Battle on the Ice

SAMRIS On the sur­face of a flat roof, the elec­tric heat­ing cable is usu­al­ly laid in a “snake”
DEVI For the effec­tive oper­a­tion of a sys­tem based on self-reg­u­lat­ing cables in our cli­mate, a wire with a spe­cif­ic heat at 0C — 36 W / m for melt water and 18W/m in air
Ther­mo-reg­u­la­tor EMDR-10
Heat­ing resis­tance cable from TASH in sin­gle-core and two-core ver­sion:
1 — shell;
2 — cop­per braid;
3 — insu­la­tion;
4 — wires

Option when the cable is passed in a loop inside the down­pipe
SAMRIS When the cable is laid on the roof, it makes sense to install snow reten­tion ele­ments that are attract­ed to the roof bat­ten using self-tap­ping screws or anchor bolts
Effi­cien­cy Absence of ici­cles, thawed areas on the roof in the area of ​​val­leys and gut­ters — a sign of the effec­tive oper­a­tion of the sys­tem
SAMRIS Installed sys­tem does not spoil the appear­ance of the build­ing
Battle on the IceCop­per mount­ing tape for cable

Win­ter in our area is rarely equal­ly cold or, con­verse­ly, warm. More often than not, thaws are replaced by frosts, frosts- thaw. ATIn such a sit­u­a­tion, most own­ers of coun­try hous­es have a dif­fi­cult prob­lem- icy cor­nices and ici­cles on gut­ters. You can fight ice with the help of an anti-icing sys­tem.

Why ice- this is bad

Under cer­tain weath­er con­di­tions, the weight of an ici­cle in just one day can increase by sev­er­al tens of kilo­grams. Thus, a pic­turesque ice cone will pose a very real threat to all res­i­dents of the house. So what, you think, the prob­a­bil­i­ty of an ici­cle falling is not too great, but on occa­sion it can be knocked down by any means at hand. Why waste mon­ey installing some kind of anti-icing sys­tem?

In fact, the prob­lem of roof icing is much broad­er than the ques­tion of whether an ici­cle will fall or not. Not only that, the fail­ure of suf­fi­cient­ly mas­sive ice mass­es cre­ates a real dan­ger to peo­ple’s lives and can dam­age not only vehi­cles, but also the archi­tec­tur­al ele­ments of the house. Due to the accu­mu­la­tion of ice, the mechan­i­cal load on the roof ele­ments, the brack­ets for fas­ten­ing down­pipes and gut­ters increas­es, which inevitably leads to a reduc­tion in their ser­vice life, which means an increase in your costs for the cor­re­spond­ing repairs. Since drains and gut­ters are clogged with ice, water in the autumn-spring peri­od and in win­ter dur­ing thaws either flows onto the facade or lingers on the roof sur­face. ATin the lat­ter case, leaks are pos­si­ble. And then the upper floors of the house and parts of the facade near the drains and val­leys (that is, the lines of joints of the roof planes) suf­fer. ATAs a result, you are faced with the prob­lem of mechan­i­cal clean­ing of the roof. This work is very time-con­sum­ing, and the roof itself can suf­fer con­sid­er­able dam­age, because most roof­ing mate­ri­als (met­al tiles, gal­va­nized steel, cop­per) are very sen­si­tive to mechan­i­cal stress.

It turns out that it is nec­es­sary to deal with ice. And here the elec­tric heat­ing sys­tem of those sec­tions of the roof, where the prob­a­bil­i­ty of its for­ma­tion is most like­ly, can come to the res­cue. ATin sys­tems of this kind, spe­cial cables are used as a heat­ed ele­ment, laid in gut­ters and gut­ters. Thanks to this, the melt­ed snow does not turn into ice, but flows down to the ground in the form of melt water.

All on ice!

What can be opposed to the onslaught of nature? Per­haps only mod­ern tech­nol­o­gy. When cre­at­ing anti-icing sys­tems, engi­neers pro­ceed­ed from con­sid­er­a­tions that it is more prof­itable to heat melt water with­out let­ting it freeze than to melt the already formed ice. ATIn this case, much less pow­er will be need­ed, which means that ener­gy con­sump­tion will become more eco­nom­i­cal. So the main task of the sys­tem- dur­ing the win­ter and off-sea­son, to accom­pa­ny the water formed on the roof to ground lev­el, sim­ply pre­vent­ing it from freez­ing on the roof ele­ments and in the gut­ters, and at the same time to exclude leaks, dam­age to the facade fin­ish and down­pipe fas­ten­ers. This idea, quite sim­ple in its essence, is imple­ment­ed in the form of a com­plex engi­neer­ing com­plex. The prin­ci­ple of its oper­a­tion is sum­ma­rized as fol­lows.

