Aqua-Hot 375-LP User manual

AVERTISSEMENT. Assurez-vous de bien suivre les
instructions données dans cette notice pour réduire au
minimum le risque d’incendie ou d’explosion ou pour
éviter tout dommage matériel, toute blessure ou la
mort.
— Ne pas entreposer ni utiliser d’essence ou ni d’autres
vapeurs ou liquides inflammables à proximité de cet
appareil ou de tout autre appareil.
— QUE FAIRE SI VOUS SENTEZ UNE ODEUR DE GAZ :
• Évacuez le véhicule.
• Coupez l’alimentation en gaz au réservoir ou à la
source.
• Ne touchez à aucun interrupteur ; ne pas vous
servir du téléphone ou de la radio du véhicule.
• Ne pas démarrer le moteur du véhicule ni aucune
génératrice électrique.
• Appelez le fournisseur de gaz le plus proche ou un
technicien qualifié.
• Si vous ne pouvez rejoindre ni un fournisseur ni un
technicien qualifié, appelez le service des
incendies le plus proche.
• Ne pas rétablir l’alimentation en gaz tant que la
fuite n’a pas été réparée.
— L’installation et l’entretien doivent être assurés par
un installateur ou un service d’entretien qualifié ou
par le fournisseur de gaz.
© 2011 Aqua-Hot Heating Systems Inc.
WARNING: If the information in these instructions is
not followed exactly, a fire or explosion may result
causing property damage, personal injury, or death.
— Do not store or use gasoline or other flammable va-
pors and liquids in the vicinity of this or any other
appliance.
— WHAT TO DO IF YOU SMELL GAS
• Evacuate all persons from the vehicle.
• Shut off the gas supply at the gas container or
source.
• Do not touch any electrical switch or use any
phone or radio in the vehicle.
• Do not start the vehicle’s engine or electric
generator.
• Contact the nearest gas supplier or qualified
service technician for repairs.
• If you cannot reach a gas supplier or qualified
service technician, contact the nearest fire
department.
• Do not turn on the gas supply until the gas leak(s)
has been repaired.
— Installation and service must be performed by a quali-
fied installer, service agency, or the gas supplier.
OWNERS MANUAL
375 LP

Comfort Zone #1: Comfortable Cabin Heat.
Get heat where you want it, when you want it! Because the Aqua-Hot system heats by zones, your bed-
room, living room, and bathroom can be custom temperatures. And don’t hesitate to crank up the heat,
because the Aqua-Hot system doesn’t remove moisture from the air. From now on, you will have to
blame the dry skin and itchy eyes on Mother Nature!
Comfort Zone #2: Quiet Operation
Say goodbye to rude awakenings from the forced air furnace, you’re an Aqua-Hot owner now! The Aqua-
Hot is quiet when operating, so you’ll never have to turn up the TV, yell across the room, or have an inter-
rupted night of sleep again due to your heating system.
Comfort Zone #3: Continuous, On-Demand Hot Water
Take long, guilt free showers knowing there is no recovery time for the next shower or load of laundry.
The freedom to take a shower when you want makes your RV experience feel much more like home.
Comfort Zone #4: Low Emissions
Aqua-Hot’s new low emission systems are fumeless and odorless. It’s good for you,
good for your neighbor, and good for the environment.
Comfort Zone #5: Over 160 Factory-Trained Service Centers
You won’t need to service your Aqua-Hot often, but when you do, you can be confident in our Certified
Service Centers that are close by and trained to assist you with all of your Aqua-Hot specific needs.
Comfort Zone #6: Adds Value
The NADA Recreational Vehicle Guide lists Aqua-Hot as adding thousands of dollars to the value of an
RV. That value will pay off when it’s time to trade up or sell.
Comfort Zone #6: Low fuel Costs
Aqua-Hot’s TribridHot technology powers the Aqua-Hot system by pulling heat from one or a combination
of heat sources. When shore power is available, simply plug it in. When dry-camping or in very cold
conditions, use the Propane Burner.

— Page 4 — © 2009 Aqua-Hot®375-LP Hydronic Heating System Owner’s Manual
CAUTION:
Before welding or plasma cutting on any
coach; it is necessary to disconnect the
electric wiring to the Aqua-Hot System.
Failure to disconnect the wires from the
Aqua-Hot System before using a welder or a
plasma cutter on the coach may cause dam-
age to the Aqua-Hot.
AVERTISSEMENT. Assurez-vous de bien suivre les
instructions données dans cette notice pour réduire au
minimum le risque d’incendie ou d’explosion ou pour
éviter tout dommage matériel, toute blessure ou la
mort.
— Ne pas entreposer ni utiliser d’essence ou ni d’autres
vapeurs ou liquides inflammables à proximité de cet
appareil ou de tout autre appareil.
— QUE FAIRE SI VOUS SENTEZ UNE ODEUR DE GAZ :
• Évacuez le véhicule.
• Coupez l’alimentation en gaz au réservoir ou à la
source.
• Ne touchez à aucun interrupteur ; ne pas vous
servir du téléphone ou de la radio du véhicule.
• Ne pas démarrer le moteur du véhicule ni aucune
génératrice électrique.
• Appelez le fournisseur de gaz le plus proche ou un
technicien qualifié.
• Si vous ne pouvez rejoindre ni un fournisseur ni un
technicien qualifié, appelez le service des
incendies le plus proche.
• Ne pas rétablir l’alimentation en gaz tant que la
fuite n’a pas été réparée.
— L’installation et l’entretien doivent être assurés par
un installateur ou un service d’entretien qualifié ou
par le fournisseur de gaz.
WARNING: If the information in these instructions is
not followed exactly, a fire or explosion may result
causing property damage, personal injury, or death.
— Do not store or use gasoline or other flammable va-
pors and liquids in the vicinity of this or any other
appliance.
— WHAT TO DO IF YOU SMELL GAS
• Evacuate all persons from the vehicle.
• Shut off the gas supply at the gas container or
source.
• Do not touch any electrical switch or use any
phone or radio in the vehicle.
• Do not start the vehicle’s engine or electric
generator.
• Contact the nearest gas supplier or qualified
service technician for repairs.
• If you cannot reach a gas supplier or qualified
service technician, contact the nearest fire
department.
• Do not turn on the gas supply until the gas leak(s)
has been repaired.
— Installation and service must be performed by a quali-
fied installer, service agency, or the gas supplier.
You must winterize the Aqua-Hot when
freezing temperatures are present if the
Aqua-Hot is turned off. This includes when
the coach is being used and the electrical
element and diesel burner switch are in the
off position, or when the coach is in stor-
age.
Not winterizing the Aqua-Hot when the
aforementioned conditions are present will
result in serious damage to the Aqua-Hot’s
Domestic Water Heating System, requiring
complete system replacement not covered
under the Aqua-Hot warranty.
WARNING!

— Page 5 —
© 2011 Aqua-Hot®375LP Hydronic Heating System Owner’s Manual
Introduction
Introduction to the Aqua-Hot Hydronic Heating System ...............................................Page 6
Operating Instructions
Activating the Aqua-Hot Heating System ......................................................................Page 8
Zone Thermostat Operation............................................................................................Page 10
Using the Domestic Water Heating System....................................................................Page 10
Aqua-Hot Operational Flow-Chart.................................................................................Page 11
Maintenance
Monthly Maintenance.....................................................................................................Page 12
Replenishing the Antifreeze and Water Heating Solution..............................................Page 12
Annual Maintenance.......................................................................................................Page 12
Winterization
Winterizing the Domestic Water Heating System..........................................................Page 13
De-Winterizing the Domestic Water Heating System....................................................Page 13
Troubleshooting
General Information........................................................................................................Page 14
Appendices
Appendix A: Antifreeze Types......................................................................................Page 14
Appendix B: Antifreeze Mixture Water Quality Recommendations.............................Page 15
Appendix C: Antifreeze Terms and Mixture Ratio........................................................Page 16
Appendix D: Measuring Propylene Glycol Using a Refractometer ..............................Page 18
Warranty
Limited Warranty Statement...........................................................................................Page 21
TABLE OF CONTENTS

— Page 6 — © 2009 Aqua-Hot®375-LP Hydronic Heating System Owner’s Manual
INTRODUCTION
This manual should be maintained in legible
condition and kept in a safe, easily-accessible location for
future reference.
Please read the complete Owner’s Manual prior to operat-
ing the Aqua-Hot Hydronic Heating System. Also, be sure
to fill out and mail in the “Warranty Registration” card
located at the front of this manual.
The Aqua-Hot Heating System is a Hydronic Heating System
(heating with hot water) that provides interior zone heating
where and when it is needed, as well as a continuous, on-
demand supply of domestic hot water. Both heating features
are accomplished by a 12 Volt-DC powered Propane-Burner
and a 120 Volt-AC powered Electric Heating Element, which
maintain the temperature of the Aqua-Hot’s antifreeze and wa-
ter heating solution. Be sure to reference Figures 1-A through 1
-C for a complete component overview.
Danger, Warning, Caution, and Note Boxes:
Danger, Warning, Caution, and Note boxes appear throughout
this manual as a means of alerting the operator to important
information.
INDICATES THAT PERSONAL INJURY IS LIKELY OR IMMI-
NENT.
Indicates that serious damage to the heater will occur and
personal injury is possible as well.
Indicates that damage to the heater is possible.
NOTE: Indicates information that requires special attention by
the operator.
Figure 1-A
NOTE: This Aqua-Hot product utilizes a propylene glycol
based antifreeze and water heating solution. This
propylene glycol based solution is a Boiler type anti-
freeze that is “Generally Recognized as
Safe” (GRAS) by the FDA. For additional informa-
tion regarding this “GRAS” antifreeze product, please
reference Appendix A, contact the Aqua-Hot Heating
Systems Technical Support Department at
1-800-685-4298, or visit the web site at
www.aquahot.com.

— Page 7 —
© 2011 Aqua-Hot®375LP Hydronic Heating System Owner’s Manual
Zone 1 Relay
Zone 2 Relay
120 Volt-AC
Relay
Fuse Block
Ground Strip
INTRODUCTION
Figure 1-B
Figure 1-C
Interlock Switch
Propane Burner
Controller
Zone 1
Circulation
Pump
Propane Burner
Drain Valve
Zone 2
Circulation
Pump

— Page 8 — © 2009 Aqua-Hot®375-LP Hydronic Heating System Owner’s Manual
Indicator
Light
375-LP I.D. Label
Figure 2
The Aqua-Hot’s Exhaust is HOT!
DO NOT park in areas where dry conditions exist under-
neath the vehicle as a fire may result (i.e., in a dry, grassy
field)!
DO NOT operate the Aqua-Hot’s Propane-Burner inside
an enclosed building!
The Heater must be switched OFF when refueling.
DO NOT operate the Propane-Burner and/or Electric Heating
Element without the antifreeze and water heating solution in
the Aqua-Hot’s Boiler Tank. Failure to do so will cause serious
damage to the Heater.
OPERATING INSTRUCTIONS
Activating the Aqua-Hot Heating System:
Propane-Burner:
Turn the Burner switch ON; reference Figure 3. This proce-
dure will activate the Propane-Burner and the indicator light
located adjacent to the Burner switch. Allow 10-20 minutes for
the Aqua-Hot System to reach operating temperature. Please
note that the Propane-Burner is the primary heat source for
heating both the interior and the domestic hot water (such as
when cool ambient temperatures exist and/or when there is a
high demand for domestic hot water).
Electric Heating Element:
Turn the Electric switch ON; reference Figure 3. This proce-
dure will activate the 120 Volt-AC Electric Heating Element
and the indicator light located adjacent to the Electric switch.
Allow 1-2 hours for the Aqua-Hot System to reach operating
temperature.
Figure 3

— Page 9 —
© 2011 Aqua-Hot®375LP Hydronic Heating System Owner’s Manual

— Page 10 — © 2009 Aqua-Hot®375-LP Hydronic Heating System Owner’s Manual
OPERATING INSTRUCTIONS
Zone Thermostat Operation
Interior Room Thermostat:
Simply adjust each Interior Room Thermostat to the desired
temperature. Then, whenever an Interior Room Thermostat
“calls for heat,” the Aqua-Hot’s Circulation Pump and Interior
Heat Exchanger Fans will be activated. These devices, to-
gether, will supply warmth and comfort to each interior heat-
ing zone. The Aqua-Hot must be at operating temperature in
order for the zones to function. Please contact the specific
motorhome manufacturer for the exact location of the Interior
Room Thermostats.
Fresh Water Tank Thermostat:
Simply adjust the Thermostat for Bay Heating to a minimum
of 40°F. This will prevent freezing of the domestic water
storage system. Please contact the specific motorhome manu-
facturer for the exact location of the Fresh Water Tank Ther-
mostat.
Using the Domestic Water Heating System
When the Aqua-Hot is at operating temperature, the domestic
water is automatically heated as it is being used. Because the
Aqua-Hot does not store any hot water, simply open any hot
water faucet and a continuous supply of domestic hot water
will be present within a few seconds. This hot water feature is
continuous and is accomplished by the Aqua-Hot’s Domestic
Water Heating System. The Propane-Burner switch on the
Interior Switch Panel must be ON in order to obtain a con-
tinuous supply of hot water (e.g., during showers); be sure to
also activate the Electric Element switch for maximum hot
water capacity. Reference Figure 4.
NOTE: The Aqua-Hot’s “Domestic Water Priority System”
disables the interior zone heating fans and the zone
circulation pumps whenever domestic hot water is
being used on a continuous basis (e.g., during show-
ers). Once the demand for continuous domestic hot
water ceases, the Aqua-Hot will enable the fans and
the pumps to operate and provide heat to the Heating
Zones.
Indicator
Light
Burner switch must
be ON to obtain a
continuous supply of
hot water.
Activate the Electric
switch for maximum
hot water capacity.
Figure 4
NOTE: Both the propane-burner and electric heating ele-
ment are thermostatically controlled. Either, or both,
heating sources will automatically maintain the tem-
perature of the Aqua-Hot’s antifreeze and water
heating solution between approximately 160⁰Fand
190⁰F(±5).Therefore,toheatthemotorhome/
domestichotwater,simplychoosethedesiredheat
source(s)andleavetheswitch(es)(i.e.,Burnerand
orElectricElement)ON.

— Page 11 —
© 2011 Aqua-Hot®375LP Hydronic Heating System Owner’s Manual
OPERATING INSTRUCTIONS
Aqua-Hot Operational Flowchart
Heat source is selected from the
Interior Switch Panel.
Propane-Burner is activated
by the Burner switch. Electric Heating Element is activated by the Electric
The Boiler Tank heats the
antifreeze and water heating
solution to 190*F.
Heating Zone Thermostat
calls for heat. A hot water faucet (e.g., kitchen sink, shower, etc.) is opened.
The heated antifreeze and water heating
solution flows through the Hydronic Heat-
ing System transferring heat to the heat
exchanger, which is, in turn, transferred to
the surrounding zone.
The cooled antifreeze and water heating
solution is returned to the boiler tank to
be reheated.
Continuous hot water is supplied
to the faucet.

