Note: Descriptions are shown in the official language in which they were submitted.
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Danfoss A/S, 6430 Nordborg, Denmark
Method of regulating room temperature and means
` for performing this method
T~e invention relates to a method of regulating room temperature,
wherein the room is supplied with heat under the influence of a
ther~ostat, particularly a thermostatic valve of a hot water
heating installation, and the actual desired value is reduceable
from a day-time desired value set for the habitation o~ a person
by supplying electric power to a heating resistor associated with
a tharmostat sensor to a desired value which is lower than the
lnherent desired value of the thermostat, and to means for perform-
in~ this method.
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~E-~S 2~ 53 511 discloses a method of this kind in which the
~ensors o~thermostatic valves of à hot water heating installation
c~n be heated by heating resistors in order to achieve a so-called
night reduction whereby the room temperature at night is reduced
to a lower value than the day-time desired value. The day-time
desired value of each room corresponds to the inherent desired
value of the thermostatic valve and can be selected by setting a
knob. The heating resistors are controlled by switches which can
be operated by a synchronous clock. Several voltages are~available
at the secondary side of a transformer having a plurality of
tappln~s. Consequently, each heating-resistor can be supplied
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with an electric power wnich differs from that of the other heating
resistors. This results in dif~eren~ sizes of reductions in the
desired value during the night.
The invention is based on the problem of developing a method of
the aforementioned kind so that novel regulating possibilities are
provided~
~his problem is solved according to the invention in that the
~nherent desired value of the thermostat is higher than the day-
time desired value by a predetermined amount and the heating
resistor is also supplied with electric power during the day so
that the day-time desired value results from the setting at the
thermostat and the heating of the thermostat sensor and that, to
achieve a regulated characteristic with higher desired value, the
supplied electric power is reduced.
Since the day-time desired value, that is to say the value desired
by the user o~ the room during the normal hours of the day, lies
balow the inherent desired value of the thermostat resulting from
its constructional parameters (for example by reason of the pre-
stressing of a desired value spring), the thermostat sensor has to
be heated by the heating resistor not only during night reduction
but also to achieve the normal day-time desired value. This gives
the prerequisite that the actual desired value can not only be
lo~ered but also raised. This occurs by reducing the electric
power. Thls resùlts in a number of new regulating po~ibilities
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as will hereinafter be described in more detail.
Preferably, the electric power during day-time operation is such
that the day-time ~esired value is from 1 to 3 C, preferably about
2 ~, below the inherent desired value of the thermostat. ~his
~an~e is then also available for increasing the actual desired
v~ lu~ .
It is favourable if, when changing the actual desired value from a
first to a second value, the electric power is smoothly altered
along a ramp function. The smooth change can take place continuous-
ly or in small steps. This will avoid the user experiencing
uncomt`ortabla surges in the temperature. Also, one obtains a good
current distribution.
Particularly during the heating-up phase of the room, the actual
dasire~ value should be raised smoothly. The inclination of the
r-~mp is salected with reference to the inertia properties of the
room to be`heated and the associated radiator. If in the case of
a plurality of thermostatic valves the actual desired value is to
be smoothly increased simultaneously, there is no danger of the
valves immediately opening completely, which would impair the
the
proper distribution of~hot water. This is particularly important
in the case of remote centraI heating where charging is according
to the number of cubic meters.
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Preferably, the actual desired value is increased at a spacing
before the time when use of the room is to be expected and is
gradually returned to the day-time desired value at a spacing
aI'ter this time~ Such temporary increase in the desired value
pre-heats the room and makes sufficient heat energy available so
that the coldness from the cold walls that cooled off during the
`night will not ha~e an unpleasant effect. The graàual reduction
of the actual desired value is practically unnoticeable by the
users .
Particularly comfortable regulation is achieved if the actual
desired value is smoothly increased during the hours of the evening
up to an increased desired value which remains constant. When the
u3er of the room is no longer working in the evening but is sitting
quietly and relaxed, this increase in temperature is found to be
particularly pleasant.
