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United States Patent Application |
20110290896
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Kind Code
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A1
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Jonsson; Ulf
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December 1, 2011
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CONTROLLING A HEATING/COOLING SYSTEM
Abstract
In a hydronic heating/cooling system, liquid is led along a main supply
pipe (1) to a supply manifold (2) and distributed into heating loops (3).
The heating loops (3) return to a return manifold (4). At least one of
the manifolds (2, 4) has actuators (6) for controlling the flow in the
heating loops (3). Actuators with fast operating times are used and
valves of the actuators are controlled to close at different times in
different heating loops (3).
Inventors: |
Jonsson; Ulf; (Upplands Vasby, SE)
|
Assignee: |
UPONOR INNOVATION AB
Virsbo
SE
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Serial No.:
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148100 |
Series Code:
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13
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Filed:
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February 16, 2010 |
PCT Filed:
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February 16, 2010 |
PCT NO:
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PCT/IB10/50682 |
371 Date:
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August 5, 2011 |
Current U.S. Class: |
237/59; 237/81 |
Class at Publication: |
237/59; 237/81 |
International Class: |
F24D 3/10 20060101 F24D003/10 |
Foreign Application Data
Date | Code | Application Number |
Feb 18, 2009 | FI | 20095147 |
Claims
1. A method for controlling a hydronic heating/cooling system in which
liquid is led along a main supply pipe to a supply manifold and
distributed in the manifold into heating loops, the heating loops
returning to a return manifold, and at least one of the manifolds having
actuators for controlling the flow in the heating loops, the method
comprising using actuators with fast operating times, and preventing the
simultaneous closure of actuator valves in different heating loops.
2. A method according to claim 1, wherein the endings of duty cycles are
detected and, if two or more duty cycles end substantially
simultaneously, a delay is added to at least one duty cycle.
3. A method according to claim 2, wherein the duty cycles are defined to
end substantially simultaneously if the difference between the ends of
the duty cycles is shorter than an operation time of the actuators.
4. A method according to claim 2, wherein the length of the delay is
equal to or longer than the operation time of the actuators.
5. A method according to claim 1, wherein the actuators control the flow
in the heating loops on and off such that during a duty cycle the flow is
high and between the duty cycles the flow is off.
6. A method according to claim 1, wherein the duty cycles in different
heating loops overlap partly.
7. A hydronic heating/cooling system comprising a main supply pipe, a
main return pipe, at least one supply manifold, at least one return
manifold, heating loops from the supply manifold to the return manifold,
and actuators for controlling the flow in the heating loops arranged to
at the supply manifold and/or the return manifold, the actuators having
fast operating time and means for preventing the simultaneous closure of
actuator valves in different heating loops.
8. A system according to claim 7, comprising the system comprises means
for detecting the endings of duty cycles and means for adding a delay to
at least one duty cycle if two or more duty cycles end substantially
simultaneously.
9. A system according to claim 7, wherein the actuators are arranged to
control the flow in the heating loops on and off such that during the
duty cycle the flow is high and between the duty cycles the flow is off.
10. A non-transitory computer-readable medium having encoded thereon
software for controlling a hydronic heating/cooling system in which
liquid is led along a main pipe to a supply manifold and distributed in
the manifold in to heating loops, the heating loops returning to a return
manifold, and at least one of the manifolds having actuators for
controlling the flow in the heating loops, wherein the software comprises
instructions that, when executed by a control unit, cause a control to
detect endings of the duty cycles and prevent the simultaneous closure of
actuator valves in different heating loops.
Description
BACKGROUND OF THE INVENTION
[0001] The invention relates to a method for controlling a hydronic
heating/cooling system in which liquid is led along a main supply pipe to
a supply manifold and distributed in the manifold into heating loops, the
heating loops returning to a return manifold, and at least one of the
manifolds having actuators for controlling the flow in the heating loops.
[0002] The invention further relates to a hydronic heating/cooling system
comprising a main supply pipe, a main return pipe, at least one supply
manifold, at least one return manifold, heating loops from the supply
manifold to the return manifold, and actuators for controlling the flow
in the heating loops arranged to at the supply manifold and/or the return
manifold.
[0003] Yet further the invention relates to a software product of a
control system of a hydronic heating/cooling system in which liquid is
led along a main pipe to a supply manifold and distributed in the
manifold in to heating loops, the heating loops returning to a return
manifold, and at least one of the manifolds having actuators for
controlling the flow in the heating loops.
[0004] In hydronic heating systems the liquid acting as medium is
typically led to a supply manifold, and the heating pipes forming the
actual heating loop extend from the supply manifold and, having made a
loop in the space to be heated, return to a return manifold. Valves
controlling the liquid flow in the heating pipes are arranged to either
the supply manifold or return manifold or both. The valves are
actuator-operated and the operation of the actuators is controlled by a
control system. Controlling the actuators is quite complex, and it is
necessary to take into consideration in the control system several things
related to temperature control, reliable operation of the system, and
acoustic problems caused by the system, for instance. An example of a
hydronic heating system is described in the document JP 2001004157.
