Note: Descriptions are shown in the official language in which they were submitted.
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HEATING SYSTEM
This invention relates to a heating system, and in particular to a system
suitable for use
in supplying heat and hot water to a building in an, environmentally efficient
manner.
It is known to provide a heating system including a hot water storage tank or
cylinder in
which a heat exchange coil is provided to permit water within the cylinder to
be heated
by hot water or another fluid heated by a boiler, for example a gas or oil
fired boiler.
The output from the boiler may also be supplied to a space heating system, for
example
including a series of radiators, to provide heat to a building.
It is also known to provide, in the cylinder, an additional input coil
connected, in use, to
a solar water heater panel or other device whereby the water within the
cylinder can be
heated using solar energy. Depending upon the environmental conditions and
upon the
quantity of hot water required, the solar input may be sufficient, alone, to
heat the water
within the cylinder, or at least part thereof, to the desired temperature.
Alternatively,
the water may be heated using the solar energy driven circuit in combination
with the
output of the boiler. In such a mode of operation, the solar derived energy
raises the
base temperature of the water within the cylinder, thereby permitting a
reduction in the
energy requirement from the boiler to achieve a given water temperature and so
permitting energy savings to be made. Under some conditions, the boiler output
alone
may be used to provide the hot water.
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The cylinder may include a further coil to permit heat to be extracted from
the hot water
within cylinder for use by another heat demand, for example, to operate a
space heating
system, an underfloor heating system, a swimming pool, or other heat demands.
The control systems used in such heating systems are relatively complex.
It is an object of the invention to provide a heating system of this general
type of simple
and convenient form. In particular, the invention relates to a control system
associated
with the heating system to permit operation thereof in a simple, convenient
and efficient
manner.
According to the present invention there is provided a heating system
comprising a hot
water tank or cylinder having a first input coil whereby water within the
cylinder can be
heated using solar energy, a second input coil whereby water within the
cylinder can be
heated by a boiler, and a third, output coil whereby heat can be extracted
from the water
within the cylinder, the system further comprising a heat demand, and control
means
operable to determine whether the heat demand is supplied from the boiler,
from the
third coil.
Preferably, the control means comprises a mixer valve operable to control the
supply of
hot fluid from the boiler to the heat demand. The mixer valve preferably
further
controls the supply of cooled fluid from the heat demand back to an input
thereof. The
control means preferably comprises a control valve operable to control the
supply of
heated fluid from the third coil to the heat demand. Preferably, the control
means
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additionally includes a control pump operable to return cooled fluid from the
heat
demand to the third coil.
A controller is preferably provided to control the operation of the components
of the
control means. The controller preferably receives temperature signals
representative of
the fluid temperature in parts of the system and uses the temperature signals
in
controlling the operation of the control means. The temperature signals are
preferably
derived from temperature sensors operable to sense the fluid temperature at
the third
coil and at the output from the mixer valve. Preferably, a differential
temperature
sensor is provided, the output of which is used to control the operation of
the control
pump and the control valve.
Preferably the heat demand comprises an underfloor heating system. However,
this
need not always be the case and the invention is also applicable to the
operation of, for
example, a series of radiators. Further, by appropriate design, the invention
could be
used in controlling the operation of two or more heat demands of different
types.
The invention will further be described, by way of example only, with
reference to the
accompanying drawings, in which:
Figure 1 is a diagrammatic representation of a heating system in accordance
with one
embodiment of the invention;
Figures 2 to 4 are views similar to Figure 1 illustrating alternative
configurations; and
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Figures 5 and 6 illustrate wiring schemes suitable for use in the heating
systems of
Figures 1 to 4.
Referring to Figure 1 there is illustrated a heating system comprising a hot
water
cylinder 10 to which cold water can be supplied through an inlet 12, and from
which hot
water can be drawn through an outlet 14. Hot water from the cylinder 10 is
supplied, in
use, to the sinks, basins, baths and/or showers of a domestic building, and/or
to
dishwashers, washing machines, etc.
