Aqua-Hot 450 D User manual

OWNERS MANUAL
© 2011 Aqua-Hot Heating Systems Inc.
450 D

— Page 2 — © 2011 Aqua-Hot®450-D Hydronic Heating System Owner’s Manual

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
There’s no need to burn propane each time heat or hot water is needed. Aqua-Hot’s TribridHot technol-
ogy powers the Aqua-Hot system by pulling heat from one or a combination of heat sources. When driv-
ing or idling, the Aqua-Hot system uses the engines surplus heat. When shore power is available, simply
plug it in. When dry-camping or in very cold conditions, use the Diesel Burner.

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.
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!

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© 2011 Aqua-Hot®450-D 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 9
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
Diesel-Burner Blinking Fault Indicator light...................................................................Page 14
Appendices
Appendix A: Antifreeze Types......................................................................................Page 16
Appendix B: Antifreeze Mixture Water Quality Recommendations..............................Page 16
Appendix C: Antifreeze Terms and Mixture Ratio........................................................Page 16
Appendix D: Measuring Propylene Glycol Using a Refractometer ..............................Page 18
Warranty
Limited Warranty Statement .........................................................................................Page 23
TABLE OF CONTENTS

— Page 6 — © 2011 Aqua-Hot®450-D Hydronic Heating System Owner’s Manual
INTRODUCTION
The Aqua-Hot Heating System is a Low Emissions Hy-
dronic Heating System (heating with hot water) that sig-
nificantly improves your level of comfort, is good for the
environment and adds thousands of dollars in value to
your RV.
The Aqua-Hot Heating System is actually four sys-
tems in one:
• Interior heating system providing quiet, comfortable
interior heat with independent temperature zones that
provide cabin-wide even temperatures.
• Bay heating system keeps pipes and tanks from
freezing in the bay storage area.
• Tank-less hot water system provides a steady flow of
continuous hot water.
• Engine preheating system reduces engine wear
caused by cold starting by preheating the engine
from 30°f to 90°f in one hour.
Your Aqua-Hot System is powered by TribridHot™
technology, using one or a combination of sources:
• The Vehicle’s Engine: When driving or idling, the en-
gines surplus heat is transferred to the Aqua-Hot pro-
viding interior heat and limited hot water without
burning any other fuel.
• The 120v AC Electric Element: When plugged into
shore power, the electric element lets you use the
power you are already paying for to provide interior
heat and meet your light duty hot water needs.
• The Diesel Burner: The Aqua-Hot’s most powerful
heat source provides all of your heating and hot wa-
ter needs in really cold temperatures or when dry
camping.
You can even combine power sources. TribridHot™. It’s
technology at it’s warmest.
This manual should be maintained in legible condi-
tion and kept in a safe, easily-accessible location for
future reference.
Please read the complete Owner’s Manual prior to
operating the Aqua-Hot Hydronic Heating System.
Also, be sure to fill out and mail in the “Warranty
Registration” card Included in this manual.
NOTE: This Aqua-Hot product utilizes a propylene glycol
based antifreeze and water heating solution. This
propylene glycol based solution is a Boiler type
antifreeze that is “Generally Recognized as
Safe” (GRAS) by the FDA. For additional information
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.
Aqua-Hot I.D. Label
Figure 1
NOTE: Indicates information that requires special attention by
the operator.
Danger, Warning, Caution, and Note Boxes:
Danger, Warning, Caution, and Note boxes appear
throughout this manual as a means of alerting the opera-
tor to important information.
Indicates that damage to the heater is possible.
CAUTION:
450 D
INDICATES THAT PERSONAL INJURY IS LIKELY OR IMMINENT.
DANGER!
Indicates that serious damage to the heater will occur
and personal injury is possible as well.
WARNING!