A very important regulating possibility is that, to correct the
proportionàl band error of the thermostat, the desired value is
changed in relation to the e~ternal temperature. The lower the
external temperature and the higher the quantity of flow, the
larger will also be the regulating departure of a proportional
valve. This error can now for the first time be corrected auto-
matically.
A particularly simple change in the electric power is obtained in
that the heating resistor is intermittently fed with current and,
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for the purpose of changing the actual desired value, the
pulse-pause ratio of the current is altered. One can use
comparatively long cycle and pause periods because the
inertia o~ the thermostat sensor results in a steady mean
value.
In some cases, it is advisable to measure the
voltage drop across a resistor through which the current
supply flows and deliver an error signal i~ the voltage drop
~alls below a lower limiting value or rises above an upper
1() limiting value. In this way, one can detect in good time a
short circuit or an interruption in the region of the heating
resistor.
Thus, the invention relates to a central heating
control arrangement arranged to control a plurality of
thermostats, each adjustable to a set value and having a
respective sensor associated with a respective heating
rQsistor. The control arrangement comprises: a main
microprocessor provided with a digital store for storing a
desired heating program, and having a data signal coding
~0 apparatus arranged to transmit coded output data signals each
comprising the address of a zone at which a thermostat, or
plurality of thermostats to be controlled similarly are
located, and a command representing the electric power to be
fed to the heating resistors. A plurality of control units
are each arranged to control a thermostat or group o~
thermostats in a respective zone, wherein each control unit
comprises a respective subsidiary microprocessor, is provided
with a decoding apparatus to enable it to recognize its own
zone address in the data from the microprocessor, and is
arranged to control electrical heating power to the heating
resistor(s) in question in accordance with command associated
with that zone address. Power supply lines provide power to
the heating resistors and are arranged to serve also as a
data channel connecting the main microprocessor to the
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control units. The control arrangement is such that the heat
command is on the basis that the thermostat in question is
set to a temperature higher than the d~sired day-time
temperature in the room and the heating resistor in question
is to be supplied with electrical power during the day so
that the desired day-time temperature of the room corresponds
to the thermostat setting as ef~ectively reduced by the
electrical heating o~ the thermostat sensor, and such as to
provide a higher regulated temperature in the room by
reducing the electrical power supplied to the heating
resistor in question.
Since the output data, which may contain other
information in addition to the address and the command, is
continuously computed and delivered by the main micro-
processor, the desired value of each thermostat can be
changed at any time, stepwise as well as continuously. The
main microprocessor primarily takes into account the desired
value programm stored for each zone. Since this programme is
superimposed on the inherent desired value of the thermostat,
~0 the user can change the baseline of this programme at will by
adjusting this inherent desired value. The additional
expenditure in each zone is comparatively low because the
control apparatus and the associated control element may be
o~ simple construction.
An external temperature sensor can be connected to
the main microprocessor. The respective external temperature
can then also be taken into account when calculating the
actual desired value. This can be employed particularly for
correcting the P-band error in thermostatic valves.
~0 The control element can advantageously be a
switching element which can be intermittently switched to its
conductive state by the control apparatus. It may, for
example, be a simple switching transistor.
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In particular, the control apparatus may operate the switching
element at a predetermined switching frequency but for variable
switchin~-on periods. The control apparatus need then only control
the variable switching off instant.
It is of particular advantage if the feed lines supplying the
`~lectric power also connect the main microprocessor to the control
apparltuses and at the same time form data conduits. The cost of
c~nduit3 and laying them will then be extremely low. In the
~implest case, it is sufficient for a two conductor system to
interconnect the control apparatuses and to connect the latter to
the main microprocessor.
In a pre.erred embodiment, the control apparatuses are formed by
subsidiary microprocessors. These can readily convert simple
command data to the corresponding switching times or the like.
~urther, it is favourable for auxiliary control apparatuses for
~parating ùnits each having an on-off function to be connected to
the main microprocessor by way of the two conductor system and
likawise to be operable by its output data comprising an address
and a command. The main microprocessor can then also switch
pumps, fans and other working equipment on and off at the proper
times, operation taking place with a similar data structure as for
the thermostats.