In the most “unfa­vor­able” places of the roof (gut­ters, gut­ters, val­leys andt.where ice is most often formed, and along the entire route of the melt water, a heat­ing cable is laid with pow­er sup­ply from the mains with a volt­age of 230B. Heat­ing is con­trolled by a spe­cial auto­mat­ic ther­mo­stat that receives com­mands from one or more sen­sors installed on the roof. These can be sen­sors for tem­per­a­ture, humid­i­ty and pre­cip­i­ta­tion, a sen­sor for the pres­ence of water. As soon as they sig­nal that con­di­tions are devel­op­ing in the atmos­phere con­ducive to the for­ma­tion of ice (and this usu­al­ly hap­pens dur­ing pre­cip­i­ta­tion dur­ing the cold sea­son or drip melt­ing of snow cov­er on the main part of the roof dur­ing a thaw), a ther­mo­stat (or a pro­gram­ma­ble ther­mo­stat, a kind of home weath­er sta­tion) “acti­vates” the pow­er sup­ply, and the heat­ing cable begins to gen­er­ate heat. The result­ing water flows freely and with­out hin­drance along the gut­ters, trays and gut­ters.

Why do ici­cles appear

By itself, snow falling on the roof does not pose any dan­ger. The trou­ble is that the snow mass begins to turn into ice under the influ­ence of two fac­tors.- techno­genic and nat­ur­al. Dai­ly air tem­per­a­tures fluc­tu­ate with an ampli­tude reach­ing 15C. And with fluc­tu­a­tions in the range from +3 … +5Hap­py to ‑6…-10At night, the most favor­able con­di­tions for the for­ma­tion of ice are cre­at­ed. Melt water ini­tial­ly part­ly drains, part­ly freezes, cre­at­ing ice growths on gut­ters and gut­ters. But as soon as the paths for the rapid depar­ture of water are blocked on the roof, when a neg­a­tive tem­per­a­ture sets in, it freezes. More­over, with a short expo­sure to heat (for exam­ple, the rays of the peep­ing sun), ice plugs do not melt, but only increase. ATAs a result, whole ice jams, plugs and ici­cles sev­er­al meters long and weigh­ing up to hun­dreds of kilo­grams can form, threat­en­ing the integri­ty of the water­proof sys­tem.

The main rea­son for the appear­ance of ice- tem­per­a­ture dif­fer­ence between the cen­tral part of the roof and the edge where the drains are locat­ed. It may occur for sev­er­al rea­sons. The most com­mon- this is heat removal through the upper floors and the roof, due to which the tem­per­a­ture of the cen­tral part of the roof is high­er than the tem­per­a­ture of the out­side air. The tem­per­a­ture dif­fer­ence increas­es if there are no ven­ti­lat­ed attic spaces in the house, if the under-roof space is rebuilt for liv­ing quar­ters, or heat-gen­er­at­ing equip­ment is placed there, for exam­ple, expan­sion tanks, heat­ing col­lec­tors, etc. The low­er lay­er of snow cov­er on a rel­a­tive­ly warm roof is heat­ed up, turns into melt water , which flows into cold gut­ters and freezes there, block­ing fur­ther water drainage. Mansards, tur­rets, all kinds of super­struc­tures, com­plex roofs with inter­nal cor­ners, hor­i­zon­tal plat­forms and pro­trud­ing “col­lars” of roof win­dows do not go out of fash­ion. And, alas, con­tribute to the for­ma­tion of snow cov­er. By the way, from this point of view, experts con­sid­er the most effec­tive in the con­di­tions of cen­tral Europe a pitched roof of the sim­plest form with an angle of incli­na­tion of at least 30- this is the best option for the best snowmelt.

Due to solar radi­a­tion at the bound­aries of the snow cov­er, melt­ing is acti­vat­ed. Accord­ing to mete­o­rol­o­gists, on aver­age, about 70 tem­per­a­ture tran­si­tions through the 0 mark are record­ed dur­ing the win­ter.C. It is these diur­nal fluc­tu­a­tions in the evening that lead to the rapid cool­ing of the air (and hence the drains), while the mass­es of snow on the roof, togeth­er with the ele­ments of the roof itself, can retain heat for some time.

Usu­al­ly, the sys­tem of anti-icing and heat­ing of the roof and gut­ters con­sists of sev­er­al func­tion­al sub­sys­tems. First­ly, this is the so-called “heat­ing part”- the actu­al heat­ing cables, which must be elec­tri­cal­ly safe, mechan­i­cal­ly strong, resis­tant to sun­light and pre­cip­i­ta­tion. An impor­tant com­po­nent of the “heat­ing” sub­sys­tem are all kinds of fas­ten­ers. They fix the heat­ing cables in a giv­en place on the roof and in the gut­ter struc­tures. And sec­ond­ly, the dis­tri­b­u­tion net­work- a set of pow­er and sig­nal (infor­ma­tion) cables and junc­tion box­es for switch­ing wires. This sub­sys­tem is respon­si­ble for pro­vid­ing pow­er to all ele­ments of the heat­ing part and to con­duct infor­ma­tion sig­nals from sen­sors to the con­trol pan­el. The “heart” of the anti-icing com­plex is an auto­mat­ic con­trol sys­tem, which involves spe­cial tem­per­a­ture con­trollers, tem­per­a­ture and humid­i­ty sen­sors, bal­lasts and pro­tec­tive equip­ment.

Heat runs through the wires

Now is the time to talk about the most impor­tant com­po­nents of the sys­tem. Let’s start with the most impor­tant- from heat­ing ele­ments. The role of the heater in anti-icing com­plex­es is played by spe­cial cables. Their pur­pose- con­vert the elec­tric cur­rent flow­ing through them into heat. There­fore, pow­er per unit length (spe­cif­ic heat release)- their most impor­tant tech­ni­cal para­me­ter. The cable is laid and fixed in places of expect­ed icing- along the edge of the roof and drip, in val­leys, around pro­trud­ing struc­tures (lanterns, pipes, sky­lights well as along the entire drainage sys­tem. On flat roofs and low slope roofs (up to 30) the heat­ing cable is usu­al­ly mount­ed either over the entire sur­face, or on the receiv­ing drain fun­nels and areas adja­cent to the drains.

