Aqua-Hot 375-LP User manual

SERVICE MANUAL
© 2011 Aqua-Hot Heating Systems Inc.
AHE-375-P02
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.

Table of Contents
© 2011 Aqua-Hot® 375P02-LP Hydronic Heating System Service Manual—Rev. B
General Information
Danger, Warning, Caution, and Note Box Definitions...................................................Page 6
Section 1: Introduction To The Aqua-Hot 375-LP
Technical Information ...................................................................................................Page 7
I.D. Label Sample ........................................................................................................Page 8
Operating Instructions ..................................................................................................Page 9
Aqua-Hot Heater Overview...........................................................................................Page 10-12
Aqua-Hot Operational Flow-Chart ................................................................................Page 13
Antifreeze and Water Heating Solution……………………………………………………..Page 14-15
Section 2: Interior Switch Panel
Propane-Burner Switch ................................................................................................Page 16
Electric Element Switch................................................................................................Page 16
Switch Panel Wiring Schematic.................................................................................. Page 17 - 18
Section 3: Exhaust System
Exhaust System Requirements ....................................................................................Page 20
Section 4: Aqua-Hot Components
Interlock Switch ............................................................................................................Page 21
Float Switch..................................................................................................................Page 22-23
Propane-Burner Control Thermostat ............................................................................Page 23-24
Electric Element Control Thermostat ............................................................................Page 25-26
Electric Element High Limit Thermostat .......................................................................Page 27
Propane-Burner High Limit Thermostat (Left)...............................................................Page 28
Propane-Burner High Limit Thermostat (Right) ............................................................Page 29
Low Temperature Cutoff Thermostat............................................................................Page 30-31
Interior Heating Zone Check Valve...............................................................................Page 32-33
Domestic Water Tempering Valve................................................................................Page 34-35
Interior Heating Zone Circulation Pumps 1 & 2 ............................................................Page 36-37
Stir Pump (Circulation Pump #2) ..................................................................................Page 38
Electric Heating Element ..............................................................................................Page 39-40
Electric Heating Element A.C. Relay ............................................................................Page 41-42
Interior Heating Zone Relay - Heat Exchanger Fans....................................................Page 43
Interior Heating Zone Relay - Circulation Pump ...........................................................Page 44

Table of Contents
© 2011 Aqua-Hot® 375P02-LP Hydronic Heating System Service Manual—Rev. B
Section 5: Filling/Draining The Aqua-Hot 375P With Heating Solution
Filling the Aqua-Hot................................................................................................ Page 45-47
Draining the Aqua-Hot............................................................................................ Page 48
Section 6: Propane-Burner
General Recommended Maintenance......................................................................Page 49
General Component Overview ............................................................................... Page 50-51
Propane-Burner Operational Overview ....................................................................Page 52
Controller Wiring Schematic ................................................................................... Page 53
Section 7: Detaching and Reattaching the Propane-Burner
Detaching the Diesel-Burner .................................................................................. Page 54-57
Reattaching the Diesel-Burner...…………………………………………………………Page 58-61
Section 8: Propane-Burner Components and Repair Information
Mounting Gasket .................................................................................................... Page 62
Hot Surface Igniter ................................................................................................. Page 62-64
Insulation, Refractory ............................................................................................. Page 65-66
Dual Stage Propane Gas Valve.............................................................................. Page 67-68
Combustion Blower Fan ......................................................................................... Page 69-70
Exhaust “High Back Pressure” Switch.................................................................... Page 71
Fan Validation Switch............................................................................................. Page 72
Fan Validation Switch Relay................................................................................... Page 73
Buck Boost Converter (Combustion Blower Fan) ................................................... Page 74
Buck Boost Converter (Hot Surface Igniter) ........................................................... Page 75
Flame Sensor ......................................................................................................... Page 76
Fenwal Burner Controller ....................................................................................... Page 77-79

Table of Contents
© 2011 Aqua-Hot® 375P02-LP Hydronic Heating System Service Manual—Rev. B
Section 10: Troubleshooting
The Propane-Burner switch has been turned on; however, the Propane-Burner fails
to operate .....................................................................................................................Page 78
The Propane-Burner switch has been turned on and the Propane-Burner’s Blower
Motor has begun to operate; however, the Propane-Burner does not ignite ................Page 81
The Propane-Burner switch has been turned on; however, multiple attempts are
required before the Propane-Burner will ignite .............................................................Page 81
The Aqua-Hot’s exhaust system “woofs/pops” when the Propane-Burner Ignites........Page 81
The Propane-Burner will ignite, but short cycles (only runs for a short amount of
time before shutting down) ...........................................................................................Page 81
The Aqua-Hot is operating, but an interior and/or fresh water tank heating zone is
not working….…………………………………………………………..……………………..Page 82
The Aqua-Hot is at operating temperature; however, the interior and/or fresh
water tank heat exchanger fans are not operating .......................................................Page 82
The Aqua-Hot is operating, but the domestic hot water system is not producing
hot water ......................................................................................................................Page 82
The Electric Element switch has been turned on; however, the Aqua-Hot’s
120 Volt-AC electric heating element does not operate ...............................................Page 83
Appendix A: Wiring Diagram .........................................................................................Page 84-85
Appendix B: Wire Gauge Chart...........................................................................................Page 87
Appendix C: Winterization Process....................................................................................Page 88
Appendix D: Extreme Cold Weather Operation ............................................................Page 89-90

