Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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G061 C~
Facade ~Ieating
The invention relates to a facade hea-ting arrangement
comprising a supporting structure that can be fastened to a
wall, usually an outer wall, of a building and which con-
tains pro~iles, or mullions, usually oE m~tal, particularly
aluminium extrusions. The profiles are usually arranged as
vertical or upright metal section horizontal metal section
members or cross members. The structure is connected to and
thermally insulated from a facade skin that comprises the
uprights and cross members of the outer wall and the window,
usually ~ormed from double gla~ed panels. The facade
heating arrangement also comprises a heating device ~or
heating the supporting structure.
A metal Eacade construction of -this type is known, ~or
example, from German Patent Specification 21 32 921. The
heating device of the known construction is formed by a hot
water circuit which extends through cavities of the
metal section uprights and metal section cross members.
Owing to the thermal separation between the facade skin and
the supporting structure of the facade construction formed by
the uprights and cross members, the supporting structure
forms a heating body of large area radiating heat substan-
tially only towards the inside of the building, so that, with
an appropriate s~lpply of hot water, a building heating system is
obtained that can be used for a transition or warm up
period, or as an additional heating system that coopera-tes
with other heating sys-tems.
It has been found that the joining together of the hot
water channels which extend in the sectional cavities of the
uprights and cross members makes the contruction o~ the
facade heating arrangement complicated since a li~uid-
impermea~le connection has to be made and maintained between
the uprights and cross members and special precaution~s;have
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to be taken to avoid short circuits or dead points in the
heating circuit.
The heat loss through a window, even a double ~lazed
window, is inherently greater than through a brick wall for
example, and a relatively warm person st:anding in a room
near a window with an appreciably lower outside temperature
would feel some discomfort.
The present invention provides a heating arrangement and
method safely to overcome or at least alleviate such heat
loss and associated personal discomfort.
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~ ccordingly, the invention is intended to solve the
problem of so contructing a facade heating construction of
the general type described initally that a special, imper-
meable contruction of the connection between the uprights
and the cross members is not necessary, that maintenance and
repair wor~ on the heating device and also on the entire
facade construction is simplified and a good controllability
is achieved that is not dependent on the position of indiv-
vidual temperature sensors, for example on the sunny side or
shaded side of the building.
In accordance with one aspect of the present invention,
there is provided a facade heating arrangement comprising a
thermally conductive support structure arranged to be
mounted on the inside of, and to extend away from, a wall of
a building adjacent a window therein, and heating means
arranged to effect thermal transfer to the support structure
and thereby to the atmosphere in front of the window,
wherein the thermally conductive support structure comprises
an elongate profile having a groove therein, the heating
means comprises an elongate electrical heater that has a
negative temperature coefficient of heating capacity, and
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wherein the heater is mounted in the groove and is embedded
in its raspective groove in a material having good thermal
conductivity thereby to enhance thermal transfer from the
heater to the profile.
In accordance with another aspect of the present invention,
there is provided a method of heating the atmosphere inside a
building adjacent a window in a wall thereof, wherein a
thermally conductive support structure is mounted on the
inside of said wall adjacent the window so as to extend away
therefrom, wherein an elongate heater having a negative
temperature coefficient of heating capacity is mounted in a
groove of an elongate profile of the support structure and
embedding the heater in a material having good thermal
conductivity so as to effect good thermal transfer to the
profile and thereby to the atmosphere adjacent the window.
Advantageously, the heater comprises a heater cable having a
positive temperature coefficient (PTC) of resistivity, and
comprises an elongate cable having a pair of parallel
stranded metal bus bar conductors enclosed within a
conductive polymeric material having a PTC characteristlc,
and surrounded by an insulating jacket.
In addition to solving the problem stated above, the
construction of the electrical heating device described
herein makes it possible also to carry out repair work in
specific areas of the facade without it being necessary to
shut down the heating device in the other heated parts of the
facade. So called hot spots on the heat-radiating surfaces
of the uprights and cross members that face the interior of
the building are avoided by virtue of the self-regulating
property of the heating cable arising from its PTC
characteristic.
