Snowmelt system
From Wikipedia, the free encyclopedia
A snowmelt system is used to remove snow and ice via embedded electric cables or hydronic PEX tubing. Common areas for snowmelt systems are: driveways, walkways, parking areas, stairways, loading docks, and around car washes.
A snowmelt system is usually installed during the original construction in concrete, asphalt, or under pavers. Retrofit electric systems can also applied to existing concrete or asphalt using saw cutting technology.
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Advantages
Maintenance
Arguably, an electric snowmelt system requires less maintenance than a hydronic snowmelt system because there are no moving parts or corroding agents like water used to operate the system. A snowmelt system may extend the life of the concrete, asphalt or under pavers by eliminating the use of harsh salts and chemicals, and damage from snow removal devices.
Aesthetics
A snowmelt system is not visible when installed and does not add extra height or require additional materials than a standard concrete, asphalt or under paver pour.
Efficiency
Most new snowmelt systems operate in conjunction with an automatic activation device that will trigger the system on when it senses precipitation and freezing temperatures. These types of devices ensure the system is only on during useful periods and eliminates wasteful energy consumption.
Environmentally friendly
Snowmelt systems are environmentally friendly compared to the use of salt and chemicals to melt the snow, which causes calcium chloride to run into rivers and other critical water supplies. Current systems are more cost effective in the long run than continual salt dumping and removal, and reduce waste by extending the life of the cement.
Opponents argue that snowmelt systems can impact the environment negatively by warming the atmosphere.
Low operation costs
A 35-50 watt per sq. ft. electric snowmelt system can melt snow on a 300 sq. ft. area for under $.50 per continuous hour of operation. The time to melt snow off a driveway (per storm) is usually just a few hours.
An hydronic snowmelt systems costs roughly $.14 to $.25 a sq. ft. to operate, depending on your location.
Technologies
Electric snowmelt systems
Electric snowmelt systems are composed of three basic components: heating cable, control unit and an activation device.
The heating cable is built to withstand harsh conditions to make it suitable for outdoor usage. The cable should be UL listed and many consist of a twin conductor with DEP/XLPE insulation, polyolefin jacketing (providing flexibility and UV protection). Many cables are rated at 220° F and produce around 30-50 watts per square foot.
The control units are wall-mounted control panels. The controls include line and load terminal blocks and operating contactors. Many control units come equipped with a 4-hr timer for manual operation of the snowmelt system.
The activation device is a sophisticated aerial-mounted device that activates the snowmelt system when it senses precipitation. High-end activation devices feature: adjustable temperature trigger points, adjustable delay off cycle, and upgradeable remote activation. The activation device enables the snowmelt system to run 100% automated.
Hydronic snowmelt systems
The heating element in a hydronic system is a closed-loop tubing made of a flexible polymer or synthetic rubber that circulates a mixture of hot water and propylene glycol (antifreeze). The fluid is warmed to temperatures of 140 to 180 F to warm surrounding concrete/asphalt/concrete pavers and melt snow and ice. Technology for hydronic snowmelt systems is based on the same technology as underfloor heating systems.
Installation
Installation for both hydronic and electric snowmelt systems should begin as close as possible to the electrical. Use care to ensure the tubing and cables are spaced evenly over the entire area to be heated. It is not required to install the heating cables or tubes beneath the entire surface of the area. More economical installations heat only a pair of 2-foot-wide tire tracks on a driveway or a 3-foot center portion of a sidewalk, etc.
Electric snowmelt systems
Concrete – new pour
Proceed with standard method of pouring concrete. The heating cable is secured to the re-mesh with wire ties at intervals of 3-6”, concrete is then poured on top of the heating cables. Spacing of cables should never exceed 6”.
There should be a minimum of 2” and max 4” of concrete covering the heating cables. Concrete mixture must not contain sharp stones as these may damage the cable. The concrete should be allowed to set for 30 days before the heating cables are turned on. For this reason, the best installation time is during summer months.
Asphalt - new
Not all snowmelt systems can withstand the heat and compression of newly poured asphalt. Check manufacturer recommendations before proceeding with an asphalt installation. The cable is laid out on the base surface (usually sand), and the asphalt is hand shoveled onto the heating cable and base surface.
Insulation is recommended, but not required. One-inch rigid insulation can be installed underneath the base surface, or it can be laid on the base surface and the GX cable can be secured on top of the insulation.
Brick paver – new
Installing a snowmelt system under brick pavers is the easiest method of installation, and cable heating systems are the most effective systems for pavers. The cable is simply laid out on the base surface over the area to be heated, and the pavers are installed as normal over the cables.
The snow sensor is mounted by either attaching the mounting hub to a rigid ½" or ¾" conduit or by installing screws through the mounting tabs. Installation will vary between manufacturers.
Hydronic snowmelt systems
The most crucial part of a successful hydronic heating system depends on proper tube spacing and layout. It is recommended to lay the tubes in a spiral or serpentine pattern to help distribute the heat evenly. Specification for spacing will vary between manufacturers. A faster rate of snowmelting will require closer spacing of tubing, typical spacing is 6”. Another heat factor is the amount of insulation used under the slab.
Like electric snowmelt systems, hydronic snowmelt systems must be installed in the base surface material (sand or compacted crush stone). Ensure the subgrade is well compacted before beginning tube installation. Tubing can be fastened with cable ties to either the re-mesh, re-bar or below slab insulation.
Hydronic tubes should not be placed directly on top of solid bedrock; this will cause the heating tubes to conduct heat into the earth.
References
[1]Woodson, R. Dodge. Radiant Floor Heating. New York: McGraw-Hill, c. 1999.
External links
Radiant Heat Systems for Carwash Owners
[1]
Radiant Heated Driveway Systems; Safe and Energy Efficient
[2]