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© 2011 Aqua-Hot®450-D Hydronic Heating System Owner’s Manual
INTRODUCTION
Wire Harness
Port
AC Wiring
Port
Product I.D.
Label
Zone 1 Circulation
Pump Zone 2 Circulation
Pump Drain Valve Interlock
Switch
Diesel-Burner
Diesel Burner
Controller
Back of Unit
Figure 2
Domestic Hot
Water Outlet
Engine Preheat
Inlet
(From Engine) Engine Preheat
Circulation
Pump
Engine Preheat
Outlet
(To Engine)
Domestic Cold
Water Intlet

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Figure 3
INTRODUCTION
Figure 4
Top of 450-D
Heating Zone
Return Ports
Product
I.D. Label Air Release
Valve Expansion
Tank
Wiring Harness
Port
Diesel Fuel
Inlet/Outlet
Ports
Heating
Zone Outlet
Ports
AC Wiring Port
Heating Zone
1 Outlet Port
Heating Zone
2 Outlet Port
AC Junction
Box
Wire Harness
& Harness
Port
Zone 1 Circulation
Pump Zone 2 Circulation
Pump
Interlock
Switch

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© 2011 Aqua-Hot®450-D Hydronic Heating System Owner’s Manual
OPERATING INSTRUCTIONS
DO NOT operate the Diesel-Burner and/or Electric Heat-
ing Element without the antifreeze and water heating so-
lution in the Aqua-Hot’s Boiler Tank. Failure to do so will
cause serious damage to the Heater.
Activating the Aqua-Hot Heating System:
Diesel-Burner:
Turn the Burner switch ON; reference Figure 5. This pro-
cedure will activate the Diesel-Burner and the indicator
light located adjacent to the Diesel-Burner switch. Allow
10-20 minutes for the Aqua-Hot System to reach operat-
ing temperature. Please note that the Diesel-Burner is
the primary heat source for heating both the interior and
the domestic hot water (such as when cool ambient tem-
peratures exist and/or when there is a high demand for
domestic hot water).
Electric Heating Element:
Turn the Electric switch ON; reference Figure 5. This pro-
cedure will activate the 120 Volt-AC Electric Heating Ele-
ment and the indicator light located adjacent to the Elec-
tric switch. Allow 1-2 hours for the Aqua-Hot System to
reach operating temperature.
Engine Preheat Element:
In order to use the Engine Preheat element on the Aqua-
Hot system, both the Diesel-Burner AND the Engine Pre-
heat switch must be turned ON; reference figure 5. Allow
the Engine Preheat element to function for one hour be-
fore starting the vehicle’s engine.
The Aqua-Hot’s Exhaust is HOT!
DO NOT park in areas where dry conditions exist un-
derneath the vehicle as a fire may result (i.e., in a dry,
grassy field)!
DO NOT operate the Aqua-Hot’s Diesel-Burner inside
an enclosed building!
The Heater must be switched OFF when refueling.
WARNING!
CAUTION:
Figure 5
Indicator
Light

— Page 10 — © 2011 Aqua-Hot®450-D Hydronic Heating System Owner’s Manual
OPERATING INSTRUCTIONS
Zone Thermostat Operation
Interior Room Thermostat:
Simply adjust each Interior Room Thermostat to the de-
sired temperature. Then, whenever an Interior Room
Thermostat “calls for heat,” the Aqua-Hot’s Circulation
Pump and Interior Heat Exchanger Fans will be acti-
vated. These devices, together, will supply warmth and
comfort to each interior heating zone. The Aqua-Hot
must be at operating temperature in order for the zones
to function. Please contact the specific motor home
manufacturer for the exact location of the Interior Room
Thermostats.
Fresh Water Tank Thermostat:
Simply adjust the Thermostat for Bay Heating to a mini-
mum of 40°F. This will prevent freezing of the domestic
water storage system. Please contact the specific motor
home manufacturer for the exact location of the Fresh
Water Tank Thermostat.
Using the Domestic Water Heating System
When the Aqua-Hot is at operating temperature, the do-
mestic 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 sup-
ply 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 Heat-
ing System. The Diesel-Burner switch on the Interior
Switch Panel must be ON in order to obtain a continu-
ous supply of hot water (e.g., during showers); be sure
to also activate the Electric Element switch for maxi-
mum hot water capacity. Reference Figure 4.
NOTE: Both the Diesel-Burner and Electric Heating Element
are thermostatically controlled. Either or both heating
sources will automatically maintain the temperature
of the Aqua-Hot’s antifreeze and water heating solu-
tion between approximately 160⁰F and 190⁰F(±5).
Therefore, to heat the motorhome/domestic hot wa-
ter, simply choose the desired heat source(s) and
leave the switch(es) (i.e., Diesel-Burner and or Elec-
tric Element) ON.
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 Heat-
ing Zones.
Figure 6
Indicator
Light
Burner switch must
be ON to obtain a
continuous supply of
hot water.
Activate the Electric
switch for maximum
hot water capacity.