Resis­tive cables have a con­stant con­stant resis­tance along their entire length and con­sist of a heat-gen­er­at­ing met­al core, insu­la­tion, cop­per braid and an out­er sheath. Today on the Euro­pean mar­ket there are resis­tive cables man­u­fac­tured by such com­pa­nies as SPECIAL SYSTEMS AND TECHNOLOGIES, or CCT (Europe), THERMO, KIMA Heat­ing Cable (Swe­den), CEILHIT (Spain), ENSTO, TASH (Fin­land), NEXANS Nor­way AS (ALCATEL, Norway/France), DEVI (Den­mark).

As a rule, either cable sec­tions or cable sup­plied in coils (drums) are used for lay­ing. Sec­tions- these are ready-made prod­ucts in which a piece of cable of a fixed length is docked at the fac­to­ry with the help of a spe­cial sleeve with the so-called “cold end”- a sup­ply wire designed to con­nect the heat­ing (“hot”) cable to the elec­tri­cal net­work. The length of the “cold ends” is also fixed and is 0.75–3m. The ends of the sup­ply wires are brought into the dis­tri­b­u­tion ter­mi­nal box, where they are joined with oth­er elec­tri­cal wires, through which pow­er is sup­plied from the pow­er shield. So basi­cal­ly the heat­ing sec­tion- the main ele­ment of the anti-icing sys­tem, and the cou­plings con­nect­ing the cold wires to the con­stant­ly heat­ing and cool­ing heat­ing cable,- the most crit­i­cal ele­ment of the whole struc­ture. The dura­bil­i­ty of the sys­tem depends on the reli­a­bil­i­ty of the cou­plings, so man­u­fac­tur­ers usu­al­ly test the heat­ing sec­tion under very harsh con­di­tions. Many firms con­nect the heat­ing con­duc­tors of the cable to the “cold” wires using mechan­i­cal­ly crimped bush­ings. Those are placed in a plas­tic box and then filled with spe­cial mas­tic. This ensures the reli­a­bil­i­ty and tight­ness of the con­nec­tion. Sec­tions can­not be cut.

Anoth­er vari­ant- lay­ing the heat­ing cable from the coils. Such a cable is cut direct­ly at the instal­la­tion site, and heat-shrink­able cou­plings are used to con­nect pow­er wires or oth­er heat­ing sec­tions.

Most com­pa­nies pro­duce both ready-made heat­ing sec­tions and coiled cables. Thus, cables of the DSIG series from DEVI, Ther­mo­ca­ble SVK from THERMO, Tas­su from ENSTO are sup­plied in sec­tions with a fixed length of heat­ing and pow­er wires. Cables in reels are offered by CEILHIT, NEXANS, DEVI, TASH, etc. But you can­not make cuts of any length: the length of the cable is deter­mined by such char­ac­ter­is­tics as resis­tance, pow­er den­si­ty and the volt­age used. The pow­er of heat release depends on the size of the seg­ment. Tofor exam­ple, to obtain the required pow­er of 30W/rmm for a cable with a resis­tance of 70ohm/rmm need length 15.5m. If it is less, the cable will over­heat, if more- will not reach the rat­ed lin­ear pow­er.

The prob­lem of ice for­ma­tion is most rel­e­vant not in cold win­ters, but dur­ing peri­ods of thaws, when the air tem­per­a­ture pass­es through zero and the water from the melt­ed snow freezes almost imme­di­ate­ly. Some­times at +3…+4Since it is sleet with rain, and it is sim­ply nec­es­sary to heat the gut­ters. Bot­tom line- the tem­per­a­ture at which snow melt­ing on the roof stops. ATnature, this process stops at 0C. But since the build­ing los­es some of its heat through the roof, water can drip from the gut­ters even at ‑10C. Often the roof does not have prop­er ther­mal insu­la­tion; many hous­es, espe­cial­ly recon­struct­ed ones, have attic floors, through which the most intense heat loss occurs, and, accord­ing­ly, the for­ma­tion of ice on the roof is more intense.

Oper­a­tion of anti-icing sys­tems at tem­per­a­tures below ‑15C is usu­al­ly not need­ed. First­ly, in this case, frost usu­al­ly does not form and the amount of mois­ture decreas­es sharply due to the heat loss of the roof itself. Sec­ond­ly, under such con­di­tions, the amount of pre­cip­i­ta­tion in the form of snow is reduced.

It is not scary if the snow falls in frosty weath­er. To melt it, you will, in the­o­ry, have to put 3 or 4 strands of cable. But this is an increase in the cost of the sys­tem by 2 or 3 times. There­fore, it makes sense to wait until it gets warmer and the snow begins to melt. That is why the oper­at­ing mode of the sys­tems is lim­it­ed from below by a tem­per­a­ture of ‑6 … ‑15FROM.

