Flashing "SUPPLY" Light on SCP-120 (ETI APS-3C)


Why is the "SUPPLY" light flashing on the SCP-120 (ETI APS 3-C)?  What do the lights mean?               

• SUPPLY (green) shows that power is present.

• SUPPLY (green, blinking) means either the pavement temperature sensor is missing from the system or is not functioning. The pavement temperature sensor is included and must be connected to pins 10 and 11 for proper operation.  A good ohm reading is 95-107 Ohms on 200K ohm scale.

• SNOW (yellow) shows that there is a snow/ice signal originating from at least one of the CIT–1, GIT–1, and/or SIT–6E sensors attached to the system.

• HEAT (yellow) shows that there is a call for heat. This happens during snow and for the Hold-On Time thereafter or when the Heater Cycle switch is operated

• EMC (yellow) shows that the interfaced Energy Management Computer is presently overriding local system control.

• TEMP LIMIT (red) shows that either the pavement temperature is above the set High Tem- perature Limit and there is a call for heat or the ambient air temperature is above the High Temperature Limit setting. The APS–3C can be configured to monitor slab temperature or ambient air temperature but not both. 


Written by Scott Rosenbaum
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