Ice and Snow Melting

8/2/2019 Ice and Snow Melting

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2.1 General informationDEVIs ice and snow melting systemconsists of deviflex or devi-iceguard heating cables ordevimat heating mats, devireg

thermostats, and installation

accessories. DEVIs ice and snowmelting systems are applied for roofconstrucions and ground areas.

Provides safety

DEVIs ice and snow melting systemis designed to provide safety forpeople, vehicles, and buildingssafety through safe walking anddriving during winter and safety interms of less damage to buildings.

The system is flexibleDEVIs ice and snow melting systemworks well with most common sur-face covering materials such asasphalt, concrete, and tiles.Besides, it can clear ice and snowfrom all types of roof constructions,roof gutters, downpipes, and valleygutters.

Works automatically

DEVIs ice and snow melting system

operates fully automatically. It auto-matically registers the need for iceand snow melting and it switchesthe heat on and off as required.

An economical alternative

The devireg thermostats withadvanced moisture sensors ensurethat optimal results are achievedwith the least possible amount ofenergy. The costs of installing andrunning DEVIs ice and snow meltingsystem are low when the preventive

advantages of the system are takeninto consideration, i.e. snowshovelling and salting becomesunnecessary. Furthermore, therepairing costs caused by ice, snowand salt are saved.

Provides comfort

With DEVIs ice and snow melting

system the area is kept free fromice and snow at all times so heavysalting, snow shovelling or frostdamages are avoided.

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2.2 Ground applicationsThe most common DEVI ice andsnow melting applications onground are car parks, driveways,pavements, outdoor steps, loadingplatforms, and bridges.

Installed output

When the required W/m2 of an iceand snow melting system is to bedetermined, there are severalconsiderations to be made:

1. The place where the system it isto be installed geographicallocation and specific application.

2. The requirements the system isto meet, e.g. the time of ice andsnow melting.

The installed rating for Denmark is200-250 W/m2. In comparison the

corresponding rating for Russia is250-500 W/m2.

In places such as bridges andloading platforms the cables arealso susceptible to the influence ofcold weather and wind from bothabove and below. In these placesthe output should be increased byup to 50% to compensate for theextra amount of cold. Therefore, it is

advisable to use an appropriateinsulation material below the cablesin order to minimise the downwardheat loss. Where it is not possible toinsulate below the heating cables,we recommend an output of

300-500 W/m2

.

Typical installed ratings of variousground applications are shown inthe table below.

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Area Output in Denmark Output in Russia

Car parks 200-250 W/m2 250-300 W/m2

Driveways 200-250 W/m2 250-300 W/m2

Pavements 200-250 W/m2 250-300 W/m2

Outdoor steps, insulated 200-250 W/m2 250-300 W/m2

Loading ramps, insulated 200-250 W/m2 250-300 W/m2

Bridges, insulated 200-250 W/m2 250-300 W/m2

Outdoor steps, not insulated 300-375 W/m2 300-400 W/m2

Loading ramps, not insulated 300-375 W/m2 300-400 W/m2

Bridges, not insulated 300-375 W/m2 300-400 W/m2

The general guidelines for choosing the output for the installation are presented below.

Outdoor dimensioning Output on ground Output on ramps, bridges

temperature (not insulated)

-10C 200 W/m2 250 W/m2

-15C 250 W/m2 300 W/m2

-20C 300 W/m2 350 W/m2

-25C 350 W/m2 400 W/m2

-30C 400 W/m2 450 W/m2

-35C 450 W/m2 500 W/m2

-40C 500 W/m2 550 W/m2

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The installed output should behigher if:

1. The installation is placed in anarea with frequent wind duringwinter. A wind speed of 10 m/s

results in an additional relativetemperature drop of approx. 5C.The higher the wind speed, thebigger the temperature drop.

2. The installation is placed on ahigh geographical location. Werecommend adding 50 W/m2 perevery 1000 m for locations over1000 m above sea level.