To date, man­u­fac­tur­ers pro­duce resis­tive cables of either sin­gle-core (with one heat­ing core) or two-core design (one core- heat­ing, sec­ond- con­nect­ing). A sec­tion with a sin­gle-core heat­ing wire is con­nect­ed to the mains at both ends, and a two-core cable- only from one end (on the oppo­site end there is a plug, inside which the heat­ing and con­nect­ing cores are con­nect­ed). Using two-core heat­ing cables is some­what eas­i­er to install, but they are slight­ly more expen­sive than sin­gle-core ones. The heat­ing con­duc­tors are pro­tect­ed by high mol­e­c­u­lar weight poly­eth­yl­ene insu­la­tion, on top of which anoth­er lay­er of insu­la­tion is applied, and then a cop­per shield­ing braid. Out­side, the cable is pro­tect­ed by a high-strength sheath made of polyvinyl chlo­ride (PVC) or flu­o­ropoly­mer com­po­si­tions.

Of course, each man­u­fac­tur­er makes sure that its cable lasts as long as pos­si­ble and is as reli­able as pos­si­ble. For exam­ple, in THER­MO’s Ther­mo­ca­ble SVK resis­tive cables, the cur­rent-car­ry­ing cores are pro­tect­ed by a tinned cop­per shield braid. The inter­nal insu­la­tion of the cores is made of sil­i­cone rub­ber, resis­tant to tem­per­a­ture extremes. AThigh-strength poly­ester film acts as addi­tion­al insu­la­tion. The cable itself is rein­forced with fiber­glass, and the out­er sheath is made of PVC. CEILHIT cables with Teflon-coat­ed cores appeared on the Euro­pean mar­ket, which allows not only to increase the max­i­mum oper­at­ing tem­per­a­ture of the heat­ing ele­ment (up to 50–60C), but also to improve the uni­for­mi­ty of heat dis­si­pa­tion.

As a sep­a­rate vari­a­tion in the class of resis­tive “heater wires”, the so-called zone cables can be men­tioned. They are rep­re­sent­ed, for exam­ple, by the prod­ucts of HEATTRACE (Great Britain) and CCT. The heat-gen­er­at­ing ele­ment here is a piece of high-resis­tance alloy wire, super­im­posed in a spi­ral on two insu­lat­ed con­duc­tive wires. More­over, the step of con­nect­ing the “spi­ral” with these cores- no more than 1m. Thus, heat release zones con­nect­ed in par­al­lel are formed. The cable has many heat­ing zones and can be used in pieces. By cut­ting them, you do not risk dis­rupt­ing the oper­a­tion of the entire chain. Zon­al cables are some­times referred to as “qua­si-self-adjust­ing”, since dur­ing instal­la­tion they can be cut “in place” into pieces that are mul­ti­ples of the length of the heat­ing zone, direct­ly on the object. This reduces cable wastage.

Zone wires have a spe­cif­ic heat release from 15 to 200W / m (depend­ing on the sec­tion of the spi­ral) and are pow­ered from one end. They are rec­om­mend­ed to be laid on roofs, in long and extra long drains (40m and more), as well as in sys­tems where the absolute absence of ice is nec­es­sary. ATAs a result, it turns out that in this case, the rigid char­ac­ter­is­tic of the zon­al cable devel­ops from a dis­ad­van­tage into an advan­tage.

A sep­a­rate type of resis­tive cables can be con­sid­ered their armored ver­sions with an addi­tion­al sin­gle or dou­ble braid of gal­va­nized steel wires.- for reli­able pro­tec­tion against mechan­i­cal dam­age. The main scope of such cables- lay­ing in a con­crete screed when arrang­ing heat­ing sys­tems for open areas, ramps, steps, as well as con­crete drainage trays.

cable type Main pur­pose Pow­er range, W/m Sec­tion length Applic­a­bil­i­ty on roofs Price, $/m
Resis­tive Heat­ing of pipelines, trays, drains 5–30; fixed pow­er Fixed, 10–200 m Lim­it­ed 2.5–5
Self-adjust­ing Heat­ing of pipelines, trays, drains 5–60; vari­able pow­er Any up to 150 m, cut­ting on site Com­plete 13–25
Zon­al Heat­ing of pipelines, trays 10–80; fixed pow­er with the pos­si­bil­i­ty of slight cor­rec­tion Any up to 150 m, cut­ting on site Heat­ing of long drains 3–10
Armored Heat­ing of open areas, drains 20–60; fixed pow­er Fixed, with the pos­si­bil­i­ty of cut­ting in place 1–2 m Heat­ing of drains, drop­pers, con­crete trays 2–4

In EU, resis­tive cables with “armor” are main­ly rep­re­sent­ed by prod­ucts of the SST com­pa­ny. It pro­duces, in par­tic­u­lar, a resis­tive two-core cable TSB of increased pow­er (up to 30W/m) for heat­ing roofs, gut­ters and out­door areas. The prod­uct has high mechan­i­cal strength and resis­tance to short-term over­loads. If nec­es­sary, you can choose a cable with a high spe­cif­ic heat, for exam­ple, an armored EM2-XR from RAYCHEM with a pow­er of up to 130W/m ToAmong the “light­ly armored” cables are PSV cables (two-core, with a coax­i­al cop­per-steel met­al braid) from CEILHIT, Kima Armor D from KIMA, as well as the light­weight armored cable MBk man­u­fac­tured by SST in a poly­mer sheath.

