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Hi-E2
Page 21
properly adjusted. Also be sure that the combustion air
filter is clean and that there is no blockage of the vent
or combustion air inlet. See later section on
combustion air filter service.
4B. Induced-Draft Combustion System
The Hi-E2 pool heater has an advanced
combustion system which makes it highly efficient and
reliable. This system is illustrated in Figure 29.
A special corrosion resistant high-speed blower
pulls flow through the system and exhausts it to the
outdoors. Air is pulled into the system through a
combustion air supply duct, when provided, and
through an air filter into a venturi. The venturi
functions much like an automobile carburetor venturi -
i.e. when air is forced through it, a “negative” pressure
is created at the venturi throat. This negative pressure
pulls gas through a metering orifice, resulting in an
optimal mixture of air and fuel gas. The air and gas are
thoroughly mixed in the venturi tailpipe, pulled through
a special burner and ignited in the combustion
chamber. Hot combustion products are then pulled
through a highly efficient downward-flow heat
exchanger. Combustion products are cooled below
their dew point and condensate water is formed and
drained away. Flow then enters the blower, where it is
forced out of the heater at the vent terminal or through
a vent pipe to the outdoors.
4C. Heater Components and Their
Operation
1. Gas valve / Regulator - The gas valve
controls gas flow into the venturi. It provides
flow only when the temperature control
require heat and only if all safety controls
enable operation. It is also a negative
pressure regulator. It regulates the gas
pressure to 0.2” WC less than the air
pressure at the venturi inlet. This is necessary
for proper operation of the venturi system
and cannot be done with common (positive
pressure) gas valves.
2. Combustion blower - The combustion
blower is a specially designed to handle moist
combustion products, having special plastic
housing and impeller. It is powered by a
brushless DC motor.
3. Temperature Control - The Teledyne Laars
Flex Temp control is an electronic control
which senses water temperature by means of
a thermistor and controls heater operation to
bring the water to that selected. It has two
temperature setting knobs which are typically
used to set pool and spa temperatures. A
selector switch determines which setting is
chosen.
4. Ignition Control - The ignition control
provides energy for ignition of the air/gas
mixture, monitors the flame and controls the
combustion blower and gas valve. When the
temperature control requires heat, the ignition
control starts the blower, providing a pre-
purge of the combustion chamber. Then it
applies electrical power to a “hot surface”
igniter. When the igniter is hot enough, it
opens the gas valve. It has sophisticated
means to sense ignition and flame condition
so that unburned gas will not escape. After
the burner is shut off, it continues blower
operation to provide a post-purge period.
Figure 29. Combustion System Diagram.