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4 Description of the product
4.1 General description
4.2 Operating Principle
4 Description of the product
This Andrews Water Heater is a gas fi red, low NOx, direct fi red water
heater, with an integrated stainless steel tank. Fully automatic electronic
controls are integrated into the heater, with a wide range of control strate-
gies and sensors
4.2.1 Combustion and condensate gains
The burner heats the primary water fl owing through the heat exchanger.
If the temperature of the fl ue gases is lower than the dew point (approx.
55°C), water vapour condenses inside the heat exchanger. The energy
released during this condensation process (referred to as latent heat) is
also transferred to the primary water. The cooled fl ue gases are dis-
charged through the fl ue gas discharge pipe. The condensed water is
discharged through a siphon.
4.2.2 Control system
The fl ow (or charging) temperature is continuously monitored by the
controls and the burner along with the pump are modulated to maintain
a precise fl ow temperature from the heat exchanger into the DHW tank.
Multi-layers of control level thresholds, ensure the heater operates safely
at all times.
The electronic control system ensures that your water heating system
is smart and reliable. This means that the heater responds practically to
negative environmental infl uences (such as limited water fl ow or high fl ue
temperatures). In the event of such adverse infl uences, the controls will
seek to modulate back the burner in the fi rst instance, applying a lockout
condition if all other control methods have not been eff ective.
4.2.3 Gas/air regulation
The heater is equipped with a casing that also serves as an air box. The
fan draws the combustion air from within the casing, which is supplied
via the chosen fl ue system. The gas is injected into the venturi and mixed
with the combustion air. The fan speed is controlled on the basis of the
settings, the heat demand and the prevailing temperatures measured by
the temperature sensors. The gas/air ratio control ensures an accurate
mixture of the required amounts of gas and air. This provides optimum
combustion over the entire heat input range at all times. The gas/air mix-
ture goes to the burner, where it is ignited by the ignition electrode.
16
MAXXfl o EVO Lite
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