WarmlyYours SCP-120 - Manual (Page 4)

Initial Settings
When fi rst placing the system in service, the hold-on time should be set to an initial value.
Three to fi ve hours is suggested as a starting point. If the heaters turn off before the snow is com-
pletely cleared and the melt water evaporated, increase the hold-on time by an hour or two. If the
heaters operate for several hours after the pavement is clear and dry, decrease the hold-on time by
an hour. Continue this process until satisfactory performance is achieved.
The small amount of energy wasted by a slightly excessive hold-on time is secondary to com-
plete snow clearing and melt water evaporation. Incomplete operation is not desirable since
this can result in re-freezing melt water which creates a slippery ice fi lm.
If The System Turns Off Too Soon
If the system turns off before the pavement is clear and dry, toggle the heaters on for the hold-
on using the HOLD-ON switch on the front panel of the control. Repeat as many times as is neces-
sary until the pavement is clear and dry. If the heaters remain operating after the pavement is clear
and dry, terminate the hold- on cycle with the HOLD-ON switch. Normal operation resumes if it starts
snowing during hold-on.
Energy Management Computer (EMC) Interface
The SCP-120 interfaces an EMC via relays. Inputs from the EMC include OVERRIDE ON
which causes heater operation and OVERRIDE OFF which inhibits heater operation. These functions
are independent of weather conditions and the status of the hold-on timer. The interface provides fi ve
system status contact closures for the EMC including SUPPLY, SNOW, HEATER, ALARM and TEM-
PERATURE LIMIT.
Absent signals from the EMC, the SCP-120 control panel controls the heaters based on envi-
ronmental conditions. Automatic snow melting control is the default condition of the system.
SCP-120 Front Panel
The SCP-120 has indicators, adjustments and a switch for local control of the snow melting
system. Indicators include LED lights for SUPPLY, SNOW, HEAT, EMC, TEMP LIMIT and GFEP.
Adjustments provided allow for the calibrated adjustment of system HOLD-ON time from zero to ten
hours (or off) and TEMP LIMIT for the high-limit temperature adjustment with a range of 40° to 90°F
(4° to 32°C). The HEATER TOGGLE switch allows for the starting and stopping of a manual HEATER
CYCLE.
Figure 2 shows the SCP-120 front panel layout.