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This heating cable is preferably arranged in such a manner
that is two stranded conductors which run parallel to and
spaced from each other by being embedded in a conductive
poly~er can be supplied, for example, by 220 volt alternating
current~ The temperature-sensitive
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resistance material located between the heating cables forMs
the heat-resistance over the entire length of the heating
cable. This heat-resistance may be considered as a number
oE heat resistance elements connected in parallel with each
other which, owing to the positive temperature coeEficient
of their resistance, e~fect the selE-regulation of the
heating cable by means of those heat-resistance elements
which adopt higher temperatures owing to thermal irregulari-
ties in the system increasing their resistance value,
reducing the current passing thr~ugh them and, thereby,
decreasing the reduction in the heating capacity in the
relevant heat-resistance element in order to lower the tem-
perature. A polymeric carrier matrix which contracts on
cooling and expands on heating, contains conductive par-
ticles, especially carbon particles, whlch come increasingly
into contact on cooling to produce more conductive pathways,
but, on heating, are drawn apart and increasingly lose con-
tact with each other with a reduction in the overall eEfec-
tive conductor cross-section.
Each individual section of the heating cable has this
self-regulating property over its entire length, so that no
separate control circuits, such as thermostats, are required
in order, for example, to adjust the heat energy delivered
for each portion of the facade according to whether the
respective portion is on the sunny, shady or windy side of
the building or is located in a region of the building in
which additional heat sources operate.
The self-regulating property of the heating cable can
be obtained also with other physical principles or mecha-
nisms. For example, as the hea~ing means in the heating
cable, a lossy dielectric ha~ing a negative temperature
coefficient of power loss may lie between the conductors of
the cable, or heating conductors having a pronounced posi~
tive temperature coeficient of resistance may be wrapped in
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the form of a helix around connection conductors extending
on opposite sides of a spacer strip, so that the individual
portions of the helix between the connection conductors form
the parallel-connected heating elements.
The heater used in the present invention may be a self-
regulating heater sold by the Chemelex 3ivision of Raychem,
and preferably is selected, according to the power output
required, form Raychem's QTV range, for example a 10 QTV 2
or a 15 QTV 2 heater. In general, suitable heaters for use
in the present invention are described for example in
Raychem's U5 Patent Nos. 4188276, 4459473, and 4426339,. The
heaters may be enclosed within a metal braid or foil for
earthing and/or enhancing thermal transfer.
A further advantage of the self-regulating heater used
in the present invention over the hot water system pre-
viously used for facade heating, lies in its ability to
limit the temperature to which the profiles, or mullions, of
the facade support structure may be raised. This tem-
perature may thus be maintained at less than about 55C,
which is the temperature at which injury could be caused to
a person touching the support structure.
In general, the support structure will comprise one or
more, and usually four, profiles that form a closed, usually
rectangular, loop for mounting around a window. Each pro-
file may contain a separate heating element, or a single
heater may extend along the lengths of each of the profiles.
The size, i.e. total length, of the support structure will,
of course, depend on the size of the window, and it would
extend away ~rom the wall into the room typically for a
depth of about 15 centimetres. The thermal transfer mecha-
nisms are typically thermal conduction from the heater into
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the support structure profiles, usually an aluminium or
other metal extrusion, and then radiationv and/or convec-
tion, from the support structure inwardly towards the air in
front of the window. The dep-th of the support structure
will accordingly be chosen in dependence on the surface area
of the window so as to maintain a speciEied minimum tem-
perature, of say 18C at the centre of the window.
The heater may be mounted as a snap-fit into the
groove, so that the good mechanical retention will enhance
the thermal transfer. Thermal transfer from the heater may
be further enhanced by embedding the heater in a potting
compound or o-ther material having good thermal conductivity.
