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Boiler Bypass

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Does anyone know how to adjust a boiler bypass valve? I have a Teledyne Laars Mighty Therm HH 0250C boiler with a manual bypass valve. I accidently hit the valve handle and can't figure out how to get it back to where it should be.



Suggestions are greatly appreciated. Thank you, David

Comments

  • RayWohlfarth
    RayWohlfarth Member Posts: 1,518
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    The bypass is typically adjusted to be sure the return water to the boiler is above 140 degrees F to avoid condensing 
    Ray Wohlfarth
    Boiler Lessons
    David80908
  • HomerJSmith
    HomerJSmith Member Posts: 2,468
    edited March 2023
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    I personally hate ball valves as a control method on a boiler bypass. It because ball valves have such a low valve authority. Before a ball valve starts regulating it is 90% closed. For a fixed valve, a globe valve mounted in the right direction is a better choice. Yes, globe valves are directional.
    The original setting of that ball valve may have been just an guesstimate. There are stick on thermometers that you can put on the return pipe to the boiler below the bypass and in a worse case scenario, at start up with all zones calling for heat, monitor the return temp and set the valve so that the return water is above 130 deg.

    I prefer a motorized sensor monitoring bypass valve. That is because the inlet temp to the boiler must be above 130 deg for condensing in the heat exchanger and flue not to occur. All boilers condense at start up, but it is sustained condensation that one wants to avoid. There are also operational changes in return water temperatures as when more zone valves open as an example that is why I prefer a sensor actuating valve. Whether the sensor is in the valve body or exterior to the valve is immaterial.
    Caleffi make a modulating bypass valve that has good reviews. I have used Taco I-Series set point motorized valves. Today I would go with the Caleffi boiler bypass valve. https://www.supplyhouse.com/Caleffi-280166A-1-Female-NPT-ThermoProtec-Thermostatic-Mixing-Valve-140-Degrees-F-Tset
    https://www.supplyhouse.com/Taco-I075C2S-2-3-4-2-Way-Setpoint-I-Series-Mixing-Valve-w-Sensor
    ZmanDavid80908
  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 15,631
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    Measure your supply water temp and return water temp when the boiler is running full bore from a cold start with a load on it. You want the supply water temp to be about 20 degrees warmer than the return. It looks like the manual calls for 20gpm through the boiler with a 20 degree TD across the boiler.


    I think this is the correct manual attached
    David80908
  • hot_rod
    hot_rod Member Posts: 22,263
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    Measure your supply water temp and return water temp when the boiler is running full bore from a cold start with a load on it. You want the supply water temp to be about 20 degrees warmer than the return. It looks like the manual calls for 20gpm through the boiler with a 20 degree TD across the boiler.


    I think this is the correct manual attached

    Piped primary/ secondary? Doesn't look like the boiler is piped this way? If not I wonder how well it runs with one zone calling, like the master?

    I'd say more open then closed if that is a 250,000 boiler.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
    ZmanDavid80908
  • David80908
    David80908 Member Posts: 2
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    You guys are awesome! It is amazing how much this adjustment affects the system. I will work with these adjustments to get the system back on line. Thank you so much!!