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System noises

Simply Rad
Simply Rad Member Posts: 184
Hello to all and thanks for the help

I have been a Vitodens installer since 2004 in my area of Colorado.  There have been a couple of random Vitodens installed by other contractors and one by one I have adopted them into my service.  This particular Vitodens is an 11-44 and I have been servicing it for the last 3 years.  The unit was installed in 2006 and has worked great for the client until a month ago.  All of a sudden the system creates a loud bang and whistle when the DHW pump starts.  The bang is also associated with a fluctuation in the pressure gauge. After the initial  bang the system operates flawlessly satisfying the DHW load.   There are a number of installation flaws in the DHW system.  First, the DHW pump was a Taco 014, which is a bit big for the boiler design flows.  Next, the DHW piping is only 1" from the tank to the DHW tank(Triangle tube Smart 80 tank). .    The system had a 1" control valve(zonevalve) in the DHW piping along with the DHW pump.  My first attempts removing the pump and inspecting it and the check valve.   I removed the control valve from the DHW system. Also, I made sure the air was eliminated from the tank 

This attempt worked for a few hours(of coarse I left and everything was quite).  Then the client called and said the bang and whistle were back.  I felt that the pump was too large for the DHW system so I asked the client to close the boiler return ball valve until the whistle stopped(velocity noise from a Taco 014 working with 1" copper).  The whistle stopped and the band got quieter?

For next attempt, I brought out a Grundfos 26-99 pump to replace the Taco 014.  Installed it and turned on the DHW and bang...the noise is still there.  I started the pump on medium setting, The weird thing is the pump was quite on medium and high setting but the pump whistled on low setting?  this is the opposite of what I would thing ( I thought the high flow rate would cause the 1" pipe to whistle like a horn?) 

Another clue is the boiler pump does not make any noises and it follows the same path through the boiler as the DHW pump does?  The expansion tank is working(16 psi in air pressure) and the system fluctuates form 15-18 psi in operation. 

Thanks in advance for the input and have a great day
Jeffrey Campbell


    PLUMMER Member Posts: 42
    Pressure fluctuations

    Is a sign of air, and or a well oversized circ. I would look for air first. Its possible the oversized circ is actually drawing air into the system. Since the problem is new, we have to look at what could have changed, or what can change. The 26-99 is still too much pump if you think the 14 is too big. Have you monitored flow or DT? Quick head loss calc? Unless you can positively confirm the ex tank is 100% and if its older than 5yrs. I would replace it just as a maintenance item.

    Could something be plugged up , reducing flow and creating pressure changes in the piping. Cleaning of the spirovent screen for example. Are there any signs of mineral build up in the system. Is the heat exchange coil clean? I don't know where your located, but I serviced one in kremling while I was on vacation. Differences in water source from there to steamboat. One appeared brand spanking new, the other not so much. Good luck, sounds like you have a one off. But a good handle on it. You know it will end up being something simple in the end.
  • Snowmelt
    Snowmelt Member Posts: 1,415

    What made you think the 26-99 is the right bump, that pump is the same as the same as a 009 pump, if you go to the flow pro on taco John has a good webinar on this called tanks for the memory. He explains how to size the pump. Also if you had a picture we would be better off. I would think you would need a air separator in there somewhere.
  • Simply Rad
    Simply Rad Member Posts: 184
    Pump size

    Viessmann recommends this size pump in their manual for the DHW and boiler pump for this model boiler. BTW 26-99 is a 3 spd pump with a wide range of operation.  .  As for air the boiler has and air eliminator as does the Smart 80 DHW tank. Also, I forgot to mention the DHW tank is piped backwards...supply in the bottom and return to boiler on top so there the pump could be pulling air from the top of the HX tank.  But I did manual bleed the air from the air vent for that tank    I live in Steamboat. Yes there could be some debris or blockage in the piping but I would like to eliminate all other possibilities before I replace the piping.

    Jeffrey Campbell
  • Mark Eatherton
    Mark Eatherton Member Posts: 5,853
    Bypassing check valve on the heating pump?

    Try closing the ball valve on the heating pump and then try calling on the DHW pump. The BANG sounds like a check that is sticking open, and the whine is water bypassing it until the check becomes fully seated.

    Got snow? :-)

    Call me when you get a chance.

    It's not so much a case of "You got what you paid for", as it is a matter of "You DIDN'T get what you DIDN'T pay for, and you're NOT going to get what you thought you were in the way of comfort". Borrowed from Heatboy.