The groove containiny the heater ~lay be closed by a cover,
which may itselE be a snap-fit on or in the groove, or may
be secured by clips or screws.
~ dvantageously, the groove or grooves containing the
heater or heaters open into the room so that should any
maintenance or replacement oE the heating system be necessary,
access thereto is easily obtained without disturbing the
mounting of the support structure on the wall.
When the support structure is mounted on the wall, it
is preferred that it be thermally insulated therefrom,
thereby to enhance the proportion of heat that is radiated
across the surface of the window.
Embodiments of facade heating arrangements, each in
accordance with the present invention, will now be
described, ky way of example, with reference to ~he accom-
panying drawings, in which:
Fig. 1 shows a horizontal section through the metal
facade construction, in the region of a
upright; it should be mentioned that the view
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in Figure 1 may also be regarded as a ver-
tical section through the metal facade
construction in the region of a horizontal
cross member;
FigO 2 shows a cross-section of a modification of
Figure 1, wherein, in the region of a upright
or cross member, additional profile grooves
having additional heating cables have been
provided;
Fig. 3 shows a cross-section of a further modifica-
tion of Figure l;
Fig. 4 shows a cross-section of a part o a metal
facaae construction in which the metal sec-
tions of the supporting structure which form
the uprights have been omitted, wherein that
part of a proEiled framework which lies
on the inside of the building and which is
thermally insulated towards the outside of
the building is to be regarded as a cross
membe~ which is provided with grooves
opening towards the inside of the buildiny
for receiving heating cables;
: Fig. 5 shows a schematic equivalent circuit diagram
of a heating cable portion;
Fig~ 6 shows an enlarsed view in section of a part
of a upright or cross member in the region
of a proEile groove containing a heating
cable;
Figs 7 & 8 show enlarged views in section
of modified embodiments of Figure 6;
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Figs. 9 show a range of other shapes of profile
to 13 grooves with heating cables extending
therein showing, in section, part of the
corner reyion of a cross member or upright;
and
Fig. 14 shows a section through a upright or cross
member to which the grooves carrying the
heating cables have been fitted by fastening
a groove carrier.
In Figure l, two adjacent double glazing panels are
designated l and 2. The insulating glass panels 1 and 2 are
held between a metal framework 3 on the inside of the room
of a building and a metal framework member 4 on the outside
of the room. Elastic mounting elements S and 6 separate the
framework members 3 and 4, which are clamped together, for
example, by means oE screws. Details oE this arrangement
have been omitted from the drawing for the sake of clarity
since they are known to a person skilled in the art. On the
o~side of the building, a cover 7 is clipped, using suitable
locking means, on to the outer framework member 4 over the
exposed fastening points.
~ he elastic mounting elements 5 and 6 form a first
thermal insulation of the metal facade construction, this
thermal insulation acting between the outer framework member
4 and the inner framework member 3. A second thermal insu-
lation of the metal facade construction is provided between
the inner framework member 3 and a hollow section 8 of
substantially rectangular cross-section which forms an
upright member (or alternatively a cross member), and takes
the form of two insulatihg webs 9 and 10 made of high-
rigidity plastics material which are each anchored by dove-
tail extensions in correspondingly constructed grooves of the
metal sections 3 and 8.
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On its innermost side within the room, the hollow sec-
tion 8 is provided with grooves 11 and 12 which open towards
the inside of the building and which, in the embodiments
shown in Figures 1 to 3, are formed by flanges projecting
away from the inside profiled outer surface of the box sec-
tion. According to an alternative embodiment (not shown in
the drawings) these grooves may, however, also be positioned
inside the rectangular outer contour of the hollow section
8.
Heating cables 13 and 14 which are generally dumb-bell
shaped in cross-section extend inside the grooves 11 and 12,
rep~sectively, in the longitudinal direction of the hollow
section 8, which heating cables fill the relevan-t groove to
provide a good transfer of heat between the heatin~ cables
and the hollow section 8.
