DS-224 Rain/Snow Sensor Controller

The DS-224 is an advanced low voltage version of the DS-2B. It is primarily designed for hydronic pavement snow melting applications and battery/solar powered railroad deice and lubrication control. The 24VAC/VDC supply means less expensive wiring, no requirement for conduit, and lower installation costs.

The unit is housed in a two gang PVC enclosure. The overall dimensions of the DS-224 are 4¾”(120) x 7″(178) x 2¾”(70). The unit weighs 2 pounds. The user may access all electronics by removing the four front cover screws.

The DS-224 can be powered from a 22-28VAC/VDC source. Peak power consumption is 15 VA at startup, 8.5 VA steady state triggered, 5 VA steady state untriggered. Power input is polarity protected for a DC supply. The unit provides a single 24VAC/30A or 24VDC/20A normally open load contact set. This contact set is paralleled with a low power contact set to provide remote control and activation monitoring. Operational temperature range is -40°F to +185°F (-40°C to +85°C).

Trigger Temperature (TT) is adjustable from 34°F-44°F (1.1°C-6.6°C) using an on-board control. When ambient air temperature (AT) is below this trigger point precipitation is assumed to be snow or freezing rain. When above the trigger point, precipitation is assumed to be rain.

“Delay Off” refers to the internal drying cycle timer of the DS-224. The timer is used to allow the DS-224 to dry the heated surface through evaporation once precipitation has stopped. The drying cycle reduces the chance that moisture left behind by the melting process will refreeze into ice. This timer is restarted by each precipitation detection. Therefore, the DS-224 will continue to operate as long as precipitation and trigger temperature is detected, then for the “Delay Off” time once rain or snow stops. It is assumed that, when operating as a sensor, the DS-224 is supplying an activation signal to an external control system. All “sensor” modes provide a minimum 2 minute closure, reducing cycling of the external controller. The Delay Off cycle has been extended for hydronic applications and is determined by the Long Delay (LD) switch setting, DEL switch setting and the DEL adjustment. Delay Off is 30-90 minutes in non-LD “controller” mode and 2-6 hours in LD “controller” mode.

The Low Temperature Cutoff (LTC) option is typically used on deicing or snow melting systems with limited output capacity. If selected, the sensor will not trigger if precipitation is detected below 15°F(-9° C). However, if the deicing system has been activated, precipitation continues, and the ambient temperature drops below 15°F, (-9° C) LTC will be ignored. This assures that water left behind on the surface during the heating cycle will not immediately refreeze into ice as a result of deactivating the deicing system.

The DS-224 also features a new innovation, a Trigger Sensitivity Adjustment. Previous units have always detected and triggered on the first drop of rain, the first flake of snow. While this has always provided a highly reliable detection it may create “nuisance” triggers in some installations. Snow blowing off a roof or falling from a tree could cause the system to activate for a delay cycle when its not needed, increasing operating costs. The sensitivity adjustment allows setting the number of seconds the precipitation grid must see continuous rain or snow before the sensor is triggered and ranges from 3 seconds to 4 minutes. A higher sensitivity setting assures quick detection no matter the conditions. A lower sensitivity setting will allow a few stray drips of rain or flakes of snow to be ignored but a heavier downfall will trigger the system.

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The DS-8 Rain/Snow Sensor Controller