The cylinder 10 includes three heat exchanging coils 16, 18, 20. Although
three such
coils are illustrated, it will be appreciated that a greater number of coils
may be
provided, if required or desired. The first coil 16 is an input coil and is
connected to a
solar panel 22 operable to heat the fluid passing along a solar circuit 24
including the
panel 22 and the coil 16. The fluid preferably comprises water, ideally
incorporating an
anti-freeze liquid, but it will be appreciated that this need not be the case
and that other
fluids could be used. In use, the fluid passing around the solar circuit 24 is
heated in the
panel 22, heat from the fluid passing to the water within the cylinder 10 as
the fluid
passes through the coil 16. The precise details of the solar panel 22 and the
solar circuit
24 are not of importance to the invention and so will not be described in
further detail.
The second coil 18 is, likewise, an input coil connected, through a control
valve 26 to
the output of a boiler unit 28, for example in the form of a gas or oil fired
boiler. The
boiler unit 28 includes a pump 30 operable to supply hot fluid under pressure
therefrom
along or through a boiler circuit 32 to the second coil 18, depending upon the
operation
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of the control valve 26. A space heating circuit 34 including a series of
radiators 36 is
connected to the boiler circuit 32 via a second control valve 38 such that,
depending
upon the position of the second control valve 38, the operation of the boiler
unit 28 and
associated pump 30 can be used to supply heated fluid to the radiators 36. It
will be
5 appreciated that the output from the boiler unit 28 can be supplied to
either or both of
the second coil 18 and the radiators 36, depending upon the operation of the
control
valves 26, 38.
It will be appreciated that the heating system described thus far is capable
of heating the
water within the hot water cylinder 10 either by using heat energy derived
from the
solar circuit 24 or by using heat energy derived from the boiler unit 28, or a
combination thereof. When the environmental conditions are such that
sufficient hot
water can be supplied at the desired temperature using just the solar circuit
24, then the
boiler unit 28 is either not used or is used to supply heat to the radiators
36. Where the
environmental conditions do not permit hot water to be provided from the solar
circuit
24 alone, the boiler unit 28 may be used to boost the provision of hot water,
and where
the environment conditions are poor, the boiler unit 28 may used to provide
the majority
or all of the hot water requirement.
In addition to the features described hereinbefore, the heating system further
includes an
additional heat demand in the form of an underfloor heating circuit 40.
Although the
additional heat demand described herein is in the form of an underfloor
heating system,
the invention is also applicable to other arrangements, for example
arrangements in
which the additional heat demand is a network of radiators, a swimming pool
heating
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circuit, or the like. The underfloor heating system 40 is arranged to derive
heat energy
from either the water stored in the hot water cylinder 10 via the third coil
20 thereof or
from the boiler unit 28, a control means 42 being provided to control this. As
illustrated
in Figure 1, the underfloor heating system 40 includes a feed line 44 and a
return line
46. The feed line 44 is connected to the third coil 20 via a line 48
incorporating a third
control valve 50, forming part of the control means 42. The feed line 44 is
also
connected to the boiler circuit 32 via a mixing valve 52 forming another part
of the
control means 42. The return line 46 is connected to the return side of the
third coil 20
via a line 54 incorporating a control pump 56 forming another part of the
control means
42, and is also connected to the return side of the boiler circuit 32. The
return line 46 is
further connected to the mixing valve 52 so that, depending upon the operation
of the
mixing valve 52, a proportion of the relatively cool fluid returning from the
underfloor
heating system 40 along the return line 46 can be returned to the feed line 44
thereof.
The operation of the control means 42 comprising third control valve 50, the
control
pump 56 and the mixing valve 52 is controlled by a control unit 58 dependent
upon
demand signals and temperature information derived from a series of
temperatures
sensors 60, 62, 64 operable to sense the temperature at, at least, the third
coil 20 and the
feed line 44 of the underfloor heating system 40. The control unit 58 further
controls
the operation of the first and second control valves 26, 38 to determine
whether or not
the boiler unit 28 is used to heat the water within the cylinder 10 and the
radiators 32.
In part, in order to achieve this, the control unit 58 uses signals
representative of the
water temperature within the cylinder 10 and room thermostats.
