D.8.A External - Remote Set Point; D.8.B External Firing Rate - Bradford White OmniTech BONH1250 Installation And Operation Instructions Manual

8.D.8.a External – Remote Set Point.
External (0 – 10VDC or 4 – 20mA)
• An External heat demand can be
initiated by a Building Management
System (BMS) using a 0-10VDC or
4-20mA signal. This input can be
configured for Remote Set Point or
Remote Firing Rate operations.
• With Remote Set Point selected, the
unit will initiate a heat demand once
the analog input signal exceeds
the Demand On value. Once the
demand is initiated, the analog input
signal must be lower than Demand
Off to remove the heat demand.
With an active demand, the unit will
locate the set point according to the
analog input signal.
• Using the default values for Boiler
Max Set Point (180°F), Boiler
Min Set Point (140°F), Demand
Minimum (2.5VDC), Demand
Maximum (10.0VDC), the unit will
linearize the set point, as shown in
Figure 36.
8.D.8.b External Firing Rate
With External Firing Rate selected,
the unit will initiate a heat demand
once the analog input signal exceeds
the Demand On value. Once the
demand is initiated, the analog input
signal must be lower than Demand
Off to remove the heat demand. The
external analog signal will activate
stages as shown in Figure 37. In
this control mode, if the unit outlet
temperature exceeds the Auto Reset
High Limit setting, the boiler will
shut down and an "Auto Reset High
Limit" condition will appear on the
Messages screen. Once the outlet
temperature decreases below the
value of (Auto Reset High Limit –
Reset Differential), the boiler will turn
back on at the firing rate set by the
analog input signal.
C O N F I G U R A T I O N
Figure 36. External Set Point Example
Figure 37. External Firing Rate Example
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