Aqua-Hot 400 Series Service Manual page 8

Hard water possesses a high-level of calcium and mag-
nesium ions, which deplete the propylene glycol antifreeze's
corrosion inhibitors. This, in turn, causes the antifreeze and
water heating solution to begin to turn acidic, which can
corrode the Aqua-Hot's boiler tank and associated compo-
nents prematurely. Therefore, concentrated propylene gly-
col should be diluted with distilled, de-ionized, or soft water
that is 80 PPM or less in total hardness. The local water
agency should have up-to-date water quality reports that
should indicated is the local tap water in within this guide-
line.
Antifreeze Terms and Mixture Ratio:
The following information addresses the process of se-
lecting an antifreeze and water mixture ratio that provides
adequate freeze, boiling, and rust/anti-corrosive protection.
A 50/50 mixture of propylene glycol/ water ratio is recom-
mended, which will result in a freeze pint of –28°F and a
boil point of approximately 222°F. Additionally, if the anti-
freeze and water heating solution contains over 70 percent
antifreeze, the freezing point is actually raised, resulting in
less freeze protection.
The following information should be utilized for the pur-
pose of clarifying some terms commonly associated with
antifreeze.
Freeze & Burst Point:
Antifreeze lowers the freezing point of any liquid to
which it has been added by preventing the formation of ice
crystals; however, as the ambient temperature continues to
decline, the water solution will attempt to attain a solid
state. The point in which the water begins to solidify is
termed "freeze point". Although the water in the solution
has begun to freeze, producing a slushy consistency, the
antifreeze in the solution will continue to combat the nor-
mal expansion of the solution as it freezes. The point in
which the solution can begin to expand due to colder tem-
peratures is called the "burst point". Once the solution
reaches the burst point, the potential is present for rup-
tured pipes to occur. The burst point of the antifreeze and
water heating solution is dependent upon the brand of pro-
pylene glycol.
Boiling Point:
The Aqua-Hot utilizes the antifreeze and water heating
solution as a transportation means for the heat produced
from the internal processes. The antifreeze absorbs the
heat created until its boiling point is reached. It is at this
point when the liquid turns to gas and is expelled to prevent
that heating system from overheating. Each time the boiling
point is reached, a loss of efficiency occurs because the
heat produced is expelled rather then used for the function
of the heating system. Therefore a higher boiling point is
desired in order to combat the loss of efficiency, which al-
lows the antifreeze to transport the heat created from the
internal process throughout the motor home where it can be
used productively rather than dissipating due to its change
from liquid to gas.
Rust and Anti-Corrosive Inhibitors:
Another major function of antifreeze is to provide protec-
tion to the internal metal components of the Aqua-Hot hy-
dronic heating system from corrosion and rust. Antifreeze is
able to preform this function by the addition of rust-and-
anticorrosive inhibitors, which are designed specifically to
activate in a water solution.
© Aqua-Hot® AHE-400-P01 Service Manual Rev.B June 2014
Section #: Title
Introduction to the Aqua-Hot 400LP
p.
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