A particularly recommended apparatus is characterised by a full-
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wave rectifier, a coding apparatus which impresses the output data
of the main microprocessor bit by bit of the rectified alternating
voltage in the region of its zero positions as voltage gaps with
two different widths, and decoding apparatus associated with each
control apparatus for detecting the voltage gaps and their widths
and deriving the respective bit therefrom. The voltage gaps can
`be readily produced, for e.~ample by a switching element, and can
ba ra~dily detected. Since they are disposed in the region of the
7ero positions, they do not affect the supplied electric power.
Preferred e~amples of the invention will be described in more
detail with ret~erence to the drawing, wherein:
Fis. 1 is a schematic block diagram of equipment according to the
lnvention.
Fi~. ~ shows the thermostat attachment of a valve and the associa-
te~ control apparatus.
Fi~, 3 ls a diagram showing the intermittent supply of the electric
P~
Fi~. 4 is a time diagram showing the change in the actual desired
value agàinst the day time desired value TS upon rapid heating.
Fig. 5 is a time diagram showing the change in the actual desired
value against the day time desired value TS during comfort heating
in the evening.
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Fig. 6 shows against the e~ternal temperature T the change in
actual desired value relatively to the day-time desired value TS
for correcting the proportional error.
Fig. 7 is a day-5ime diagram of a curve for a desired value pro-
~ramme course showing the departure of the actual desired value
`from the inherent desired value ES of the thermostat.
Fi3. 8 i~ a time diagram showing the electric voltage Ul with
i~pre~ed voltage gaps, and
Fi~. 9 is a modification of the Fig. 1 equipment.
Fig. 1 shows a main microprocessor 1 which is arranged at a central
location Z and provided with a desired value programme store 2.
With tha aid of the setting knobs 3, programmes can be stored for
the zones I, II and III of a hot water heating installation,
particularly times, quantities and angles of inclination of the
chan3aq. `Further, the main microprocessor 1 is connected to an
~tarnal temperature sensor 4. The inputs 5 are for the supply of
othar values, ~or e~ample internal temperatures, wind speed,
posltior. of the sun etc. ~he main microprocessor 1 has a plurality
of outpu~ 6 through which different parts of the installation can
be operated, for example circulating pumps, a priority switch for
hot water, rapid heating of the boiler, night-time illumination
etc.
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For the regulation here of interest, it is the output 7 that is
important. Through it, output data D are delivered to a codin~
apparatus 8. The output data comprise at least one address for
the individual zones I, II and III and a command which charac-
t~rises the size of an electric power. As a rule, however, the
output data comprise additional information, for example synchro-
nisation signals, temperature information etc. We are here con-
cerned with digital output data which are superimposed in the
coding apparatus 8 on a current I flowing in the two cables 9 and
10 of a two conductor system 11. A ~uLl-wave rectifier 12 is
cornected to the source of an alternating voltage U so that a
rectified alternating current corresponding to Fig. 8 flows in the
two conductor system 11. The coding apparatus 8 comprises a
switching element which (a) has no influence at all on the zero
posieions of the half voltage waves or (b) provides the zero
positions with a broad gap in the curren~ or (c) provides them
with a ~narrow gap in the voltage. The broad voltage gap can for
æ~mple correspond to the value 1 and the narrow voltage gap to
th~ value 0.
The hot water heating installation comprises a plurality of
th~rmostatic valves 13 which are disposed in a plurality of zones
I, II and III of a house to be heated. Cenerally, there are more
than the illustrated number of zones, for example eight. In the
illustrated example, each zone corresponds to one room and there-
fore contains only one thermostatic valve. However, it is also
possible to take a plurality of rooms in which the actual desired
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value i3 to be influenced similarly and to combine them to one
~one with a pLuraiity of thermostatic valves. The thermostatic
valve 13 comprises a housing 1~ and a thermostat attachment 15.
