Ds−824, Recommended switch settings by function, Typical wiring – King Electric DS-824 User Manual
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in "controller" mode (DEL on) the Delay Off time can be adjusted from 30-90 minutes (LD Off) or 2-6 hours
(LD On) using the “Delay Adjust” control. Note the “Forced Manual On” function at the low end of the Delay
Adjust control. The relay will close when this area is entered and open when exited. Only use the “Forced
Manual On” function for testing. Never leave the Delay Adjust control near the “Forced Manual On” area
during normal operation.
The Low Temperature Cutoff (LTC) option is typically used on snow melting
systems with limited output capacity. If selected, the sensor will not trigger if
precipitation is initially detected below 15
°F. However, if the deicing system
has been activated, precipitation continues, and the ambient temperature
drops below 15
°F, LTC will be ignored. This assures that water on the
surface from melting snow will not immediately refreeze into ice as a result of
deactivating the deicing system.
The DS-824 precipitation sensor can detect even a single snow flake or rain
drop. However, if the DS-824 is mounted in an area susceptible to high winds,
dripping condensation, or blowing ground snow, nuisance triggering of the
sensor may occur. While proper placement is the best remedy, the Sensitivity
control can also be used to reduce nuisance triggering. An internal timer
checks the precipitation sensor for moisture once per second and keeps a
running count of the number of continuous seconds the grid is triggered. The highest sensitivity setting
(toward More) requires 3 seconds of continuous precipitation detection before the unit triggers. The lowest
sensitivity setting (toward Less) requires a full 4 minutes 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 within 1-2
minutes. 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.
POWER MUST BE CYCLED FOR CONFIGURATION SWITCH CHANGES TO TAKE EFFECT
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>15
°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>15
°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
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Typical Wiring
The sensor supply voltage can be in the range of 22-28 VAC/VDC. The supply input leads (IN A and
IN B) are not polarity sensitive and can be connected to either polarity of a DC supply. A standard
24VAC 20VA HVAC-type transformer will supply enough power for the DS-824 and an optional CDP-2
indoor control/display panel.
The two load leads of the DS-824 do not supply power directly to your load. The relay inside the DS-
824, like a switch or thermostat, is used to switch a voltage of your choice. While not as convenient as
directly supplying power for the load this allows you to operate the DS-824 from one voltage while controlling
a load of a different voltage without adding an external relay or contactor. For example, the DS-824 can be
powered from 24VAC but can directly control a 12VDC signal for a contactor coil or can operate from
24VAC and provide a dry contact thermostat-style closure for a boiler. The following diagrams show some
possible wiring schemes for connecting the DS-824 to your load. For clarity the GROUND lead is not
shown.
24 VAC/VDC SUPPLY
IN A
IN B
YELLOW
YELLOW
LOAD
DS−824
SWITCHED 24V
RETURN
24VAC/VDC Sensor Supply, Supply Voltage Out
IN A
IN B
YELLOW
YELLOW
LOAD
DS−824
24 VAC/VDC SUPPLY
24VAC/VDC Sensor Supply, Dry Contact Thermostat-Style Control
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