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© 2011 Aqua-Hot®450-D Hydronic Heating System Owner’s Manual
OPERATING INSTRUCTIONS
Aqua-Hot Operational Flow-
chart
Heat source is selected from the
Interior Switch Panel.
Diesel-Burner is activated
by the Burner switch. Electric Heating Element is
activated by the Electric
switch.
The cooled antifreeze and water
heating solution is returned to the
boiler tank to be reheated.
Heating Zone Thermostat
calls for heat.
The heated antifreeze and
water heating solution flows
through the Hydronic Heat-
ing System transferring
heat to the heat exchanger,
which is then transferred to
the surrounding zone.
A hot water faucet (e.g.,
kitchen sink, shower, etc.) is
opened.
Continuous hot water is
supplied to the faucet.
“Engine Preheat” switch on
the Interior Switch Panel is
activated.
The engine’s coolant is
circulated through the
Aqua-Hot’s internal Engine
Preheat System, where the
heat from the Boiler Tank
is transferred to the
engine’s coolant.
The Boiler Tank heats the
antifreeze and water heat-
ing solution to 190*F.

— Page 12 — © 2011 Aqua-Hot®450-D Hydronic Heating System Owner’s Manual
Maintenance Schedule
Monthly Maintenance:
Check the Aqua-Hot’s antifreeze and water heating solu-
tion to ensure that it is at the proper level. This can be
accomplished by visually checking the coolant level in the
Aqua-Hot’s Expansion Tank; reference Figure 7. Please
note that the coolant level should be checked only when
the Aqua-Hot is at maximum operating temperature (i.e.,
immediately after the Diesel-Burner cycles OFF). When
maximum operating temperature, the antifreeze and wa-
ter 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 replen-
ishing, remove the Expansion Tank’s cap and fill the Ex-
pansion 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
8. Hold the valve open until all air is released. If neces-
sary, refill the Expansion Tank again. Be sure the valve is
closed when finished by hand-tightening. Reference Ap-
pendices A through C in order to determine the correct
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. Reference Appendix D for information about
MAINTENANCE
the tool and usage instructions for measuring the tank’s
freeze protection level.
Annual Maintenance:
To keep the Aqua-Hot running smoothly, it is ideal to
have the Diesel-Burner tuned-up annually. A tune-up
should consist of a new Fuel Nozzle and Fuel-Filter; ref-
erence Figure 9. To ensure maximum Diesel-Burner per-
formance, always use the recommended Fuel Nozzle and
Fuel Filter when replacing these parts. Reference the
Aqua-Hot’s Service and Parts Manual for spare parts in-
formation and detailed replacement instructions, contact
the Aqua-Hot Heating Systems Technical Support De-
partment 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.
DO NOT operate the Diesel-Burner and/or the Elec-
tric Heating Element without the antifreeze and water
heating solution in the Aqua-Hot’s Boiler Tank; do-
ing 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 Sys-
tems Technical Support Department at 1-800-685-
4298, or visit the Web site at www.aquahot.com.
Figure 8
Figure 7
Fluid will reach
Expansion Tank
line when hot
Expansion
Tank Cap
Air-Release
Valve Expansion Tank
Connection
Fuel Nozzle
Part Number:
FLX-013-150
Fuel Filter
Part Number:
FLE-120-100
Figure 9
DANGER!
WARNING!
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 CLEAN-
ING OR SERVICING, DISCONNECT ALL POWER SUPPLIES!

