HTP SSC-119SE - Manual (Page 8)

8
LP-200 REV. 3.25.14
Return
– The plumbing line running from the tank (or heat exchanger) to the inlet of the collector. This line incorporates the circulation
pump.
D. SYSTEM DESIGN
PRESSURIZED CLOSED LOOP SYSTEMS
A closed loop system uses non-potable HTF and must be pressurized to less than 72.5 psi. Closed loop systems require an expansion
tank to accommodate HTF expansion. The system should be designed to minimize stagnation after the tank temperature has been met;
extensive stagnation may increase pH levels and glycol deterioration.
The expansion tank and plumbing must be properly sized so that the safety pressure relief valve will not activate except in the event of
component failure or extreme conditions. The pressure release must be set at no more than 90 psi. (There may be exceptions in
engineered designs for tall buildings.)
E. FLUID QUALITY
Water quality is very important. Water in direct flow through the solar collectors must first meet potable water requirements; any fluid
circulated through the collectors should be non-corrosive to copper. In addition, water quality must meet the following requirements.
Hardness: Less than 7 grains
Chloride levels: Less than 100 ppm
pH levels: 6-8
TDS: Less than 2000 ppm
Sodium: Less than 20 mGL
In order to meet health and safety regulations,
glycol used should be food grade propylene glycol, FDA rated as “generally recognized
as safe” (GRAS). If using a glycol/water mix, distilled water is preferred. If distilled water is unavailable, the water must meet the above
requirements. The glycol content of the liquid must not exceed 50%, unless the manufacturer specifies that a different ratio is
recommended for use with solar water heaters. Glycol should be checked periodically to prevent it from becoming acidic. Please refer
to guidelines provided by the glycol manufacturer regarding glycol maintenance.
F. CORROSION
Both copper and stainless steel are susceptible to corrosion when, amongst other factors, high concentrations of chlorine are present.
NOTE: Leakage of the solar water heater due to corrosion caused by improper water quality IS NOT covered by product warranty.
G. FREEZE PROTECTION
Freeze protection must be implemented in any regions that may experience freezing conditions at any time throughout the year.
“Freeze tolerance limits are based upon an assumed set of environmental conditions. Extended periods of cold weather, including
ambient air temperatures below the specified limit, may cause freezing in exposed parts of the system. It is the owner’s responsibility to
keep the system’s freeze protection levels maintained in accordance with the supplier’s instructions if the air temperature is expected to
approach the specified freeze tolerance limit.”
Closed loop systems: In areas with temperatures not falling below 23
o
F, a differential solar controller with freeze protection may be
used (e.g. requiring pump to circulate if the manifold temperature approaches freezing). In an open loop system, a freeze valve (which
opens to allow water to dribble out) could also be considered.
Closed loop systems: In areas with temperatures falling below 23
o F, a propylene glycol/water mix should be used to provide freeze
protection. Please refer to glycol manufacturer’s specifications about the temperature ranges the liquid can withstand. Only food grade
propylene glycol, FDA rated as GRAS, should be used.
NOTE: HTP DOES NOT WARRANT THE SOLAR WATER HEATER AGAINST FREEZE-RELATED DAMAGE.
PART 3 - GENERAL SOLAR INFORMATION
A. SYSTEM DESCRIPTION
By using the sun’s energy to heat water, solar hot water heating systems help reduce the nation’s dependence on polluting fossil fuels.
This reliable, efficient solar water heater meets the certification requirements of SRCC-OG-300.
Basic components of the solar water heating system include: the solar collector(s), a solar water heater, a circulator pump, a differential
solar control, and an expansion tank. The types of solar systems in which the solar water heater can be installed include: