HEATING SYSTEM AND METHOD

Abstract

 Heaters for homes come in various shapes and size, such as gas heaters burning gas to convert gas to heat. These heaters have most of the time to support multiple flows of water, commonly at different temperatures. It is an object of the invention to provide a heating system with lower complexity and improved efficiency. The current invention provides for a heating system comprising: a flow-through electrical heater for heating a primary heat conductive fluid; a fluid buffer for buffering the primary heat conductive fluid, wherein the fluid buffer comprises: a buffer input in fluid communication with the flow-through electrical heater for receiving the heated primary heat conductive fluid; a first heat exchanger having a first primary side for flow through of the primary heat conductive fluid and a first secondary side for flow through of a first secondary heat conductive liquid and being arranged for exchanging heat between the primary heat conductive fluid and the first secondary heat conductive liquid, wherein the first primary side is arranged downstream of the buffer input; a second heat exchanger having a second primary side for flow through of the primary heat conductive fluid and a second secondary side for flow through of a second secondary heat conductive liquid and being arranged for exchanging heat between the primary heat conductive fluid and the second secondary heat conductive liquid, wherein the second primary side is arranged downstream of the buffer input and wherein the second secondary heat conductive liquid is separated from the first secondary heat conductive liquid; and control means arranged for controlling the temperature of the first secondary heat conductive liquid exiting the first heat exchanger and/or the second secondary heat conductive liquid exiting the second heat exchanger, wherein the control means comprise a flow sensor for detecting flow of the second secondary heat conductive liquid through the second secondary side of the second heat exchanger; and flow control means arranged for controlling flow of the first secondary heat conductive liquid through the first heat exchanger based on measurements of the flow sensor.

Description

FIELD OF THE INVENTION

[0001] The invention relates to the field of heating systems, methods for heating systems and computer program products for heating systems.

BACKGROUND OF THE INVENTION

[0002] Homes are mostly heated for comfort of living, especially in mild and colder climates. Heaters for homes come in various shapes and size. A well-known example are the gas heaters burning gas to convert gas to heat. The heat is carried by water in a closed circuit of pipes from the gas heater to a radiator and from there back to the gas heater.

[0003] Most modern homes provide hot tap water to the occupant. The hot tap water may be heated by the same gas heater as the gas heater heating the home. The water for heating the house is not refreshed due to it being in a closed circuit and thus not suitable for drinking. Therefore, this type of gas heater has to accommodate two separate flows of water along the gas burner resulting in a complex system. Furthermore, the gas heater can only be optimized for either heating the home or the tap water.

[0004] As another option, it is quite common to have a separate gas boiler to heat tap water and temporarily store the heated tap water in a boiler. Although these separate systems may be optimized for each individual requirement for heating, it has the disadvantage of introducing multiple systems and thus complexity.

SUMMARY OF THE INVENTION

[0005] An object of the invention is to decrease the complexity of the known heating systems. It is another object of the invention to improve the efficiency over the known systems.

[0006] According to a first aspect of the invention, a heating system comprising:

• a flow-through electrical heater for heating a primary heat conductive fluid;
• a fluid buffer for buffering the primary heat conductive fluid, wherein the fluid buffer comprises:
  • a buffer input in fluid communication with the flow-through electrical heater for receiving the heated primary heat conductive fluid;
• a first heat exchanger having a first primary side for flow through of the primary heat conductive fluid and a first secondary side for flow through of a first secondary heat conductive liquid and being arranged for exchanging heat between the primary heat conductive fluid and the first secondary heat conductive liquid, wherein the first primary side is arranged downstream of the buffer input;
• a second heat exchanger having a second primary side for flow through of the primary heat conductive fluid and a second secondary side for flow through of a second secondary heat conductive liquid and being arranged for exchanging heat between the primary heat conductive fluid and the second secondary heat conductive liquid, wherein the second primary side is arranged downstream of the buffer input and wherein the second secondary heat conductive liquid is separated from the first secondary heat conductive liquid; and
• control means arranged for controlling the temperature of the first secondary heat conductive liquid exiting the first heat exchanger and/or the second secondary heat conductive liquid exiting the second heat exchanger, wherein the control means comprise:
  • a flow sensor for detecting flow of the second secondary heat conductive liquid through the second secondary side of the second heat exchanger; and
  • flow control means arranged for controlling flow of the first secondary heat conductive liquid through the first heat exchanger based on measurements of the flow sensor.

