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Approx snow melt BTUs

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John Mills_5
John Mills_5 Member Posts: 951
We have a new customer with a boiler that serves 3 infloor zones and a 4th zone wired to a switch. We can't figure out and customer is new to the house, what that 4th zone is. Tech thinks it is snowmelt for 100+ foot long driveway. Seems to me the 150K boiler is sized right for the house and couldn't make a dent in the drive. If anything I'd guess a loop in the garage where the boiler is. SO, stab in the dark at what this 100ish foot long 25ish foot wide drive would use BTUwise for snowmelt?

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  • hot_rod
    hot_rod Member Posts: 22,158
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    At least

    100 BTU/ sq. foot of snowmwelt in my opinion. I've tried a few below that with un satisfactory results.

    ASHRAE does have a snowmelt standard now for 3 classes of performance.h

    If in fact that does have a drive way loop, and it is not a condensing boiler, be sure the boiler has adequate low return temperature protection. because tha load will keep it running cold for long periods :)probably from the first snowfall till spring tham :)

    You should be able to find a manifold box for the driveway system. Certainly there would be more than one loop in 2500 feet? Maybe not :)

    Do some more snooping to see where the mystery zone is.

    Does the system contsain glycol? That would be a good clue as to snowmelt zones.

    hot rod
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • Brad White_9
    Brad White_9 Member Posts: 2,440
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    Climate Counts

    Depends on the application and severity. You may have to "Backwards Engineer" the installation.

    Micro-climates count as much as anything. If the location gets 20" storms and five miles away means a 6-inch dump in the same storm you have an idea. (Think Finger Lakes). It has less to do with temperature as you can imagine. Boston would be in the 235 BTU/SF range and NYC would be 298, go figure. Buffalo is even less at under 200 so double go-figure. Maybe a typo but that is what I have.
    Also, what kind of storm they are expecting to keep up with.

    BTU per SF ranges can be anywhere from 100 to 300, from nuisance prevention to mission-critical chopper pads. I would figure Class 2 which is commercial-grade unless directed otherwise.
  • Doc Radiant
    Doc Radiant Member Posts: 57
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    Light, fluffy snow requires the least amount of energy, the wet, heavy stuff far more. That's why locations like NYC require so many BTUs.

    I have to agree that regardless of snow density, 100 BTUs per square foot is about the minimum requirement.
  • John Mills_5
    John Mills_5 Member Posts: 951
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    Thanks gang

    Still think it could be a garage loop. Nothing but water in the system they said. System dates to 1940s I think. I'll post a picture of the boiler when I get a chance.
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