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Overpumped system

Chris S
Chris S Member Posts: 177
A customer of mine has a hot water boiler with 6 circulators. The house is approximately 2400 s.f., and so some of the zones are rather small.  The Circs are 007 IFC, and each is set at a different speed, as the owner thinks is necessary.  The owner did a lot of reading and studying before he instructed the local oil company to install the boiler in this configuration.  It is pumping away,  and there is a spirovent between the boiler supply and the pumps.  It has an extrol 30. 

Heres the problem,  it runs great for a while, then a zone becomes airbound,  we would purge it all out & everything would be fine, then three weeks later we would be back.  I know the classic answer is that the PONP is in the right place, and that the spirvent will not allow air in in this configuration but...  Here's my question Is it possible that the circulators when they are all running are dropping the pressure to subatmospheric allowing air in,  In other words exceeding the capacity of the extrol 30?   

I would never have installed a system like this, but because I worked on it, I now own it, and I'm sure I'll be getting calls this heating season.  Any thoughts



  • Jean-David Beyer
    Jean-David Beyer Member Posts: 2,666
    Is extrol tank working?

    Could the extrol tank have failed or have the wrong pressure in it?

    Is the building very tall and 12 psi too little?

    I did not know you could adjust the speed of a Taco 007 or 007-IFC; I thought only the 00R and such could have their speeds adjusted.
  • Charlie from wmass
    Charlie from wmass Member Posts: 4,314
    need more info

    Like what is the boiler and what is the size of the header. Also are there  auto vents anywhere else or any leaks?
    Cost is what you spend , value is what you get.

    cell # 413-841-6726
  • Paul Pollets
    Paul Pollets Member Posts: 3,656

    It's wasteful to use so many pumps for such  small heat zones. Since you now own it, why not remove the pumps and replace with 1 Grundfos Alpha "smart" pump and 6 zone valves?  Pump away from a pre-charged expansion tank and enjoy low energy consumption with no air...

    If the owner doesn't understand, let him talk to the pump rep.
  • Chris S
    Chris S Member Posts: 177

    It's an Burnham MPO115  the  headers are 1 1/4" .  I did check the tank , and it is not waterlogged, pressure is good.

    As for switching it out,  not an option.  I am a Wilo stratos fan, and would gladly have installed zone valves, but the H.O. ,  a college professor designed his own system after doing his research, and will not change it now. 

    I just want to know if my theory is possible, I may go back and put a  gauge at the expansion tank to check- before the heating season starts.
  • Possible, but not likely,,,

    If the pumps were dropping the pressure allowing feed-water to enter, would that not eventually blow the relief valve? Is the feeder tied-in at the same point as the tank?(before the circ) as you know. Perhaps you just may have a bad Spirovent,,,, never had that before myself,, but it IS possible.  
  • Rich P_3
    Rich P_3 Member Posts: 34
    Taco IFC

    I had a similar situation  a while back with air entrapped in the IFC of the circulator.

    Swapped it out and it went away...Sorry no more help than that

  • Charlie from wmass
    Charlie from wmass Member Posts: 4,314
    CHeck the spirovent

    It may have deposits in it. It is unlikely all pumps are kicking in at the same time. The tank may be small for the volume of the system. With the six zones even though they are small they may have a lot more water volume. I would try a pressure test of the system as you may have a small leak. Is the air always in the same zone and location?
    Cost is what you spend , value is what you get.

    cell # 413-841-6726
  • Paul Pollets
    Paul Pollets Member Posts: 3,656
    Send em back to school!

    Perhaps you should recommend the professor spend some time on the Wall for a graduate degree in hydronics 202...
  • eComfortUSA
    eComfortUSA Member Posts: 11
    Check Spirovent


    If you have SpiroVent or any Air Eliminator, how fare away is from the first elbow on the main supply line? Should be no less than 12" other vise you have possibility to air just pass by Spirovent and build up in the  zones.

    [email protected]
  • Chris S
    Chris S Member Posts: 177

    Thanks for all the comments.  The spirovent is 18" from the first 90,  and the cold water does not feed in at the same place as the expansion tank because of a space limitation.  The extrol hangs off of the spirovent, and a larger tank would reuire some pipingi which is not a big deal, but not a quick fix either.

    The zone closest to the spirovent- the first upstream zone is the only one that becomes air bound,  and only during the worst conditions last year... when all the pumps were running.  We leave the fill valve closed after servicing, so no new water would be introduced to the sytem.  Which makes me think,  If I left it on, and the system overpressured, that would be one question answered.

    Once again thanks for all of your collective brainpower
  • check to make sure not to double check

    Had a similar problem where the circ was air bound due to a check valve n the pump and a flow check two inches away. Add insult to injury they had the flow restricted (aka balnaced) in the inlet side of the circ. Wrong wrong wrong.
  • jim lockard
    jim lockard Member Posts: 1,059
    May not like this

    Adding a cast iron air scoop to that 1 zone will solve the air problem. If you x-tank is too small it will be lifting the relief valve, you have not mentioned that so I would assume x-tank is okay. The bigger question is since you have an air out system is were is the air coming from? maybe raise the pressure and see if it goes away. Jim
  • Glen Aspen_2
    Glen Aspen_2 Member Posts: 53
    I would reiterate the question:

    where is the air coming in from? Aside from the spirovent is there also auto air vents at high points that may be introducing air under certain conditions? If so - replace with coin vents.
This discussion has been closed.