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© 2011 Aqua-Hot®450-D Hydronic Heating System Owner’s Manual
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 experi-
enced.
Winterizing the Domestic Water Heating System:
Please follow these instructions when winterizing the
Aqua-Hot’s Domestic Water Heating System; reference
Figure 10:
1. Completely drain the fresh water storage tank.
2. Disconnect the domestic water demand pump’s suc-
tion 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 fau-
cets, 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 stor-
age tank.
De-Winterizing the Domestic Water Heating System:
For de-winterization, completely fill the fresh water stor-
age tank. Open and close all interior and exterior water
faucets, one at a time, until only clear water is present/
visible. Reference Figure 10.
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 con-
tacting 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
Figure 10
Not winterizing the Aqua-Hot when freezing tempera-
tures 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 anti-
freeze 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.
Remove the hose from the Fresh Water Storage Tank and attach an adequate piece of hose onto the suction
side of the demand pump. Place this hose into a container of RV Antifreeze and allow this to pump through
the Domestic Water System until the faucets run pure antifreeze.
WARNING!

— Page 14 — © 2011 Aqua-Hot®450-D Hydronic Heating System Owner’s Manual
General Information
Should the Aqua-Hot Hydronic Heating System fail to
operate, complete the following checks:
1. Verify that the Aqua-Hot’s access cover is securely
installed. The Aqua-Hot Hydronic Heating System
will not operate if the access cover is not fully in-
stalled.
2. Ensure that the vehicle’s fuel tank contains a suffi-
cient level of fuel. The Aqua-Hot system will not oper-
ate if the fuel level is at or below 1/4 tank.
3. Ensure that the Aqua-Hot’s boiler tank has an ade-
quate supply of antifreeze and water heating solution
by checking the level at the expansion tank. If the
level is low, reference the maintenance section of
this manual for refilling instructions.
4. Check the Aqua-Hot’s electronic controller for any
RED lights indicating a fault condition.
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 Support De-
partment at 1-800-685-4298 for additional assistance or
visit the web site at www.aquahot.com.
If the Aqua-Hot’s diesel-burner switch “Indicator Light”
does not illuminate, and the diesel-burner is not function-
ing, locate the electronic controller and check the follow-
ing:
1. Check the Aqua-Hot’s electronic controller for any
RED lights indicating a fault condition. Reference
figure 11.
2. Check for loose wire connections on the electronic
controller’s terminal strips/plugs. When checking for
loose terminal strips/plugs, remove the electronic
controller faceplate by unscrewing the four cover
screws.
3. Remove the Aqua-Hot’s access cover and check for
loose plug connections on the diesel-burner control-
ler unit. Reference figure 2.
4. Ensure the vehicle’s fuel tank has a sufficient level of
fuel.
5. If the Aqua-Hot still fails to operate, please contact
the Aqua-Hot Heating Systems Technical Support
Department at 1-800-685-4298 or visit the web site
at www.aquahot.com
TROUBLESHOOTING
Electronic Controller Diagnostic
Low Tank-Level Cutoff Indicator Light
This indicator light will illuminate RED when either the 120
Volt-AC electric heating element and/or diesel-burner have
automatically shut down due to a low antifreeze and water
heating solution level inside the Aqua-Hot’s boiler tank.
This fault will automatically reset when the low level condi-
tion is corrected.
Low Battery Voltage Fault Indicator Light
This indicator light will illuminate RED and the diesel-burner
will shut down whenever the 12 Volt-DC voltage level is too
low for the Aqua-Hot to operate properly. This fault must be
manually reset after the voltage level has been restored to
the 12-Volt-DC battery system. Reference the Low
Voltage information below.
Low Voltage Fault Indicator Light and Reset Button
The Aqua-Hot’s electronic controller must be manually re-
set whenever the low battery voltage fault indicator light
has been activated. The electronic controller can be reset
by turning OFF the diesel-burner switch on the interior
switch panel for approximately 60 seconds, then turning the
switch back ON by pressing the “Low Voltage Reset” but-
ton located on the electronic controller (use a thin, straight,
nonmetallic object to access the reset button through the
small hole in the faceplate).
Figure 11
NOTE: An interlock switch prevents the Aqua-Hot from
operating when the cover is not installed and properly
in place.

