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ultra install

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george_28
george_28 Member Posts: 1
in THE MAIN WALL
Installing ultra boiler radiant in floor in basement, fan coil in air handler for upstairs and a hot water maker. Can i just run all secondary circuits 12" spaced tees and not put outdoor reset and not use the boilers domestic hot water circuit? alo primar loop sizing? Is 2" copper sized right for 3000 sq ft home.

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  • Brad White_9
    Brad White_9 Member Posts: 2,440
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    Different Temperatures

    Without OD Reset you are missing the biggest benefit of an Ultra or any condensing boiler for that matter. I would have reset to suit the high temperature zone (the AHU) and size that coil to meet capacity with no more than 140 degree water. You should be able to reset that to around 115-120 at least.

    Put the DHW on it's own priority. No sense in having the tail wag the dog.

    The radiant zone sounds like at most 20-25% of the house given basement losses and just a guess. At least that will be mixed down from the higher temperature via a mixing valve at the manifold, right?

    Tee spacing- why 12" spacing? Make them as close as possible. No harm in making the radiant zone dowstream of the AHU but I would pipe the DHW first in line or in parallel from the house heating circuit.

    As for pipe size versus heat loss, a 2" copper line will handle about 30 GPM conservatively. That would be about 100 BTUH per SF at design using a 20 degree F. drop.... huge margin of safety there!

    Fine for a short primary circuit though, low pressure drops. You may get away with 1.5" which will handle 18-20 GPM and 180-200,000 BTUH at a 20-degree F. drop.

    Modern construction should be below 30 BTUH/SF depending on glass area and climate. I figure 25-30 as a check figure for a zero design area and modern construction; this is conservative and does not substitute for a fully calculated heat loss of course.

    My $0.02

    Brad
  • Steverino
    Steverino Member Posts: 140
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    I agree w/Brad

    In my own house I have joist-trak staple up for the first floor and an air handler for second stage and the second floor as well. Piped the air handler loop from the same tees for the indirect and I use an SR-502 to signal the boiler for 180* when either dom or ahu call. Other than that the boiler follows the outdoor reset curve and condenses happily. Two inch pri. loop is overkill, keep your sec. tees as tight as practical.
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