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© 2011 Aqua-Hot® 375P02 - LP Hydronic Heating System Service Manual—Rev. B
GENERAL INFORMATION:
This manual is designed to aid trained and qualified service
technicians with the process of troubleshooting and servicing
the Aqua-Hot 375-LP Hydronic Heating System.
The Aqua-Hot features a 12 Volt-DC powered Propane-
Burner and a 120 Volt-AC, 1500-Watt Electric Heating Ele-
ment. These two heating sources are used in conjunction
with an FDA approved “GRAS” (Generally Recognized as
Safe) propylene glycol based boiler antifreeze and water
heating solution in order to provide a continuous supply of
domestic hot water, interior/fresh water tank heating, inde-
pendent interior zone heating.
Please note that all Danger, Warning, Caution, and Note box-
es, appearing as needed throughout this manual, must be
reviewed and adhered to during servicing of the Aqua-Hot in
order to avoid potential hazards which could result in injury,
death, product damage, and/or property damage.
Should additional assistance be needed, please contact the
Technical Support Department at 1-800-685-4298, Monday
through Friday between the hours of 7:00 AM and 4:00 PM
Mountain Standard Time.
Danger, Warning, Caution, and Note Box Definitions
Danger, Warning, Caution, and Note boxes appear through-
out this manual as a means of alerting the service technician
to important information.
Indicates that personal injury is likely or imminent
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 service technician.

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© 2011 Aqua-Hot® 375P02 - LP Hydronic Heating System Service Manual—Rev. B
SECTION 1: INTRODUCTION TO THE AQUA-HOT 375-LP
Figure 1
Propane Burner, Heat Input (Firing Rate)................................................................................................................................. 64,377 BTU/hr
Propane Burner, Fuel Consumption (Continuous Operation).............................................................................0.72 gal/hr, 2.72 liters/hr
Heater, Voltage/Maximum Power Consumption.......................................................................................................12 Volt-DC/122 watts
Electric Heating Element specifications ....................................................................................................................120 Volt-AC/1500 watts
Zone Heat Circulation Pump specifications ....................................................................................................(2) 12 Volt-DC/21 watts each
Number of Heating Zones..............................................................................................................maximum of 2, plus Bay Heat Exchanger
Domestic Water Heating Capacity................................................................................................................................continuous/on-demand
Dimensions ...................................................................................................................................................................16.75”H x 18”W x 29.5”L
Dry Weight.......................................................................................................................................................................... approximately 155 lbs.
Wet Weight.......................................................................................................................................................................... approximately 200 lbs.
NOTE: All vehicle installations must comply with the requirements listed in the Recreational Vehicle Industry Associ-
ation’s (RVIA) ANSI/NFPA 1192 Handbook for Recreational Vehicle Standards. To receive a copy of this handbook
and other pertinent RVIA Standards, write to: Recreation Vehicle Industry Association, 1896 Preston White Drive,
P.O. Box 2999, Reston, VA 22090-0999, call them at [phone], or visit them online at www.rvia.org.

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© 2011 Aqua-Hot® 375P02 - LP Hydronic Heating System Service Manual—Rev. B
SECTION 1: INTRODUCTION TO THE AQUA-HOT 375-LP
For installation only in a compartment that is com-
pletely closed off from living quarters and accessi-
ble only from the outdoors.
The Exhaust System MUST NOT terminate beneath
the vehicle or under an openable window or vent.
Combustion Air MUST BE supplied from outside
the vehicle.
CAUTION: THIS APPLIANCE OPERATES ON BOTH
AC AND DC POWER,
USE COPPER CONDUCTORS ONLY!
Use a 25-Amp fuse for over-current protection for
the DC power supply.
Use a circuit breaker that cuts power at 20-Amps
maximum for over-current protection for the 120-
VAC power supply.
Mount the Heater near a bay/storage door so that
the Access Cover can be easily removed for ser-
vice.
WARNING: DO NOT OPERATE APPLIANCE WITH
ACCESS COVERS REMOVED.
Minimum Heater Clearances:
Front—Open Access
Back— 0 inches
Top — 6 inches
Sides—0 inches
Install in strict compliance with local codes, NFPA
1192, and the manufacturer’s instructions
Minimum Heater Clearances:
Front - Open Access
Back - 0 inches
Top - 6 inches

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© 2011 Aqua-Hot® 375P02 - LP Hydronic Heating System Service Manual—Rev. B
SECTION 1: INTRODUCTION TO THE AQUA-HOT 375-LP

— Page 10 —
© 2011 Aqua-Hot® 375P02 - LP Hydronic Heating System Service Manual—Rev. B
SECTION 1: INTRODUCTION TO THE AQUA-HOT 375-LP
Figure 2
I.D. Label
Pump-1 and
Pump-2 Inlet
Ports
Propane Inlet
Hot Water
Outlet Port
Operating
Instructions
Cold Water
Inlet Port
Zone 1 and 2
Outlet Ports
Terminal Block
Access Area
Site Access