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1 Service (continued)
Service Manual
DHW Settings
DHW Boiler Set Point
When a DHW call for heat becomes active, the control will
use the DHW boiler set point to determine the firing rate of
the boiler based on the boiler outlet water temperature, or
system temperature when DHW is programmed as a zone.
This parameter can be changed by the installer by accessing
the DHW Boiler Set point parameter. The temperature range
of this parameter is 68°F (20°C) to 180°F (82°C). The default
value is 180°F (82°C).
DHW Tank Set Point
By installing a tank sensor, the SMART SYSTEM control can
perform the tank thermostat function. The SMART SYSTEM
control automatically detects the presence of this sensor, and
generates a DHW call for heat when the tank temperature
drops below the tank set point differential (Tank Set point
Differential parameter), and finishes the call for heat when
the tank temperature reaches tank set point + offset. This
parameter can be changed by the installer by accessing the
DHW Tank Set point parameter. The temperature range of
this parameter tank minimum set point to tank maximum set
point. The default value is 125°F (52°C).
Tank Set Point Differential
When a tank sensor is installed, the tank temperature must
drop this amount below the tank set point (DHW Tank
Set point parameter) before the boiler turns back on. The
installer can adjust this setting by accessing the Tank Set point
Differential parameter. The minimum setting is 0° (0°C), and
the maximum is 40°F (22°C). The default setting is 6°F (3°C).
DHW Boiler Offset
This parameter reflects the degrees above DHW boiler set
point the temperature has to go before the boiler will shut off.
The range is 0°F (0°C) to 40°F (22°C). The default setting is
10°F (6°C).
DHW Boiler Differential
This parameter reflects the degrees below DHW boiler set
point the temperature has to go before the boiler turns back
on. The range is 0°F (0°C) to 60°F (33°C). The default setting
is 20°F (13°C).
SH/DHW Switching Time
When a boiler has a space heating demand and it receives
a DHW demand, it will immediately switch to the DHW
demand and start a timer. Once the timer has expired, the
boiler will switch back to the space heating demand and start
another timer. Once this timer expires, it will switch back to
the DHW demand. The installer can adjust the length of time
the boiler will service the space heating demand by accessing
SH/DHW Switching Time parameter. The minimum setting
is 0 minutes and the maximum setting is 50 minutes. The
default time is 30 minutes.
DHW/SH Switching Time
When a boiler has a DHW demand and it receives a space
heating demand, the SMART SYSTEM control will start a
timer. Once the timer expires, it will stop the DHW demand
and service the space heating demand. The installer can adjust
the length of time the boiler will service the DHW demand
by accessing the DHW/SW Switching Time parameter. The
minimum setting is 0 minutes and the maximum setting is 50
minutes. The default setting is 30 minutes.
Tank Minimum Set Point
This setting controls the minimum tank set point for the tank
temperature. The installer can adjust this by accessing the Tank
Minimum Set point parameter. The minimum setting is 60°F
(16°C) and the maximum setting is the maximum tank set point
(Tank Maximum Set point parameter). The default value is 60°
(16°C).
Tank Maximum Set Point
This setting controls the maximum tank set point for the tank
temperature. The installer can adjust this by accessing the Tank
Maximum Set point parameter. The minimum setting is the
minimum tank set point (Tank Minimum Set point parameter)
and the maximum setting is 190°F (88°C). The default value is
140°F (60°C).
DHW Type
This parameter determines whether the Knight XL boiler treats
the indirect DHW tank as a separate load, or as a zone on the
primary loop. When programmed as a separate load, the boiler
will turn on the DHW pump and then turn off the boiler pump
when an indirect DHW demand begins. When programmed as
a zone, the boiler will turn on the DHW pump, leave the boiler
pump on and change the system set point to the DHW boiler set
point (DHW Boiler Set point parameter).
This setting may be changed by the installer by accessing the
DHW Type parameter. The choices are NORMAL and ZONE.
The default setting is NORMAL.
Fan Speed Limiting for Indirect DHW Tank
This parameter determines the maximum fan speed (and
therefore the maximum rate) to be used when heating an
indirect DHW tank. This setting may be used when the tank is
unable to accept all of the BTU’s available from the boiler. This
parameter may be adjusted by the installer by accessing the Fan
Speed Limiting for Indirect DHW Tank parameter. The default
value is the maximum fan speed for that model.