ProMelt Snow Melting PM-224 Detector

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PM 224 Rain and Snow Sensor Controller

The PM-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.

  • Designed for Low Voltage Hydronic and Battery Powered Systems
  • Automatic Activation means Lower Deicing Costs
  • Reliable Rain and Snow Detection
  • 24VAC/VDC Operation, Only 20 VA Required
  • You Choose The Cover Plate Color and Material
  • Full 30A @ 24VAC Control
  • Replaceable Precipitation Sensor
  • Easy Installation, Full Access to Electronics
  • 8 Different Functions, 1 Part Number
  • Adjustable Temperature Trigger Point
  • Adjustable Delay Off Cycle, Selectable 30-90 Mins or 2-6 Hrs
  • Exclusive Adjustable Sensitivity Control
  • Selectable Low Temperature Cutoff
  • Smart "Manual On" Operates for One Delay Off Cycle
  • High Power, Low Price!

The unit is housed in a two gang PVC enclosure. The overall dimensions of the PM-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.

Wiring is performed by terminating your existing wiring to the pre-installed pigtails. The PM-224 is mounted by either attaching the mounting hub to a rigid ½" or ¾" conduit or by installing screws through the four mounting tabs provided

The PM-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 -40oC to +85oC.

The table below outlines the operating modes for the PM-224. Trigger Temperature (TT) is adjustable from 34oF-44oF 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.

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PM-224 Spec and Installation Manual

SunTouch 25 years Warranty


  • Model: 81011700


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