Click here to Find a Contractor in your area.
In fairness to all, we don't discuss pricing on the Wall. Thanks for your cooperation.
Need to contact us? Visit

Primary Boiler Pump Failure?

Jake48Jake48 Member Posts: 28
I think I have a primary boiler pump failure. The pump is getting really hot but the impeller is not turning (i.e. it is not making the regular humming sound when it is pumping). So the when the boiler is overheating and faulting off due to no circulation. The temperature and pressure soars in the boiler than shuts off showing F2 on the vitodens 100-W. The upstream and downstream pipes to the pump are cold but the pump gets very hot. It is a Taco Cartridge circulater model 007-F5. When I open any of the 3 systems drains water comes out so it is full of water.

Does it sound like a pump failure?


  • Paul PolletsPaul Pollets Member Posts: 3,022
    Tech services

    Here's the link to Viessmann technical services:

    They can probably talk you through the diagnostics.
  • Jake48Jake48 Member Posts: 28
    Primary Boiler Pump Failure?

    They won't be of any help. It is an F2 fault, which their manual says 1) check pump operation, 2) check water level (like I said seems to be full of water) and 3) vent system of air (don't think that is the problem). I am looking for someone who knows whether this is a pump failure or not.
  • Jamie HallJamie Hall Member Posts: 6,708
    It surely sounds..

    as though the pump is seized.  They do sometimes.  Is there any way in which you can manipulate valves so that you can open a drain downstream from the pump without draining the rest of the system?  If so, you might find out by opening the drain and turning the pump on and seeing what happens.

    Otherwise, if you can get the pump off the system and get at the impeller, you can try to spin it by hand -- it should spin easily.

    Other problems -- if it's a capacitor start, have you checked the obvious?  is the cap. good?  If the cap. is bad, and it's capacitor start, it'll just sit there and hum and overheat.

    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England.

    Hoffman Equipped System (all original except boiler), Weil-McClain 580, 2.75 gph Carlin, Vapourstat 0.5 -- 6.0 ounces per square inch
  • TomTom Member Posts: 458

    Did you try putting an amp meter to see what its drawing for amps? For instance a 007 draws around .71 if its over 1or just under its usually seized. The name plate on the pump will tell you what it should be drawing when under load.
    Montpelier Vt
  • archibald tuttlearchibald tuttle Member Posts: 484
    amp check is best option

    . . . other than just replacing circulator although not all onboard circulators are made for easy replacement.  don't know on your unit.  ain't done one.

    in the NFN department, can't believe that no one has come up with low cost widespread implementation of flow sensor or pressure differential technology to monitor system flow for various reasons besides the obvious no-flow condition.

    in the 'good' ole days you would just see if you could follow the pipes getting hot and hot returns, but with the primary secondary approach you can get hot temps on pipes in close primary loop.

    if you are really familiar with pipe temps in normal operation you can infer lack of circulation.

    of course lack of circulation doesn't 100% mean the pump is bad so it would still be good to amp it.  don't generally air lock primary loops but you never know, have seen some funky air traps around boilers.  those who have replaced melted heatmaker cores can no doubt attest, although their pressure differential solution to checking for circulation is one of the best implementations I've seen although the technology hasn't been widely endorsed.  I would retrofit those controls in various situations if they didn't cost over a hundred bucks (plus of course labor, fittings, etc.)

  • Jake48Jake48 Member Posts: 28
    Primary Boiler Pump Failure?


    It was in fact the primary pump.

    I replaced the pump and the system is working fine now.

    I bought the Taco 007-F5 pump on Amazon for $84.99 and "free shipping" and no tax. It took 5 days to arrive. No hot water for 5 days = angry wife and kids. LOL

    To install, I killed the main power switch to the system. Then I shut the valves above and below the pump so I didn't have to drain the system. Disconnected the wires by cutting the power supply wires (they were crimped on to the pump wires). Unscrewed the ground wire. Then I cut off 1/4" of the coating on the wires to expose them. Unbolted the pump and a little residual water in the pump came out, about 1 cup. Then I put the gaskets in the grooves of the pump flanges and carefully slid the pump in place (motor must be parallel to the ground) while ensuring the gasket stayed in place. I hand tightened all 4 nuts and bolts. Then I wrench tightened them. Then I connected the ground wire to the pump using the screw on the pump. Then I connected the white power wire to the white pump wire. I connected the colored power wire (black) to the colored (yellow) pump wire. I had no crimps and no crimping tool but I had the screw on wire caps so used those to secure the wires together. Then I closed up the wire box. Then I opened the upstream and downstream valves on the pump and heard a quick little rush of water filling the pump cavity.

    Then I threw the power switch on. The pump immediately started and so did the hot water pump. The united ignited and interestingly I didn't have to hit the reset button as I expected to have to do. The unit heated up, from 80 to 174 and stopped there where it is supposed to, pressure remained constant at about 14 PSI. This time the main circulation pipes all got hot and I could hear a faint hum from the pump. I checked for leaks and there were none. Once the hot water tank was hot the hot water pump stopped and the boiler then cycled off so everything is working fine!

    One minor concern was when took the cover off the Vitodens 100 I noticed a small puddle in there. I wiped it up and saw no leaks. I am going to assume that this was caused by when I shut the unit down it cooled from 200 degrees to basement temp of 60 degrees and sat there for 5 days so condensation formed on the outside of the pipes and then dripped down.

    Someone asked me to use an amp to test the old suspect pump but I don't have one.

    Someone suggested replacing the cartridge instead of the whole pump but I was told that would cost a big percentage of the 84 bucks I paid for a brand new pump.

    Thanks for your help people!
  • Jean-David BeyerJean-David Beyer Member Posts: 2,532
    If you were like me, ...

    One thing I would do is take the old pump apart and try to see why it failed. Impeller broken, grit between rotor and stator coil, seized bearings, etc. Ohmmeter might reveal short circuits. (Probably would not detect shorted turns in the windings.)

    Doing this might just save you a recurrence of the problem. Say, if it was grit in the bearings, you would want to know where the grit came from. If the blades wore out on the impeller, you might have been suffering from cavitation in there. And so on. And even if you are a mechanical klutz, you will not wreck anything you were going to keep around anyway.
This discussion has been closed.


It looks like you're new here. If you want to get involved, click one of these buttons!