[0005] The document JP 2001336809 discloses a floor heating system
comprising a plurality of thermally operated valves. When the thermally
operated valves are opened they are energized sequentially in order to
minimize the electric inrush current.
BRIEF DESCRIPTION OF THE INVENTION
[0006] It is an object of the present invention to provide a novel
solution for controlling a heating/cooling system.
[0007] The method of the invention is characterised by using actuators
with fast operating times, and preventing the simultaneous closure of
actuator valves in different heating loops.
[0008] The system of the invention is characterised in that the actuators
have fast operating time and the system comprises means for preventing
the simultaneous closure of actuator valves in different heating loops.
[0009] The software product of the invention is characterised in that the
execution of the software product on a control unit of the control system
is arranged to provide the following operations of detecting endings of
the duty cycles and preventing the simultaneous closure of actuator
valves in different heating loops.
[0010] The idea of the invention is that in a hydronic heating/cooling
system liquid is led along a main supply pipe to a supply manifold and
distributed into heating loops. The heating loops return to a return
manifold. At least one of the manifolds has actuators for controlling the
flow in the heating loops. Actuators with fast operating times are used
and valves of the actuators are controlled to close at different times in
different heating loops. Fast actuators provide an extremely versatile
control function, and when the valves are controlled to close at
different times, hydraulic impacts caused by valve closure cannot become
disturbing in view of acoustic problems caused by the piping structure
and hydraulic impact.
BRIEF DESCRIPTION OF THE FIGURES
[0011] Some embodiments of the invention are described in greater detail
in the attached drawings in which
[0012] FIG. 1 is a schematic representation of a hydronic heating/cooling
system,
[0013] FIG. 2 is a schematic representation of duty cycles of two
actuators in different loops according to one embodiment,
[0014] FIG. 3 is a schematic representation of duty cycles of two
actuators in different loops according to another embodiment, and
[0015] FIG. 4 is a flow chart describing an operation of a control system
controlling a hydronic heating/cooling system.
[0016] In the figures, some embodiments of the invention are shown
simplified for the sake of clarity. Similar parts are marked with the
same reference numbers in the figures.
DETAILED DESCRIPTION OF THE INVENTION
[0017] FIG. 1 shows a hydronic heating/cooling system. In the system,
liquid is led along a main supply pipe 1 to a supply manifold 2. The
supply manifold 2 distributes the liquid to several heating loops 3. The
heating loops 3 make the liquid to flow through the rooms or spaces to be
heated or cooled. If the system is used for heating, the liquid can be
warm water, for example. On the other hand, if the system is used for
cooling, the liquid flowing in the pipes is cool liquid that cools the
rooms or spaces.
[0018] The pipes forming the heating loops 3 return to a return manifold
4. From the return manifold 4, the liquid flows back again along a main
return pipe 5.
[0019] Actuators 6 are arranged to the return manifold 4. The actuators 6
control the flow of the liquid in the loops 3.
[0020] A control unit 7 controls the operation of the actuators 6. The
actuators 6 can also be arranged to the supply manifold 2. Further, there
can be actuators both in the supply manifold 2 and in the return manifold
4. Either one of the manifolds 2 and 4 can further comprise balancing
valves. The balancing valves can be manually operated, for example.
[0021] The system can also comprise a circulation pump 12 and a connection
between the main supply pipe 1 and the main return pipe, the connection
being provided with a mixing valve 13. A separate circulation pump 12
and/or a connection between the pipes 1 and 5 is, however, not always
necessary.
[0022] A hydronic underfloor heating system distributes the needed heating
to each room in the building by controlling the hot water flow through a
heating loop in the floor. Normally, one loop per room is used but
sometimes a large room is split into two or more loops. The controller
will act on the information from the room thermostat and accordingly turn
the water flow on or off in the floor loop.
[0023] The floor loop or heating loop piping is typically made of
cross-linked polyethylene plastic pipes, for instance. These pipes can be
used in different types of floor constructions, i.e., both concrete and
wooden floors can be heated this way. It is essential that the
insulation, under the pipes, in the floor construction is good to avoid
the leakage of energy out downwards. The floor loop layout depends on the
heat demand for each room.
[0024] In a concrete floor, typically 20-mm pipes are used, the pipes
being usually attached to a re-enforcing net before the final concrete
casting. The recommendation is that the top of the pipes should be 30 to
90 mm below the concrete surface and the pipe loops should be placed at a
300-mm center distance. Concrete conducts heat well, so this layout will
lead to an even distribution of energy and give an even temperature on
the floor surface. This building method using concrete and 20-mm pipes is
an economical way of building a UFH (underfloor heating) system.