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© 2011 Aqua-Hot®450-D Hydronic Heating System Owner’s Manual
Overload Fault Indicator Light
This indicator light will illuminate RED whenever one of
the following conditions have occurred:
1. The Aqua-Hot is off due to an electrical overload
(i.e., short) in the main 12 Volt-DC power supply
circuitry.
2. The Aqua-Hot is off due to a combination of high
electrical 12 Volt-DC power loads and a high surface
temperature of the electronic controller.
The Aqua-Hot will automatically restart once the electri-
cal overload (i.e., short) and/or high-heat condition is
corrected.
Heating Zones Status Indicator Lights
These five indicator lights (separately) will illuminate
GREEN whenever a zone thermostat, for each particular
zone, is calling for heat. The GREEN indicator lights
also indicate that 12 Volt-DC power is being supplied to
the particular interior heating zone’s heat exchangers
(i.e., fan motors). If any of the five indicator lights illumi-
nate RED, it indicates that an electrical overload condi-
tion (i.e., short) has occurred in a particular heating
zone’s circuitry.
Pumps #1, #2, and #3 Indicator Lights
These indicator lights (separately) will illuminate GREEN
whenever a circulation pump is operating. If any of the
three indicator lights illuminate RED, it indicates that an
electrical overload condition (i.e., short) has occurred in
the particular component’s circuitry.
Engine Preheat Pump Indicator Light
This indicator light will illuminate GREEN whenever the
engine preheat circulation pump is operating. Please
note that this light will only be active if the engine pre-
heat switch is ON in conjunction with either the diesel-
burner and/or the electric element switch. If this indicator
light illuminates RED, it indicates an electrical overload
condition (i.e., short) has occurred in this particular com-
ponent’s circuitry.
NOTE: The low temp cutoff light must be illuminated and
heater must be up to operating temperature for the
heating zone status indicator lights to illuminate red
or green.
NOTE: Zone circulation pumps #1 and #2 are activated
whenever a zone thermostat calls for heat. The
#3 boiler tank stir pump is activated whenever
the domestic water is being used on a continu-
ous basis or the heater is not up to operating
temperature.
TROUBLESHOOTING
Electric Heating Element Status Indicator Light
This indicator light will illuminate GREEN whenever the
Aqua-Hot’s electric heating element is operating and pro-
viding heat to the Aqua-Hot’s boiler tank. Please note that
this light will only be active if the electric element switch is
in the ON position. If this indicator light illuminates RED, it
indicates an electrical overload condition (i.e., short) has
occurred in the electric heating element’s 12 Volt-DC
powered circuitry.
NOTE: The Aqua-Hot’s VDC/VAC Control Thermostat
will automatically activate the diesel-burner and/
or the electric heating element only if the diesel-
burner and/or electric element switch is in the
ON position.

