Click here to Find a Contractor in your area.
Welcome! Here are the website rules, as well as some tips for using this forum.

If you've found help here, check back in to let us know how everything worked out.
It's a great way to thank those who helped you.
Need to contact us? Visit https://heatinghelp.com/contact-us/.

Problem with outdoor wood boiler water circulation pump

wah34wah34 Member Posts: 4
I am looking for help or suggestions? I'm having trouble with my Natures Comfort outdoor wood boiler. Its several years old and I inherited it from my father that passed away a couple of years ago. So I'm having to learn or figure it out as I go.
Last winter I had it running. Several times when I went to put wood in it, the steam would build up so much that it would blow the water float and cap off and the water would come out the water fill tube.
I started my boiler this winter for the first time and it started doing the same thing. I checked the back and noticed that the control box on the circulation pump had melted.
This is my old pump




So I bought a brand new circulation pump. A Systemflo pump from Walrus America.


I had an electrician check my aquastat. He said everything was good with it
I installed the new pump. After starting a fire in the boiler, about 2 hours later, I checked the pump noticed that it was starting to get hot but I kept running it.
About 3 hours in, the new pump was extremely hot and I heard a loud mechanical squealing coming from the new circulating pump. So I shut it down.

Any ideas or suggestions or help would be greatly appreciated.

Comments

  • IronmanIronman Member Posts: 5,676
    Is the pump mounted with the motor horizontally? It has to be horizontal.

    The motor bearings are water lubricated. The silver screw on the back should be cracked open until water comes out to assure the back bearing is wet.
    Bob Boan


    You can choose to do what you want, but you cannot choose the consequences.
  • lchmblchmb Member Posts: 2,991
    how hot are you running the boiler and with what pressure? If your making steam your to hot. Did you check to verify on the pump sizing to make sure what was there was right?
  • wah34wah34 Member Posts: 4
    The way the connections for the water lines are Vertical but the pump is horizontal. If that makes sense?

    So the silver screw, how much should it be opened? How much water needs to come out of it?
  • neilcneilc Member Posts: 809
    lightning strike or surge that took out the capacitor?
  • wah34wah34 Member Posts: 4
    This is how I have it installed. arrow is pointing up.

  • wah34wah34 Member Posts: 4
    No. No lighting strike or power surge.
  • hot_rodhot_rod Member Posts: 13,493
    Looks like a high head circulator on an undersized pex line, and an open system, I'm guessing with no NPSH on the circulator.

    When the boiler boils over the pump cavitates, boils the water out of the volute then they get excessively hot and melt down. It should have about 15 psi on it at those temperature try and keep the boiler temperature below boiling will help.

    Bob "hot rod" Rohr
    trainer for Caleffi NA
    The magic is in hydronics, and hydronics is in me
    IronmanZmanSolid_Fuel_ManSuperTech
  • EBEBRATT-EdEBEBRATT-Ed Member Posts: 7,088
    Bleed pump and try to not over fire the boiler. Probably easier said than done
  • njtommynjtommy Member Posts: 1,105
    Generally the pump will be the other way around and pump water into the house. Most likely your problem is the pump and pex piping is full of air.
  • Solid_Fuel_ManSolid_Fuel_Man Member Posts: 1,978
    Get us more pictures of this system. Further away where the circulator is, and lines in the house where they come in from the boiler. Also where they are connected to your heating sysyrm.
    Serving Northern Maine HVAC & Controls. I burn wood, it smells good!
  • hot_rodhot_rod Member Posts: 13,493
    Looks like a Chinese knock off of a familiar pump brand? Not sure about quality of that product.

    Here are some specs. If it is an open system I doubt you have adequate pressure on the circulator to suppress cavitation which can lead to excessive temperature and early failure. When multiple pumps fail there is usually an application or installation glitch.

    If the boiler runs around 194F you should have 4 psi, about 10' of water above the circulator.

    At 212F where OWF often end up, you would probably need 10 psi around 23' of water above the circulator pump location.

    This has always been a challenge for the open type OWF market, finding a circulator that can work in those un-desireable conditions. And last for more than a year or two.

    Bob "hot rod" Rohr
    trainer for Caleffi NA
    The magic is in hydronics, and hydronics is in me
  • Solid_Fuel_ManSolid_Fuel_Man Member Posts: 1,978
    edited January 2018
    I've found if the circulator flange is directly mounted at the supply (lower) boiler tapping and pumping into the restrictive 1"PEX that everyone seems to use.... most circulators run for reasonable times. That Chinese knockoff likely not!

