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Gurus of Hot Water:

Had an incident at home yesterday. Son called me at work because there was a loud hammering coming from the basement, which he could hear through the radiator in his room. I could hear it too over the phone. Not willing to remote troubleshoot and too far to come home, I had him flip off the switch which provides power to boiler and all controls. He did say the noise seemed to be coming from the pump/motor (B&G Series 100).

When I came home I noted that the pressure was normal, and one of three zone valves (motorized White Rodgers) was in the open position - the one for radiators (5 free-standing) and baseboard (2 rooms) on the 2nd and 3rd floors of the house. The other valves were in the closed position.

I restored power, and tried each zone in turn by adjusting the thermostat. No problems. Pump and motor worked smooth. Has worked OK since then as well.

My boiler is an old atmospheric (Bastian-Morley), pumping away, with a B&G air separator (IAS-11) that never seems to do much. Only other thing of note: 3 of the 5 radiators and one of the baseboards in the one zone have TRVs (all installed properly on the supply side). There was some air in the 3rd floor which I bled this morning. The presence of air there is not unusual by the way.

Any ideas for the root cause of this hammering (the likes of which I have never heard before in 17 years in this house)?

--Eric Peterson


  • Steve Bukosky
    Steve Bukosky Member Posts: 9

    I first was thinking that you had a steam system but obviously not. If the coupling on the pump is good, as you imply it is, then I wonder if the water temperature ran too high and flashed to steam due to a pressure drop from a zone valve opening. I'd check to see what the high limit setting is and if it is below 190 degrees or so, I'd question if it failed for some reason.
  • Ken D.
    Ken D. Member Posts: 836

    I'm with Steve. The high limit could have stuck causing over temperature and water boiling in the system. The relay could be pitted and could stick once in a while. Also be sure the boiler gauge is accurate. Many times they aren't true and the pressure is lower than reading. Water does boil at 212 degrees at 0 psi.
  • hr
    hr Member Posts: 6,106
    Check the coupling

    on that B&G 100. Sometimes a spring breaks and causes a hammering.

    hot rod

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  • DanHolohan
    DanHolohan Member, Moderator, Administrator Posts: 16,490
    I once saw

    a broken spring coupler cut an aluminum bearing assembly in two. The motor was hanging from the wire. How no one heard that is still a mystery.
    Retired and loving it.
  • Eric Peterson_3
    Eric Peterson_3 Member Posts: 55

    High limits - I have two installed, in series, as a fail-safe. I'll check but doubt very much that *both* would have a problem.

    As for gauges, I have three - one on the boiler and one each on two of the zone manifolds. Low pressure is not the problem.

    That leaves the pump coupling. I'd like to hear a bit more about that. What should I be looking for?
    I'll take it off and take a look at it.

    For the time being I am flipping the system power off whenever I leave the house. Now that the weather has warmed up it's not a big deal.

    Thanks to all for the suggestions.

    --Eric Peterson
  • lchmb
    lchmb Member Posts: 2,997
    agree with hotrod

    I have seen many cases where the b@g break's only one of the two spring's..sound's like all (@#*^$ until you shut it off..then it fall's out..look around the circ's for metal shaving's...just make sure to keep your finger's out of there until the power is off...Just to be safe...
  • Kal Row
    Kal Row Member Posts: 1,520
    b&g's will bind up when hot and out of oil

    the the springs first stretch against the binding bearing and then the pump snaps forward causing a rhythmic hammering in the pipes – happens a lot with these, try a full ounce of 20 weight oil in the cup next to the bearing – and it doesn’t help – the pump will need to be repaired or changed – if it’s cast iron it’s cheap enough to replace it, but if it’s brass it’s more economical to do a bearing/coupling repair
  • Ken D.
    Ken D. Member Posts: 836

    Looking in the slots on the circ. bearing assy. it will be obvious if the coupler is the problem. One or both springs will be broken ( unless it's a Spirolnk type coupler in which case the coupler will be distorted or broken) and you will undoubtedly have aluminum or steel dust or shavings or rusty powder inside coupler area between motor and brg. assy. Check the weep hole under bearing assy. and open the oil cup on the bearing assy.(if possible) check for water, rust, gray or black sludge. If any are present,the shaft seal is leaking. Replace the bearing assy. or entire pump at your option. Turn off power to circulator and insert a screwdriver (not your finger) and manually turn both the motor and pump shafts. They should turn with ease. Check condition of coupler as you do this.If the bearing assy.(pump) shaft is tight or seized, replace the brg. assy. and coupler or entire pump at your option. If the motor mounts are eccentric (out of round) this can put stress on the coupler causing it to break. Remove motor and check both motor mounts and replace mounts if necessary and repl. coupler. Most times if the mounts are the cause, the bearing assy. will be ok. Check for leaks. While you're at it check the oil wick and replace as needed and relube.
  • Eric Peterson_3
    Eric Peterson_3 Member Posts: 55

    I checked the B&G documentation and added 1oz (2 Tbs) oil to the bearing cup as well as 8 drops to the two places on the motor. The bearing cup is a little ridiculous - how you are supposed to add that much oil through that little spring-loaded covering I don't know, in any case the whole assembly popped off and I could see inside - packing looked OK to me, but I added the oil anyway.

    As for Dan's and hot rod's comments, from what I could see the springs all looked OK, if there was a problem I would not think that it would be intermittent. No banging has been heard since the initial incident. Pump and motor have run smoothly.

    I also checked the air separator (IAS-11) on the near-boiler piping and there was only water. That thing doesn't seem to work at all! It *never* separates any air, yet I continue to get air in the uppermost radiators in the house (on the third floor). What gives?

  • Kal Row
    Kal Row Member Posts: 1,520
    ok - questions

    what is the piping height in feet from top to bottom? - make sure you get any runs that go into the attic?

    what does your gauge read when the system is off and cold, off and hot, running and hot?

    does you gauge appear good – ie: if you drain the system , does it go to zero?, does it move smoothly?

    what is make – model – size of you boiler, what is inside diameter of the pipes in the zone runs, apx how many feet of baseboard do you have, and apx how many feet of piping do you have, I am trying to approximate your system’s volume in gallons – to ascertain that your expansion tank is size correctly – ps If you have a #30 tank, and an avg sized home and it’s not a gravity conversion, then the tank size is probably sized ok

    is the expansion tank connected in before the pump or after the pump - eg if the pump is on the return and the exp tanks is on the supply, then the exp tank is after - but it could just as easily be connected in the return before the pump – we need to know

    air in the system causes surging, as the pumped water first compress the air ahead of it, and then accelerates over an air hump in the system – that can cause your hammering, you must determine why you are getting air in the system

    the exp tank may have failed – (an easy indicator would be if the air valve is facing down and a slight depression of it, discharges water)
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