The Drainback Series is an indirect system. It is referred to as “indirect” because the sun, through a roof-
mounted collector, heats fluid circulating in a closed-off solar loop which never comes in direct contact with
usable water stored in an insulated tank.
Methods of Heat Exchange
“DB” System – (internal heat exchanger in storage tank) - The heat exchanger wraps around the perimeter
of the storage tank, heating the potable water in the tank.
“DX” Drainback System - (internal heat exchanger in Drainback reservoir) - drainback reservoir contains a
built-in heat exchanger. As the heat transfer fluid is circulated through the solar collector loop,
simultaneously, water is circulated from the hot water tank through the finned coil heat exchanger
inside the reservoir.
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Drainback System Features:
1. Removes all water from the collectors, and their pipelines
to ensure they never freeze when the system is not
producing heat (drain mode). Each time the pump shuts off,
the water in the collector(s) and piping, which are mounted
at a slight angle, drains into the insulated reservoir tank.
2. A sight glass attached to the reservoir tank indicates that
the collector(s) has been completely drained.
3. A Differential Control senses temperature
differences between water leaving the collector
and the coldest water in the bottom of the
storage tank. When the temperature of the
water in the collector is hotter than the water in
the tank, the differential control operates the
circulating pump.
4. Less moving parts allows for fewer
maintenance concerns.