Euro­pean resis­tive cables are the cheap­est. As for import­ed prod­ucts, 1lin­earm of cable of any brand costs $1.5–5. Two-core options are more expen­sive than sin­gle-core ones by about $0.05–0.1. At the same time, the qual­i­ty of prod­ucts from dif­fer­ent man­u­fac­tur­ers is at the same fair­ly high lev­el. A domes­ti­cal­ly pro­duced resis­tive cable for the Teploskat anti-icing sys­tem from SST costs about $2.5–3 for 1lin­earm.

Unlike resis­tive cables, self-reg­u­lat­ing cables auto­mat­i­cal­ly change their heat dis­si­pa­tion depend­ing on the ambi­ent tem­per­a­ture. More­over, the amount of heat gen­er­at­ed varies, so to speak, local­ly: each sec­tion of the cable “adapts” to the con­di­tions sur­round­ing it. How does this hap­pen? The heat­ing ele­ment in self-reg­u­lat­ing cables is the so-called matrix, made of a poly­mer with the addi­tion of a con­duc­tive car­bon mate­r­i­al and locat­ed between two cur­rent-car­ry­ing cores. When the cable sec­tion is exposed to low ambi­ent tem­per­a­tures, the mate­r­i­al of the heat­ing ele­ment con­tracts, the resis­tance decreas­es, the cur­rent pass­es through the matrix, and it intense­ly releas­es ther­mal ener­gy. That is, on a cold piece of cable, the cur­rent does not flow along the wires, but across, from one wire to anoth­er. As the tem­per­a­ture ris­es, the elec­tri­cal resis­tance of the matrix becomes very high, which leads to a sharp decrease in the heat dis­si­pa­tion pow­er. The heat dis­si­pa­tion pow­er of cables also varies depend­ing on the phys­i­cal envi­ron­ment in which the cable is locat­ed, say, in melt water or in air. For effi­cient oper­a­tion of sys­tems in Euro­pean cli­mat­ic con­di­tions, accord­ing to experts, a cable with spe­cif­ic heat release at 0FROM- 36W/m in melt water and 18W/m in air.

In our mar­ket, self-reg­u­lat­ing cables are rep­re­sent­ed by mod­i­fi­ca­tions of var­i­ous pow­er (from 13 to 66W/m). Suf­fice it to say D3 from RAYCHEM-ISOPAD (Ger­many), GM-2x from RAYCHEM (USA), Kima K‑3 from KIMA, G‑Trace series from NEXANS, FSR and FSRe from CCT, RGS‑2 from THERMON, etc. Prices for them are at least 4 times high­er than for resis­tive. This is due to high­er con­sumer char­ac­ter­is­tics and the com­plex­i­ty of man­u­fac­tur­ing. As a rule, a good self-reg­u­lat­ing cable can be found for at least $11 for 1lin­earm. Prod­ucts from Europe cost $10–30 for 1lin­earm. Some­what cheap­er than Euro­pean prod­ucts (SST)- from $11.2 to $12.4.

At first glance, it seems that you can save mon­ey by look­ing for cheap­er goods in the store. In fact, the actu­al cable sys­tem with­out project devel­op­ment and instal­la­tion work is mean­ing­less. As a rule, large installers work with cer­tain sup­pli­ers of mate­ri­als and equip­ment. ATthis makes sense, because the com­pa­ny is gain­ing expe­ri­ence in design­ing and opti­mal­ly adapt­ing the sys­tem to Euro­pean con­di­tions. For exam­ple, the KPD group of com­pa­nies installs anti-icing sys­tems based on cables from DEVI, SEMRIS uses self-reg­u­lat­ing cables from RAYCHEM and ISOPAD, as well as resis­tive ones from TASH, SIM-ROSS uses prod­ucts from NEXANS, CCT- “Teploskat” sys­tem based on cables of own pro­duc­tion.

What type of cable is bet­ter to choose? Resis­tive cables pro­vide increased pow­er per unit length and, if nec­es­sary, can be laid in sev­er­al strands (for exam­ple, cables from TASH with a unit capac­i­ty of 25–30W / m is usu­al­ly mount­ed in drains and gut­ters in two or three threads). The use of increased pow­er per unit length reduces the required cable length and reduces the num­ber of fas­ten­ers. BUTa large line of cable resis­tances per unit length pro­vides the pos­si­bil­i­ty of heat­ing almost any roof­ing ele­ment. Resis­tive cables- the most elas­tic, have a small allow­able bend­ing radius (about 100mm) and fit well in place on roofs of almost any com­plex­i­ty.

Of course, this type of cable is cheap­er, but they have sev­er­al seri­ous draw­backs. One of them- the need for con­stant care and main­te­nance. ATin par­tic­u­lar, the peri­od­ic removal of debris from the roof, at least before the onset of the win­ter sea­son, which is not easy if it is a roof with a soft roof or with steep slopes. Big dis­ad­van­tage of resis­tive cables- fixed resis­tance along the entire length of the sec­tion. That is, under dif­fer­ent oper­at­ing con­di­tions of indi­vid­ual sec­tions of the cable, the heat release remains the same. Imag­ine: one sec­tion of the sec­tion lies on a clean roof, the sec­ond- under a pile of fall­en leaves, and the third- under a thick lay­er of snow. Sen­sors, react­ing to mois­ture under the snow cov­er, turn on the sys­tem, but only the seg­ment that is under the snow works effec­tive­ly, while the rest sim­ply heat the air, wast­ing elec­tric­i­ty. BUTunder a pile of foliage, the cable can even burn out.

