A high quality thermostatic mixing valve is a
required component in all OG-300 certified sys-
tems and should be plumbed in line with brass
union connections for ease of future repair or
replacement (COMPONENT #32, FIGURES
15A; 15B; 16A; 16B; 17A; 17B ). The mixing
valve shall be standard ASSE 1017 approved.
The temperatures generated by your SolaRay
AC system will vary throughout the year. In
the Northern Hemisphere the water temperature
will be hottest in the spring and summer months
while cooler temperatures are to be expected
from November through March. On sunny days
the end of day solar tank temperatures may
range between 110ºF to 180ºF depending upon
the season and hot water demand. The mixing
valve refrenced above blends the hot and cold
water supplies to deliver hot water to your fix-
tures at a safe, controlled temperature.
WARNING: SCALDING CAN OCCUR
WITHIN FIVE SECONDS WHEN WATER
TEMPERATURES APPROACH 140ºF. THE
MIXING VALVE SHALL BE ADJUSTED
BY YOUR CONTRACTOR TO PROVIDE
WATER TO YOUR FIXTURES AT NO
MORE THAN 122ºF.
The ¾” cold water supply line to the solar stor-
age tank shall be insulated with minimum
7
/
8
” X
½” pipe insulation to a minimum distance of 5’
behind the storage tank, or to the wall if closer
than 5’.
4.8 Tank Sensor Placement
Figure 18 details the proper placement of the
solar storage tank sensor. Tank sensor shall
have good thermal contact with the tank wall in
order to accurately measure the temperature of
the water at the bottom of the tank. It is recom-
mended that the sensor be installed in a brass
or copper thermalwell screwed into the lower
sensor port in the tank.
Thoroughly weatherize the wire connections in
accordance with section 4.6.2.
4.9 Tank Insulation
SunEarth heat exchanger tanks have an insula-
tion value of approximately R-17.3.
Conventional back-up electric water heaters
have insulation values between R-12 and R-20.
The R value expresses the thermal resistance of
the tank insulation. The higher the “R-value”
value the more effective the insulation material
is at preventing heat loss. The use of any solar
storage tank with and R value below R12 is
prohibited.
The storage tank should not be placed directly
on an uninsulated floor or concrete slab. In
order to prevent moisture damage to the base of
the tanks and reduce heat loss to the floor slab,
the tank should be raised off the floor on a pad.
4.10 Expansion Tank
The collector loop expansion tank shall be rated
for propylene glycol based HTF and rated to
operate up to 180ºF and at a pressure not less
than the discharge pressure setting of the pres-
sure relief valve in the collector loop.
The collector loop expansion tank should be
sized so that the acceptance volume of the
expansion tank exceeds the volume of fluid in
the collector(s); this will allow the entire con-
tents of the collectors to boil without resulting
in the pressure relief valve discharging (this is
sometimes referred to as a “steam back” sys-
tem). If the system design prevents the HTF
from boiling, even during conditions with no
hot water load, the expansion tank may be
sized for liquid expansion only (non-boiling
systems). When the stagnation temperature* of
the collector(s) is lower than the boiling point
of the HTF (at the initial charge pressure of the
system) the system design will prevent the HTF
from boiling and therefore a smaller expansion
tank (sized for liquid expansion only) may be
used for these systems (this design methodolo-
gy is referred to as “low stagnation protection”).
WARNING: WHEN USING THE LOW
STAGNATION PROTECTION METHOD
THE HTF MUST BE RATED TO OPERATE
P.15
