better idea of where the noise is originating. Close the valve and see if the noise changes. Same for changing circ speeds (does the noise stop or just change).

    As your system has the old "captive air" expansion tank it is almost impossible to remove a substantial amount of air from the system fluid. Air, water and cast iron/steel create rust, and rust can cause sleeve bearing failure in these little circs (to be fare, all wet rotor circs not just GF).

    It's possible to take the motor off to inspect the rotor, impeller, bearings etc - just remember to isolate the circ from the system (close the valves up and downstream) and turn the power off. You'll also need a metric allan wrench - if memory services me correct.

    The wallies are as usual correct regarding running the pump off it's curve - think of how your car's engine sounds when in neutral at 3,000 RPM vs driving uphill against the wind at 3,000 RPM. Like car engines, these little circs don't like to "free wheel" at higher speeds, operating better under load.

    In my 17 years with that particular manufacture I've occasionally seen where the circ's rotor rubs against the rotor can (caused by abnormal flow, abnormal system pressure or worn bearings as a result of abrasives in the system fluid).

    Probably time to replace the circ... Might be a good time to check things like strainers, water quality etc at the same time. If it was my system I would replace the tank with a newer bladder type and add a good air separation device. Less air, less corrosion, longer component life and improved heat transfer (efficiency). If investing a little bit, invest a little more by having a professional heating person inspect/update your system.

    You won't be disappointed and this will be a great, long term investment (corrosion doesn't only attack circs - damages boiler heat exchangers as well).
  • Paul Pollets
    Paul Pollets Member Posts: 3,366
    edited May 2020
    This system has several important issues beyond the leak, and circ noises that affect it's operation and efficiency, not to mention air. As it was mentioned above, the piping should be re-done using the "pumping away" method. Get the book, if you don't have it. The horizontal expansion tank should be replaced with a pre-charged 60g tank; Replace the circ pump, if required. Use a good air elimination device on the outlet of the supply. This boiler is a candidate for replacement, the existing piping shows it wasn't done by an expert.
  • dopey27177
    dopey27177 Member Posts: 433
    You need to purchase the book from Dan's site. The book Pumping away is needed, Also buy a book on water heating for buildings.

    Additionally, Go on line with a quality boiler manufacturer and down load the boiler installation and maintenance instructions.

    You need to know what and where all the boiler trim goes. You also need to know what all the controls and boiler trim is for.

    If and when you decide to replace the boiler, from the contractor you need a proposal listing all the things included in the job.

    The proposal should include drawings or sketches from the boiler manufacturer about the installation of the boiler.
    You must also give the contractor the drawing of pumping away even if the boiler manufacturer shows the pumps in a different location.

    As to the piping repairs thru out the building the contractors proposal needs to include by location what he is going to do.

    If you accept the proposal which will include the price and above all the boiler signature by both parties becomes a binding contract.

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