— Page 12 — © 2009 Aqua-Hot®375-LP Hydronic Heating System Owner’s Manual
WHEN THE AQUA-HOT IS AT MAXIMUM OPERATING TEM-
PERATURE, THE COOLANT WILL BE VERY HOT! IFTHE
AQUA-HOT’SHEATING SYSTEM IS ACCESSED, SCALDING BY
HOT VAPOR OR COOLANT COULD RESULT!
BEFORE CLEANING OR SERVICING, DISCONNECT ALL POWER
SUPPLIES!
DO NOT operate the Propane-Burner and/or the Electric
Heating Element without the antifreeze and water heating
solution in the Aqua-Hot’s Boiler Tank; doing so will cause
serious damage to the Heater.
Propylene Glycol that is “Generally Recognized As Safe”
by the FDA must be utilized for the antifreeze and water
heating solution.
NOTE: For additional information regarding this propylene
glycol-based, boiler-type antifreeze that has been
“Generally Recognized As Safe” by the FDA, please
reference Appendix A, contact Aqua-Hot Heating
Systems Technical Support Department at 1-800-685-
4298, or visit the Web site at www.aquahot.com.
Maintenance Schedule
Monthly Maintenance:
Check the Aqua-Hot’s antifreeze and water heating solution to
ensure that it is at the proper level. This can be accomplished
by visually checking the coolant level in the Aqua-Hot’s Ex-
pansion Tank; reference Figure 5. Please note that the coolant
level should be checked only when the Aqua-Hot is at maxi-
mum operating temperature (i.e., immediately after the Propane
-Burner cycles OFF). When maximum operating temperature,
the antifreeze and water heating solution should be at the level
marked “HOT” on the Expansion Tank.
Replenishing the Antifreeze and Water Heating Solution:
If the antifreeze and water heating solution needs replenishing,
remove the Expansion Tank’s cap and fill the Expansion Tank
to the “HOT” level mark. When refilling, open the Air Release
Valve located on the Expansion Tank Connection to release air
pockets; reference Figure 6. Hold the valve open until all air is
released. If necessary, refill the Expansion Tank again. Be sure
the valve is closed when finished by hand-tightening. Refer-
ence Appendices A through C in order to determine the correct
MAINTENANCE
ratio of antifreeze to water, the proper type of antifreeze, and
the water quality recommendations for the Aqua-Hot Hydronic
Heating System’s antifreeze and water heating solution.
Annual Maintenance:
No annual maintenance is required above the normal monthly
maintenance. Reference the Aqua-Hot’s Service and Parts
Manual for spare parts information and detailed replacement
instructions, contact the Aqua-Hot Heating Systems Technical
Support Department at 1-800-685-4298 for assistance or to
locate the nearest Aqua-Hot Service Center, or visit the Web
site at www.aquahot.com.
Figure 5
Figure 6

— Page 13 —
© 2011 Aqua-Hot®375LP Hydronic Heating System Owner’s Manual
Not winterizing the Aqua-Hot when freezing temperatures
are present will result in serious damage to the Aqua-Hot’s
Domestic Water Heating System. Also, be sure to use an
FDA approved, “GRAS” rated antifreeze for winterization.
NOTE: The Aqua-Hot can continue to be used for interior
zone heating once the domestic water heating system
has been drained and winterized.
The Aqua-Hot’s Domestic Water Heating System must be
completely drained of domestic water any time the heater is
stored where freezing temperatures may be experienced.
Winterizing the Domestic Water Heating System:
Please follow these instructions when winterizing the Aqua-
Hot’s Domestic Water Heating System; reference Figure 8:
1. Completely drain the fresh water storage tank.
2. Disconnect the domestic water demand pump’s suction
line from the fresh water storage tank.
3. Attach an adequate piece of hose onto the suction side of
the domestic water demand pump.
4. Place the opposite end of the hose into an adequate supply
of FDA-approved “GRAS” RV Antifreeze.
5. Open and close all interior and exterior water faucets, one at
a time, until only pure RV Antifreeze is present. Perform
this procedure for both the hot and cold faucets.
6. Remove the hose and reconnect the domestic water demand
pump’s suction line to the fresh water storage tank.
De-Winterizing the Domestic Water Heating System:
For de-winterization, completely fill the fresh water storage tank.
Open and close all interior and exterior water faucets, one at a
time, until only clear water is present/visible.
Reference Figure 8.
If disinfecting the potable water system after de-winterizing, be
sure to follow RVIA’s “Instructions for Disinfection of Potable
Water Systems on Recreation Vehicles.” These instructions
can be obtained by contacting the Recreational Vehicle Industry
Association at [phone], visiting them online at
www.rvia.com, or writing to them at the following address:
Recreation Vehicle Industry Association
1896 Preston White Drive
P.O. Box 2999
Reston, VA 20195-0999
WINTERIZATION
Aqua-Hot 375LP Heater
To Hot Water Faucets
Domestic
Hot Water
Outlet
Domestic
Cold Water
Inlet
To Cold Water
Faucets
AT—Indicates options
for mounting an
Accumulator Tank.
Fresh
Water Storage
Tank Demand
Pump
Arrows indicate directional flow of
domestic hot water
Figure 8