For covering the groove opening, a cover strip 15 of U-
shaped cross-section is clipped on to the hollow section 8
in the manner shown in Figure 1, which cover strip is
constructed in such a manner that substantially closed,
smooth outer surfaces are produced on the sides and at the
end face of the hollow section 8. The inner cover strip 15
corresponds in shape substantially to the outer cover strip
7, and it is possible to use identical covers in order to
simplify manufacture and make storage cheaper.
Figure 6 shows the detail designated E in Figure 1 on an
enlarged scale and again shows the cover strip 15 and the
groove 12 which is formed between the flanges projecting
above the oute~ surface of the hollow section ~ on the
inside of the building. The flange located near the corner
of the hollow section 8 is provided on the outside with a
longi-tudinally extending channel in which an engaging strip
of one limb of the cover strip 15 has been engaged.
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As already described, inside the groove ~2 there
extends the heating cable 14 which, owing to the appropria-te
sizing of the groove 12 with .respect to the cross-section of
the heating cable, rests against the side wAlls and on the
base of the groove and is spaced at a slight distance from
the cover strip 15, so that a good transfer o~ heat to the
parts of the metal section adjacent to the heating cable is
brought about by thermal conduction and/or thermal
radiation.
If, despite a relatively uniform removal of heat
from the heating ca~le 14 to the adjacent parts of the metal
profile and despite a heat distribution action as a result
of the transport of heat in the longitudinal direction oE
the metal profile, the temperature in a heating cable por-
tion designated L in Figure 5 rises in comparison with
adjacent heating cable portions, then, owing to the self-
regulating properties of the heating cables used here, there
is a reduction in the current ~lowing between the parallel
stranded conductors 16 and 17 as a result of the heating
conductor material 18 arranged and electrically connected
between the stranded conductors. This material can be
regarded as a parallel connection of heat resistance ele-
ments Rl~ R2, R3 ... of the equivalent circuit diagram shown
in Figure 5. ~ecause of the voltage applied to -the con-
ductors 16 and 17 which is substantially constant along the
relatively short length of the heat.ing cable portion, this
causes a reduction in the heating capacity at those heating
conductor resistance elements which have heated up more, so
that the temperature falls again. The heater is thus self
regulating.
It should also be mentioned that the stranded conduc-
tors 16 and 17 of the heater cable 14 and the heating conduc-
tor material 18 whch surrounds and connects them are covered
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by an insulation sheath 19 which ensures electrical insula-
tion with respect to the metal profiles without signiEi-
cantly hindering the transport of heat.
Figures 7 and 8 show embodiments in which a sel~-
regulating heating cable is placed in a metal profile groove
and the groove opening has then been closed by a com-
paratively narrow cover strip 20 or 21, it being possible
for the cover strip 20 or 21 to be locked on the groove
opening in the manner shown in Figures 8 and 9. The cover
strip 20, which may be made of metal or of a heat-conductive
plastics material, is so dimensioned on i.ts inwardly acing
side that .it i9 contiguous with the upper end of the heating
cable cross-section, for example of the heat cable 14, in
order to conduct heat away. A further improvement in the
removal of heat from the heating cable to the adjacent sur-
faces of the parts of the metal profile is achieved in the
embodiment shown in Figure 7 by a casting compound 22 having
good thermal conductivity, in which the heating cable is
embedded inside the profile groove. In the embodiment shown
in Figure 8, a metal foil sheath 23 on the heating cable
likewise serves to improve the transfer of heat between the
heating cable and the adjacent surfaces of the metal
profile.