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In use, the operation of the system to provide hot water and to drive the
radiator circuit
is as described hereinbefore. When it is desired to operate the underfloor
heating
system 40, the control unit 58 switches on the pump 40a of the underfloor
heating
system 40. If the temperature at the third coil 20 as detected by the sensor
60 is higher
than that at the feed line 44 of the underfloor heating system 40 as sensed by
the sensor
62, then the third control valve 50 is opened and the control pump 56 is
switched on
with the result that heat extracted from the water within the hot water
cylinder 10 is
used to heat the underfloor heating system 40. The temperature at the feed
line 44 of
the underfloor heating system 40 is monitored by sensor 64 and, if it is at a
predetermined target level, then the underfloor heating system 40 is driven
using just
the heat energy extracted from the hot water cylinder 10. If the measured
temperature is
lower than the target temperature, then the boiler unit 28 is switched on and
the mixing
valve 52 is opened so as to temporarily supplement the heat derived from the
cylinder
10 with additional heat from the boiler unit 28. The degree by which the
mixing valve
52 is opened is controlled to ensure that the desired target temperature is
maintained.
The opening of the mixing valve 52 in this manner results in the temperature
at the feed
line 44 of the underfloor heating system 40 exceeding that at the third coil
20, and hence
in the third control valve 50 being closed and the control pump 56 being
switched off.
Heat energy will then be derived just from the boiler circuit. If the
temperature sensed
by the sensor 64 is higher than the desired temperature, then the boiler unit
28 is
switched off and the mixing valve 52 is controlled to return a proportion of
the
relatively cooler fluid from the return line 46 to the feed line 44, thereby
ensuring that
the feed line temperature is maintained at approximately the desired target
temperature.
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The target temperature at the feed line 44 to the underfloor system 40 is
determined by
the control unit 58 and is related to the temperature in the area being heated
using the
underfloor heating system 40. As the temperature rises, the target temperature
at the
feed line 44 to the underfloor heating system reduces. When a point is reached
where
the target temperature, and hence the feed line temperature as achieved by the
operation
of the mixing valve 52, is lower than the temperature at the third coil 20,
the third
control valve 50 is opened and the control pump 56 operated with the result
that the
underfloor heating system 40 derives its heat energy just from the hot water
within the
cylinder 10 rather than directly from the boiler unit circuit.
If a point is reached at which the temperature at the third coil 20 exceeds
the target
temperature, the room controls will ensure that overheating of the room does
not occur,
for example by switching off the underfloor heating system 40.
It will be appreciated that, in use, where the temperature in an area heated
using the
underfloor heating system 40 needs to be raised by a relatively large amount,
then the
majority of the heat energy required to achieve the heating will be derived
from the
boiler unit circuit. However, once the area is at substantially its desired
temperature,
maintenance of that temperature can often be achieved to a large extent using
the heat
energy derived from the hot water within the cylinder. Consequently,
significant energy
savings can be made.
It will be appreciated that, whilst the boiler unit is operating, any excess
heat can be
used to heat the water within the hot water cylinder, thus the heat energy can
be-stored
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for subsequent use. Appropriate lagging or insulating of the cylinder 10 is
provided in
order to minimise heat loss from the cylinder, thereby maximising the
efficiency of the
heating system. It is envisaged that, for operation of the underfloor heating
system, the
boiler unit will be switched on when the mixing valve opens beyond a 20% open
position, and switches off when the mixing valve is moved to less than a 10%
open
position. However, other operating schemes could be used.
It will be appreciated that, in determining whether or not to open the third
control valve
and operate the control pump all that it required is information
representative of whether
the temperature at the coil exceeds that at the inlet to the underfloor
heating system.
The absolute temperatures at these locations are not required. Consequently,
it is
envisaged that the sensors 58, 60 will form part of a differential thermostat
operable to
sense the temperature difference between these locations, rather than sensing
the
absolute temperature at these locations.
Figure 2 illustrates an arrangement similar to Figure 1 but in which the
radiator circuit is
omitted.
Figure 3 illustrates and arrangement similar to Figure 1 but in which the
third coil 20 is
used to extract heat from the water within the cylinder for use by either the
radiator
circuit or the underfloor heating system, in either case the boiler unit being
able to
supply heat in the event that insufficient heat energy can be derived from the
cylinder to
meet the demand.
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Figure 4 illustrates an arrangement similar to that of Figure 2 but in which
an
alternative, four-port mixing valve 52 is used instead of the version shown,
diagrammatically in Figures 1 and 2.
5 Figures 5 and 6 illustrate wiring diagrams or schemes suitable for use in
controlling the
operation of the heating systems of Figures 1 to 4.
A number of modifications and alterations may be made to the arrangement
described
hereinbefore without departing from the scope of the invention.
