SunEarth



Misc Designs

Design Principals on Commercial Pools 

Design Principals on Combined DHW & Radiant Floor Systems 

 

 

  
 General Layout of Year-Round Pool Systems
   SunEarth advocates the use of closed-loop systems with glazed panels for pools operated year round for several reasons:  The first reason is simple, annual output of glazed systems is 30-70% greater than unglazed systems.  For seasonal pools, unglazed collectors perform on par with their glazed counterparts.  During the cooler winter season however, glazed panels maintain their output while that of unglazed units drops dramatically.  The figures below show system outputs for a 1,200 sq. ft array of our EP series vs. the average plastic pool panel calculated with F-chart.  The pool is 1,500 sq. ft. without a cover and located indoors.  The output of the glazed units is 38% greater for Los Angeles and 68% greater for Denver

F-Chart simulated output for a 1,200 sq. ft. solar array on a 1,500 sq. ft. indoor pool maintained at 82 F.


In addition to having significantly greater output for year-round applications, glazed closed-loop pool systems also offer these benefits:

  • Complete freeze protection without the need for sloped piping runs.
  • Requires flow rates that are only 1/4 that of unglazed systems.
  • Complete isolation from pool chemistry for increased collector life.
  • Use of heat exchanger eliminates diverter valve and adds almost no head requirements to existing pool pump.
  • All connections are permanently sweated instead of problematic inter-connects with plastic panels.
  • Wind load ratings to 180 MPH.
  • Ease of mounting as the collector framewall is structural member.

Show P&ID Schematic Legend
 Array Layout


click for enlarged diagram

 The array for a closed-loop pool system looks just like that of a closed-loop DHW system.  The array has isolation valves that can be used to bring down any row without affecting the others, and the valve on the outlet of the array may be used for balancing.  The air vent may be either an automatic or coin vent to eliminate trapped or dissolved air in the glycol.
 Inter-Tie With the Pool


click for enlarged diagram

 The mechanicals for a closed-loop pool system again resemble those of a closed-loop DHW system on the collector side.  There are drain and fill valves, a circulator, and expansion tank to regulate pressure in the loop.  Whereas we would find the heat exchanger connected to a storage tank in a DHW system, we simply find it connected to the pool here.  The heat exchanger is connected with balancing and bypass valves to the main filter line.  Typically valves  BV3 and BV5 are open with valve BV4 closed to divert the flow through the heat exchanger before going into the boiler.  The position of these valves can be reversed to isolate the heat exchanger for de-scaling or repair.

The only control for this type of system is a siomple differential temperature controller with sensors located on the pool filter line before the heat exchanger and on the outlet header on one of the rows.  When the controller senses that the collectors are hotter than the pool it energizes the solar pump P1.  When there is no energy to be collected, pump P1 stops and the pool water simply passes through the heat exchanger unchanged as though the solar system were not even there.
 Sizing the Heat Exchanger

   Due to the high flow rates found in pool filter circuits, tube-in-shell units are usually preferred over brazed plate units.  In addition to the smaller ST-2.6 and ST-4.7 used in DHW and spa applications, we have units several times larger for pool applications of 40 panel arrays.  The table below lists these larger units, their dimensions and the maximum array area they can handle while maintaining performance on par with open-loop designs.

SunEarth Model Number

Diameter (in)

Length (in)

Surface Area
(sq ft)

 Maximum Array Area
(sq ft)

Dry Weight (lbs)

Max Pressure (psig)

Tubeside Connection

Shellside Connection

ST-4.7

5 5/8

15 1/4

 4.7 280

XX

250

1" NPTF

1.5" NPTF

ST-9.0

5 5/8

25 1/2

 9.0 460

XX

250

1" NPTF

1.5" NPTF

ST-16.8

5 5/8

43 1/2

 16.8 780

XX

250

1" NPTF

2" NPTF

ST-21.2

8 3/4

38 1/8

 21.2 1,550

XX

250

2" NPTF

 2" NPTF
 Related Topics
 1) Sizing the Pumps and Piping  2) Sizing the Expansion Tank

 

 General Layout of Solar Combi-Systems
A solar combi-system is one in which solar is used to service space heating in addition to the traditional role of domestic water heating.  The space heating load is almost always significantly larger than the domestic hot water load and dictates a significantly expanded array with enough storage to cover the average daily combined load.  A critical item to remember is that the larger space heating fraction of the load is seasonal having a maximum in the dead of winter and going to zero over the summer months.  Since the array will be sized to carry a good portion of the winter load, it will be significantly oversized for the summer load that is limited to domestic hot water.  Such oversizing leads to frequent stagnation in the collector array, which is why drainback systems are always recommended in combi-system applications.

To carry the average daily load, storage tanks in combi-system applications are typically several hundred gallons in size.  To keep costs down, the tanks are usually of the un-pressurized type constructed from polypropylene, cross linked polyethylene, or EPDM liner.  Heat transfer into the domestic hot water is accomplished by an immersed coil in the same manner as a commercial drainback system with load-side heat exchanger.  Heat transfer into the radiant floor loop may be by direct injection if the floor loop contains water, or may be by way of a second coil immersed in the tank if the floor loop is pressurized with a glycol fluid.

Show P&ID Schematic Legend
 Drainback Combi-System with Immersed Auxiliary HX


click for enlarged diagram
 Drainback Combi-System with External Auxiliary HX


click for enlarged diagram

    
 Related Topics
 1) Sizing the Pumps and Piping