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rumbling boiler

aphco Member Posts: 13
Thanks for the input. I was over there yesterday and found out a bit more to add to the puzzle. There is only an aquastat with settings from 180 - 240 without a differential
setting so that I believe it is only a hi-limit control.

The guage appears to be accurate,and there is a distinct rumbling when the flame is on and goes off when the flame is killed. The owners say it is quieter since we purged the system and it had been quiet until another contractor had replaced a W/R 1311-102 a month or so ago. That is when the noises started. He came back and bled the system but it did not get better.

I'm thinking we need to add a strap-on aquastat to act as an operating control, and leave the existing hi-limit as a safety, BUT will the rumbling stop at lower water temp, and what if it doesn't and /or there is not enough heat at the lower water temp?

At the boiler the rumbling sounds like crackling, and in the house it sounds like mini- water hammer ( on a steam system). It appears to be most noticable on the upper zone but it may be just sound transmission from the boiler room.
The pump (Taco 007) appears to be providing proper circulation as the whole house stays at set temp, in all three zones. There are no bleeders ( coin vents) anywhere in the house except for the purge valves in the boiler room.This a typical set-up on these 40 something year old homes. Boiler room in garage, no room to work or add pipng etc.

As I am typing,I'm thinking maybe it is as simple as again purging the top floor but that doesn't explain the noise at the boiler. Also I wonder about the filtrol tank being there alongside the PRV. The system is full of water and pressure gauge verifies it.
We need to define the problem before we start spending the customer's money on solutions that do not work and as you can see we do not have a solid answer.

I will appreciate all ideas


  • aphco
    aphco Member Posts: 13
    boiler rumble

    We have a customer that complained about a hot water boiler that is making noises, intermittently. A well experienced serviceman went out and found that the boiler was rumbling or crackling similarly to the noise water heaters make as they age.

    He said it sounded like air and he purged the system to no avail. I told him to drain the system as it sounded like it could be limed up or have pieces of impeller circulating thru out the system or other minerals causing the noises. After draining and again purging the noises disappeared but seem to be slowly returning overnight.

    Further symptoms: He said the pressure gauge jumps a little when the boiler flame comes on and all is quiet when he ran the system with only the pilot burning. There is a fil-trol and tank installed as well as a PRV. Probably someone in stall the PRV when the fil-trol went bad, but the expansion tank seems ok. He found that the aqustat was set at 200 and turned it down to 180. It almost sounds as if there is not enough water in the boiler and it is starting to percolate (I have heard this in boilers that did not have enough water )

    There is no air scoop, which is common in this area.
    The pressure gauge appears to be working and after purging heat circulates to all rooms.

    I'm wondering if the fluctuation in the pressure gauge when the flame comes on is related to the noise and maybe the old filtrol is not absorbing the pressure increase, but that does not explain the noises. I do not want to start replacing tanks,PRV,etc. unless I am certain that the problem will be solved. My inclination is to remove the fil-trol and install an extrol but I am not certain that will solve the problem

    The customer complained only about the noise. The heat has worked well and still does.

    Anyone have any ideas??

  • Norm Harvey
    Norm Harvey Member Posts: 684

    The aquastat being set on 200,.. what was the actual temperature on the guage when the unit shuts down on limit? If the differential is turned up too high or the temperature probe isnt sensing accurately you can have the uunit running water temps as high as 220+ which is your percolating noise.

    Did turning the high limit down solve the problem?

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  • Empire_2
    Empire_2 Member Posts: 2,343
    Lack of flow

    Which also may contribute to the sound you are hearing. Pull pump from volute and check the status of the impeller.

