EcoSolar Energy Conscious Design Limited
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Indirect or closed loop systems
Many indirect or closed loop systems have historically been systems using a Propylene Glycol and
corrosion inhibitor, however these system are becoming less favourable as the deficiencies of
Propylene glycol are becoming understood. An indirect Glycol based system is shown in Figure 10
below.
These systems are resilient to frost however they have a higher installed cost than direct systems, can
be exposed to overheating and have increased levels of maintenance.