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two loop system one loop failure

bob young
bob young Member Posts: 2,177
i agree with Al. air problem. sometimes you must cut in an additional tee and valve to isolate zones for proper purging. good luck


  • geo_23
    geo_23 Member Posts: 18
    two loop system one loop failure

    I have a two loop system which was installed 30 years ago.
    One loop is not working correctly, why? See story below
    Complete system worked perfectly until one water valve failed.
    I thought the pump was making the noise (when it really was the noisy valve)- replaced pump with wrong undersized) pump.
    Pump would only heat the first baseboard unit in each loop - rest of loop was cold. Ran system for several days before being able to replace undersized pump with correct size. Also replaced the faulty valve.
    NOW one loop works perfectly and the other loop (oddly the one with the replaced valve) heats only the first baseboard unit - the rest of the loop
    is cold.
    Checked both loops for obstructions and both loops act as if there are NO obstructions in the line.
    Why is the one loop heating only the first baseboard (outlet line is hot) and the next baseboard inlet line is cold? (Remember both circuits worked OK prior to
    valve failure and both loops show full flow.)
    What is causing this and how do I fix it?
  • Al Letellier_9
    Al Letellier_9 Member Posts: 929
    no heat

    Not sure what you mean by a faulty "water valve" but it sounds like you have air in the sytem and it needs purging. If you have the proper valves in place, purge each loop individually. Trying to purge a split loop system from one point, doing both sides at the same time, just doesn't work.
  • geo_23
    geo_23 Member Posts: 18
    two loop system one loop failure

    Faulty valve = water valve in hydronic system stuck and would not rotate - had to remove T adapter and replace whole unit.

    I tried purging but found out afterwords that my 'purge' did not purge the system.

    The air purge valve removes the air and I ran water through the system from an exterior hose bib and got most of the air out of each circuit.

    But air /does/ seem to be a good reason for 'no flow'

    Will continue trying to get the system flowing.

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