LIMITED WARRANTY
The DS-824C is warranted against defects in workmanship and materials for two years from date of sale.
This warranty does not apply to damage resulting from accident, misuse, or alteration nor where connected
voltage is more than 5% above the configured operating voltage, nor to equipment improperly installed or
wired or maintained in violation of this Owner’s Manual. No other written or oral warranty applies. No
employee, agent, dealer or other person is authorized to give any warranties on behalf of DANFOSS.
CAUTION: Read all instructions carefully before installation.
Save this Installation Manual for future reference.
DS-824C
Units returned for warranty repair cannot be modified from shipped condition and leads must protrude a
minimum of 6 inches from the base conduit hub. Repair costs of a modified unit will be quoted as the unit
must be returned to the original, unmodified condition prior to return shipping. The customer shall be
responsible for all costs incurred in the removal or reinstallation and shipping of the product for repairs.
Within the limitations of this warranty, inoperative units should be returned, freight prepaid, to DANFOSS,
and we will repair or replace, at our option, at no charge to you with return freight paid by DANFOSS. It is
agreed that such repair or replacement is the exclusive remedy available from DANFOSS and that
DANFOSS IS NOT RESPONSIBLE FOR DAMAGES OF ANY KIND, INCLUDING INCIDENTAL AND
CONSEQUENTIAL DAMAGE. Some states do not allow the exclusion or limitation of incidental or
consequential damages so the above exclusion may not apply to you. The warranty gives you specific
legal rights, and you may also have other rights which vary from state to state.
DANFOSS ELECTRIC HEATING DIVISION
TOLL FREE: 1-888-DANFOSS (326-3677)
Option #3 for heating
FAX: 416-352-5981
Visit us on the Internet at: heating.danfoss.us
RAIN/SNOW SENSOR CONTROLLER
INSTALLATION MANUAL
INDICATOR
OFF
POWER
ENCLOSURE TYPE 3R
RAIN/SNOW SENSOR CONTROLLER
INPUT
22−28V AC/DC 500mA 50/60 Hz
CONTROL
30 A 24V AC, 20 A 28V DC
DS−824C
WARNING: NOT FOR HIGH VOLTAGE CONTROL
AVERTISSEMENT: PAS POUR LE CONTRÔLE DE HAUTE TENSION
ACTIVATED
CONTROL SWITCH
MANUAL ON
AUTOMATIC
STANDBY/RESET
Danfoss Electric Heating Division
General Safety Instructions
1. THIS UNIT SHOULD BE INSTALLED, OPENED, AND REPAIRED BY QUALIFIED PERSONNEL
ONLY!
CETTE UNITÉ DEVRAIT ÊTRE INSTALLÉE, OUVERTE, ET RÉPARÉE PAR LE PERSONNEL
QUALIFIÉ SEULEMENT!
2. To avoid shock hazard do not open the front cover with power connected to the DS-824C or any
controlled equipment. Limit input voltage to 22-28 VAC/VDC
Pour éviter la décharge électrique déconnectez toute la puissance avant d'ouvrir la couverture du DS-
824C. Limiter la tension d'entrée à 22-28 VAC/VDC
Moisture Sensor Mounting & Termination
The remote DS-824C precipitation/moisture sensor may be
mounted in a number of ways depending on the application. The
DRIP EDGE
SENSOR
GUTTER
the sensor. We do not recommend laying the sensor on its side
in the gutter. Constant immersion will corrode the grid and the
sensor may miss a windblown snow trigger.
The sensor cable comes preinstalled but may be shortened as
needed. Strip the outer insulation and shield from the cable and
terminate each conductor following the color code printed on
the circuit board for TB-1; (W)hite, (G)reen, (R)ed, (B)lack. The
bare drain wire should be installed into the (S)hield terminal.
Tighten the strain relief on the DS-824C enclosure. If additional
length is required purchase the EX-50 50 foot extension cable.
Erratic operation may result if the proper cable is not used.
Selecting a Mounting Location for the DS-824C Enclosure
The brass cylinder protruding from the bottom of the enclosure is the temperature sensor. For proper
temperature detection the DS-824C must be mounted outdoors, away from furnace vents and other
sources of heat. Note that, when powered, the DS-824C moisture grid will always remain hot. This is
normal. This allows the sensor to continuously melt snow and evaporate both rain and snow from the grid.
The DS-824 can be mounted by screwing the base conduit hub onto an appropriate size free-standing
conduit or by using the mounting holes in each corner of the enclosure.
sensor head operates at a safe 12VDC and can withstand
immersion in water. For roof and gutter deicing applications the
sensor head may be mounted against the back of the gutter with a
1” “C”-style conduit clamp. Allow part of the sensor grid to be
exposed to snowfall. The sensor will initially trigger when snow
starts falling and will remain triggered as long as the roof/gutter
heater continues to drip melted snow from the roof edge when
temperatures are below freezing. The sensor may also be installed
inside and near the top of the downspout using a 1” conduit
hanger and mounting plate. As water is melted in the gutter it will
run to the downspout,
DOWNSPOUT
hitting and retriggering
SENSOR
MOUNTING
PLATE
1" CONDUIT
CLAMP
2
External Control/Monitor Operation
Pin Color Function
1 White GND/Common
2 Red Deice On Mon A
3 Orange Deice On Mon B
4 Black Manual On
5 Green Standby/Reset
This relay, rated at 24 VAC/VDC at 400 ma, will close with the load relay and can be used to externally
monitor activation of the sensor. This terminal block is also the connection point for installing a CDP-2
interface cable.
The DS-824C provides external control/monitor capability.
