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© 2010 D 265 - 07/10
Section F1: External Input
DHW or Setpoint operation is available during External Input operation. Boiler Demands are not active when the Stand Alone
/
External
Input DIP switch is set to External Input.
EXTERNAL INPUT
The control can accept an external DC signal in place of the outdoor sensor. The control converts the DC signal into the appropriate
boiler target temperature between 50°F (10°C) and 210°F (99°C) based on the External Input Signal and Offset settings. To use
the external input signal, the External Input / Stand Alone DIP switch must be set to External Input.
When operating in the external input mode, an external signal is required in order for the control to provide heat to the heating
system. An external signal is generated by applying a voltage between 0
V
(dc) and 10
V
(dc) across the
Out +
and
Com –
terminals
(4 and 1). Voltages that exceed 10
V
(dc) will still be considered a 10
V
(dc) signal. Once voltage is applied, the control closes the
primary pump contact and the control calculates a boiler target supply temperature based on the external input signal and the
settings made in the control. The control then fires the boiler(s), if required, to maintain the target supply temperature. If the external
signal goes below the minimum voltage, the boiler target temperature is displayed as “– – –” to indicate that there is no longer a call
for heating. The primary pump and boiler pumps operate as described in section G.
INPUT SIGNAL
The control can accept either a 0 - 10 V (dc) signal or a 2 - 10 V (dc) signal. The External Input Signal setting must be set to the
proper setting based on the signal that is being sent to the control.
0 - 10 V (dc) or 0 - 20 mA
When the 0 - 10 V (dc) signal is selected, an input voltage of 1
V
(dc) corresponds to a boiler target temperature of 50°F (10°C).
An input voltage of 10 V (dc) corresponds to a boiler target temperature of 210°F (99°C). As the voltage varies between 1
V
(dc)
and 10 V (dc) the boiler target temperature varies linearly between 50°F (10°C) and 210°F (99°C). If a voltage below 0.5
V
(dc) is
received the boiler target temperature is displayed as “– – –” indicating that there is no longer a call for heating.
A 0 - 20 mA signal can be converted to a 0 - 10 V (dc) signal by installing a 500
Ω
¼ W resistor between the
Out +
and
Com –
terminals (4 and 1).
2 - 10 V (dc) or 4 - 20 mA
When the 2 - 10 V (dc) signal is selected, an input voltage of 2
V
(dc) corresponds to a boiler target temperature of 50°F (10°C).
An input voltage of 10 V (dc) corresponds to a boiler target temperature of 210°F (99°C). As the voltage varies between 2
V
(dc)
and 10 V (dc) the boiler target temperature varies linearly between 50°F (10°C) and 210°F (99°C). If a voltage below 1.5
V
(dc) is
received the boiler target temperature is displayed as “– – –” indicating that there is no longer a call for heating.
A 4 - 20 mA signal can be converted to a 2 - 10 V (dc) signal by installing a 500
Ω
resistor between the
Out +
and
Com –
terminals (4 and 1).
Section F1
External
Input
Section F: External Input Operation