[0007] The primary heat conductive fluid inside the flow-through electrical heater is heated, when the heater is on. The heated primary conductive fluid flows from the heater via the circuit to the fluid buffer. The fluid buffer stores or buffers the heated primary conductive fluid. As heated primary conductive fluid flows from the heater to the fluid buffer, relatively cold primary heat conductive fluid flows to the heater via the circuit. This relatively cold primary heat conductive fluid replaces the heated primary heat conductive fluid. This flow may have a natural cause based on that heated fluid rises and cold fluid falls. This flow may also be induced, such as by a pump. This flow may also be a combination of a natural cause and an induced flow.

[0008] The fluid buffer is a heat storage or buffer for storing or buffering heated primary heat conductive fluid. Further, the fluid buffer is a storage of relatively cold primary heat conductive fluid. Typically, the fluid buffer contains primary heat conductive fluid wherein a temperature gradient is present across the primary heat conductive fluid in the fluid buffer. This temperature gradient is relatively high in case of no or minimal flow of, swirl in or vortex in the primary heat conductive fluid in the fluid buffer.

[0009] The flow-through electrical heater has typically a large capacity compared to the capacity of the fluid buffer. Thus, the heater is able to relatively quickly heat the primary heat conductive fluid and fill the complete fluid buffer with heated primary heat conductive fluid.

[0010] The first heat exchanger exchanges heat between the primary heat conductive fluid and the first secondary heat conductive liquid. The first heat exchanger may be arranged in an inner space of the fluid buffer. More specifically, the first heat exchanger may be arranged at the lower part of the inner space. Typically, the first heat exchanger is arranged downstream of the fluid buffer.

[0011] The second heat exchanger exchanges heat between the primary heat conductive fluid and the second secondary heat conductive liquid. The second heat exchanger may also be arranged in the inner space of the fluid buffer. More specifically, the second heat exchanger may be arranged at the higher part of the inner space. Alternatively, the second heat exchanger may be integrated with the fluid buffer. Typically, the second heat exchanger is arranged downstream of the fluid buffer.

[0012] The first secondary heat conductive liquid is typically used for heating the interior of a building, such as a house. The heating of an interior typically requires a constant heating with a relatively low temperature. The first secondary heat conductive liquid is typically a liquid that circulates. The circulating liquid is typically not suitable for drinking or even for coming in contact with humans. The second secondary heat conductive liquid is typically used for hot tap water, such as for showers and/or hot tap water for sinks. The hot tap water is typically required more incidentally, such as during a shower, taking a bath or opening the hot water tap. The hot tap water typically has a relatively high temperature. Thus, the hot tap water is typically of a higher temperature compared to a liquid, such as water, for heating an interior. The hot tap water is typically suitable for drinking or at least coming in contact with humans. Thus, at least the first secondary heat conductive liquid and the second secondary heat conductive liquid should be separated.

[0013] During operation in a first situation the second secondary heat conductive liquid is stationary in the second heat exchanger. This is typically the case if no high temperature liquid is required from the system, such as if all hot tap water points are closed. During the first situation the first secondary heat conductive liquid may flow for providing heated first secondary heat conductive liquid of relatively low temperature. As the flow-through electrical heater has typically a high capacity, the flow-through electrical heater may incidentally heat the primary heat conductive fluid and the fluid buffer will equalize this such that the first secondary heat conductive liquid in the first heat exchanger is substantially heated to the same temperature over time. Alternatively, the flow-through electrical heater may heat the primary heat conductive fluid only with a part of its capacity for only providing the heat to the primary heat conductive fluid for heating the first secondary heat conductive liquid via the first heat exchanger to the required temperature.

[0014] During operation in a second situation the second secondary heat conductive liquid in the second heat exchanger is flowing. This is typically the case when a shower or bath is taken or a hot tap water point is open. The flow-through electrical heater is typically used at or close to its maximum capacity for providing heated primary heat conductive fluid. The heated primary heat conductive fluid fills the fluid buffer to provide enough heat to the second secondary heat conductive liquid via the second heat exchanger to heat the second secondary heat conductive liquid to the required high temperature. Alternatively, if the second heat exchanger is arranged outside the fluid buffer, the heated primary heat conductive fluid fills the fluid buffer with heated primary heat conductive fluid and thereafter the second heat exchanger for exchanging heat with the second secondary heat conductive fluid.

[0015] In the second situation, the control means detect flow of the second secondary heat conductive liquid. This detection may be done directly via for example a flow sensor sensing flow of the second secondary heat conductive liquid. This detection may also be done indirectly via for example a temperature drop in the primary heat conductive fluid at a location in the primary circuit.

[0016] Furthermore, the heated primary heat conductive fluid may heat the first secondary heat conductive liquid to a temperature over the maximum temperature for the first secondary heat conductive liquid. The control means adapt the heating system such that overheated first secondary conductive liquid leaving the first heat exchanger is prevented. Hence, controlling the temperature of the first secondary heat conductive liquid exiting the first heat exchanger.

