Saturday, May 23, 2009

What is a drain-back system?

It is one of the least expensive setups to use as part of the operating system for your solar thermal. The DrainBack system allows all the fluid in the panels to drain back (with gravity) to a holding tank when the system is not being used such as at night, or when the panels are producing more heat than you need.
There are two major concepts to understand when comparing the different types of Solar Water Heating Systems:
Open-Loop Systems
A system in which the domestic hot water, which comes directly out of the shower-heads and sink faucets, is itself directly heated in the solar collector.
Closed-Loop Systems (including Drainback)
A system in which a heat transfer fluid is heated by the collector, and the heat is passed to the domestic water through a heat exchanger.
Passive System
Uses no mechanical parts to circulate the water through the heating system.
Active System
Uses moving parts such as pumps, valves or controls to circulate water through the heating system.
1. Thermosyphon System – Easy installation, passive operation
2. Open-Loop Direct – Lightweight, installation
3. Pressurized Glycol – Lightweight, overheat and freeze tolerant
4. Closed Loop Drainback – Lightweight, freeze tolerant

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