[0025] Due to the good thermal conduction in concrete, the loop can be fed
with low supply temperature, normally below 35 degrees Celsius.
[0026] The step response is quite slow due to the large mass of the floor,
normally between 8 to 16 h depending on the floor thickness.
[0027] In wooden floors there are some different construction techniques
available and we can divide them into two main categories: floor loops
inside the floor construction or on top of the floor construction. It is
to be noted that all UFH wood construction techniques use aluminum plates
to distribute the heat from the pipes. This compensates for the poor heat
conduction in wood. Generally speaking, all "in floor" constructions use
20-mm pipes and the "on floor" technique uses 17-mm pipes that are
mounted in pre-grooved floorboards. However, it is self-evident to a
person skilled in the art that the diameter of the pipes can also be
different and it is determined according to the need and/or requirements
set by the system and/or environment.
[0028] Due to the poor thermal conduction in a wood floor, the loops need
a higher supply temperature than a concrete floor, normally up to 40
degrees Celsius.
[0029] The step response is quicker than for concrete, normally between 4
to 6 h depending on the floor construction.
[0030] The previously mentioned systems are primarily installed when a
house is built. In addition to these, there are UFH systems for after
installation. This system focuses on a low building height and the ease
of handling, and uses smaller pipe diameters, and the pipes are mounted
in pre-grooved polystyrene floor panels. The supply temperature and step
response are quite similar to those of wooden constructions.
[0031] The stroke cycle of the actuator 6 is preferably less than 120
seconds. The actuator 6 can be a conventional mechanical piston valve.
The actuator can also be, for example, a solenoid valve. When using a
solenoid valve the stroke time of the actuator can be very short. Thus,
the stroke time or operating time of the actuator can be for example in
the range of 0.1 to 120 seconds. Preferably actuators 6 with fast
operating time are used. Thus, the operating time of the actuators 6 is
preferably less than 10 seconds.
[0032] In the control system, the term "pulse width" refers to the on time
of the flow, i.e., the duty cycle. A minimum pulse width is preferred in
order to achieve efficient heating. However, the minimum pulse width is
preferably determined such that during the duty cycle the longest loop is
also filled with supply water. The minimum pulse width means that the
time frame of control is quite short, which means high frequency.
Preferably, the time frame is shorter than 1/3 of the response time of
the floor in the room to be heated. The time frame may vary for example
between 5 and 60 minutes. In order to achieve the feature that the duty
cycles start at different moments in different loops, the length of the
off-times between the duty cycles can be varied using a pattern or
randomly. The variation must naturally be carried out within certain
limits, such that the percentage of the duty cycles can be kept at a
desired value. Another option is to vary the pulse width using a pattern
or randomly in a corresponding manner. Yet another option is to use
different time frames in different loops. For example, in one loop the
time frame can be 29 minutes, in a second loop the time frame can be 30
minutes, and in third loop the time frame can be 31 minutes. Of course
sometimes the duty cycles start simultaneously in different loops but
using at least one of the above-mentioned systems, the duty cycles start
at different moments in most cases. Thus, the object is to prevent the
duty cycles in different loops from running synchronously.
[0033] The percentage of the duty cycle means how long the on-state of the
time frame is. In other words, if the time frame is 10 minutes and the
percentage of the duty cycle is 10%, it means that the flow is on for 1
minute and off for 9 minutes, if the percentage is 50 the flow is on for
5 minutes and off for 5 minutes, and if the percentage of the duty cycle
is 90, the flow is on for 9 minutes and off for 1 minute. If the time
frame is short enough, control can be considered continuous if the system
is slow enough, i.e., the response time of the floor is long.
[0034] This specification refers to hydronic under surface
heating/cooling. In such a system, liquid is supplied to supply loops for
cooling/heating. The liquid can be for example water or any other
suitable liquid medium. The liquid may comprise glycol, for example.
Under surface heating/cooling means that the supply loops are installed
under the floor, for example. The supply loops can also be installed in
any other suitable structure. The loops may be installed in the wall or
ceiling, for example.
[0035] In an embodiment an on/off control is combined with pulse width
modulation per room. The pulse width depends on the response in the room.
At the startup the pulse width is preferably always 50%. The time frame
for the pulse width can be 30 minutes, for example. It is important to
prevent the different channels/loops from running synchronously. Adding a
random value of -30 to +30 seconds to the time frame can prevent this.
Another possibility is to have a slightly different time frame for each
channel/loop. It is enough if the difference is 5 seconds, for example.
[0036] The maximum value for the pulse width is 25 minutes and the minimum
value is 5 minutes. The resolution can be 1 minute, for example.