    Some outdoor boiler manufacturers have supply and return tapping both low on the boiler in an effort to get adequate head at the inlet of the circulator. Problems seem to happen when people put a 3/4" nipple between the circulator and the boiler..... Or pump into the boiler (PONPC). That never works well!

    PEX and circulator should be sized for the heatloss and reasonable headloss. Generally 1-1/4 pex in the minimum with 1-1/2pex being ideal. But few will spend the money on properly sizing the lines let alone proper insulation for them..........

    High head circulators, undersized lines, and open systems, most end up boiling over and having water issues.
    Serving Northern Maine HVAC & Controls. I burn wood, it smells good!
  • hot_rodhot_rod Member Posts: 13,493
    I don't know if Taco still offers that OWF specific circulator. That was about you best chance of reasonable success on open, restrictive pipe sized systems.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    The magic is in hydronics, and hydronics is in me
  • IronmanIronman Member Posts: 5,676
    A B&G PL 36 is their offering.
    Bob Boan


    You can choose to do what you want, but you cannot choose the consequences.
  • leonzleonz Member Posts: 332
    If you invest in a B+G NRF 25 and set it on speed one which is 12 gallons per minute you should be fine it. I have a B+G NRF 25 circulator without the check valve and it has been working flawlessly for three years plus now as I had it on hand fed set up before I bought different boiler.

    You don't have to mess with the NRF 25 at all just, remove the old circulator and install the B+G with the electric motor facing inwards with the flow arrow in the correct position and lube the new gaskets with gasket lube or vaseline and install it slowly making sure the gaskets are seated and tighten the bolts down a little at a time going from one to the other until they are tight.

    When the heating season is over you should think about purchasing isolation flanges with gauge ports so you can have a vacuum gauge on the inlet side and a pressure gauge on the outlet side so you can check the condition of the circulator as needed.

    When a circulator fails it creates a huge vacuum and the impeller causes cavitation and the air bubbles and a forest eater or other type boiler will boil over and pop the relief valve.

    You will see this occur on a vacuum gauge and you will know the circulator is bad. A circulator that is in good condition will not create a vacuum.

    Aaron;
    we need your dad to tell us the story again about the pedestal pump he had to check one day and how much hell he caught afterward from Mister Bosch that day.










  • ZmanZman Member Posts: 5,870
    I agree that you would be wise to replace the pump with a quality one sized correctly for the application.
    To correctly size the pump, at a minimum, one would need the model of the boiler and heat exchanger as well as the type and length of the piping to and from.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • Terry OTerry O Member Posts: 67
    hot rod said:

    I don't know if Taco still offers that OWF specific circulator. That was about you best chance of reasonable success on open, restrictive pipe sized systems.

    Yep... they are still offered and we try selling as a replacement when customer comes in with an old dead wet rotor. TACO model number is 2400-20-WB.

    https://www.taco-hvac.com/uploads/FileLibrary/101-131.pdf
    Terry O
  • EYoderEYoder Member Posts: 60
    I worked on a Nature's Comfort model this year with the same issues. Main culprit was an ashpan that didn't seal tight causing ongoing boiling issues. The pump they supply is oversized for most lines that are used, that combined with boiling caused cavitation. The lines to the house went up high with no way plumbed to purge air.. a combination of issues.

    Stepping down to a smaller circ, adjusting doors until they fit tight, keeping the aquastat set below 180 (even 170) and running at least one continuous circ does wonders. A wood boiler should never boil. Period.
    wah34
  • woodburnernc175woodburnernc175 Member Posts: 1
    i have a natures comfort 175 had the same problem boiling over i realigned the top door and added rubber hood latches from the old jeep cj to help keep the ashpan tight parts store or ebay and make sure your door seals are new solved my problem also i have mine set at 145 on and 160 shutoff temp with a 5 degree leway produces plenty of heat without overheating the pump also make sure your arrow is pointing down towards the in pipe to the house good luck
  • GroundUpGroundUp Member Posts: 991

    i have a natures comfort 175 had the same problem boiling over i realigned the top door and added rubber hood latches from the old jeep cj to help keep the ashpan tight parts store or ebay and make sure your door seals are new solved my problem also i have mine set at 145 on and 160 shutoff temp with a 5 degree leway produces plenty of heat without overheating the pump also make sure your arrow is pointing down towards the in pipe to the house good luck

    Those are prime temperatures for flue and firebox condensation, and in a mild steel boiler like the NCB you're asking for caustic ash and unnecessary creosote- both creating corrosion. Ideally, you'd want your return temperatures a bare minimum of 140 degrees under full heat load.
Sign In or Register to comment.

Welcome

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