The operating element located within this attachment is connected
by w~y of a capillary tube 16 to a temperature sensor 17 disposed
in a housing 18. If the sensor 17 ComDrises a liquid-vapour
~illin~, the temperature-dependant vapour pressure is effe~tive in
the operating element of the attachment and the valve assumes a
position of equilibrium because a desired value spring acts
oppositely to the operating element. The attachment has a knob 19
with the aid of which the inherent desired value ES of the
thermostatic valve can be changed by, for example, adjusting the
~e31red value spring. If the sensor 17 has a liquid filling, the
knob 19 can be used to change the position of the operating element
in the attachment~
Applie~ to the sensor 17 there is an electric heating resistor 20
which can be fed by way of the two conductor system 11 with a
~urrent de`pending on the half-wave voltage U1 of Fig. 8 when a
~ontrol element in the form of a switching elèment 21, for example
a switchin2 transistor, has been brought to the conductive state~
~peration is by way of a control apparatus in the form of a
subsidiary microprocessor 22 associated with a decoding apparatus
23 which may also form part of this microprocessor 22. The de-
coding apparatus 23 scans the zero positions of the half-wave
voltage U1, determines the bits therefrom and stores those values
whlch are connected to the address of the associated zone. 9y
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reason of in~ormation received for this section, the switching
element 21 is brought to the conductive state. The switching-off
time is controlled depending on time as a basis of the stored
command data, as is shown in Fig. 3. The individual blocks corres-
pond to a plurality of half-~aves. The switching-on point is
fi~ed by tha cycle period of fifteen seconds. It will be seen
~th~t the switchinæ-on period decreases in the order of the blocks
d, ~, f and ~ so that in this way heating of the sensor 17 is
variabla by the heating resistor 20.
The housing 18 accommodates the stated components 17, 20, 21, 22
and 23.
~he inherent desired value ES of the thermostatic valve that would
obt~in if the heating resistor is not effective has a higher value
than dasired by the user in the course of a normal day. Fig. 7
shows that the inherent desired value may for example be 23 C
~heraas the day-time desired value is only supposed to amount to
~l~C. Thia reduction by 2 C is achieved with the aid of the
heatin~ resistor 20. The day-time desired value TS is therefore
~omposed of two components, the inherent desired value S~ and the
electric power supplied to the heating resistor 20~ If the elec-
tric power is changed, the reduction in relation to the inherent
desired value is altered. If one changes the inherent desired
value, the entire desired value programme is displaced.
Since heating power is already required to achieve the day-time
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desired value, the actual desired value can not only be decreased
in relation to the day-time desired value but also increased. ror
e~ample, if heating power correspond~ng to the block e in Fig. 3
1s required to reach the day-time desired value, the actuai desired
value can be raised by reducing the heating power according to the
~locks f and g.
A re~ulating characteristic working with such an increase is
evident from Fig. 4. Starting from the day-time desired value TS,
this shows that the actual desired value is suddenly increased by
l.5 C and later returnsgradually to the day-time desired value by
way of a ramp function. The increase in desired value takes place
half an hour before use is expected to commence tO hour) and
remains unchanged for a further hour after commencement of use.
The desired value is then returned linearly for a further hour.
~he users who arrive find the room to be comfortable. The coldness
potantial of the walls that have cooled off during the night is
eliminated as rapidly as possible. The gradual return of the
temperaturè is practically unnoticed by the user.
~he time diagram of Fig. 5 illustrates a regulat~on for comfort.
In tha evening, the actual desired value is gradually raised by
l~5 C above the day-time desired value TS over a course of three
hours, in this case between 7 p.m. and 10 p.m. Subsequently, this
increased desired value remains unchanged until, say, midnight.
The rise takes into account that a person sitting quietly finds a
somewhat higher temperature to be comfortable than a person who is
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workin& and moving about. This temperature increase is eliminated
when the user retires to go to sleep.
Fig. 6 shows against the external temperature T that the tempera-
ture can be varied by 1C. ~elow an external temperature of -9C,
there is zero correction. Above ~9 C, the correction is 1 C.