3. Significant snowfalls areobserved in the area. If there ismore snow than what equates to6.3 mm of water every 6 hours,50 W/m2 should be added.

Products for ground applications

For ice and snow melting applicationsthe deviflex heating cables with aminimum output of 17 W/m ordevimat cable mats with a mini-mum output of 200 W/m2 can beused. For applications in asphalt werecommend deviflex/devimat

DSVK.

To control the system the devireg

850, 610, 330, or 316 with a groundand/or air sensor should be used.

Installation under asphalt

There are two main installationmethods for asphalt:

1. Cables are covered with sand orconcrete before the asphalt is

applied.Before the asphalt is applied, athin layer of sand or concrete (atleast 2 cm) should be used tocover the top of the cables toprotect them from the heat of theasphalt. Allow the asphalt to coolto a temperature of 130C-140Cbefore it is applied.

For this installation method werecommend a deviflex cable such

as the DSIA or the DSIG.

2. Asphalt is applied directly ontothe cables or mats.

DEVI recommends the deviflex ordevimat DSVK for asphalt installa-tions as it can resist 240C for ashort time. With this type of cable it

is not necessary to cover the cablewith sand. This reduces the timeand installation costs. In order notto damage the cables, heavymachinery (rollers or asphalt layingmachines) should not be used onthe cables.

The asphalt should have a minimumthickness of 5 cm measured fromthe top of the deviflex heatingcables.

An electrician should measure thecable resistance and the insulationresistance before and after theasphalt is applied.



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Installation under concrete tiles

Special care must be taken not todamage the heating cables whenthey are installed under tiles.

The area must be completely level,

free of stones or other sharp objectsand all holes should be filled.

The heating cables must be installedclose to the tiles, typically in a layerof sand (2-3 cm).

Installation under concrete

Installing deviflex cables ordevimat mats in concrete is similarto the procedure for tiles or asphalt.

The cables should be well securedwith devifast fitting bands (whichmay be fastened to the metalarmouring) so they are not dislod-ged when the concrete is applied.The concrete must cover the cablescompletely without leaving any airpockets.

The concrete mixture must notcontain sharp stones as these maydamage the cables.

The concrete should be allowed toset for 30 days before the heatingsystem is turned on.

An electrician should measure thecable resistance and insulationresistance before and after theconcrete is applied.

In places where the heating cablesare to cross expansion joints, thecables must not be subject tomechanical strain in connection with

movements in the construction.

Car parks

Normally, a car park is a large areawhere fast ice and snow melting isrequired. There are a number ofadvantages to be gained frominstalling an ice and snow melting

system. It reacts quickly andefficiently against snow and appearsto be an excellent preventive featureagainst ice. The problem of removingsnow from occupied parking bays iseliminated and as an extra advantagethe car park may be used to the full.

For this kind of ice and snow meltingsystem to work efficiently it shouldincorporate the devireg 850 withstar/delta function and a deviflex

cable or a devimat heating mat.

Example

An ice and snow melting systemhas to be installed in a 150 m2 carpark in Denmark.

For that application we choose adeviflex DSIG-20 and an installedoutput of 250 W/m2, which issufficient for Danish climateconditions.

1) Calculation of total required out-put: 150 m2 x 250 W/m2 =37.5 kW

2) Choice of nearest DSIG cable(s):for this purpose it will be 12deviflex DSIG-20 heating cableswith 3175 W, 158 m, 400 V.The total effect will be 38.1 kW.

If the installation is equipped with astar/delta switch, the number of

cables must be dividable by 3 orthe load should be evenly distributedon 3 phases. This ensures a steadyload of the phases.

3) Calculation of C-C distance:

C-C =20 W/m x 100 cm/m

= 8 cm250 W/m2

4) Choice of thermostat:We choose the devireg 850because of the size of the area.

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Driveways

One of the great advantages of anice and snow melting system is theautomatic clearing of drivewayskeeping them passable at all times -night and day. This is especially

important in specific situations wherea free passage is needed for ambu-lances or other types of vehicles.