Preferably, the pulse width modulation counter is reset by a change of a
set point which prevents delays in the system.
[0037] A heating cycle is defined as the time between one heating request
and the next heating request.
[0038] Maximum and minimum room temperatures are monitored and saved
during a full heating cycle.
[0039] The pulse width is adjusted at timeout, at heat-up modes or after a
heating cycle.
[0040] The master timeout for pulse width adjustment can be for example
300 minutes.
[0041] The control system comprises an appropriate means for performing
the desired functions. For example, a channel block calculates the
control signal based on the set point, the room temperature and the
energy required. The energy is pulse width modulated and the energy
requirement is calculated by measuring the characteristics of the room
temperature over time.
[0042] One way to describe this is that it is a traditional on/off control
with self-adjusting gain.
[0043] In an embodiment, the pulse width modulation output can be adjusted
between 15 to 70% of the duty cycle. The start value is 50%. The maximum
and minimum values during an on/off cycle are stored and evaluated and
the duty cycle is adjusted if needed.
[0044] The pulse width modulation timer is restarted if the set point
increases more than 1 degree, for example.
[0045] FIG. 2 shows a duty cycle 8a of an actuator. At moment t.sub.1 the
control unit 7 gives the actuator 6 a closing command. At moment t.sub.2
the actuator is fully closed. The stroke time or operating time is
denoted in the figure with reference numeral 9.
[0046] FIG. 2 further shows another duty cycle 8b of an actuator in
another heating loop. In this case, too, the pulse width of the duty
cycle 8b is such that the duty cycle 8b ends simultaneously with the duty
cycle 8a at moment t.sub.1 if no extra action is taken. This is denoted
in FIG. 2 with reference numeral 10. However, the control unit 7 detects
that in such a case two actuators 6 would close simultaneously.
Therefore, the control unit 7 adds a delay 11 to the duty cycle 8b.
Because of the added delay 11, the duty cycle 8b is made longer such that
the actuator 6 starts to close at moment t.sub.2 and is fully closed at
moment t.sub.3. The length of the delay 11 is equal to or greater than
the operating time 9 of the actuators. Thus, the simultaneous closure of
the actuators in different heating loops is prevented.
[0047] FIG. 3 shows another case in which the second actuator operating
according to the duty cycle 8b is not going to close exactly
simultaneously with the first actuator at moment t.sub.1, but the second
actuator is going to close at moment t.sub.4. However, because the
difference between the moments t.sub.1 and t.sub.4 is shorter than the
operating time 9 of the actuators, the closing of the actuators would
happen partly simultaneously or overlap. This would also cause acoustic
problems and/or hydraulic impacts. Therefore, the control unit 7 adds the
delay 11 to the second duty cycle 8b, whereby in this case the
simultaneous closure of the actuators is also prevented. Thus, the
closure of the second actuator starts at moment t.sub.3 which is after
the moment t.sub.2 when the first actuator is fully closed. In this case
the length of the delay need not be as long as the operating time 9 but
the delay 11 could be shortened by the time between the moments t.sub.4
and t.sub.1. However, adjusting the delay 11 is not necessary, because
typically the length of the delay 11 is much shorter than the length of
the duty cycles 8a, 8b.
[0048] FIG. 4 is a flow chart according to the operation of the
above-described control system. In block A the endings of the duty cycles
are detected. In block B it is analysed whether two or more duty cycles
end simultaneously. If the result of this analyzation is "no", the loop
returns the block A. However, if two or more duty cycles end
simultaneously the procedure continues to block C. Block C comprises the
step that the simultaneous ending of the duty cycles is prevented. Thus,
in block C a delay is added to at least one duty cycle, for example.
[0049] The control unit 7 can comprise a software product whose execution
on the control unit 7 is arranged to provide at least some of the
above-described operations. The software product can be loaded onto the
control unit 7 from a storage or memory medium, such as a memory stick, a
memory disc, a hard disc, a network server, or the like, the execution of
which software product in the processor of the control unit or the like
produces operations described in this specification for controlling a
hydronic heating/cooling system.
[0050] Preventing the simultaneous closure of the actuators limit pressure
changes in the pipes. Limiting the pressure changes prevents noise
problems. The difference between the closing commands given by the
control unit 7 to the actuators 6 should thus be at least as long as the
operating time 9 of the actuators. Preventing the simultaneous opening of
the actuators also reduces pressure changes and thus prevents noise
problems. Thus, applying the operation using delays described in
connection with FIGS. 2 and 3 can also be applied to the starting moment
of the duty cycles 8a, 8b.
[0051] In some cases the features described in this application can be
used as such regardless of other features. The features described in this
application may also be combined as necessary to form various
combinations.
[0052] The drawings and the related description are only intended to
illustrate the idea of the invention. The invention may vary in detail
within the scope of the claims.
* * * * *