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New Solar DHW System for NW School

Paul Pollets
Paul Pollets Member Posts: 3,415
Here's some pics from a project we're about to complete and commission next week.

The 4 panel array has 120 vacuum tubes (Viessmann VitoSol 300T) in 4 arrays.

The storage tank is a custom AOSmith SS 250g tank. The solar tank will feed the (2) commercial water heaters located below the solar tank room. The pump module is a Viessmann Divicon with internal FPHX. An Onicon BTU & flowmeter will track data for the school's "Dashboard". BACnet interface by Viessmann.


  • jumper
    jumper Member Posts: 1,667
    how much?

    How much did it cost and how many BTU will it produce?
  • Paul Pollets
    Paul Pollets Member Posts: 3,415

    The system will produce 40K btu's/hr at peak load. Due to the specific peak loads which are reduced in June-Aug, as the school only has 10% of students present, the racks were tilted to 45 degrees rather than 25. This lowers the system output during the strongest solar months.

    As for cost, it was less than 1/2 the price of a drainback system that was originally proposed for the facility. I'd rather not share the specifics.
  • solradman
    solradman Member Posts: 53
    Less then half.

    Please explain that.  Other than the flat plates needing a beefier mounting system one would think the rest of the system would be a wash.
  • Paul Pollets
    Paul Pollets Member Posts: 3,415

    I'm not sure what you're asking to explain... The original drainback system used 12 flat panels, compared to 4 arrays. The drainback piping was designed from the basement level requiring the pumps to pump up 85 ft. The amp load was over 40 amps. This design uses 12-14 amps with all pumps running.
  • JamieLeef
    JamieLeef Member Posts: 13
    flow meters

    Nicely piped system. And good to know that AO will make a 250 gal tank. You should consider the flow meter range limitations of the Onicon units - looks like the F1100 series. Those will not reliably read below about 3/4 GPM. Based on reviewing many flow measurement studies on commercial and residential buildings I believe there are often a lot of flows in the range from 0.2 to 0.75. Seems like low flow but it can add up to lots of volume and lots of Btu. This will mean that you will be underreporting your solar heat delivery to the building. If the system seems to be underperforming (assuming anyone actually watches the BACNET) you might want to check to see what you might be missing. Check out the Tricon meters.
  • Paul Pollets
    Paul Pollets Member Posts: 3,415

    The flowmeter was specified by the mechanical engineering team based on average flow rates from the heat exchanger into the storage tank. We're about to set up the internet connection this week which will allow monitoring. From what I've observed, flow rates vary between 2 and 5gpm in December. The array produces 110 degree water when ambient temp is 25.
This discussion has been closed.