
The drainback reservoir should be installed at the
highest location practicable. The benefits of this
include: reduced risk of pump cavitation; reduced
pumping head required to fill the system allowing
smaller pumps to be used; and reduced piping above
the drainback reservoir allowing smaller drainback
tanks. In buildings with two or more floors, it is
beneficial to install the drainback on the uppermost
floor, preferably near the ceiling.
Drainback reservoirs are factory insulated to pro-
vide both heat retention and a noise buffer against
the sound of falling water.
If your Cascade Drainback system includes the
optional flow meter it should be plumbed so that
the top of the flow meter is level with the top of the
drainback tank so that the flow meter also provides a
visual check of the fluid level in the system. The top
and bottom of the flow meter should be supported to
relieve stresses on the connecting unions.
DO NOT install the pressure relief valve
(COMPONENT #9) on the drainback tank at this
time. The COMPONENT #9 is threaded in place
after the solar loop piping has been filled with water.
See Section 4.13 for instructions on charging the
system.
4.12 Electrical Requirements
When electric element is used as the auxiliary heat
source a properly licensed contractor shall make the
230 VAC electrical connection to the water heater
or solar storage tank. If your solar contractor is not
allowed by law to make these connections consult a
licensed electrician.
Never activate the circuit breaker controlling the
electrical heating element until the solar storage
tank is completely filled with water. This will
prevent “dry firing” of the heating element. The
electrical heating element will be destroyed almost
instantaneously if not completely submerged in
water when activated. Make sure the water heater
circuit breaker is off until the solar storage tank is
completely filled.
We recommend the use of a 115 VAC differential
control with a factory installed six foot line cord.
The installation requires one 115 VAC outlet to
be installed near the solar storage tank. Plug the
control into the outlet. The circulation pump line
cord is plugged into the receptacle on the side of
the controller. A 230 VAC control and circulation
pump may be substituted, but troubleshooting the
components in the future becomes more difficult.
4.13 Heat Transfer Fluid (HTF)
The HTF must be a non-toxic fluid that meets
FDA Generally Recognized as safe (GRAS)
Classification. The Cascade Drainback System uses
water to meet this requirement.
Water used fill the collector loop must meet certain
minimum standards for purity. Impurities in the
dilution water can increase metal corrosion, and
cause the formation of scale and other deposits on
the heat exchanger’s internal heat transfer surfaces.
Distilled or deionized water is recommended.
4.14 Flushing and Filling the System
Once the components have been plumbed it is time
to fill the solar storage and collector loop with water
as follows:
4.14.1
STEP 1
– Fill the solar tank with water and
check that there are no leaks on the potable side of
the system.
Do this by opening the cold water isolation ball
valve to the solar tank (COMPONENT #8) and
opening a hot water outlet, such as a faucet, until the
water runs freely. When the tank is filled, inspect all
threaded fittings and solder joints for leaks.
4.14.2
STEP 2
- Fill the solar loop piping with
water.
First connect a washing machine hose to the boiler
drain (COMPONENT #11) located at the low-
est point in the system. Open the boiler drain
(COMPONENT #11) and begin filling the system
directly from a fixture at mains pressure or by using
a utility pump. If your system has a flow meter
(FM), or sight glass, continue filling the solar loop
piping until the water level is visible. When the
water rises to within 1” of the top of the flow meter
or sight glass, close the boiler drain (COMPONENT
#11). Install the mandatory pressure relief valve
(COMPONENT #9) on top of the drainback res-
ervoir. If your system does not have a flow meter
or sight glass attach a washing machine hose to the
female fitting on top of the drainback reservoir using
an appropriate hose to pipe fitting (3/4” Male Hose
Thread X 3/4” FIP). Place the other end of the hose
in a basin drain or mid-size bucket. Open the lower
boiler drain (COMPONENT #11) and begin filling
the solar loop piping from a tap or by using a utility
P.15