[0017] The combination of the flow sensor and the flow control means provide a means of controlling the output of energy in the form of controlling the temperature of the first secondary heat conductive liquid exiting the first heat exchanger. Indirectly, the energy output and thus the temperature of the second secondary heat conductive liquid exiting the second heat exchanger is controlled by redirecting energy from the first heat exchanger to the second heat exchanger if flow is detected.

[0018] Due to the ability of the system to provide heated and separated liquid supplies with minimal elements, the complexity of the system is reduced. Furthermore, by applying a flow-through heater in combination with a buffer and two heat exchangers configured as claimed and described, the heater system provides for a system with improved efficiency. Also, the system provides for increased safety employing only electricity instead of gas for heating the primary heat conductive fluid.

[0019] In an embodiment of the current invention, the heating system is arranged for providing the first secondary heat conductive liquid flowing out of the first heat exchanger of a first temperature and the second secondary heat conductive liquid flowing out of the second heat exchanger of a second temperature, which temperatures are different. In a further embodiment of the current invention, the second temperature is higher compared to the first temperature. In an embodiment of the current invention, the first heat exchanger is a low temperature heat exchanger and the second heat exchanger is a high temperature heat exchanger.

[0020] The low and high temperatures are relative to each other. The range of the low and high temperatures may partly overlap. The range of the low and high temperatures may be arranged at a distance on the temperature scale. The low and high temperature ranges pertain to the secondary heat conductive liquids outputted from the respective heat exchangers. The secondary heat conductive liquid should be preferably in the specified range, although during start and stop of the flow of the secondary heat conductive liquid, the secondary liquid may temporarily be outside the temperature range. The temperature range of the second secondary liquid, which is the high temperature range, may be in the range of 30°C to 90°C, more preferably 35°C to 85°C, most preferably 40°C to 80°C, even more preferably 45°C to 75°C. The temperature range of the first secondary liquid, which is the low temperature range, may be in the range of 10°C to 65°C, more preferably 20°C to 60°C, most preferably 25°C to 55°C, even more preferably 25°C to 50°C. Due to the low number of components, while still providing secondary heat conductive liquid for two different temperature ranges provides for a system of low complexity. Furthermore, the system uses the combination of the flow-through electrical heater, the buffer and the arrangement of the heat exchangers to provide an efficient and safe heating system.

[0021] The control means comprise flow control means which may comprise a pump and/or a valve, such as a remote controllable valve. The control means may further comprise a controller configured for adjusting the flow control means based on measurements from the flow sensor. Preferably, the flow sensor is arranged downstream and in proximity of the second secondary side.

[0022] In an embodiment of the current invention, the first and second heat exchangers are arranged inside the fluid buffer. As the heat exchangers are arranged inside the fluid buffer, the system is further reduced in complexity, especially during installation the number of components that need to be installed and connected is reduced. Furthermore, the fluid buffer may equalize the temperature of the primary heat conductive fluid leaving the flow-through electrical heater more, such that the heated second heat conductive liquid leaving the second heat exchanger is advantageously of more even temperature allowing a narrower temperature range specification.

[0023] In a further embodiment of the current invention, the heat exchanger arranged inside the fluid buffer is a plate heat exchanger. A plate heat exchanger provides more efficient heat exchange between the primary fluid and the respective secondary heat conductive liquid.

[0024] In an embodiment of the current invention, the heat exchanger arranged outside the fluid buffer is a tube heat exchanger. A tube heat exchanger is an efficient type of heat exchanger, easily installed and manufactured, thus lowering complexity.

[0025] In an embodiment of the current invention, the primary heat conductive fluid is a primary heat conductive liquid. Liquids have the advantage that the installation is simplified as leaks are less prone compared to gasses. In a further embodiment of the current invention the liquid is water, preferably with enhanced conductivity by the addition of additives to enhance the heat generation of the flow-through electrical heater.

[0026] In an embodiment of the current invention, the fluid buffer has a volume V [m3], wherein the flow-through electrical heater has a maximum flow rate Q [m3/s] and wherein V / Q is in the range of 0.5 to 30 seconds, preferably 0.5 to 10 seconds, more preferably 0.5 to 5 seconds, most preferably 0.5 to 2.5 seconds. The ratio of V/Q is important for the delay time before the secondary fluid is heated at start up. As the second heat exchanger may be arranged inside the fluid buffer or directly behind the fluid buffer. This ratio determines for a large part the delay time before secondary second heated liquid is outputted from the second heat exchanger. If, in a further embodiment, the first heat exchanger is also arranged inside or directly behind the fluid buffer, then the ratio determines for a large part also the delay time before first secondary heated liquid is outputted from the first heat exchanger.