— Page 16 — © 2011 Aqua-Hot®450-D Hydronic Heating System Owner’s Manual
APPENDIX C: ANTIFREEZE TERMS AND MIXTURE RATIO
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 50/50 mixture ratio is recom-
mended, which will result in a freeze point of approxi-
mately –28⁰F. and a boil point of approximately 222⁰F.
The following information should be utilized for the pur-
pose of clarifying some terms commonly associated
with antifreeze.
Freeze Point and Burst Point:
Antifreeze solution lowers the freezing point of any liq-
uid, to which it has been added, by preventing the forma-
tion of ice crystals; however, as the ambient temperature
continues to decline, the water in the solution will at-
tempt to attain a solid state. The point in which the wa-
ter begins to solidify is termed the “freeze point.” Al-
though the water in the solution has begun to freeze,
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 heat-
ing solution is dependent upon the brand of propylene
glycol antifreeze employed.
APPENDIX B: ANTIFREEZE MIXTURE WATER QUALITY RECOMMENDATIONS
In order to ensure maximum performance and longevity
of an Aqua-Hot heating system’s boiler tank and associ-
ated components, it has been determined that there is a
need to use distilled, de-ionized, or soft water in combi-
nation with concentrated propylene glycol for the Aqua-
Hot’s antifreeze and water heating solution. Please
note that this is only necessary when mixing concen-
trated propylene glycol antifreeze with water; suppliers
of pre-mixed antifreeze are responsible for the use of
high-quality (distilled, de-ionized, or soft) water when
preparing their antifreeze for sale.
Hard water possesses a high-level of calcium and mag-
nesium ions, which deplete the propylene glycol anti-
freeze’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, con-
centrated propylene glycol should be diluted with dis-
tilled, 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.
APPENDIX A: ANTIFREEZE TYPES
The following information addresses the necessary us-
age 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 those propyl-
ene glycol based “boiler” type antifreezes deemed
“Generally Recognized as Safe” (GRAS) by the FDA
should be utilized.
Because of the significant impact various types of anti-
freeze 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 avail-
able. 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 prod-
ucts are formulated specifically for “winterizing” applica-
tions 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 Sys-
tem. This type of antifreeze is not formulated to transfer
heat, which is essential to the heating system’s function-
ality 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
System.
Automotive Antifreeze/Coolant:
These types of propylene glycol based antifreeze prod-
ucts are formulated specifically to protect automotive en-
gines against corrosion, freezing temperatures, and over-
heating. They also have excellent heat transfer and ther-
mal conductivity characteristics. Although these types of
antifreeze products are considered less toxic and safer
than ethylene glycol for people, pets, and the environ-
ment, they are not “Generally Recognized as
Safe” (GRAS) rated by the FDA. Therefore, they must be
marked with a “harmful if swallowed” warning. This addi-
tional warning is required because these types of anti-
freeze products contain high levels of chemical rust in-
hibitors. Due to their potentially hazardous properties,
they should never be used in the Aqua-Hot’s Hydronic
Heating System.

— Page 17 —
© 2011 Aqua-Hot®450-D Hydronic Heating System Owner’s Manual
APPENDIX C: ANTIFREEZE TERMS AND MIXTURE RATIO
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 proc-
esses. 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 boil-
ing 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 boil-
ing point is desired in order to combat the loss of effi-
ciency, which allows the antifreeze to transport the heat
created from the internal process throughout the mo-
torhome 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.
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 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. There-
fore, water is added to the mixture because it is an ex-
cellent heat conductor. PPG antifreeze solution, mixed
with water, that is 35% to 50% propylene glycol is rec-
ommended to provide the best performance combination
of the aforementioned functions. If excess propylene
glycol exists within an antifreeze and water heating solu-
tion, the water’s heat absorption properties are compro-
mised, which could ultimately inhibit the Aqua-Hot from
providing adequate domestic hot water and interior heat-
ing.
Additionally, if the antifreeze and water heating solution
contains over 70 percent propylene glycol, the freezing
point is actually raised, resulting in less freeze protec-
tion. Please reference the attached graphical represen-
tation regarding the percentage of antifreeze to water
and how it directly affects the solution’s freezing point.

— Page 18 — © 2011 Aqua-Hot®450-D Hydronic Heating System Owner’s Manual
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

— Page 19 —
© 2011 Aqua-Hot®450-D Hydronic Heating System Owner’s Manual
WARNING!
Use extreme caution in gathering your antifreeze sample. When draining the Aqua-Hot heating system.
extremely 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 anti-
freeze 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 sam-
ple to rest on the prism for approxi-
mately 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 eyepiece.
You will see a circular field with gradua-
tions 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 por-
tion 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 solution
and the propylene glycol concentra-
tion. Clean the prism carefully 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 — © 2011 Aqua-Hot®450-D Hydronic Heating System Owner’s Manual
Date Service Performed Service Center
OWNER’S SERVICE LOG