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33-1197 Solahart Owner‟s Manual – Thermosiphon Systems - Revision H – Nov 2013

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HERE'S HOW IT WORKS
Solahart thermosiphon solar water heaters are available in two series:
Closed Circuit Series – J, KF, LCSC & BTC models
Open Circuit Series – L & LCSD models
Both series transfer heat absorbed from the sun by the solar collectors to the water storage tank through the Natural
Thermosiphon Principle without the need for pumps or sensors.
The Solahart collectors absorb solar energy. The low-iron content solar glass allows more solar energy to pass through and
be retained than conventional glass.

In the Closed Circuit Series, heat is absorbed by the collector and
passed to the „Hartgard‟ heat transfer liquid inside the collector. As the
temperature of the „Hartgard‟ increases, the hot fluid rises up through
the collector by the Natural Thermosiphon Principle, into the heat
exchanger jacket around the potable water storage tank. Here, the heat
is transferred to the potable water, cooling the „Hartgard‟ fluid.
The cooler fluid is then forced back down into the collectors through
the displacement action of further hot fluid rising up into the heat
exchanger jacket.
Diagram of Closed Circuit Series
The cooler fluid that has been forced down is again heated
in the collectors and rises back up to pass the heat to the
potable water in the storage tank. This circulation repeats
until all water in the storage tank is heated.

Open Circuit Series

Closed Circuit Series

For the Open Circuit Series, heat is collected directly by the potable
water circulating through the collector. As the potable water heats up, it
rises by the Natural Thermosiphon Principle, directly to the storage
tank. As the heated potable water travels through to the storage tank,
the cooler potable water returns to the collectors. This circulation
repeats until all water in the storage tank is heated.
Diagram of Open Circuit Series