The highest sensitivity setting (toward MORE) triggers on first detection. As the control is adjusted
clockwise precipitation must be detected for a longer period to be considered valid. The lowest sensitivity
setting (toward LESS) requires 120 seconds of detection before the unit triggers. If a trace amount of snow
blows onto the grid from a drift or overhang it will likely be melted and evaporated in less than a minute.
Similarly, a very light snowfall may also clear quickly from the grid. If these conditions should be ignored
by the sensor the SENSITIVITY control can be adjusted as required. However, to prevent non-triggering
during a true event, it is recommended that
the user start at highest sensitivity (MORE), then adjust
while monitoring operation over time.
The Low Temperature Cutoff (LTC) option is typically used on snow melting
systems with limited output capacity where melting cannot be maintained at
very low temperature. If selected, the snow sensor will clear a trigger below
5
°
F (-15
°
C) even if snow is still falling. It will resume normal operation
above 9
°
F (-13
°
C). However, the sensor will remember if it was triggered
before the drop below 5
°
F or if snow was detected during the cold period. If
so, the sensor will execute one Delay-Off cycle when the temperature rises
above 9
°
F in order to melt any snow left behind during the cold period. This
is referred to as RECOVER mode.
Care should be exercised in using this mode as the potential
exists for ice to be formed on the melting surface.
THE UNIT MUST BE IN STANDBY/RESET TO CHANGE CONFIGURATION SWITCHES
L'appareil doit être en mode STANDBY/RESET pour modifier commutateurs de configuration
Recommended Switch Settings by Function
Function
Trigger
LD Off
LD On
LTC
DEL
RAIN SNOW
Snow sensor w\o LTC
TT>AT
2 Min
2 Min
OFF
OFF
OFF
ON
Snow sensor w\LTC
TT>AT>5
°
F
2 Min
2 Min
ON
OFF
OFF
ON
Snow controller w\o LTC
TT>AT
30-90 Min
2-6 Hr
OFF
ON
OFF
ON
Snow controller w\LTC
TT>AT>5
°
F
30-90 Min
2-6 Hr
ON
ON
OFF
ON
Precipitation sensor
Not Used
2 Min
2 Min
X
OFF
ON
ON
Precipitation controller
Not Used
30-90 Min
2-6 Hr
X
ON
ON
ON
Rain sensor
AT>TT
2 Min
2 Min
X
OFF
ON
OFF
Rain controller
AT>TT
30-90 Min
2-6 Hr
X
ON
ON
OFF
LT thermostat w\o LTC
TT>AT
2 Min
2 Min
OFF
X
OFF
OFF
LT thermostat w\LTC
TT>AT>5
°
F
2 Min
2 Min
ON
X
OFF
OFF
X = Do Not Care
Fine Adjustment for Efficient Operation
The DS-824C is shipped with the TRIG TEMP and DELAY OFF adjustments in the center position,
representing 39°F (3.9°C) and 60 minutes of Delay-Off time respectively. It is also set for highest
4
SENSITIVITY. Depending on local conditions the user may find that fine adjustment of the controls may
provide more satisfactory operation. If the sensor does not trigger during very wet snows the trigger
temperature may need to be adjusted higher. Constant triggers from snow falling from trees or overhangs
may be reduced by adjusting SENSITIVITY. The Delay-Off time can also be adjusted to provide clean
melt-off without excessive running time. Fine adjustment can both save operating expense and provide
more reliable operation. However, to keep reliability high, always make adjustments in small increments.
Use Care When Replacing the Front Cover. Do Not Pinch the Gasket or Overtighten the Screws.
Manual Override Switch Operation
An override switch mounted on the side is provided for testing and special operational requirements.
Placing the switch in the AUTOMATIC position will allow the sensor to operate normally, activating the
controlled equipment as needed. Placing the switch in MANUAL ON will close the load relay, activating the
controlled equipment. The “STANDBY/RESET” position prohibits triggering of the unit, clears any active
delay timer, and opens the load relay. In order to reduce excessive runtime for the heater
the “Manual
On” mode will remain in effect for up to 40 hours, then return to “Automatic” mode, even if the
switch is still in the “Manual On” position. However, any trigger of the system will restart the 40
hour “Manual On” timer.
You may put the DS-824C back into “Manual On” mode by switching to
AUTOMATIC, then back to MANUAL ON. This will also restart the 40 hour timer.
If the override switch
is placed in MANUAL ON for less than 2 seconds, then switched back to AUTOMATIC the controller
will execute one Delay-Off cycle
. This can be used to clear a frost, hail, or drifted snow buildup without
the danger of leaving the system in a continuous “Manual On” condition. “Standby/Reset” can still be used
to clear this Delay-Off cycle.
Typical Load Wiring
The Yellow load leads are N.O. contacts and do not supply power directly to your load
The relay inside the DS-824C acts as a switch. While not as convenient as directly supplying power for the
load this allows you to operate the DS-824C from one voltage while controlling a load of a different voltage
without adding an external relay or contactor. For example, the DS-824C can be powered from 24VAC but
can directly control a 12VDC signal for a contactor coil or provide a dry contact thermostat-style closure for
a boiler. The following diagrams show some possible wiring schemes for connecting the DS-824C
.
BROWN
BLUE
YELLOW
YELLOW
LOAD
SWITCHED 24V
RETURN
DS−824C
POWER INF
24 VAC/VDC SUPPLY
24VAC/VDC Sensor Supply, Supply Voltage Out
5
