Snow Melt PowerMat 120V, 3 x 15 ft., 45 sq.ft., 18.75A


Snow Melt PowerMat 120V, 3 x 15 ft., 45 sq.ft., 18.75A
Part Number: WHMA-120-0315
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Support Questions

Electric-resistance heating cables and systems have no polarity. This includes all current WarmlyYours heating elements.

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Yes. The manufacturer's splice that connects the heating element to the cold lead should be entirely embedded in a noncombustible material (like asphalt, concrete, or mortar) within the outdoor surface that is being heated. 

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GFEP is the National Electric Code (NEC) required protection for fixed outdoor deicing and snow-melting equipment, which may be accomplished by using circuit breakers equipped with ground-fault equipment protection (GFEP) of 30 mA. It is important to understand that this required equipment protection is NOT the same as a 5 mA GFCI used for personal protection.

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To ensure optimal performance, snow melting heating elements should be installed so that they are consistently 2"-3" from the finished surface. For installations using pavers, the maximum thickness for pavers installed over heating elements is 2.5". 

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Power requirements are measured in Amps and based on three factors: the watts per sq. ft. of the snow melting cable or mat, the area powered and the voltage used for the application. Our product is rated at 50 watts per sq. ft., so that is a constant factor. Most snowmelt projects are powered with 240V AC – not all, but most. The one factor that is always variable is the area to be heated/powered. That is based on your project. For a point of reference, let’s use the example above of a 350 sq. ft. concrete patio.

The formula is (50 W/sq. ft. x area of 350 sq. ft.) / V (240V) = Amps, so 17,500 / 240V = 72.9 Amps

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Yes, you can retrofit a snow melting system into a preexisting driveway made of concrete or asphalt. You can do this by using an appropriate tool to cut properly spaced lines (or trenches for tire tracks heating) in the surface. Then you can place the the heating elements in the lines (or trenches) before sealing them with either hot asphaltic sealer for asphalt retrofits, or backer rod and expansion joint sealer (SikaFlex or similar) for concrete retrofits. Of course, you'll want to make sure this step is done in accordance with the filler manufacturer’s recommended procedures. Check out our snow melting retrofit guide for more information about this process. 

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If a cable is damaged during installation, recheck the system for continuity and confirm the integrity of the insulation with a megohmmeter, or "megger" tester, referring to the installation and testing instructions. If the cable fails any of these tests, take the following actions: clear a 3 foot square working area around the damaged section of cable, and record the cable part number from the UL tag and the location where you purchased the product. Call WarmlyYours with the above information. WarmlyYours will provide further assistance and supply a splice kit suitable for repairing the particular cable.

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To calculate the system's approximate operating costs, multiply the total kilowatts of the system by the cost per kilowatt in your area. Let's use the example of a 350 sq. ft. of concrete patio (residential application), with 240 VAC.

Total Watts: multiply area in sq. ft. x 50 Watts
350 x 50 = 17,500 Total Watts

Kilowatts: (the unit in we purchase electricity) take the Total Watts and divide by 1000
17,500 Total Watts / 1000 = 17.5 Kilowatts.

Kilowatt Rate: use the national average of .12 cents per Kilowatt-hours so how much do we pay for 17.5 kWatts?
17.5 kW x .10 = $1.75 for every full hour of operation.

Hours of Operation: We use a typical 6 hour snowfall for our example.
$1.75 x 6 hours = $10.50 for that snowfall.

All of this will vary due to "after-run time". "After run time" is where the system remains on extra hours after the snow has completed falling, to ensure complete pavement snow melting and drying.

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The most common spacing for snow melting systems is 3“ from wire to wire. However, we can design snow melting systems based on your local climate and weather expectations that might have different cable spacings to ensure the most efficient system possible. We also offer snow melting mats with 3" and 4" spacing.

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Yes, as long as the paver isn't resting on exposed cable. The cable has to be embedded according to the installation cross section drawing.

Cover to an uncompacted depth of 1.5” (38mm), leveled to grade. A compactor that's applicable to the thickness and application can be used to compact the sand. The paver installer(s) must take care not to walk on the hot-cold factory splice and to avoid damaging the Heating Cables with shovels or rakes. At no time shall the compactor directly contact the wire.