There are two options when an iceand snow melting system isinstalled in a driveway:

1. Covering the entire area withheating cables or mats.

2. Covering just the area affectedby car tyres.

We recommend the first option forall major driving areas with heavytraffic. The cleaning of snow and iceformations, which can occur with thesecond option, will be complicated.

The second option is recommendedfor minor areas, like driveways toprivate garages. If the driving areahas a slope, we recommend theentire area be covered with heatingcables or mats.

When installing ice and snow melt-ing systems on steep slopes it maybe necessary to provide some formof drainage for the melted water atthe bottom of the slope. The drainsystem should also be protectedagainst ice formations.

Example

In this example we have chosen amedium-sized driveway with a

length of 10 m and a width of 2 m.The cables are to be installed in thetwo tyre tracks with a width of0.5 metre each.

For this application the installedoutput is 250 W/m2 and the chosencable is the deviflex DSIG-20.

1) Calculation of the area where thecable is to be installed:10 m x 0.5 m x 2 = 10 m2

2) Calculation of the total output forthe area: 10 m2 x 250 W/m2 =

2500 W.

3) Choice of cable: The deviflex

DSIG-20, 2520 W, 126 m heatingcable.


10 m2 x 100 cm/m= 7.9 cm

126 m

5) Choice of thermostat: Since the

area is rather small, we choosethe devireg 330 with atemperature sensor.


PavementsAn ice and snow melting systemcan ensure a safe walking area forpedestrians. Apart from keeping

pedestrian streets free from snowthe snow melting system providesclean entrances for all shops.


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Outdoor steps

An ice and snow melting systemmay be used as an efficientpreventive feature against slipperyand dangerous steps.

We recommend that outdoor stepsare insulated if they are open under-neath and susceptible to cold. If, onthe other hand, the steps are solid,they need not to be insulated.

The output/m2 in the steps shouldalways be higher than the output/m2

in the area immediately before thesteps. If this is not observed,accidents may occur if the areabefore the steps is free of ice whilethe steps are slippery.

When calculating the cable lengthfor a step application, remember totake into account the extra piece ofcable which is led down the front ofeach step.

The cables are laid backwards andforwards in evenly spaced loopsalong the step.

As the heating cables are notinstalled on the vertical part of thesteps, the steps, the first cable loopshould be laid as close as possibleto the edge of each step (5 cm) toensure an efficient melting of ice.

When the cables are installed allstones or sharp objects should beremoved from the surface as theymay damage the cables.

The cables are installed directly onthe concrete and must be coveredwith 3-5 cm of concrete.

Example

We have an example of steps:12 steps with a depth of 0,32 m, aheight of 0,17 m and a stair width of1,00 m.

With a DTIP - 18 heating cable anda required output of 250 W/m2 theC-C distance will be:

C-C =18W/m x 100cm/m

= 7.2 cm250 W/m2

As each step is 0,32 m deep, thereis room for 4 cable runs on eachstep amounting to 4 m of cable perstep.

4 m of cable x 12 (steps) = 48 m of

cable plus the cable running downthe front of each step: 12 x 0.17 m= 2 m.

This gives a total of 50 m cable andtherefore, a deviflex DTIP-18 cable,935 W and 52 m, is appropriate.

The total area of the steps is:12 x 1 m x 0,32 m = 3.84 m2

And therefore, the installed rating is:935 W/3.84 m2 = 244 W/m2

If there is any cable left, it should beinstalled in the area in front of thesteps.

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Loading areas

Loading areas must be safe to workon and therefore, they should bekept free of ice and snow. DEVIsice and snow melting systemreduces the risk of accidents and

ensures that the work can be doneat all times.

Loading ramps are generally openand consequently, they are moresusceptible to the cold weather.We recommend that all loadingareas and loading platforms are wellinsulated to avoid heat lossdownwards. Where it is not possibleto insulate below a loading area, theoutput per m2 must be increased to300-400 W/m2.

