Appendix
©Aqua-Hot®
250-D03 Diesel Series Service Manual
REV 220302
p. 103
Antifreeze
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 specifically 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.
In order to provide the best freeze protection, boil-over
protection, anti-corrosion, and rust protection, a mixture of
50/50 “GRAS” approved
Propylene Glycol
antifreeze and
distilled or de-ionized water is recommended. Reference Page
101 for measuring the antifreeze mixture with a refractometer
and also the table below for the mixture ratios.
Failure to utilize a propylene glycol which has been deemed
Generally Recognized As Safe (“GRAS”) by the FDA could
result in serious bodily harm to damage to the Aqua-Hot
system�
Freeze
Point (°F)
Concen-
tration (%)
0
-4
-7
-9
-12 -15 -18 -23 -29 -34 -40 -46
0
12 19 25 30 34 38 44 49 53 57 60
Propylene Glycol