— Page 14 — © 2009 Aqua-Hot®375-LP Hydronic Heating System Owner’s Manual
APPENDIX A: ANTIFREEZE TYPES
Should the Aqua-Hot Hydronic Heating System fail
to operate, complete the following checks:
1) Verify that the Aqua-Hot’s access cover is se-
curely installed. The Aqua-Hot Hydronic Heat-
ing System will not operate if the access cover
is not fully installed.
2) Ensure that the main propane tank contains a
sufficient level of propane.
TROUBLESHOOTING
3) Ensure that the Aqua-Hot’s boiler tank has an ade-
quate supply of antifreeze and water heating solu-
tion by checking the level at the expansion tank. If
the level is low, reference the maintenance section
of this manual for refilling instructions.
4) Verify that the wires attached to the ground strip
are firmly attached; reference Figure 1-B
If the Aqua-Hot Heating System’s failure to operate is
not resolved with the aforementioned checks, please
contact the Aqua-Hot Heating Systems Technical Sup-
port Department at 1-800-685-4298 for additional as-
sistance or visit the web site at www.aqua-hot..com
The following information addresses the necessary
usage of a propylene glycol based “boiler” type anti-
freeze in the Aqua-Hot. Propylene glycol is a safer
alternative to the more toxic ethylene glycol anti-
freeze; however, as mandated by IAPMO
(International Association of Plumbing and Me-
chanical Officials), only those propylene glycol based
“boiler” type antifreezes deemed “Generally Recog-
nized as Safe” (GRAS) by the FDA should be util-
ized.
Because of 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 expla-
nation regarding two additional prominent types of
antifreeze/coolant available. The following informa-
tion 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, how-
ever, that RV & Marine antifreeze can be utilized to
winterize the Aqua-Hot’s Domestic Hot Water
Heating System.
Automotive Antifreeze/Coolant:
These types of propylene glycol based antifreeze
products are formulated specifically to protect auto-
motive engines against corrosion, freezing tempera-
tures, and overheating. They also have excellent
heat transfer and thermal conductivity characteris-
tics. 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 inhibi-
tors. Due to their potentially hazardous properties,
they should never be used in the Aqua-Hot’s Hy-
dronic Heating System.

— Page 15 —
© 2011 Aqua-Hot®375LP Hydronic Heating System Owner’s Manual
APPENDIX B: ANTIFREEZE MIXTURE WATER QUALITY RECOMMENDATIONS
In order to ensure maximum performance and lon-
gevity of an Aqua-Hot heating system’s boiler tank
and associated components, it has been determined
that there is a need to use distilled, de-ionized, or
soft water in combination with concentrated propyl-
ene glycol for the Aqua-Hot’s antifreeze and water
heating solution. Please note that this is only neces-
sary when mixing concentrated propylene glycol an-
tifreeze with water; suppliers of pre-mixed antifreeze
are responsible for the use of high-quality (distilled,
de-ionized, or soft) water when preparing their anti-
freeze 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 pre-
maturely. Therefore, concentrated propylene glycol
should be diluted with distilled, de-ionized, or soft
water which is 80 ppm 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.