[0027] Furthermore, the heat capacity of the flow-through electrical heater should be selected such that the maximum amount of heat outputted from the heater via the heated primary heat conductive fluid reduced by the amount of heat lost in the heating system exceeds the amount of heat needed from the heated secondary liquids. Most of the time also a maximum flow rate of the secondary liquid is required. Hence, the heat capacity of the flow-through electrical heater has a minimum capacity Q. Typically, the maximum temperature and flow rate of the second secondary liquid provide a basis for the calculation of the minimum capacity Q of the flow-through electrical heater. Part of this calculation may be the efficiency of the transport of heat generated by the flow-through electrical heater to the respective heat exchangers.

[0028] Furthermore, the fluid buffer causes the heated primary fluid to be at least partly mixed with the primary fluid already present in the fluid buffer. Thus, the fluid buffer equalizes the temperature of the primary fluid. This equalization causes the secondary liquid with a heat exchanger in the inner space to be heated more equally. Thus, providing the advantage of a more evenly heated secondary liquid, such that a narrower temperature range for the secondary liquid may be complied to.

[0029] Hence, a well selected ratio provides for a heating system that may react appropriately to the different demands, such as short delay and narrow temperature range.

[0030] According to another aspect of the current invention, a method for heating comprising the steps of:

• circulating a primary heat conductive fluid;
• heating the primary heat conductive fluid with a flow-through electrical heater;
• buffering the heated primary heat conductive fluid;
• exchanging heat between the primary heat conductive fluid and a first secondary heat conductive liquid;
• exchanging heat between the primary heat conductive fluid and a second secondary heat conductive liquid, wherein the heat exchange is downstream from where the primary heat conductive fluid is heated; and
• controlling the temperature of the first secondary heat conductive liquid exiting the first heat exchanger.

[0031] According to another aspect of the current invention, a computer program product comprising a computer readable medium having computer readable code embodied therein, the computer readable code being configured such that, on execution by a suitable computer or processor, the computer or processor, when connected to a heating system according to the current invention or a method performed, is caused to perform the step of:

• controlling the temperature of the first secondary heat conductive liquid exiting the first heat exchanger.

[0032] According to another aspect of the current invention, a conductivity adaptor for adapting the electrical conductivity of a heat conductive fluid in a heating circuit having a flow-through electrical heater, comprising:

• a dispenser for dispensing a fluid for changing the electrical conductivity of the heat conductive fluid;
• a sensor for detecting the electrical conductivity of the heat conductive fluid;
• a controller configured for receiving electrical conductivity measurements from the sensor, for receiving an electrical conductivity setpoint, for comparing the received measurements with the electrical conductivity setpoint and for controlling the dispenser based on the comparison such that the electrical conductivity of the heat conductive fluid approaches the electrical conductivity setpoint.

[0033] The flow-through electrical heater may apply the principle of ohmic heating, wherein the electrical heater provides an electrical current to flow-through the primary fluid. The primary fluid has a particular resistance. A current flowing through a resistance cause a temperature rise or heat generation, in this case in the primary fluid. The flow-through electrical heater may also apply the principle of friction heating. As the primary fluid is electrically conductive, the primary fluid contains charged particles, such as differently charged particles, positively and/or negatively charged ions. The flow-through electrical heater may apply an alternating current of a certain frequency and a certain amplitude. This alternating current may influence the flow of the ions of the primary fluid. This influence may cause the ions to move relative to uncharged and/or oppositely charged particles in the fluid. The relative movement of the ions may cause friction of the ions with the other particles of the primary fluid. And this friction causes a temperature rise in the fluid. In a preferred embodiment of the current invention the flow-through electrical heater is a flow-through alternating current electrical heater applying the principle of friction heating as described above. In a more preferred embodiment the flow-through alternating current electrical heater is applied in a heating system for a building, such as a domestic building. In an even more preferred embodiment the flow-through alternating current electrical heater is directly connected to the mains power supply. This embodiment provides the advantage of preventing efficiency loss due to the conversion from alternating current to direct current. Furthermore, the complexity is reduced as no conversion of electricity is needed.

[0034] Tests show that the conductivity of the primary fluid, which is preferably liquid, more preferably water, influences the efficiency of the flow-through electrical heater. Hence, adjusting the conductivity may be required to reach or closely reach the optimal efficiency of the heater. The current invention provides an adaptor for adapting this conductivity for enhancing the efficiency of the heater.

