Strap-on Thermal Switch shut-off location... Need for dielectric break?

Post in 'The Boiler Room - Wood Boilers and Furnaces' started by SIERRADMAX, Feb 20, 2013.

  1. SIERRADMAX

    SIERRADMAX
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    Feeling the Heat

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    About ready to do a tie-in to my oil boiler. One concern I have is the low cost option to control the oil boiler when the econoburn is in operation.

    I have the Caleffi mixing valve on the return (set to 142 degF). I've opted for a thermal switch to break contact at 160, restore at 150 to control firing of the oil boiler. I obviously have to place this on the supply line between the bypass "T" and the weighted check (see drawing). If my pipe fitting is correct, I'll have about 7'-6" between these two items.

    My concern is two fold related to pipe heat transfer.

    1. 160 degF supply water temps from the econoburn radiate triggering the thermal switch to knock power to the oil boiler before the mixing valve opens sending HW through the primary loop.
    2. When econoburn is not in operation, the oil boiler does just the same thing and radiates heat through the piping.

    If I were to place the thermal switch somewhere in the middle (say 3' +/-) from the weighted check, will this be enough distance to avoid these potential troubles?
     

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