`3atween thase two external temperatures, the correcting temperature
riaas steadily. In this way, one compensates for the P-band error
o~ the thermostatic valves.
~ig. 7 shows a curve P with the course of the programme from O to
24 hours. The day-time desired value is about 2C below the
inherent desired value of the thermostat. This takes into account
a ~asic reduction of 1.5 C and a P-band error correction of 0.5 C.
At night, a night-time reduction of 9C in relation to the inherent
~e3irad value takes place between midnight and 4 a.m. to reach,
3ay, 15C. This is achieved by strongly heating the sensor 17.
At 4 a.m., an increase takes place to the day-time desired value
and iat ~.30 a.m. there is a further rise by 1.5C because the
~irst users of the room are to be expected by 7 a.m. The section
h of curve P therefore corresponds to Fig. 4. The normal day-time
d~alrad value TS is set for from 9 a.m. to 7 p.m. There is then a
~radual rise by 1.5C to increase the feeling of comfort. The
portion g of curve P therefore corresponds to Fig. 5. There is
therefore a cold phase A1, a heating phase A2, a warm phase A3 and
a cooling phase A4. The length of the heating-up phase A2 depends
on the extent to which the room had previously cooled off and what
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heat-storing properties the room and radiators have.
rig. 7 shows in chain-dotted lines a branch Pl of the graph in
which the desired value constantly rises along a ramp function
during the heating-up phase A2.
-~lthough all ramp functions are illustrated as straight lines,
they may be composed of small steps.
The entire system is preferably operated at mains frequency and
with a reduced voltage of, say, 24V. In one embodiment, the main
microprocessor 1 operated so that it transmitted new output data
to the individual subsidiary microprocessors 22 every three seconds
~h~ data are stored and cancelled upon the arrival of new data.
.~ccordin~ly, only those data are employed that had last been
transmitted before expiry of the 15 second cycle.
~hs main microprocessor may also detect the mains voltage and, in
ralation to any fluctuations in the mains voltage, alter the
len~th of the current blocks tFig. 3). For examplP, the mean
value of voltage U is measured and fed to the main microprocessor
1 by way of an input 5.
Fig. 1 also diagrammatically indicates how a monitoring appliance
24 measures the voltage drop during current supply at a resistor
25 in series with the heating resistor 20 and, upon a departure of
tha measured value from a predetermined range, delivers an error
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signal to operate a light signal generator 26. The user of the
room can therefore notice the error if the heating resistor happens
to be short cireuited or tnere is an interruption in the current.
~i~. 9 shows that, in addition to the control apparatuses 22 for
the thermostatic valves 15 of radiators 27, the two conductor
`system 11 could be connected to auxiliary control apparatuses 28
to 34 for additional operating units which each have an on-off
funetion. Merely by way of example, these auxiliary control
apparatuses have the following function: The auxiliary control
apparatus 28 operates a frost safety device. The auxiliary control
apparatus 29 switches on the fuel and/or air supply for a heating
boilar 35. The auxiliary ccntrol apparatus 30 switches on a
eirculating pump 36 for heating a hot water supply heater 37. The
a~Yiliary control apparatuses 31 so operate the mixing valve 39 by
way of a eontrol device 38 that the boiler temperature increases
rapidly~. The a~xiliary control apparatus 32 operates a circulating
pump 40 in the forward direction. The auxiliary control apparatus
33 may serve to switch illumination on. The auxiliary apparatus
34 sarvas to switch on a fuse. The auxiliary control apparatuses
are likewise each operated by an address in the output data D and
~witched by a command likewise contained in the output data. In a
concrete heating installation, only the auxiliary control appara-
tuses required for this purpose need be provided. The main micro-
processor 1 at the central location Z is able to operate all
auxiliary control apparatuses in addition to the control appara-
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tuses ~2 for the thermostatic valves 15 but these poss bilitiesneed not be utilised fully.
It need not be apparent from the outside that the thermostat is
3et to a higher inherent desired value t~lan the day-time desired
value. It is only necessary to adjust the setting scale at the
~he~ ostat by the 2 C reduction brought about by the heating.
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