Aqua-Hot 400 Series Service Manual page 4

Aqua-Hot 450D
Introduction:
This service and parts manual is designed to aid trained and
qualifi ed service technicians with the process of troubleshooting
and servicing the Aqua-Hot 450D Hydronic heating system.
About the Aqua-Hot:
The Aqua-Hot 450D heating system features a 12V DC powered
diesel-burner and a 120VAC 1650 Watt electric heating
element. 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, independent interior
zone heating, and engine preheating. Be sure to reference
Figures 5 through 8 for a complete component overview.
Understanding the Aqua-Hot 450's Major Systems:
The basis for the Aqua-Hot heating system's functionality is
the antifreeze and water heating solution, which is comprised
of water that is distilled, deionized, or soft, as well as FDA-
approved "GRAS" propylene glycol based boiler antifreeze.
Through this solution's ability to maintain and transfer heat, the
Aqua-Hot's three major systems: the domestic water system,
engine preheat system, and interior heating system, are able to
function effectively. This antifreeze and water heating solution
is contained within the Aqua-Hot's boiler tank and is heated
by the diesel-burner when its operating criteria are met and/
or by the electric heating element when its operating criteria
are met. In order for the diesel-burner to be considered as a
heating source by the Aqua-Hot, it must have an adequate fuel
supply, receive power from the Reporter, and be selected as a
heating source from the interior switch panel. In order for the
electric heating element to be considered as a heating source
by the Aqua-Hot, it must receive power from either a generator
or from shore power and be selected as a heating source from
the interior switch panel. Once the antifreeze and water heating
solution achieves operating temperature (as determined by
the Aqua-Hot's control thermostat/ETS Module), the domestic
water system, the engine preheat system, and the interior
heating system are permitted to operate as needed.
Domestic Hot Water Priority System:
The Aqua-Hot 450D is a Hot Water Priority System. Meaning
that the Aqua-Hot 450D cannot heat the interior of the motor
home, and produce continuous hot water simultaneously. When
Domestic Hot Water is being used, the interior heating system
will shut down, until no more Domestic Hot Water is called for.
The domestic hot water priority system is responsible for
providing hot water whenever a hot water faucet is opened,
such as with a shower or sink.
When hot water is requested, domestic water from the motor
home's fresh water tank is transported through a copper coil in
the Aqua-Hot's boiler tank where heat is transferred from the
heated antifreeze and water heating solution to the domestic
water fl owing through the copper coil. The heated domestic
water then fl ows through the tempering valve to be mixed with
cool water from the fresh water tank to achieve an appropriate
temperature before it fl ows to the faucet requesting hot water.
Engine Preheat System:
The engine preheat system is responsible for heating the motor
home's engine block in order to make it easier to start-up when
cool weather conditions exist.
When the engine preheat system is activated via the interior
switch panel, the motor home's engine coolant is circulated
through a dedicated copper coil in the Aqua-Hot's boiler tank,
where heat from the antifreeze and water heating solution is
transferred to the motor home's engine coolant. The heated
engine coolant is then transported back to the engine where it
transfers the heat to the engine to gradually warm it.
Additionally, the Aqua-Hot 450D includes a motor-aide feature,
which uses the circulation of the motor home's engine to
transport the engine's coolant from the Aqua-Hot's boiler
tank to the motor home's warm engine and back to the boiler
tank. Through this process, the boiler tank is kept heated,
which reduces the time required to bring the tank to operating
temperature for interior heat and continuous domestic hot
water. This motor-aide feature is part of the engine preheating
feature and plumbing system, and requires no action on the
user's behalf to function.
Interior Heating System:
The interior heating system is responsible for providing heat to
the motor home's interior in order to maintain the temperature
at a comfortable level.
For interior heating, it is the room thermostats that trigger
the Aqua-Hot's interior heating system. When a thermostat
recognizes that heat is required in a particular area, it sends a
signal to the Aqua-Hot's Reporter calling for heat. The Aqua-Hot
responds by activating the circulation pump for that zone, which
sends the heated antifreeze and water heating solution through
the Heating Loop corresponding to the zone requesting heat.
The fans on the heat exchangers in the zone calling for heat
are also activated; therefore, as the heated solution fl ows over
©Aqua-Hot® 450D Service Manual
Introduction
p. 3