Application Guide

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Shared Boiler and Mixing Valve with Optional Tandem Sensors A670-4 Mechanical
670 Application Settings
Setting Name Value
Application Mode Mixing
Mixing Type Floating
Boiler Type Enable
Optional 654 Application Settings
Setting Name Value
Application Mode 090
A1 = Normally Closed Freeze Protection Aquastat
B1 = Boiler Enable
HX = Heat Exchanger
M1 = Actuating Motor 741
P1 = System Pump
P2 = Heat Exchanger Pump
S1a, S1b = Snow/Ice Sensor 090 or 094
S4 = Outdoor Sensor 070
S5 = Boiler Return Sensor 082
S6 = Mix Supply Sensor 082
V1 = 3-Way Mixing Valve 710 through 714
X1 = Transformer 009
Legend
670
Optional
654
S4
S5
P2 P1
S6
V1
HX
M1
S1a
S1b
A1
Description
The WiFi Snow Melting Control 670 operates a snow melting zone warmed from a heat source that is shared with other loads
in a building. The system uses a mixing valve to regulate the water temperature and a heat exchanger isolates the glycol-
filled snow melting system loop from the water-filled main heating system. The 670 is paired with a Snow Melting Control 654
to provide Tandem Snow/Ice Detection using a Snow/Ice Sensor 090 or 094. Tandem sensors double the detection area to
provide increased reliability and redundancy in case of sensor failure.
• The system pump operates continuously when heating the slab during melting/idling/storm operation.
• The slab temperature is controlled by adjusting the mixing valve position.
• When the mixing valve is open, the heat exchanger pump and the boiler enable are on.
• The slab target is determined by the melting/idling/storm setpoint and by the measured outdoor air temperature.
• A normally-closed aquastat protects the heat exchanger from freezing by shutting off power to the system pump.
• Either snow/ice sensor will start the melting operation if snow or ice is detected. Both sensors must be dry in order to
stop melting.