Airxcel Aqua-Hot 600 Series, Installation Manual

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System Schematics
©Aqua-Hot® 600D Installation Manual p. 53
Antifreeze
the brand of propylene glycol antifreeze employed.
Rust and Anti-Corrosive Inhibitors
Another major function of antifreeze solution is to provide
protection to the internal metal components of the Aqua-Hot
Hydronic Heating System from corrosion and rust. Antifreeze is
able to perform this function by the addition of rust and anti-
corrosive inhibitors, which are designed specifi cally to activate
in a water solution.
Summary
Antifreeze solution has three basic functions: freeze
protection, boil-over protection, and rust/anti-corrosion
protection.
Propylene glycol antifreeze solution is also primarily
responsible for heat transfer; however, propylene glycol itself
does not possess acceptable heat transfer characteristics.
Therefore, as water is an excellent heat conductor, it is
added to the mixture. Propylene glycol antifreeze solution,
mixed with distilled water, at a ratio of 35% to 50% is
recommended to provide the best performance combination
of the aforementioned functions. If excess propylene glycol
exists within the heating solution, the water’s heat absorption
properties are compromised. Ultimately, this could inhibit the
Aqua-Hot from providing adequate domestic hot water and
interior heating.
Additionally, if the antifreeze and water heating solution
contains over 70% propylene glycol, the freezing point is actually
raised, resulting in less freeze protection. Please reference the
attached graphical representation regarding the percentage
of antifreeze to water and how it directly affects the solution’s
freezing point.