    Mike T.
  • Guy Woollard
    Guy Woollard Member Posts: 82

    I have seen this phenomenon before where therre was a mineral buildup on the base of the boiler. It becomes hardened by the higher temps and forms a distinct layer. Water is getting between the actual boiler material and the mineral wall, and percolating. There are boiler cleaning solutions that are readily available that will break up the mineral base so that you can flush it out of the system. Flush into a pail- you'll be surprised what comes out.
    When you are into this process, isolate the boiler from the feeder and check it for any pressure loss, as the minerals had to come from somewhere.
  • Ed_26
    Ed_26 Member Posts: 284
    boiler noise

    What is the make/model of boiler? Copper fin-tube or cast etc.?
  • aphco
    aphco Member Posts: 13
    more info

    This is a cast iron hot water heating boiler. I'm not certain of the make, could be Weil McClain, appears to be original to the 40+ year old house. We have soft water around here but mineral buildup could be a possibility anyway.
    We drained the boiler and replaced the drain cock to be certain of full draining, but there was very little sediment. If it is mineral build up, do you have any suggestions on proper cleaner. We have never had the need to clean a HWH boiler.
  • Ed_26
    Ed_26 Member Posts: 284
    boiler noise

    Your post says another co. was there & replaced a part first. Then the noise began.... Has the manifold gas pressure been checked? Mains pressure? Which gas? If metered, has meter been clocked? Perhaps the problem really is overfiring? Or malfunctioning gas valve. Especially if system/controls that old.
  • Will in DSM
    Will in DSM Member Posts: 1
    no boiler pressure

    I am noticing a "rumbling" noise in our residential system and I find that there seems to be no pressure in the boiler. Boiler temp is being maintained and the house is being heated but I fear something is amiss. Any ideas??
  • was the pump

    Was the orginal pump a B&G on return? In fact, is the pump on the return side of boiler? If so, years of no ponpc will pop the reilf valve often and add water to the system and then replacing withh the wet rotor pump will make it worst... Look at the releif valve, been replaced recntly? Like how many times? If all this are there, u have a good layer of lime built-up inside the base of boiler..
    EBEBRATT-Ed Member Posts: 15,346

    Probably mineral or sludge buildup. Boil it out with chemicals.

  • aphco
    aphco Member Posts: 13
    More than likely this was a B&G # 100 originally, as was just

    > Was the orginal pump a B&G on return? In fact,

    > is the pump on the return side of boiler? If so,

    > years of no ponpc will pop the reilf valve often

    > and add water to the system and then replacing

    > withh the wet rotor pump will make it worst...

    > Look at the releif valve, been replaced recntly?

    > Like how many times? If all this are there, u

    > have a good layer of lime built-up inside the

    > base of boiler..

  • aphco
    aphco Member Posts: 13

    My guess is that it was a series 100 (B&G) and yesit is on the return. All of the installations in this area were done like that 30-40 years B.D.H.W. (before Dan Holohan's writings) and have always worked. Even wouthout any coin vents on the rads.
    The present pump is a Taco 007 wet rotor. What difference will the wet rotor make in this case? Also what is "ponpc".

    I really appreciate the input from everyone. Taking this info and adding it to the locally obtained info, it is starting to look like there may be a leak in the system which has led to a build up of sediment that is causing the percolating.

    Even replacing the boiler may not be the cure because there may still be a leak underground that slowly but regularly is adding fresh water and air.
  • Weezbo
    Weezbo Member Posts: 6,232
    most likely over heating combined with too low a flow through

    the boiler, APHCO.
  • Weezbo
    Weezbo Member Posts: 6,232
    Will, i would check three things,

    1. the auto fill strainer.

    2. the expansion tank.

    3. the auto air eliminator/s.
  • I like what the BDHW.....

    As you said, BDHW, all the pump(s) were installed on the return side with B&G series 100 ( in this part). That's what the way my dad, my uncle and others was thaught back then .. Come to replacing these too early, too often failure of these oil leaker bearing assy on these pumps... Taco and B&G came out with these new wet rotor pumps with higher rpm motor and higher pumping curve. My customers' system were getting air bounded problems and constant leaky reilef valves replacment due to water logged tank... Thanks to the P&M magazine for allowing St. Holohan to write these articles relating to these aforementioned problem and the famous PONPC... Point Of No Pressure Change .... Pumping away, etc... Many boilers I've seen with the wet rotor pump(s) on return were doomed and leaky due to limed up condition... Want to know more? Get another Dan's book, "Pumping Away" as well buy some bricks too...
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