Self-reg­u­lat­ing cables change their heat dis­si­pa­tion depend­ing on ambi­ent con­di­tions and tem­per­a­ture. Tofor exam­ple, mod­els GM-2x from RAYCHEM, FSR 31 from CCT this indi­ca­tor varies from about 10 to 40W/m A resis­tive cable of sim­i­lar pow­er con­stant­ly emits its 30W / m, but in win­ter such pow­er may not be enough, and in spring- too much. BUTtak­ing into account the most impor­tant para­me­ter of the sys­tem- elec­tric­i­ty con­sump­tion, then here the self-reg­u­lat­ing cable is out of com­pe­ti­tion. He him­self “feels” where and how much pow­er to apply. If melt water is divert­ed to the drainage sys­tem, it is more expe­di­ent to lay not resis­tive, but self-reg­u­lat­ing cables in the pipes. They are also placed where there is a dan­ger of clog­ging roofs and gut­ters with fall­en nee­dles, seeds and leaves of trees.

Self-reg­u­lat­ing cable is expen­sive, but it can be cut into pieces of almost any length (from 20cm). The resis­tive one is laid in sec­tions of a fixed length, usu­al­ly not coin­cid­ing with the length of the gut­ters. You have to “round” up to the near­est sec­tion, which means that the cable con­sump­tion increas­es. The more cable is laid, the greater the amount of work, that is, the cost of instal­la­tion increas­es. FROMon the oth­er hand, a resis­tive cable is more suit­able when you have to deal with a lot of the same type of nodes (for exam­ple, 10 down­pipes 10 meters high).m). By choos­ing a sec­tion of the desired length, cable over­run can be reduced to a rea­son­able min­i­mum.

According to the weather service…

There are lim­its on the installed capac­i­ties of the heat­ing part of the sys­tems, deter­mined on the basis of prac­tice. Fail­ure to com­ply with them leads to the inop­er­abil­i­ty of the sys­tem in the spec­i­fied tem­per­a­ture range, and a sig­nif­i­cant excess- to exces­sive con­sump­tion of elec­tri­cal pow­er with­out any improve­ment in per­for­mance.

On the hor­i­zon­tal sec­tions of the roof, the total spe­cif­ic pow­er per unit area of ​​the sur­face of the heat­ed part (tray, gut­ter andt.n.) must be at least 180–250W/m2. Lin­ear pow­er of heat­ing cables in gut­ters should be at least 20–30W per 1m of length and grow as the length of the drain increas­es to 60–70W/m The esti­mat­ed pow­er of the entire sys­tem for a coun­try house depends not so much on the area of ​​​​the roof, but on its con­fig­u­ra­tion, the length of the drain­pipes and trays, the height (num­ber of storeys) of the build­ing. ATaver­age is 3–4kW. A sim­ple gable roof needs 2 times less pow­er than a com­plex one.- with tur­rets, attics, val­leys, junc­tions andt.e. Telling­ly, the type of cable does not affect the design pow­er includ­ed in the project. After all, the main task- so that it is suf­fi­cient for the effec­tive func­tion­ing of the entire sys­tem.

Heat­ing cables- although the main, but not the only com­po­nent of the anti-icing sys­tem. Many believe that the sys­tem should be turned on when it snows, some­one else- that she must act all win­ter. Last thing- it’s like drown­ing ban­knotes. In fact, the anti-icing com­plex works accord­ing to a giv­en algo­rithm, either acti­vat­ing the heat­ing or turn­ing it off and trans­fer­ring the sys­tem to stand­by mode.

The con­trol func­tion is assigned to spe­cial tem­per­a­ture con­trollers man­u­fac­tured by DEVI, ENSTO, RAYCHEM, Dan­ish OJ ELEKTRONIK, Ger­man EBERLE. For small, sim­ple roofs, the sim­plest option is suit­able- based on a tem­per­a­ture sen­sor and a ther­mo­stat that turns on the sys­tem only in a giv­en tem­per­a­ture range (usu­al­ly from ‑10 to +3–4FROM). Let’s say the ther­mo­stat ETR-1447 ($137) from OJ ELEKTRONIK responds to air tem­per­a­ture from ‑10 to +10C, and DTR-3102 ($110) from EBERLE can be set to oper­ate between ‑15 and +15C. To con­trol the anti-icing sys­tem on com­plex roofs, it is rec­om­mend­ed to install a pro­gram­ma­ble ther­mo­stat, often called a weath­er sta­tion. At the same time, in addi­tion to tem­per­a­ture sen­sors, the kit includes sen­sors for the pres­ence of mois­ture and pre­cip­i­ta­tion con­trol. “Weath­er sta­tions” col­lect and ana­lyze infor­ma­tion about tem­per­a­ture and humid­i­ty, after which they auto­mat­i­cal­ly select the oper­at­ing mode of the ther­mo­stat. In addi­tion, vio­la­tions in the sys­tem oper­a­tion are mon­i­tored, which is indi­cat­ed by a sound sig­nal and tex­tu­al infor­ma­tion on the liq­uid crys­tal dis­play of the ther­mo­stat. con­trol block EM 524 87 with tem­per­a­ture and humid­i­ty sen­sors from EBERLE costs about $490, and a sim­i­lar set Devireg 810 from DEVI with a built-in diag­nos­tic sys­tem will cost $430.