Example loading areas

DEVIs ice and snow melting systemhas to be installed in a 2.5 m x15 m non-insulated loading area.

1) Choice of product and requiredoutput per m2: the cable to beused is a deviflex DSIG-20 andthe installed rating is 350 W/m2.

2) Calculation of area: 2.5 m x 15 m= 37.5 m2

3) Calculation of total required out-put: 37.5 m2 x 350 W/m2 =13125 W.

4) Choice of cable: three deviflex

DSIG-20 cables, 4575 W, 229 m,400 V are chosen for thisinstallation.

5) Calculation of the total length ofthe cable to be installed:3 x 229 m = 687 m.


C-C = 37.5 m2

x 100 cm/m = 5.5 cm687 m


Bridges

Bridges are even more susceptibleto cold weather than loading areasas they are almost alwayscompletely open. This reduces theeffect of the heating cablesconsiderably and therefore, theunder side of bridges should be wellinsulated. Where this is not possible,the output per m2 should beincreased to 300-400 m2.

The devireg 850 with star deltafunction and the deviflex 400 Vheating cable will in most cases bethe most appropriate ice and snowmelting system for bridges.

The heating cables should never belaid across the section joining of abridge.


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2.3 Roof applicationsDEVIs ice and snow melting systemfor roofs and roof gutters can beinstalled in virtually any type of roofconstruction where there is a needto prevent melt water deposits in

roof gutters and reduce damages toconstructions like frozen facadesand roofs.

The ice and snow melting systemshould be installed along the edgeof the roof or in places where thereis a risk of ice and snow formations.In roof gutters and downpipesdamage is prevented by an efficientand free draining of melt water,which naturally ensures that the

system functions satisfactorily.

Electronic devireg thermostatsensure that optimal results areachieved with the least possibleamount of energy. In order toachieve these results sensors andthermostats read the weather withtotal accuracy, automaticallyswitching the heating on and off atexactly the right moment.

The typical areas of use are roofconstructions, roof gutters, down-pipes, and valley gutters.

Required output

To determine the required output

(W/m2

) of an ice and snow meltingsystem for a roof it is important toconsider the type of roof constructionin question and the local weatherconditions.

In general, all roofs fall into twocategories:

1. A cold roof. A cold roof is a well-insulated roof with a low upwardheat loss. A cold roof willtypically cause ice formations inthose periods when the sunmelts snow formations on theroof.

2. A hot roof. A hot roof is not wellinsulated or/and the attic is usedas a living area. Hot roofs meltthe snow to a certain extent andthe water from the melted snowthen moves downwards to theedge of the roof where it freezes.

The installed rating in gutters shouldtherefore be higher in hot roofs thanin cold roofs. This will ensure efficien-cy, even at low temperatures.

For roof applications cables with

15-25 W/m are used. If the cablesare installed on top of a roof bymeans of a meltable material, themaximum rating of the heatingcable must not exceed 20 W/m.

The required output per m2 will besimilar to that of ground applica-tions.

Gutters running along the edge of acold roof, generally require30-40 W/m. In comparison therequired rating for hot roofs is40-50 W/m. For these applications2 or 3 deviflex cables can bechosen in order to obtain thenecessary output per m, and insome cases even more.

For further information, please referto the diagram below:

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Area Cold roof Hot roof Max. rating Cable rating

Valley gutter, 200-250 W/m 2 250-300 W/m2 300 W/m2 15-25 W/mroof surface

Downpipes, 30-40 W/m 40-50 W/m 50 W/m 15-25 W/mplastic roof gutters

Downpipes, 30-40 W/m 40-50 W/m 100 W/m 15-25 W/mmetal roof gutters

Downpipes, wooden 30-40 W/m 40 W/m 40 W/m 15-25 W/mroof gutters

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Roof gutters and downpipes

The cable is led back and forthalong the gutter as many times asnecessary in order to achieve theneeded output. Two lengths ofcable (back and forth) is usually

adequate.

