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A CF is required whenever heat is needed for the
secondary heating load such as an indirect domestic
hot water tank. A CF is generated when 24VAC is
applied across the D W contacts P1 (terminals 1 and
3). Once the voltage is applied, the control turns on the
Dem 2 segment in the display and the controller oper-
ates the heater stages to maintain the BOIL TARGET
2 at the system sensor.
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When Mode 3 is selected, the Controller provides ded-
icated D W operation.
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A sensor is required to be installed in the tank and con-
nected to the Com and the Sys/D terminals (6 and 4).
A CF for D W is generated when the temperature at
the D W sensor drops the tank differential setting
below the desired D W tank temperature. The TANK
TARGET setting is used to set the desired D W tank
temperature. Once a CF is generated, the Dem seg-
ment turns on in the LCD.
The Controller then operates the heater to maintain
the programmed heater target temperature at the
heater outlet sensor. The heater target temperature is
set using the BOIL TARGET item in the adjust menu.
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Tank differential is subtractive to the set point that
operates completely below the TANK TARGET. It is
selected using the TANK DIFF item in the adjust menu.
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When Mode 5 is selected, the Controller uses outdoor
reset to control the water temperature. Outdoor reset
adjusts the target temperature based on the outdoor
air temperature and the reset ratio; as the outdoor air
temperature rises, the need for heat drops and the set-
point is reduced The reset ratio is determined from the
eater Start, eater Design, Outdoor Start and
Outdoor Design settings.
(# DO NOT use D W override on termi-
nal 3.
• During a D W demand the boiler pump contact is
closed unless Indirect D W priority is selected.
During Indirect D W priority, the boiler pump con-
tact is off.
• After the burner shuts off the boiler pump remains
on for the Pump DLY time setting in order to purge
heat from the boiler to the system.
•During dedicated D W operation (Mode 3), the
boiler pump contact closes whenever there is an
internal CF .
• During external direct drive operation (Mode 8), the
boiler pump contact closes whenever there is a
CF .
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The controller operates the pump based on the Pump
DLY setting. Once the heater shuts down, the con-
troller keeps the pump running for the time selected.
When Pump DLY is set to OFF, there is no purging.
When Pump DLY is set to ON, the pump runs continu-
ously. When on is selected and the control is
configured for outdoor reset, the pump continues to
run even during Warm Weather Shut Down (Mode 5).
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If the pump has not operated at least once every 70
hours, the control turns on the output for 10 seconds.
This minimizes the possibility of the pump seizing dur-
ing a long period of inactivity.
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A setpoint is a fixed water temperature target that the
heater is to maintain at the system sensor. The heater
maintains the heater target using the proportional or
the PID logic together with the heater differential. The
setpoint temperature is set using the BOIL TARGET
item in the adjust menu.
9./+8.8+,6//7
A call for heat (CF ) is required whenever heat is
required for the primary heating load. This CF is
generated when 24VAC is applied across the
enable/disable connection P1 (terminals 1 and 2).
Once the voltage is applied, the control turns on the
Dem 1 segment in the display and the controller oper-
ates the heater to maintain the BOIL TARGET 1 at the
system sensor.
10