The tem­per­a­ture range at which there is a risk of ice for­ma­tion and, there­fore, it is nec­es­sary to use cable heat­ing is “set” on the ther­mo­stat pan­el. The sys­tem works accord­ing to a more com­plex algo­rithm than a sim­ple ther­mo­stat. If the out­door tem­per­a­ture is with­in the spec­i­fied range and the sen­sors have detect­ed the appear­ance of mois­ture or pre­cip­i­ta­tion, the ther­mo­stat auto­mat­i­cal­ly turns on the sys­tem. As soon as it gets warmer, and the sen­sors “report” that there is no pre­cip­i­ta­tion and ice, the sys­tem will go into “stand­by mode”.

For exam­ple, in the Teploskat sys­tem from CCT, the PT200E con­troller ($186, togeth­er with auto­mat­ics- $230) to which a dig­i­tal tem­per­a­ture sen­sor, a water sen­sor and a pre­cip­i­ta­tion sen­sor are con­nect­ed. The con­troller mon­i­tors not only the spec­i­fied tem­per­a­ture range, but also the pres­ence of pre­cip­i­ta­tion in the form of snow. The pre­cip­i­ta­tion sen­sor, made in the form of a “cup” with heat­ing and two con­tacts that close when snow gets on them, gives a sig­nal to turn on the sys­tem dur­ing a snow­fall. The cables heat up, the snow and ice in the gut­ters and trays begin to melt, the melt water flows down. If the snow has stopped, the pre­cip­i­ta­tion sen­sor trans­mits a cor­re­spond­ing sig­nal to the con­trol cab­i­net. But at the same time, the sys­tem still acts on the water sen­sor, which is installed in the low­est place (some­where near the drain­pipe) to con­trol whether all the mois­ture is on the glass. After all, it may hap­pen that heavy snow will fall for a short time. It will stop going, but it will still take some time for the melt water to go down freely along all inclined planes. It turns out that the main work is per­formed on three sen­sors. A sit­u­a­tion may arise when there is no snow, but at 0There has been a thaw. The snow on the roof is start­ing to melt. If mois­ture appears on the water sen­sor, the sys­tem will auto­mat­i­cal­ly acti­vate.

The tem­per­a­ture sen­sor is installed in the shade, in a ven­ti­lat­ed place, away from heat sources, air con­di­tion­ers, chim­neys, so that the mea­sure­ments are the most objec­tive. The pre­cip­i­ta­tion sen­sor is best placed in an open area so that noth­ing hangs from above. It is advis­able to choose a place of instal­la­tion so that in case of strong wind the fall­en snow does not blow off the sen­sor. Final­ly, the water sen­sor is placed at the low­est point in the drainage sys­tem. You should not dis­count the “ori­en­ta­tion” of devices to the car­di­nal points. It is advis­able to put the water sen­sor on the south side, because it is there that the water begins to melt dur­ing the thaw. As a rule, one set of automa­tion is mount­ed on a coun­try house.

Installation and cost

You can order the design and instal­la­tion of a cable sys­tem in a spe­cial­ized com­pa­ny. In prin­ci­ple, there are not so many of them. If you decide to deal with ici­cles, it is bet­ter to call a spe­cial­ist on the spot. Depar­ture, mea­sure­ments and cal­cu­la­tion, as a rule, are free (but a num­ber of com­pa­nies charge $fifty). In order to find out the approx­i­mate cost of the sys­tem by phone, you need to know at least the total length of the trays and down­pipes and tell in a nut­shell what kind of roof you have. If the roof is sim­ple (two or four slopes), the length of the trays and pipes is known, you will most like­ly be told quite accu­rate­ly how much the work, mate­ri­als and equip­ment will cost. If the roof is com­plex, it is dif­fi­cult to talk about any­thing with­out going to the site and tak­ing mea­sure­ments.

But the spe­cial­ist will mea­sure indi­vid­ual heat­ed sec­tions of the roof, try to iden­ti­fy areas that are dan­ger­ous in terms of snow accu­mu­la­tion and ice for­ma­tion. The height of the build­ing is also deter­mined; length, height and width of the roof; roof pitch; length and diam­e­ter of drain­pipes; length and dimen­sions of trays, gut­ters. FROMyou will dis­cuss the loca­tion of the heat­ed areas of the roof, eval­u­ate the spe­cif­ic heat­ing pow­er for all nodes of the sys­tem, the num­ber of threads and type of heat­ing cable, and, if nec­es­sary, dis­cuss the algo­rithm of the sys­tem.

The issue of fix­ing the heat­ing cable in the drain chan­nels is very impor­tant, since it is not enough just to throw the cable into the tray- it should lie exact­ly in the place where the water flows. Some installers offer “pro­pri­etary” plas­tic fas­ten­ers from cable man­u­fac­tur­ers. Instal­la­tion in this case is quick, and you will be charged less mon­ey for the work. But if the plas­tic fas­ten­ers are of unknown ori­gin, they will last one, max­i­mum two sea­sons. Oth­er com­pa­nies use strips of gal­va­nized sheet, from which spe­cial clamps are bent. They are attached in such a way that they do not leave any dam­age in the trays (at the top of the pipe).