In general, if the dimensioning out-door temperature is above -20C,you need:

2 lengths of cable in a gutterconnected to a cold roof;

3 lengths of cable in a gutterconnected to a hot roof.

If the dimensioning temperature isbelow -20C, you need:

3 lengths of cable in a gutterconnected to a cold roof;

4 lengths of cable in a gutterconnected to a hot roof.

The heating cables can be installedin different ways in roof gutters anddownpipes but in most cases thesame cable is used for both roofgutters and downpipes.

In roof gutters the heating cablesare fixed at the correct distance(C-C distance) by devifast spacingclips. In downpipes a metal chain ishung inside the pipe to which thedevifast spacing clips are thenattached. If the cable length doesnot exceed 50 cm, a metal chain isnot needed but spacing clips arestill necessary.

Alternatively, a rope can be used forinstallations in downpipes. In thiscase the cable is fixed with specialmetal clips.

If a self-regulating heating cable

(the devi-iceguard

) is used for roofapplications, it is usually enough touse 1 m of cable per 1 m of roofgutter and downpipe. With self-regulating heating cables it is notnecessary to use a metal chain inthe downpipe. The cable has to beprotected from the sharp edges ofthe downpipe.

Example

The following example is intendedfor a plastic gutter with a length of13 m and a 5 m long downpipe atthe end.

1) Calculation of necessary cablelength: two cable lengths in thegutter will require:

2 x (13 m + 5 m) =36 m of cable.

2) Choice of cable: we have chosena deviflex DTIP 18, 680 W, 37 m

and by folding the cable, we areable to cover both the gutter andthe downpipe with an installedoutput of 36 W/m.

In order to keep the cable in thecorrect position in the gutter,devifast spacing clips should beused. The cable in the downpipeshould be attached to a metal chain.

3) Choice of thermostat:a devireg 316 with an outdoorsensor is suitable for thisinstallation.

Valley gutters

The installation of heating cables invalley gutters typically concernslarger buildings. The heating cableis led backwards and forwardsalong the the gutter so the correctoutput per m2 is achieved, similar toground applications.

We recommend devifast fittingbands to fasten the cable in the val-ley gutter and devifast plasticcable holders to attach the cable tothe metal chain in the downpipe.

The devifast

is fixed by means ofhotmelt or silicone.

Often several downpipes are placedin the middle of the valley gutter. Ifonly a short length of the cable isled down the pipe devifast spacingclips should be used in order toavoid crossing cables.

If the cable is led all the way downthe pipe, it must be supported by achain hanging down from the top ofthe downpipe.

The hook or supporter bar of thechain must by no means be placedon top of the cables in the gutter.

Example

The following example is intendedfor a valley gutter with an area of10 m x 0,30 m and a 3 m longplastic downpipe at the end.

We have chosen a deviflex DTIP-18 heating cable and would like aninstalled rating of 250 W/m2.

1) Calculation of installation area:The installation area of the cableis:

10 m x 30 cm = 3 m2

2) Calculation of total requiredoutput:

250 W/m2 x 3 m2 = 750 W

Remember the heating cable for thedownpipe:

2 x 3 m = 6 m, 6 m x 18 W/m = 108 W



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This gives the following total output:

750 W + 108 W = 858 W

3) Choice of cable: in DEVI's cableprogramme we find the deviflex

DTIP-18, 935 W, 52 m to be themost appropriate cable for thisexample.

4) Calculation of C-C distance:the distance between the cablesfor the valley gutter is calculatedas follows:

C-C =3 m2 x 100 cm/m

= 6.5 cm52 m 6 m

In order to keep the cable in thecorrect position in the gutter,devifast fitting bands and spacingclips should be used.

5) Choice of thermostat:a moisture sensor is chosen forthe registration of ice and snowand therefore, a devireg 850thermostat with a set of sensorsfor the roof and gutter system ischosen.