— Page 16 — © 2009 Aqua-Hot®375-LP Hydronic Heating System Owner’s Manual
APPENDIX C: ANTIFREEZE TERMS AND 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 is recommended. Antifreeze so-
lution with 50% propylene glycol will result in a freeze
point of approximately -28ºF and a boil point of ap-
proximately 222ºF.
Aqua-Hot sells CAMCO propylene glycol based anti-
freeze solution in the following packages:
The following information should be utilized for the
purpose of clarifying some terms commonly associated
with antifreeze.
Freeze Point and Burst Point:
Antifreeze solution lowers the freezing point of any
liquid, to which it has been added, by preventing the
formation of ice crystals; however, as the ambient tem-
perature 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, producing a “slushy” consistency, the antifreeze
in the solution will continue to combat the normal ex-
pansion 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 so-
lution reaches the burst point, the potential is present
for ruptured pipes to exist. The burst point of the anti-
freeze and water heating solution is dependent upon the
brand of propylene glycol antifreeze employed.
Boiling Point:
The Aqua-Hot utilizes the propylene glycol based (PPG)
antifreeze and water heating solution as a transportation
means for the heat produced from the internal processes.
The PPG antifreeze solution absorbs the heat created until
its boiling point is reached; it is at this point that the liquid
turns to a gas and is expelled to prevent the heating system
from overheating. Each time the boiling point is reached,
a loss of efficiency occurs because the heat produced is
expelled rather than utilized for the function of the heating
system. Therefore, a higher boiling point is desired in or-
der to combat the loss of efficiency, which allows the anti-
freeze to transport the heat created from the internal proc-
ess throughout the motorhome where it can be utilized
productively rather than dissipating due to its change from
a liquid to a gas.
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. An-
tifreeze is able to perform this function by the addition of
rust and anti-corrosive inhibitors, which are designed spe-
cifically to activate in a water solution.
Summary:
Antifreeze solution has three basic functions: freeze pro-
tection, boil-over protection, and anti-corrosion and rust
protection.
PPG 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. PPG antifreeze solution , mixed with water, that
is 35% to 50% propylene glycol is recommended to pro-
vide the best performance combination of the aforemen-
tioned functions. If excess propylene glycol exists within
an antifreeze and water heating solution, the water’s heat
absorption properties are compromised, which could ulti-
mately inhibit the Aqua-Hot from providing adequate do-
mestic hot water and interior heating.
Additionally, if the antifreeze and water heating solution
contains over 70 percent propylene glycol, the freezing
point is actually raised, resulting in less freeze protection.
Please reference the attached graphical representation re-
garding the percentage of antifreeze to water and how it
directly affects the solution’s freezing point.
NOTE: As the installer of this Aqua-Hot system, you must
refer to the information and chart in Appendix E
to determine the percentage of propylene glycol
your antifreeze solution should contain for the
level of protection you require.
NOTE: Propylene glycol based antifreeze solution is not
100% propylene glycol. It is a mixture of propylene
glycol, rust and anti-corrosive inhibitors, and water.

— Page 17 —
© 2011 Aqua-Hot®375LP Hydronic Heating System Owner’s Manual
APPENDIX C: ANTIFREEZE TERMS AND MIXTURE RATIO

Figure 1
Eyepiece
Calibration Screw
Daylight Plate
Assembly
Main Prism
Assembly
CALIBRATE THE REFRACTOMETER
Aqua-Hot Part Number MSX-907-162
APPENDIX D: MEASURING PROPYLENE GLYCOL USING AREFRACTOMETER

Warning
1. Use extreme caution in gathering your antifreeze sample. When draining the Aqua-Hot heating system. ex-
tremely hot liquid may be in the Boiler Tank and could cause personal injury.
NOTE: Refractometers may have more than one scale. Make sure you are reading the scale marked “Propylene”
for measuring the antifreeze solution in the Aqua-Hot system.
Basic Operation
1. Open daylight plate, and place 2
-3 drops of the sample on the
main prism. Close the daylight
plate so the liquid sample spreads
across the entire surface of the
prism without air bubbles or dry
spots. Allow the sample to rest on
the prism for approximately 30
seconds before going to step #2.
(This allows the sample to adjust
to the ambient temperature of the
refractometer).
2. Hold daylight plate in the direction
of a light source and look into the eye-
piece. You will see a circular field with
graduations down the center (you may
have to focus the eyepiece to clearly see
the graduations). The upper portion of
the filed should be blue, while the lower
portion should be white.
3. Take the reading where the
boundary line of blue and white
cross the graduated scale. The
scale will provide a reading of the
freezing point of antifreeze solu-
tion and the propylene glycol con-
centration. Clean the prism care-
fully using a damp soft cloth. Do
NOT immerse in water.
USING THE REFRACTOMETER TO TEST ANTIFREEZE SAMPLE
APPENDIX D: MEASURING PROPYLENE GLYCOL USING AREFRACTOMETER

— Page 20 — © 2009 Aqua-Hot®375-LP Hydronic Heating System Owner’s Manual
This area provided for notes.