The high­er the skill lev­el of installers, the few­er holes in the roof. ATtrays and pipes do not make holes, the wires are fixed with fas­ten­ers in the upper part. BUTif the cable is laid on the roof, it makes sense to install snow reten­tion (the lat­ter is “attract­ed” to the roof sheath­ing using self-tap­ping screws or anchor bolts).

Instal­la­tion tech­nol­o­gy depends on the mate­r­i­al of the roof. For exam­ple, cables are usu­al­ly not laid out on nat­ur­al tiles, since almost no ice forms on its sur­face. Due to the fragili­ty of the mate­r­i­al, walk­ing on the roof and drilling holes in it is quite dif­fi­cult, so only trays and pipes are heat­ed.

If the roof is cov­ered with met­al tiles, make sure that the num­ber of holes in the roof is min­i­mal. Many com­pa­nies (SEMRIS, KPD, CEILHIT) in this case, first stick a rub­ber­ized fab­ric on the roof, to which the heat­ing cables are attached. Soft roofs are good with a thick roof­ing cake, the role of addi­tion­al pro­tec­tion here is played by a con­tin­u­ous lay­er of mois­ture-resis­tant ply­wood. If, as an addi­tion to the heat­ing of gut­ters, snow reten­tion devices are to be fixed on such a roof, a con­sci­en­tious installer will ensure that all open­ings are care­ful­ly sealed with sealant.

When it comes to the com­par­a­tive cost of anti-icing sys­tems for roofs based on resis­tive and self-reg­u­lat­ing cables, a four­fold dif­fer­ence in price does not mean that the total cost of the sys­tems will also dif­fer sev­er­al times. After all, many com­po­nents (con­trol cab­i­net, pow­er sup­ply sys­tem, fas­ten­ers) are the same for all types of heat­ing ele­ments. So the dif­fer­ence is not so big: a sys­tem with self-reg­u­lat­ing cables is 30–40% more expen­sive.

Con­trol gear from dif­fer­ent installers is rep­re­sent­ed by dif­fer­ent brands, but in any case, these are prod­ucts of rep­utable man­u­fac­tur­ers: ABB, LEGRAND, SIEMENSGENERAL ELECTRIC andt.e. An intro­duc­to­ry machine, a con­troller that con­trols the sys­tem, a start­ing relay (through which the sys­tem is switched on), an RCD (resid­ual cur­rent device with a leak­age cur­rent of 30mA) and group automa­ta are mount­ed in a sin­gle con­trol cab­i­net, which looks like an elec­tri­cal pan­el.

How much does it all cost togeth­er? For exam­ple, the snow melt­ing and anti-icing sys­tem from SIM-ROSS based on NEXANS cables (Nor­way) pro­vides for lay­ing cables with a capac­i­ty of 35–40 mm in stan­dard gut­ters and gut­ters.W / m, and along the edge of the roof (band 50–60 widecm) cable pow­er den­si­ty 300–350W/m2. Thus, say, for a roof with a perime­ter of 60m (the area of ​​one floor is 200m2) height 12m with four drains you will need a sys­tem with an instal­la­tion capac­i­ty of 12.2kW. Con­sid­er­ing that there are approx­i­mate­ly 35–40 days in a year when weath­er con­di­tions con­tribute to the for­ma­tion of ice and snow, it is pos­si­ble to deter­mine the elec­tric­i­ty con­sump­tion for the sea­son. When used as a “weath­er sta­tion” con­trol sys­tem, this indi­ca­tor will not exceed 6–10thou­sandkWh. The cost of mate­ri­als and equip­ment for a roof with the spec­i­fied para­me­ters will be about 2200.

The basic cost of instal­la­tion for dif­fer­ent installers ranges from 30–35 to 50% of the cost of mate­ri­als and equip­ment (for a one- and two-sto­ry coun­try house). If high-alti­tude work is required relat­ed to the con­struc­tion of scaf­fold­ing, the instal­la­tion of tow­ers or aer­i­al plat­forms, then these ser­vices are paid sep­a­rate­ly.

Ser­vice main­te­nance costs about $100–250 per year. Dur­ing rou­tine main­te­nance, a com­pa­ny spe­cial­ist inspects the exter­nal con­di­tion of the heat­ing sec­tions, tight­ens the con­tacts in the ter­mi­nal box­es, tests the con­trol cab­i­net and the oper­a­tion of all automa­tion. ATMost of the work is car­ried out in the sum­mer or in the off-sea­son, before bring­ing the sys­tem into “com­bat readi­ness”.

But be sure that with the advent of cold weath­er, you will not have to inde­pen­dent­ly wage a hope­less bat­tle with ice on the roof. Mod­ern tech­nol­o­gy has achieved much greater suc­cess in this mat­ter.

The edi­tors would like to thank the rep­re­sen­ta­tive offices of RAYCHEM, DEVI, CEILHIT, as well as SAMRIS, SPECIAL SYSTEMS AND TECHNOLOGIES, KPD for their help in prepar­ing the mate­r­i­al

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