DXR Drainback
Page 3
INTRODUCTION
“
Conservation for today… Energy for tomorrow…
”
Alternate Energy Technologies, LLC., (AET) would like to extend our congratulations on your purchase of an
EagleSun Solar Water Heating System. Years of research and development, backed by critical engineering, has
brought the finest solar products you can buy. Please take time to read this booklet thoroughly. Each step is
outlined completely and clarified by diagrams where necessary.
“The solar energy system described in this manual, when properly installed and maintained, meets the minimum
standards established by the SRCC. This certification does not imply endorsement or warranty of this product
by SRCC.”
Your EagleSun system has been designed to be a complete solar appliance interface that incorporates ease of
installation and maximum efficiency for years of trouble-free service. The system uses the sun’s energy to heat your
water, reducing your electricity consumption. The EagleSun system will pay for itself many times over the life of
the system. All installations require a connection to your existing home water system. Only a qualified installer,
regulated by the local code compliance office or the “Authority Having Jurisdiction”, should do the installation.
Your installation contractor should be familiar with the applicable building codes. The codes are intended to protect
the health, safety, and welfare of the public.
THEORY OF OPERATION
Your EagleSun system collects heat by circulating water between the solar collectors, a drainback reservoir and
simultaneously, between a heat exchanger inside the reservoir and your existing water heater. Since only thermally
efficient tap water is used, maximum safety and performance is assured. The EagleSun drainback system is ideally
suited to cold regions with many freezing days each year or areas with aggressive water conditions. EagleSun
drainback systems provide a fail-safe method of ensuring that collectors and collector loop piping never freeze by
removing all water from the collectors and collector piping loop when the system is not collecting heat. The
simplicity of the drainback method provides reliable operation that makes this system an asset to any home located
in extreme hot o colder climates.
As the sun comes up in the morning and starts to shine on the solar collectors, the collectors will begin to heat up. A
differential temperature control senses temperature differences between water leaving the solar collector and the
coldest water in the water heater. When the collector sensor temperature is about 12° F warmer than the tank sensor
temperature, the controller turns on the pumps. When the temperature difference drops to about 5° F, the pump is
turned off. In this way, the water always gains heat from the collector when the pump operates. The solar installer
manually sets the differential temperature of the controller at the time of the system installation. The pumps are very
quiet, but, you may hear a trickling noise as water returns into the drainback reservoir during operation.
When the pumps turn on, the water in the collector loop is circulated through the collector and gets heated. The
return water from the solar collectors that accumulates in the drainback tank then heats the heat exchanger through
which potable water from the water heater is circulated. The heated potable water is then circulated back to the
water heater. When there is no longer a marked difference between the temperature at the solar collector and at the
water heater (5° F) the controller automatically turns the pumps off – since there is no heat to be gained. This
process is repeated continually throughout the day, so that by the end of the day, the water in the water heater is hot.
This is all done automatically and requires no interaction on the part of the system owner.
Freeze protection is provided when the system is in the drainback mode. Water in the collectors and exposed piping
drains into the insulated drainback reservoir tank each time the pump shuts off. A slight tilt of the collectors is
required in order to allow complete drainage. A sight glass attached to the drain-back reservoir tank shows when the
reservoir tank is full and the collectors have been drained. In this way the drainback system is protected from freeze
damage and overheating at all temperatures including during prolonged periods of stagnation.
The collector and collector plumbing should be sloped back toward the drainback reservoir at 1/4" per foot
minimum to allow the system to drain.