Shielded cable can be connected to TB2 to access this feature.
Connecting Black (4) to White (1) will activate the “Manual On”
function. Connecting Green (5) to White (1) will activate the
“Standby/Reset” function. See the “Manual Override Switch
Function” for a description of these modes. The Red/Orange
(2/3) leads are connected to an internal low power monitor relay.
Power & Activation Indicator
A green lamp shines through a lens on the cover of the DS-824C to indicate operational status. If this lamp
is OFF the DS-824C is not receiving power. If this lamp is steady ON the DS-824C is powered but not
triggered. If this lamp is FLASHING the DS-824C is powered on and triggered, the main relay is closed,
and attached equipment should be activated. Note that, even though snow or rain may have stopped, the
DS-824C indicator will continue to flash during the Delay-Off drying cycle.
Preseason Snow Detection Testing
It is always a good idea to test the operation of the DS-824C prior to the winter season. Procure some
clean water and, if the outdoor temperature is above the trigger point, a can of spray component cooler.
Clean the moisture grid following the procedure outlined above and allow it to dry. Apply power to the DS824C, drip some of the water onto the moisture grid, then spray the temperature sensor protruding from the
base of the enclosure with the component cooler. Once the temperature sensor has reached the trigger
point with water still present on the grid the DS-824C will activate. The user should hear the internal
control relay close and see the green lamp blink. Proper operation has been confirmed. Allow the grid to
dry completely. To clear the Delay-Off timer place the override switch into “Standby/Reset”, and then back
to the “Automatic” position.
Moisture Grid Maintenance & Replacement
It is recommended that the DS-824C be powered down and the grid wiped clean with clear water at least
once every 4 months. Heavy deposits may be removed using a non-metallic scouring pad (Scotch-BriteTM
or equivalent.) However, after a number of years, the corrosive elements left behind when water is
evaporated out of the moisture grid will eventually damage the grid rings. The moisture grid can be easily
replaced by ordering and installing an MG-6 “Moisture Grid Assembly.” Reference the “Moisture Sensor
Mounting & Termination” section for information on replacing the precipitation grid.
Use Care When Replacing the Front Cover. Do Not Pinch the Gasket or Overtighten the Screws.
Maintain your enclosure's integrity and improve reliability
Specify the DANFOSS EX-50 when precipitation sensor extension is required
7
24 VAC/VDC SENSOR SUPPLY
SECONDARY POWER SUPPLY
24 VAC/VDC Sensor Supply, Secondary Voltage Out
DS−824C
POWER INF
BROWN
BLUE
YELLOW
YELLOW
LOAD
DO NOT DRILL HOLES THROUGH THE ENCLOSURE FOR MOUNTING!
NE FONT PAS LES TROUS DE FORET PAR LA BOÎTE POUR LE SUPPORT!
This can allow water into the enclosure. It is recommended that a weatherproof condulet or junction box be
mounted below the DS-824 for termination of the power and load pigtails to the building wiring.
Use Care When Replacing the Front Cover. Do Not Pinch the Gasket or Overtighten the Screws.
CONTROL/MONITOR JACK
CONFIGURATION SWITCH
TEMPERATURE ADJUST
DELAY OFF ADJUST
SENSITIVITY ADJUST
GRID TERMINAL
SWITCH JACK
INPUT POWER
LOAD
DS−824C
POWER INF
BROWN
BLUE
24 VAC/VDC SUPPLY
24VAC/VDC Sensor Supply, Dry Contact Thermostat-Style Control
These are just some of the possible wiring schemes that can be used to connect the DS-824C to your load
for control. Remember, these are only suggestions. You should always consult a qualified
electrician or inspector to assure conformance with applicable local and national
electrical codes! Remember, this device is designed for low voltage use only!
6
YELLOW
YELLOW
LOAD
Setting the Configuration Switches and Adjustments
The following paragraphs and table outline the operating modes for the DS-824C
and explain the functions of the adjustments. Trigger temp (TT) is adjustable from
34°F-44°F (1°C-6°C) using the TRIG TEMP control. When ambient air
temperature (AT) is below this setting precipitation is assumed to be snow. When
above this setting, precipitation is assumed to be rain.
The DEL configuration switch activates the Delay-Off drying cycle timer on the DS824C. The timer allows the DS-824C to continue to operate and dry the heated surface through
evaporation once precipitation has stopped. The drying cycle reduces the
chance of moisture left behind refreezing into ice. This timer is restarted by
each sensor trigger. Therefore, the DS-824C will continue to operate as long
as it is triggered, then for the Delay-Off period once the trigger clears. All
"sensor" modes (DEL off) provide a 2 minute Delay-Off time. When in
"controller" mode (DEL on) the Long Delay (LD) configuration switch
determines the time span of the drying cycle. The Delay-Off time can be adjusted from 30-90 minutes (LD
Off) or 2-6 hours (LD On) using the DELAY OFF control.
The DS-824C precipitation sensor is very sensitive and can detect a single snow flake or rain drop.
However, if the DS-824C is mounted in an area susceptible to high winds, overhanging trees, or blowing
ground snow, nuisance triggering 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 and compares cleared time with triggered time.
3
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
Snow controller w\o LTC TT>AT 30-90 Min 2-6 Hr OFF ON OFF ON
2 Min 2 Min ON OFF OFF ON
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.
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
DS−824C
POWER INF
BROWN
BLUE
24 VAC/VDC SUPPLY
24VAC/VDC Sensor Supply, Supply Voltage Out
5
SWITCHED 24V
YELLOW
RETURN
YELLOW
LOAD
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