Roof constructionsDuring winter the followingunpleasant phenomenon may appear(especially with hot roofs):A large quantity of snow and iceaccumulates on the unheated lowerpart of the roof. It graduallycondenses and converts into a big

massif of ice. In the spring or whenthe weather gets mild during winter,this massif can roll down the roof,damaging roof gutters and otherroof constructions and creating aserious threat to everything or

everybody standing next to thehouse.

A typical output for a roof is 250 W/m2.

To prevent the accumulation of ice,heating cables should be installed inthe lower part of the roof. Whenheating cables are installed onroofs, the installation is often com-bined with a snow-stopping unit toprevent snow sliding. This snow-stopping unit is typically installed50-100 cm from the edge of theroof.

The heating cable is installed incable loops which are placed fromthe edge of the roof and 50-100 cmup the roof towards the snow-stopping unit. It is important thatthe cable is installed in cable loopsup and down the roof and not as astraight line along the roof.The cable must be secured at

suitable intervals as the installationis exposed to harsh weatherconditions.

In some cases the cable may alsobe covered by shielding sheets inthe same metal material as that ofthe main roofing. This protects the

cable from mechanical damage,direct sunrays, and fallen leaves,seeds etc.

Example

The following example is intendedfor a cold roof. The roof is 8 m longand the cable is installed in loopsfrom the edge and 0,5 m up theroof. The installed rating on the roofmust be 250 W/m2.

1) Calculation of installation area:The installation area is:

8 m x 0.5 m = 4 m2

2) Calculation of total requiredoutput:

4 m2 x 250 W/m2 = 1000 W

3) Choice of products: in thisexample the installation can becarried out with a deviflex

DTIP-18, 1075 W, 59 m and adevireg 316 with an outdoorsensor.

4) Calculation of C-C distance:The C-C distance between thecable loops is:

C-C =4 m2 x 100 cm/m

= 6.8 cm59 m

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2.4 Product choiceThe product choice depends on the area of use and the output. For an overview, please refer to the table bellow.


Area of use Choice of rating Product choice

Normal Maximum deviflex devimat devi-

min. 17W/m 300 iceguard

Car parks 200-300 W/m2 300 W/m2 X XDriveways 200-300 W/m2 300 W/m2 X XPavements 200-300 W/m2 300 W/m2 X XInsulated:Steps 200-300 W/m2 300 W/m2 XLoading platforms 200-300 W/m2 300 W/m2 X XBridges 200-300 W/m2 300 W/m2 X XNon-insulated:Steps 300-375 W/m2 400 W/m2 XLoading platforms 300-375 W/m2 400 W/m2 X XBridges 300-375 W/m2 400 W/m2 X X

Roof; tiles, metal 300-375 W/m2 350 W/m2 X XRoof; tar paper 150-300 W/m2 20 W/mcable X X

Cold roof

Roof gutter/downpipe:Metal 30-40 W/m 50 W/m X XPlastic 30-40 W/m 40 W/m X XWood 30-40 W/m 40 W/m X X

Hot roof

Roof gutter/downpipe:Metal 40-50 W/m 50 W/m X XPlastic 40-50 W/m 40 W/m X X

Wood 40 W/m 40 W/m X X

Choice of devireg thermostat

DEVI has developed a variety ofdevireg electronic thermostats forcontrolling the outdoor applicationsto meet the various frost, ice andsnow problems. Electronic thermo-stats regulate the temperaturequickly and precisely, and bychoosing the optimal thermostatboth safety and financial benefits

may be achieved.

The DEVI outdoor thermostat pro-gramme includes the followingitems: the devireg 316, thedevireg 330, the devireg 610, andthe devireg 850. Depending onyour requirements and the situationof the installation, the type of iceand snow melting thermostat willvary.

In order to ensure economic runningcosts and exploit the optimal com-fort of the ice and snow meltingsystem we recommend that thedevireg 850 be used. This isespecially relevant for applicationswhere the total output exceeds6 kW.

Thanks to its intelligent, digitalsensors the devireg 850 systemworks with an incredible accuracyenabling a reduction of the energyconsumption to the lowest possiblelevel without compromising safety.

Ice and Snow Melting

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