[0035] According to another aspect of the current invention, a method for adapting the electrical conductivity of a heat conductive fluid in a heating circuit having a flow-through electrical heater, comprising the steps of:

• detecting the electrical conductivity of the heat conductive fluid;
• receiving electrical conductivity measurements;
• receiving an electrical conductivity setpoint;
• comparing the received measurements with the electrical conductivity setpoint; and
• based on the comparison dispensing a fluid for changing the electrical conductivity of the heat conductive fluid such that the electrical conductivity of the heat conductive fluid approaches the electrical conductivity setpoint. The method provides the same advantages as the adaptor.

[0036] According to another aspect of the current invention, a computer program product comprising a computer readable medium having computer readable code embodied therein, the computer readable code being configured such that, on execution by a suitable computer or processor, the computer or processor is caused to perform a method for adapting the electrical conductivity of a heat conductive fluid in a heating circuit having a flow-through electrical heater, comprising the steps of:

• receiving electrical conductivity measurements of the heat conductive fluid;
• receiving an electrical conductivity setpoint;
• comparing the received measurements with the electrical conductivity setpoint; and
• based on the comparison controlling dispensing of a fluid for changing the electrical conductivity of the heat conductive fluid such that the electrical conductivity of the heat conductive fluid approaches the electrical conductivity setpoint.

[0037] According to another aspect of the current invention, a heating system comprising a conductivity adaptor for the primary heat conductive fluid. According to another aspect of the current invention, a method for heating comprising also the steps for adapting the electrical conductivity of the primary heat conductive fluid.

BRIEF DESCRIPTION OF THE DRAWINGS

[0038] The invention will be apparent from and elucidated further with reference to the embodiments described by way of example in the following description and with reference to the accompanying drawings, in which:

Figure 1 schematically shows a first heating system according to an embodiment of the current invention;

Figure 2 schematically shows a second heating system according to an embodiment of the current invention;

Figure 3 schematically shows a third heating system according to an embodiment of the current invention;

Figure 4 schematically shows a fourth heating system according to an embodiment of the current invention;

Figure 5 schematically shows a fifth heating system according to an embodiment of the current invention;

Figure 6 schematically shows a method for heating according to the current invention;

Figure 7 schematically shows a method for adapting the electrical conductivity of a heat conductive fluid according to the current invention; and

Figure 8 schematically shows an embodiment of a computer program product, computer readable medium and/or non-transitory computer readable storage medium according to the current invention.

[0039] The figures are purely diagrammatic and not drawn to scale. In the figures, elements which correspond to elements already described may have the same reference numerals.

LIST OF REFERENCE NUMERALS

Fp	flow direction of the primary fluid
Fs1	flow direction of the first secondary liquid
Fs2	flow direction of the second secondary liquid
Fin	three-way valve input flow
Fout	thee-way valve output flow
100	heating system
110, 110'	primary circuit
111	primary heat conductive fluid
112	primary temperature sensor
113	primary temperature signal
114	first check valve
115	first primary pump
116	first primary pump control signal
117	second check valve
118	second primary pump
119	second primary pump control signal
120	flow-through electrical heater
121	heater control signal
122	heater temperature sensor
123	heater temperature signal
130	fluid buffer
131	fluid buffer inner space
132	fluid buffer temperature sensor
133	buffer temperature signal
135	fluid buffer input
136	fluid buffer output
140	first heat exchanger
141	first primary side
142	first secondary side
143, 143'	first conduit
144	first secondary heat conductive liquid
149	external heat exchanger
150	second heat exchanger
151	second primary side
152	second secondary side
153, 153'	second conduit
154	second secondary heat conductive liquid
155	manually operated valve
160	control means
161	flow sensor
162	flow sensor signal
163	flow control means
164	first secondary pump
165	first secondary pump control signal
166	first secondary valve
167	first secondary valve control signal
169	controller
170	dispenser
171	reservoir
172	dispenser valve
173	dispenser valve control signal
175	expansion vessel
180	three-way valve / three-way thermostat valve
181	three-way valve control signal
182	three-way thermostat valve
192	conductivity sensor
193	conductivity sensor signal
200	method for heating
210	circulating a primary heat conductive fluid
220	heating the primary fluid with a flow-through electrical heater
230	buffering the heated primary fluid
240	exchanging heat between the primary fluid and a first secondary heat conductive liquid
250	exchanging heat between the primary fluid and a second secondary heat conductive liquid
260	controlling temperature of the first secondary heat conductive liquid
300	method for adapting the electrical conductivity of a heat conductive fluid
310	detecting the electrical conductivity of the heat conductive fluid
320	receiving electrical conductivity measurements
330	receiving an electrical conductivity setpoint
340	comparing the received measurements with the electrical conductivity setpoint
350	dispensing a fluid for changing the electrical conductivity of the heat conductive fluid
1000	computer program product
1010	computer readable medium
1020	computer readable code

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

[0040] The following figures may detail different embodiments. Embodiments can be combined to reach an enhanced or improved technical effect. These combined embodiments may be mentioned explicitly throughout the text, may be hint upon in the text or may be implicit.

