System Schematics
System Schematics
©Aqua-Hot®
400D Installation Manual
Rev 220504
©Aqua-Hot®
400D Installation Manual
Rev 220504
p. 51
p. 50
Antifreeze Types
Antifreeze Types
The following information addresses the necessary usage
of a propylene glycol based “boiler” type antifreeze in the
Aqua-Hot. Propylene glycol is a safer alternative to the more
toxic ethylene glycol antifreeze; however, as mandated by
IAPMO (International Association of Plumbing and Mechanical
Officials), only propylene glycol based “boiler” type antifreezes
deemed “Generally Recognized As Safe” (GRAS) by the FDA
should be utilized.
Due to the significant impact various types of antifreeze can
have on a hydronic heating system, including the level of safety
provided, it has been recognized that there is a need to provide
an explanation regarding two additional prominent types of
antifreeze/coolant available. The following information should
be utilized as an educational means of ensuring that the proper
type of propylene glycol based antifreeze is selected.
RV & Marine Antifreeze
These types of propylene glycol based antifreeze products
are formulated specifically for “winterizing” applications only.
Although RV & Marine antifreeze is often “Generally Recognized
As Safe” by the FDA, it should never be used in the Aqua-
Hot’s Hydronic Heating System. This type of antifreeze is not
formulated to transfer heat, which is essential to the heating
system’s functionality and does not contain rust inhibitors.
Please note, however, that RV & Marine antifreeze can be
utilized to winterize the Aqua-Hot’s Domestic Hot Water Heating
Systems.
Automotive Antifreeze/Coolant
These types of propylene glycol based antifreeze products
are formulated specifically to protect automotive engines
against corrosion, freezing temperatures, and overheating.
They also have excellent heat transfer and thermal conductivity
characteristics. Although these types of antifreeze products are
considered less toxic and safer than ethylene glycol for people,
pets, and the environment, they are not “Generally Recognized
As Safe” (GRAS) rated by the FDA. Therefore, they must be
marked with a “harmful if swallowed” warning. This additional
warning is required because these types of antifreeze products
contain high levels of chemical rust inhibitors. Due to their
potentially hazardous properties, they should never be used in
the Aqua-Hot’s Hydronic Heating System.
Antifreeze Mixture Quality
Recommendations
In order to ensure maximum performance and longevity
of an Aqua-Hot heating system’s boiler tank and associated
components, it has been determined that there is a need to
use distilled, deionized, or soft water in combination with
concentrated propylene glycol for the Aqua-Hot’s antifreeze and
water heating solution.
Please note that this is only necessary when mixing
concentrated propylene glycol antifreeze with water; suppliers
of premixed antifreeze are responsible for the use of high-
quality (distilled, deionized, or soft) water when preparing their
antifreeze for sale.
Hard water possesses a high-level of calcium and magnesium
ions, which deplete the propylene glycol antifreeze’s corrosion
inhibitors. This, in turn, causes the antifreeze and water heating
solution to begin turning acidic, which can corrode the Aqua-
Hot’s boiler tank and associated components prematurely.
Therefore, concentrated propylene glycol should be diluted with
distilled, deionized, or soft water which is 80ppm or less in total
hardness. The local water agency should have up-to-date water
quality reports, which should indicate if the local tap water is
within this guideline.
Antifreeze Terms & Mixture Ratio
Propylene Glycol Based Antifreeze Solution
The following information addresses the process of selecting
a propylene glycol based antifreeze solution that provides
adequate freeze, boiling, and rust/anti-corrosive protection.
A propylene glycol antifreeze solution that is 35% to 50%
propylene glycol to distilled water is recommended. Antifreeze
solution with 50% propylene glycol will result in a freeze point of
approximately -28°F and a boil point of approximately 222°F.
Freeze Point and Burst Point
Antifreeze solution lowers the freezing point of any liquid, to
which it has added, by preventing the formation of ice crystals.
However, as the ambient temperature continues to decline, the
water in the solution will attempt to attain a solid state. The
point in which the water begins to solidify is termed the “Freeze
Point”. Although the water in the solution has begun to freeze
and starts producing a “slushy” consistency, the antifreeze
in the solution will continue to combat the normal expansion
of the solution as it freezes. The point in which the solution
can begin to expand, due to colder temperatures, is called the
“Burst Point”. Once the solution reaches the burst point, the
potential is present for ruptured pipes to exist. The burst point
of the antifreeze and water heating solution is dependent upon
NOTE:
The installer of the Aqua-Hot system must refer to
the information and chart to determine the percentage of
propylene glycol the antifreeze solution should contain for
the level of protection needed.
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 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.
