1
Service
10
Service Manual
1
Service
General Operation
How the boiler operates
The Knight XL uses an advanced stainless steel heat exchanger
and an electronic control module that allows fully condensing
operation. The blower pulls in gas and air and pushes flue
products out of the boiler through the heat exchanger and
flue piping. The control module regulates blower speed to
control boiler firing rate. The gas valve senses the amount of
air flowing into the boiler and allows only the right amount
of gas to flow.
How the control module operates
The Knight XL control module receives input from boiler
sensors. The control module activates and controls the
blower and gas valve to regulate heat input and switches
boiler, DHW and system pumps on and off as needed. The
user/installer programs the module to meet system needs by
adjusting control parameters. These parameters set operating
temperatures and boiler operating modes. Boiler operation
can be based on boiler outlet water temperature, boiler return
water temperature or system supply temperature, depending
on the parameter setting.
Sequence of operation
Table 1 shows control module normal sequences of operation
for space heating and DHW operation. The combined
operation sequence is for a typical application, programmed
to provide DHW priority.
Access modes
User
The user can adjust space heating set point using the UP and
DOWN buttons at any time during normal operation. By
entering the USER code (0704), the user can also change
temperature units, time and date, and night setback settings.
In user mode, the following parameters can be viewed but not
changed: Boiler outlet water temperature in DHW mode;
boiler model number; software version; total operating hours,
and total cycles.
Installer
Most parameters are available only to the installer, accessible
only by entering the installer access code (5309).
Saving parameters
To save parameters:
Press the ENTER/RESET button.
To keep parameter settings only for a current operating cycle:
Press the MENU/EXIT button 1 time to return to the
parameter listings; press again to return to the menu listings.
Summary of Contents for KNIGHT 399 - 800
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