Snow and Ice Melting Systems: Control Strategies (Part III)

 

As cool (hot?) as it is to have a snow and ice melting (SIM) system, selecting the right control strategy is the key to success. Otherwise, the system won’t operate as expected, or it might waste energy operating when not required.

 

 

Control Options

 

Available SIM control devices fall into a few categories:

 

1. GOOD: Semi-automatic electronic control

 

A semi-automatic control requires a person to activate the system manually, sometimes using a delay, and to set the run-time. This system provides electronic slab temperature control by modulating the heating fluid temperature or by cycling the circulator/heat source. This control uses temperature sensors to monitor supply/return fluid temperatures. The installer sets the maximum fluid temperature delta, typically to 25°F (14°C), to help prevent thermal shock to the slab. A slab sensor installed in the melting area senses slab temperature (pre-set by the installer) to prevent overheating, which is good for the longevity of concrete and efficiency of the system.

 

Summary: An affordable type of control with good safety for many residential applications

 

 

 

2. BETTER: Fully automatic control with moisture sensing

 

A fully automatic system uses a moisture sensor, with an integrated outdoor temperature sensor, placed in the melting area. When the sensor detects cold air temperature and moisture, then it activates the melting system. (How does it detect the moisture in dry snow or ice? First, it melts the snow or ice with the integrated heating element. Then, the melted water conducts low-voltage electricity across the metal rings on the sensor surface. If it’s cold and there is moisture on the sensor, then it must be snowing or icing.)This system does everything the “semi-automatic” system does, plus more. For instance, automatic controls allow the option to idle the SIM area, keeping it warm between snowfalls to improve response time when the next snowfall begins.

 

Summary: Automatic controls can improve safety and save energy for residential and commercial systems.

 

 

Outdoor moisture sensor within a ramp for a hotel parking garage.

Outdoor moisture sensor within a ramp for a hotel parking garage. Click here to learn more…

 

 

3. BEST: REHAU Smart Controls (RSC) system with weather anticipation

RSC is a PC-based system that accesses weather forecast data to predict incoming snow or ice and activate the system just in time.

 

When installed, the latitude and longitude coordinates are used to get the closest weather information from either National Weather Service or Environment Canada. The system can be programmed to warm the melting area a certain amount of time before the snowstorm begins, so that it’s ready to melt the first snowflake. With these capabilities, owners have ultimate control for safety, efficiency and protection of heated areas.Read more.

 

Summary:  Smart controls offer the ultimate performance for critical outdoor areas.

 

 

videostill-devices-360874

Click here to learn more…

 

 

Outdoor Moisture Sensor Installation

 

The outdoor moisture sensor is the only way that the automatic control knows when there is snow or ice. If it doesn’t get the weather exposure it needs, then it may not activate the SIM system.  The sensor must be in the driveway, ramp, sidewalk–the critical area–to sense the worst-case snow exposure. The cable is 65 ft (20 m) long and can be extended, so there is no need for the sensor to be close to the mechanical room. In other words, don’t position the sensor under a parked car, close to a roof eave, under a deck, beside a bush or near other “protection” from blowing snow. You also don’t want the sensor installed where melting snow from a roof might activate it even if the driveway is dry.

 

 

 

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Here’s a sensor socket. Click here to learn more…

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Here’s another sensor socket. Click here to learn more…

 

 

 

Therefore, be sure to install the moisture sensor in a location where it will detect the most important moisture, such as:

 

 

– The area most likely to be hit with falling or blowing snow

 

– The last place to be warmed by sun – shady areas

 

-The last place to be dried after drainage – lower areas

 

 

Make sure the location you choose gets “cleaned” by drainage (doesn’t easily get covered by dirt) and  is level with the mounting surface (not in a dip or on a rise).

 

 

Typical SIM outdoor moisture sensor with cable.

Typical SIM outdoor moisture sensor with cable. Click here to learn more…

 

 

Zoning

In large facilities with distinct weather areas (e.g.,  East and West ramps), zoning may be achieved through separate sensors connected to separate circulators for each area. Some large SIM systems have three or more distinct zones.

 

In large residential projects, using separate manifolds  with their own dedicated circulation pumps for each area can allow a different type of zoning flexibility. For instance, a homeowner with a large SIM system could have a manual switch to deactivate the circulator for “guest parking,” operating that area only when needed.

 

This SIM system has seven distinct zones, each with its own manifold (not shown) and circulator pump in a range of sizes based on size of zone.

This SIM system has seven distinct zones, each with its own manifold (not shown) and circulator pump in a range of sizes based on size of zone. Click here to learn more…

 

 

 

By Lance MacNevin