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Service Manual
21
1 Service (continued)
E: 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.
This parameter can be changed by the installer by accessing
parameter E1. The temperature range of this parameter is
60°F (16°C) to 190°F (88°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 (parameter E3),
and finishes the call for heat when the tank temperature
reaches tank set point. This parameter can be changed by the
installer by accessing parameter E2. The temperature range of
this parameter is 68°F (20°C) to 190°F (88°C). 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 (parameter E2)
before the heater will turn on. The installer can adjust this
setting by accessing parameter E3. The minimum setting is 0°
(0°C), and the maximum is 40°F (22°C). The default setting
is 6°F (3°C).
Boiler Set Point 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 20°F (13°C). The default setting is
10°F (6°C).
Boiler Set Point Differential
This parameter reflects the degrees below DHW boiler offset
the temperature has to go before the boiler shuts off. 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
parameter E6. The minimum setting is 0 minutes and the
maximum setting is 200 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 parameter E7. The minimum setting is 0 minutes and
the maximum setting is 200 minutes. The default setting is 30
minutes.
Tank Minimum Set Point
This setting controls the minimum user set point for the tank
temperature. The installer can adjust this by accessing
parameter E8. The minimum setting is 60°F (16°C) and the
maximum setting is the maximum tank set point (parameter
E9).
Tank Maximum Set Point
This setting controls the maximum user set point for the tank
temperature. The installer can adjust this by accessing
parameter E9. The minimum setting is the minimum tank set
point (parameter E8) and the maximum setting is 185°F (85°C).
DHW Type
This parameter determines whether the Knight XL 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 raise the system set point to the DHW boiler set
point (parameter E1), if it is higher than the current SH set
point.
This setting may be changed by the installer by accessing
parameter E10. 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
parameter E11. The default value is the maximum fan speed for
that model.