Solar Skies Mfg, LLC
106 Donovan Drive • Alexandria, MN 56308 • Ph 320-762-1151 Fax 320-762-1460
CD1065.doc Last Revision: 12/23/2010
PART 6: HEAT TRANSFER FLUID QUALITY
Two heat transfer fluids may be used in drain back systems: Distilled water or glycol/water mix. Water in direct flow
through the drain back tank must first meet potable water requirements and, in addition, the following:
TOTAL DISSOLVED SOLIDS
<600 ppm
TOTAL HARDNESS
<200 ppm
CHLORIDE
<40 ppm
FREE CHLORINE
<5 ppm
MAGNESIUM
<10 ppm
Table 2
Lime scale may form inside the header pipe in areas with “hard” water (> 200 ppm) where a direct flow format is used. In
such regions, it is advisable to install a water softening device to ensure the long term efficient operation of the collector,
or use a closed loop for the solar circulation loop.
In order to meet health and safety regulations, drain back system antifreeze fluid should be food grade polypropylene
glycol, FDA rated as “generally recognized as safe” (GRAS). Using proper concentrations of glycol, solar systems can be
operated at ambient temperatures as low as -60
o
F. Freeze tolerance limits are based upon an assumed set of
environmental conditions. Refer to the glycol manufacturer’s specification sheet for recommended concentrations. If using
a glycol/water mix, the water must meet the above requirements, and the glycol content of the liquid must not exceed
50%, unless the manufacture specifies that a different ratio is recommended for use with solar water heaters. HTP
recommends using a pre-blended glycol/water mix. Glycol may need to be changed periodically (every 3-5 years) to
prevent it from becoming acidic; please refer to the guidelines provided by the glycol manufacturer regarding replacement.
NOTE: SOLAR SKIES MFG. DOES NOT WARRANT THE DRAIN BACK TANK AGAINST FREEZE
RELATED DAMAGE.
PART 7: STARTING YOUR DRAIN BACK SYSTEM
NOTE: DO NOT MOVE ON TO THESE STEPS UNTIL THE ENTIRE SOLAR SYSTEM, INCLUDING ALL PIPING,
SOLAR COLLECTORS, SENSORS, PUMP, CONTROLS, AND ELECTRICAL CONNECTIONS, ARE PROPERLY
SECURED, INSULATED, LABELED AND INSTALLED.
A. FILL THE DRAIN BACK RESERVOIR
1. Attach hose to solar loop fill valve. The location of the fill valve varies depending on numerous factors, including
whether the drain back tank has a heat exchanger.
2. Open fill valve and the pressure relief valve on the drain back tank).
3. Slowly fill the drain back reservoir to the top of the sight glass.
4. When full, shut off fill valve and close the relief valve.
5. Remove fill hose.
B. START-UP PROCEDURE
Once the system is filled as prescribed above:
1. Plug the controller cord into a standard 115 VAC wall outlet.
2. Turn on pump and let run for 5 minutes.
3. Check for leaks at collectors and in attic, if applicable.
4. If no leaks are found, switch controller to automatic mode.
If the sun is shining and the tank is cool, the pump should turn on and begin circulating water. Check control settings to
maximize your system performance.