[0041] Figure 1 schematically shows a heating system 100 according to an embodiment of the current invention. The system comprises a circuit or primary circuit 110, 100' for circulating a primary heat conductive fluid 111. The circuit may comprise one or more pipes, ducts, conduits or tubes carrying, conducting or conveying the fluid inside. The system may further comprise an expansion vessel 175 for equalizing the pressure in the primary circuit. The expansion vessel may be arranged at any location in the primary circuit. The system further comprises a flow-through electrical heater 120 arranged in-line with the circuit for heating the primary fluid. In-line in the context of this description means that two items are in fluid communication, such as that the circuit and the flow-through electrical heater are in fluid communication with each other. The primary heat conductive fluid is preferably a primary heat conductive liquid, such as water with an additive.

[0042] The system further comprises a fluid buffer 130 arranged in-line with the circuit for buffering the primary fluid. The fluid buffer comprises an inner space 131 holding the primary fluid. The fluid buffer further comprises a fluid buffer input 135 in fluid communication with and downstream of the flow-through electrical heater. The fluid buffer further comprises a fluid buffer output 136 in fluid communication with and upstream of the heat exchangers.

[0043] The system may further comprise a first conduit 143, 143' carrying a first secondary heat conductive liquid 144, a first heat exchanger 140 for exchanging heat between the primary fluid and the first secondary heat conductive liquid, and a first secondary valve 166 or a valve 166 arranged for preventing flow of the first liquid through the first heat exchanger if closed. The first heat exchanger comprises a first primary side 141 for fluid communication of the primary heat conductive fluid and a first secondary side 142 for fluid communication of the first secondary heat conductive liquid. Typically, the surface between the sides is large to enhance heat exchange between the two sides.

[0044] The system may comprise an external heat exchanger 149. This external heat exchanger may be a radiator in a building heating the inside of the building. The first conduit, the first heat exchanger and the external heat exchanger may form a loop for circulating the first liquid. The circulation of the first secondary heat conductive liquid may be stimulated by a pump.

[0045] The system further comprises a second conduit 153, 153' carrying a second secondary heat conductive liquid 154, a second heat exchanger 150 for exchanging heat between the primary fluid and the second secondary heat conductive liquid, and a flow sensor 161 for detecting flow of the second secondary heat conductive liquid. Although the figure shows a Venturi flow sensor, other flow sensors, such as flow nozzle sensor, wedge flow sensor, vortex flow sensor, etc., may be used. The second heat exchanger comprises a second primary side 151 for fluid communication of the primary heat conductive fluid and a second secondary side 152 for fluid communication of the second secondary heat conductive liquid. Typically, the surface between the sides is large to enhance heat exchange between the two sides.

[0046] The system may comprise a manually operated valve 155. The manually operated valve is arranged in-line with the first conduit. Furthermore, the other end of the first conduit may be connected to a water supply, such as a drinking water supply, for providing drinking water as the second secondary liquid. The manually operated valve may be a hot water tap, for example in building. If the manually operated valve is open, the second secondary liquid may flow through the conduit, which will be detected by the flow sensor.

[0047] Both the first and the second heat exchangers are in fluid communication downstream with a first check valve 114 and second check valve 117 respectively followed downstream by a first primary pump 115 and a second primary pump 118 respectively.

[0048] The heater heats the primary fluid. The buffer buffers the primary fluid. The heat may be extracted from the primary fluid via the first and/or second heat exchangers. The heat exchangers may be arranged after, such as directly after, the buffer as shown. The buffer buffers the heat generated by the heater.

[0049] The flow-through electrical heater may apply the principle of ohmic heating, wherein the electrical heater provides an electrical current to flow-through the primary fluid. The primary fluid has a particular resistance. A current flowing through a resistance cause a temperature rise or heat generation, in this case in the primary fluid. The flow-through electrical heater may also apply the principle of friction heating. As the primary fluid is electrically conductive, the primary fluid contains charged particles, such as positively and/or negatively charged ions. The flow-through electrical heater may apply an alternating current of a certain frequency and a certain amplitude. This alternating current may influence the flow of the ions in the primary fluid. This influence may cause the ions to move relative to differently charged particles, uncharged and/or oppositely charged particles in the fluid. The relative movement of the ions may cause friction of the ions with the other particles of the primary fluid. And this friction causes a temperature rise in the fluid. In a preferred embodiment of the current invention the flow-through electrical heater is a flow-through alternating current electrical heater applying the principle of friction heating as described above. In a more preferred embodiment the flow-through alternating current electrical heater is applied in a heating system for a building, such as a domestic building.

