Advanced Thermal Solar, LLC

Sizing your system

The average family uses 26 gallons of hot water per adult and 13 gallons per child; each day. 

For a family of 4 (2 adults and 2 children) typical hot water use would be about 78 gallons of hot water per day. * Calculation: 1 gal of water weighs 8.34lbs. 78 gallons X 8.34lbs X 65 degrees = 42,284 BTUs per day required. The suggested system would be (3) 10-tube panels with our 79-gallon tank, which can produce about 45,000 BTUs in full summer sun. 

For a household of 2 (two adults) typical water use would be 52 gallons per day. * Calculation: 1 gal of water weighs 8.34lbs. 52 gallons X 8.34lbs X 65 degrees = 28,189 BTUs per day required. The suggested system would be (2) 10-tube panels with our 55-gallon tank, which would produce about 30,000 BTUs in full summer sun. 

Note: Solar output varies in different parts of the country so these numbers should only be used as a rough guide, which should be confirmed by an engineer.

*The 65 degrees is based on raising cold ground water temperature from 55 degrees F to 120 degrees F, and (1) One BTU of heat will raise 1 lb of water 1 degree F.

Sizing your heating system

Home Type or Characteristics ..... Heat loss (Btu/hr/ft2)

1) No insulation in walls, ceilings, or floors; no storm windows; windows and doors fit loosely .... 90 to 110 (Btu/hr/ft2)

2) R-11 insulation in walls and ceilings; no insulation in floors over crawl spaces; no storm windows; doors and windows fit fairly tight. ..... 50 to 70  (Btu/hr/ft2)

3) R-19 insulation in walls, R-30 in ceilings, and R-11 in floors; tight-fitting storm windows or double pane windows. ..... 29 to 35(Btu/hr/ft2)

4) Superinsulated house with R-24 wall insulation, R-40 in ceilings, and R-19 in floor; tight-fitting storm windows or double pane windows; vapor barrier sealed carefully during construction. ..... 21 to 25 (Btu/hr/ft2)

5) Earth-sheltered house with little exposure; well insulated. ..... 10 to 13 (Btu/hr/ft2)

Your solar heating system can provide either a portion of your heat or a majority of your heating!

Note: In most cases during the summer a heat dump, swimming pool or drain back tank will be required with a solar heating system.

SIZING YOUR EXPANSION TANK How much Glycol Mix is required)

Using the charts below the combined fluid capacity of the solar collectors and the volume of fluid in the pipes can be calculated to determine the total volume of fluid in your system.






10 TUBE MODEL 0.17
20 TUBE MODEL 0.34
30 TUBE MODEL 0.50

Copper Pipe Capacity (US Gal/100 ft)
Pipe Size Type M Type L Type K
3/4" 2.7 2.5 2.3
1" 4.5 4.3 4
1-1/4" 6.8 6.5 6.3
1-1/2" 9.5 9.2 8.9
2" 16.5 16.1 15.7
2-1/2" 25.4 24.8 24.2
3" 36.2 35.4 34.5

The table below provides the maximum closed loop volumes allowable for various Amtrol expansion tanks.  

(Precharge before filling of 12 psi & final loop charged pressure of 20 psi) 

Amtrol Model
Total Volume Acceptance Volume Maximum Solar Loop Volume
(gal) (gal) (gal)
Extrol 15 2 1 3
Extrol 30 4.4 2.5 11
Extrol 60 7.6 2.5 6
Extrol 90 14 11.3 59
Extrol SX-30V 14 11.3 59
Extrol SX-40V 20 11.3 51
Extrol SX-60V 32 11.3 29
Extrol SX-90V 44 34 183
Extrol SX-110V 62 34 150
Extrol SX-160V 86 46 200

Sizing the Drainback Tank (If desired)

Sizing of drainback tanks; standard rule is to select a tank that is twice the loop volume. 


How do the evacuated tubes work?...

This is a dry system that transfers heat by conduction, if a tube ever broke the system will still operate and no liquid would ever get discharged. 

We now have three SRCC OG100 certified evacuated tube collectors models available ; our 10 tube, 22 tube and 30 tube collectors. Each of our models are fabricated using high quality 18 gauge (0.050") Type 304 Stainless steel framing.

The evacuated double-walled glass tube provides a thermally insulated "Thermos" bottle. The outer glass tube is clear, and the surface of the inner glass tube is coated with a special material that absorbs the sun's energy. This combination of technology provides an ideal heat source for the heart of the system, which is the "heat tube".

The heat tube is located inside the thermally insulated, solar absorption area of the tube. Inside the heat tube is a small quantity of purified water and some special additives. The "heat tube" is hollow and the space inside it is evacuated to reduce the "vapor pressure" of the water inside the heat tube.  Based on the principle of water boiling at a lower temperature with decreased air pressure, by evacuating the heat pipe, the boiling point temperature is reduced. The heat pipes used in solar collectors have a boiling point of only 85F. So when the heat pipe is heated above 85F the water vaporizes. This steam rapidly rises to the top of the heat pipe transferring heat. As the heat is lost at the condenser (top), the steam condenses to form a liquid (water) and returns to the bottom of the heat pipe to once again repeat the process.

When the hot steam rises through the condenser  bulb, it gets so hot it would burn your hand instantly if touched.  The condenser bulb is placed into a copper heat exchanger where water or glycol is circulated transferring the heat from the copper to the liquid medium.

The technology is so efficient that even on cloudy days you will still be capturing reflective radiant energy! The energy output from just one of our tubes can provide up to1500 BTU's per day of free solar energy, (see graphs below)

How much tilt angle should you use?

Changing the angle can increase or decrease radiation rates for various portions of the year.

  • Solar Pool heating systems (Reduce Tilt Angle setting for enhanced Summer performance)
  • Solar heating systems (Increase Tilt Angle setting for enhanced Winter performance)
  • DHW systems (Median Tilt of Angle 55 degrees setting for year round use)


© 2008- 2012, Advanced Thermal Solar, LLC

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What is your DHW system doing for you in the winter when your preheated water ONLY gets warm?


120F or more      100%

110F                    86%

100F                    71%

90F                      57%

80F                      43%

70F                      29%

60F                      14%

50F                       0%

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