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Yes, WarmlyYours Snow Melting Heating System can be installed with quartzite stones. Start with 4” to 8” (102mm to 203mm) of crushed rock aggregate base. Rebar or wire mesh should be staked on top of this base and then heating cables or mats will be tied to this mesh with plastic zip ties. Heating system needs to be covered with 1” to 1.5” (51mm to 76mm) of finished mortar or sand. Stone Pavers will be installed on top but must NOT be any thicker than 2.5” (63.5mm). See cross-section in the documents section and in the manual.

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Yes, the leads are not direct burial rated. The leads must be protected in compliance with local electrical codes.

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Yes.  Information on how to install under permeable pavers can be found in section 4.6 of the Installation Manual

.  Excavate 18” and fill with #2 aggregate/stone.
.  4” of #57 stone
.  2” of #9 stone to serve as the paver setting bed.
.  The heating cable is installed within the #9 stone layer.

To maximize the amount of heat transferred from the heating cable to the pavers, the stone separating the cable and pavers needs as much contact with both as possible. Crushed stone with fines transfers the most heat, but doesn’t drain, so it isn’t used in a permeable installation. Instead, smaller drainage stone (#9) is used because it has more contact with the cable and transfers more heat than larger stone.
Note: do not install the cable at the top so it’s touching the pavers. Potential movement by the pavers over time could wear through the protective coating of the cable and short out the entire installation.

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A properly designed and installed system will handle most snow melting demands. Some snow events may have a very rapid snow fall rate, and some may not. No 2 events are ever exactly the same. Our system typically can melt 1" - 3“ of snow per hour, on average. However, it is important to understand that a system may not melt snow at very cold temperatures. This is simply because the system cannot generate enough BTUs to overcome the heat loss generated by very low temperatures.
In order to estimate cost of operation, the Warmly Yours Electric Snow Melting Operating Cost Calculator is a useful tool that can help illustrate what it would cost to operate the system.

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No, a sensor is not required with the snow melt system. However, certain automatic controllers require a temperature/moisture sensor to sense atmospheric conditions and may also require an in-slab, high temperature limit sensor to be installed (notably, asphalt installations).

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Yes. The NEC requires 2“ minimum of non-combustible material below, and 1.5“ minimum of non-combustible material above the heating cable.

The drawback is whether or not the pervious concrete will fail under load, thereby damaging the heating cable and voiding warranty. The cable should be attached to rebar in this case to insure the strongest support.

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Test the Snow Melt cable or mat using a digital ohm meter as shown here.  Also test the snow melt cable or mat using a Mega Ohm meter as shown here.  And this video shows how to do the Ohm test.

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Reflective insulation is not effective with conductive heating, which is how embedded floor heating and snow-melting systems transfer heat. To be effective, the reflective insulation surface needs to face an air space (air gap), which allows the reflected heat to be redirected.

An effective solution considers the insulating material's R-Value. This is the rating of a material's insulating properties. The "R" stands for "resistance" and refers to the material's resistance to heat flow, or temperature conduction.

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A 2 pole single-phase 240V circuit works by continuously monitoring the current flowing through both hot wires of the circuit. If it detects even a slight imbalance between the current on each hot wire (indicating a ground fault), it will quickly trip, cutting off power to the circuit. Essentially, it compares each leg of the 240V circuit and trips if they are not precisely equal.

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Yes, the sensor wires may be trimmed.  Most local code requirements call for 6“-7“ of extra wire from the gang box.

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Specifications

Electrical

Amps 18.75 A
Ohms 6.4 Ω
Voltage 120 V
Watts 2250 W
Watts Per Sq. Ft. 50

Warranty / Certifications

Approvals cCSAus Listed
Warranty 10 years

Performance

BTU Per Hour 7677 Btu
Heated Coverage 45 ft²

Product Dimensions

Cold Lead Length 20′
Coverage 45 ft²
Heating Element Spacing 3″
Heating Element Thickness 5/16″
Height 0.3125″
Length 15′
Size 3′ x 15′
Size and Power 3x15 ft - 50 W/sq.ft.
Weight 10.6 lbs
Width 3′

Appearance

Color Green

Identifiers

Product Line Name PowerMat
SKU WHMA-120-0315
UPC (GTIN-12) 881308020576

Installation

Surface Types Asphalt, concrete or in mortar under pavers

Logistics

UNSPSC Code 40101842




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