[0050] The system further comprises control means 160. The control means comprise a controller 169. The flow control means may be the same or a subset of the control means. The control means further comprise the flow sensor. The flow sensor outputs a flow sensor signal 162 providing an indication of the flow of the second secondary liquid as measured by the flow sensor. The controller is arranged to receive the flow sensor signal. The control means further comprise the first secondary valve. The first secondary valve 166 takes a first secondary valve control signal 167 as input for controlling the position of the valve. The valve has preferably at least two modes of operation, being open and closed. The controller is further arranged to control the valve control signal. If flow or a certain predefined level of flow is detected, the controller may trigger and the control may signal the valve to go in the close mode.

[0051] In an alternative embodiment, the valve is more opened, such that the flow rate through the heat exchanger of the second secondary liquid is increased, such that the outputted second secondary liquid is lower in temperature. This is especially an alternative in case that the capacity of the external heat exchanger is large or a large buffer is present in the second secondary circuit.

[0052] In an alternative embodiment, the control means comprise a first secondary pump 164. The first secondary pump comprises a first secondary pump control signal 165. This signal may be used to control or stimulate the flow of the first secondary liquid. The pump may be used in combination with the first secondary valve 166.

[0053] A natural circulation of the primary fluid may occur as the heater heats the primary fluid and the heat exchangers extract heat from the primary fluid. In this embodiment, the circulation of the primary fluid is stimulated or controlled by primary pumps 115, 118. The first and second primary pumps are controlled by the first and second primary control signals 116, 119 respectively. The controller may be arranged to output the primary pump control signals. The first and second check valve prevent flow of the primary heat conductive fluid in the wrong direction. The preferred flow direction of the primary heat conductive fluid is indicated by an arrow Fp. The preferred flow direction of the first secondary heat conductive liquid is indicated by an arrow Fs1. The preferred flow direction of the second secondary heat conductive liquid is indicated by an arrow Fs2.

[0054] The flow-through electrical heater may comprise a heater temperature sensor 122, preferable measuring the temperature of the casing of the heater. The heater temperature sensor may output a heater temperature signal 123. The controller may be arranged to receive the heater temperature signal. The flow-through electrical heater may comprise a heater control signal 121 for controlling the amount of heat generated in the primary fluid. The controller may be configured that if the temperature of the casing of the heater exceeds a predefined temperature to switch the pump on to circulate the primary fluid. And the controller may be further configured that if the temperature of the casing does not decrease or exceeds a second predefined temperature, the heater is controlled to switch off or decrease the heat generated in the primary fluid. This mechanism provides a safety measure preventing overheating of the flow-through electrical heater.

[0055] In a further embodiment, the control means may comprise a primary temperature sensor 112 arranged for measuring the temperature of the primary fluid. The primary temperature sensor outputs a primary temperature signal 113. The controller may be arranged to receive the primary temperature signal. If the primary temperature exceeds a predefined temperature and the pump is already on, the controller may be configured to switch off the heater as to further improve overheating prevention.

[0056] In a further embodiment, the control means may comprise a fluid buffer temperature sensor 132 arranged for measuring the temperature of the primary fluid in the inner space of the fluid buffer. The fluid buffer temperature sensor outputs a fluid buffer temperature signal 133. The controller may be arranged to receive the fluid buffer temperature signal. If the primary temperature in the inner space exceeds a predefined temperature and the pump is already on, the controller may be configured to switch off the heater as to further improve overheating prevention.

[0057] In a further embodiment, the control means comprise at least two, preferable all, of the group of a primary temperature sensor, heater temperature sensor and fluid buffer temperature sensor. The combination of sensors advantageously improves the overheating prevention of the heater. The combination of sensors also advantageously improves the control of the temperature of the primary fluid in the fluid buffer as well in the first and second heat exchangers, such that the temperature of the first and second secondary liquids is controlled with a higher accuracy. Furthermore, fluctuations of the temperature of the first and/or second secondary liquids are reduced.

[0058] In a preferred embodiment the flow-through electrical heater is a flow-through alternating current electrical heater. The conductivity of the primary fluid influences the efficiency of the heater, hence the need for optimizing the conductivity of the primary fluid. As the primary fluid is preferable inert, the conductivity optimization is typically done during installation, but in another embodiment, the conductivity optimization may be done during operation, such as constantly or at regular intervals.

