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Circulator Periodically "Sticks"

drosner
drosner Member Posts: 45
in THE MAIN WALL
I have hot water heating and domestic hot water (DHW) both fed from a gas fired high efficiency heater. Its a pretty old system with 6 zones - some 100+ years old, some from more modern times. The other day I had a burst pipe in one of my zones and I had a plumber repair the pipe and they purged the air in the radiators in that zone.

A day after my hot water stopped being hot and I went to check it out. From feeling the pipes I figured out that the flow into the DHW was getting stuck. The pipe into the circ was hot but from the circ into the DHW tank was cold. I checked all the electrical controls and everything looked good. I could also hear the circulator running and the motor casing was hot.

On a whim I hypothesized that maybe it was just "stuck" somehow (think I read that somewhere). So I opened up the drain valve on the system and hoped releasing the pressure would do something. It must have because when I turned everything back on I could hear water rushing through the circ and the flow was restored.

Problem is that this happened again a few days later so whatever I did was only temporary. Does anyone have any idea what is going on and how I should address with a proper long term solution? Opening the drain again resolved the problem the second time...

Thanks for any guidance here!


Comments

  • rick in Alaska
    rick in Alaska Member Posts: 1,459
    Most likely you have air in the boiler line feeding the DHW tank that will have to be bled. You should not hear any water noise when it is running. Probably when you opened up the drain valve it purged enough air to get it running, then the air built up again and it quit. That zone will have to be purged out to get rid of the problem. We will need to see pictures of the piping to it in order to tell you how to do that.
    Rick
  • JohnNY
    JohnNY Member Posts: 3,284
    What Rick said. You've got entrained air in the system. You've got to get that out.
    Contact John "JohnNY" Cataneo, NYC Master Plumber, Lic 1784
    Consulting & Troubleshooting
    Heating in NYC or NJ.
    Classes
  • drosner
    drosner Member Posts: 45
    Thanks for the responses!

    I've got some automatic air bleed values in the system and I can purge the air in all the radiators. Is this as simple as that? My system has a decent amount of shut-off valves so I could probably isolate the circuit for the DHW if there is some other option you guys recommend.

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