Medium commercial, take two: Gulf Coast State heats up with solar

In our next example of a commercial solar design, we fly to the Florida’s coast. This very efficient, simple system design for a building at Gulf Coast State College features vacuum-tube panels.

Medium commercial, with 2 Solar Phoenixes

Medium commercial drainback system with two Solar Phoenixes and storage tank

For last week’s solar system design example, we were in Los Angeles — we discussed a medium-sized commercial system for a two-building apartment complex. Like that one (click here to read about it), this example is also a medium commercial system, but we’re using additional backup and more panels. The bid, through Coleman-Russell in North Carolina, has been accepted, and it’ll be fun to see the progress as this building goes up. This design for a medium commercial system works great for schools, like Gulf Coast State. The building, the Advanced Technology Center, features 39 public lavatories, eight kitchen sinks and 15 service sinks. The engineer, Anton Lie of Schmidt Consulting, and I agreed on two Solar Phoenixes and a 119-gallon indirect storage tank for this drainback system. There’ll also be eight vacuum-tube collectors, though flat-plate collectors would work the same in this hot climate and cost less.

10 tube panel array 092612

Diagram of array with multiple 10-tube vacuum collectors

The Solar Phoenix water heaters will produce 670 gallons per hour (GPH) per hour on a 100-degree rise. This is full backup heat – that is, covering everything the building would use if hot water needs were constant and full-bore. Solar will, of course, keep the Phoenixes from firing, reducing gas use and maintaining their use for true backup. The eight solar collectors here will crank out 336,000 btus per day. With the 238 gallons of available storage in the Phoenixes and the 120-gallon tank, we’ll have 357 total gallons of storage for the solar at any given time. If we take those tanks from 60 degrees to 180 degrees, they will hold 359, 856 btus. So the storage is perfectly matched with what the solar can contribute. In the fall, when the solar may start to fall short, the Phoenix’s burner will fire just enough to make up for what the solar cannot produce — no full-fire water heater with no brains burning lots of gas. If the solar falls short on meeting demands, the internal burner will only fire enough to make up the shortage. The Phoenix or Versa Hydro will soon be available with all the built-in solar controls and btu meter. OK, here’s the parts list:

  • 2 ea.      Modulating and condensing stainless Phoenix water heaters (PH199-119SNHX)
  • 1ea.       Superstor Ultra 119-gallon stainless-steel indirect tank (SSU-119)
  • 1 ea.      Stainless-steel 15-gallon drainback tank with site glass (SSU-15DB)
  • 8 ea.      30-tube vacuum tube collectors (HP-30SC)
  • 2 ea.      Balancing valves (930-013)
  • 1 ea.       BX solar controller (940-014)
  • 2 ea.      VFS (vortex flow sensor) and RPS (digital pressure sensor) 10′ wire (940-015)
  • 1 ea.      RPS pressure sensor (940-020)
  • 1 ea.      VSF flow sensor (940-022)
  • 2 ea.       1″ sweat connection for VSF and RPS (925-047)
  • 1 ea.       DL3 data logger/BACnet gateway (940-044)
  • 1 ea.       1.5″ 185° Solar-compatible antiscalding valve (925-219)

Field-supplied components will include:

  • Solar drainback pump (6 feet lift at 8 GPM)
  • Taco 008 stainless, or Grundfos 15-42 stainless pump
  • W/1″ flanges
  • Tank to tank transfer pump (3 fthd at 3 GPM)
  • Taco 006B5 1/2″, or Grundfos UPS 15-10 1/2″
  • 2 ea. concentric vent kits
  • 1″ copper pipe and 240° insulation using 18/2 stat wire for solar sensors

I anticipate working with the contractors as the system goes forward, providing any technical support they may need. I already know they’ll need a controller hookup detail with programming instructions. I’ll keep you posted.

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