In the embodiment shown in Figure 2, in addition to the
grooves 11 and 12 with heating cables 13 and 14 accommodated
therein, further profile grooves 24 and 25 with heating
cables 26 and 27 inserted therein are provided. The
grooves 24 and 25 open on the hollow section 8 in a direc-
t.ion parallel to the window, it being possible to provide
for these grooves and the heating cables accommodated
therein a construction such as that shown in Figures 7 and
8. It will be appreciated that in the embodiment shown in
Figure 2, as a modification of the construction shown, the
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grooves 11 and 12 with the flanges forming them may also be
omitted, so that the hollow profile 8 presents a smooth sur-
face towards the inside of the building. This form oE
construction is suitable for those uprights and cross mem-
bers of a metal facade construction that are situated imme~
diately in front oE a ceiling or an internal wall of a
building, so that the grooves are freely accessible for
receiving heating cables in the hollow profile 8.
The explanation just given for the embodiment shown in
Figure 2 applies correspondingly to the embodiment shown in
Figure 3. The facade construction of Figure 3 differs,
however, from that shown in Figure 2 in that grooves 28 and
29 for receiving heating cables 30 and 31, respectively,
which open parallel to the window are not arranged near the
surEace of the hollow section 8 that faces the inside of the
building but are provided on the hollow profile 8, in the
manner shown, in the vicinity of the thermal insulations
formed by the insulation strips 9 and 10 towards the fra-
mework member 3.
Finally, Figure 4 shows a metal facade construction in
which grooves 32 and 33 which receive heating cables are
located, in a manner corresponding to the construction of
the grooves 11 and 12 in the embodiment shown in Figure 1,
on the surface of the metal framework member 34 that faces
the inside of the building, which framework member
corresponds to the framework member 3 of the embodiment
shown in Figure l. Owing to the thermal insulation be~ween
the inner framework member 34 and an outer framework member
35 which is obtained as a result of the elastic mounting
element 5, the heat produced by the heating cables at the
inner framework member 34 substantially is not conducted
towards the outside of the building to the framework member
35 but is effective for radiant heating of the interior of
the building.
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Figures 9 to 13 show further embodiments of grooves
fitted to the metal uprights (profiles) and/or the metal
cross members (profiles). These grooves, as in the
exemplary embodiments described previously, are each an
integral component of the relevant metal profile and are
adapted to the particular cross-sectional shape of the
heating cable. In the embodiments shown in Figures 9 and 10,
a heating cable of circular cross-section is used, but it
should be pointed out thak heating cables of rectangular or
oval cross-section may also be used.
In the embodiments shown in Figures 11 and 12, the
grooves receiving the heating cables are fitted to the rele-
vant upright or the relevant cross profile in such a manner
that the grooves open towards each other and the heating
cables are pushed into the grooves outwards from the centre
of the enclosure formed around the window by the profiles,
or mullions.
Figure 13 shows the larger cross-sectional dimension of
the ribbon-shaped heating cable oriented perpendicular to
the plane of the facade. It will be seen that, in this
embodiment, the groove receiving the heating cable is com-
paratively flat. At the transition of the groove from a
upright to a cross member in the corner region of the sup-
porting structure, the ribbon-shaped heating cable can be
bent easily and does not need to be bent on its edge.
Whereas in the embodimen-ts described previously, the
parts of the meta~ profile or mullion containing the heating
cables and the grooves are integrally connected to the
upright or cross member of a framework, in the embodiment
shown in Figure 1~ a heating cable carrier 44 is in the form
of a correspondingly shaped metal profile strip containing
the heating cables 40 and 41 in grooves 42 and 42, respec-
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tively, which open at the side. The carrier 44 is Eastened,
for example firmly screwed, to the hollow section 8 of a
upright or cross member. The entire arrangemen-t can be
covered by a cover strip 45 in the manner shownS the cover
strip 45 also serving to close off the profile grooves 42
and 43. The embodiment shown in Figure 14 has the advanta~e
that even already erected facades can subsequently be
equipped with a heating device of the kind described herein,
so that this embodiment is suitable for reconstruction
measures. Thermally conductive inserts between the hollow
section 8 and the heating cable carrier 44 are able to
ensure a good transfer of heat as result of a reliable
mechanical contact between these parts.
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