[0059] In this preferred embodiment, the heating system may comprise a conductivity adaptor for adapting the electrical conductivity of a primary heat conductive fluid 111 in a heating circuit 110 having a flow-through electrical heater 120. The conductivity adaptor comprises a dispenser 170 for dispensing a fluid for changing the electrical conductivity of the heat conductive fluid. The dispenser may comprise one reservoir 171 for holding either a fluid for increasing or a fluid for decreasing the conductivity of the primary heat conductive fluid. Alternatively, the dispenser may comprise two reservoirs for holding a fluid for increasing and a fluid for decreasing the conductivity of the primary heat conductive fluid. In an alternative embodiment, a reservoir may hold primary heat conductive fluid with unadapted conductivity for diluting the primary heat conductive fluid with adapted conductivity in the primary circuit. The reservoir may be in fluid communication with the primary circuit 110, 100' via a dispenser valve 172 controlling the dispensing of the fluid in the reservoir into the primary circuit. The dispenser may be detachable connectable to the primary circuit. Alternatively, the dispenser may form an integral part of the primary circuit.

[0060] The conductivity adaptor further comprises a conductivity sensor 192 for detecting the electrical conductivity of the heat conductive fluid. The adaptor further comprises a controller, which may be the controller 169 as described above or may be a separate controller. The conductivity sensor outputs a conductivity sensor signal 193. The controller is arranged to receive this conductivity sensor signal. The dispenser valve is controlled by the dispenser valve control signal 173. The controller is arranged to output the dispenser valve control signal. The controller is configured to execute the following steps:

• receiving electrical conductivity measurements from the sensor;
• receiving an electrical conductivity setpoint;
• comparing the received measurements with the electrical conductivity setpoint; and
• controlling the dispenser based on the comparison such that the electrical conductivity of the heat conductive fluid approaches the electrical conductivity setpoint. The conductivity adaptor as described provides the advantage of very accurately controlling, regulating and/or setting the conductivity of the primary fluid such that the heater is fed with primary fluid of substantially optimal conductivity for substantially optimal functioning of the heater.

[0061] Figure 2 schematically shows a second heating system 200 according to an embodiment of the current invention. The first and second primary pumps from the first embodiment are replaced by one three-way valve 180 followed downstream by one first primary pump 115. The three-way valve has two inputs, wherein the input flow is indicated with Fin, and one output, wherein the output flow is indicated with Fout. The three-way valve typically prevents the flow of the primary heat conductive fluid in the opposite direction. The advantage of this configuration is that the primary circuit only needs one pump.

[0062] In an alternative embodiment, the three-way valve is a controllable three-way valve. The control means may comprise this controllable three-way valve. The controllable three-way valve is controllable via a three-way valve control signal outputted from for example the controller. This three-way controllable valve may be controlled such that if the flow sensor senses flow of the second secondary heat conductive liquid, that more primary heat conductive fluid is directed through the primary side of the second heat exchanger. Typically, the three-way controllable valve directs all primary heat conductive fluid through the primary side of the second heat exchanger.

[0063] In an alternative embodiment, the three-way valve is a three-way thermostat valve. The control means may comprise this three-way thermostat valve. The three-way thermostat valve allows a minimal flow of primary heat conductive fluid through the second primary side of the second heat exchanger. If the thermostat senses a temperature drop in this flow, heat is extracted from this flow as the second secondary heat conductive liquid flows or increases in flow. This temperature drop may be compensated by the three-way thermostat valve by directing more primary heat conductive fluid through the second primary side. This three-way thermostat valve may be combined with other control means, such as a first secondary valve 166 and a flow sensor 161 as described above, or three-way thermostat valve may work autonomously. If the three-way thermostat valve is combined with other control means, the thermostat signal may be connected to the controller for signalling the temperature and/or setting the valve configuration.

[0064] In an alternative embodiment, the three-way valve, such as a controllable three-way valve, a three-way thermostat valve or a three-way controllable thermostat valve, is arranged upstream instead of downstream of the two heat exchangers. If the three-way valve is arranged upstream, the three-way valve comprises one input and two outputs. The input receives heated primary heat conductive fluid and the outputs are in fluid communication with the respective primary sides of the heat exchangers. This embodiment provides the same advantages as described above for the embodiment in figure 2.

[0065] Figure 3 schematically shows a third heating system 300 according to an embodiment of the current invention. In this embodiment the heat exchangers are arranged sequentially in comparison to the heat exchangers in figure 1 and 2, which are arranged in parallel.

[0066] In a first mode the second secondary heat conductive liquid is not flowing through the second secondary side of the second heat exchanger. The primary heat conductive fluid outputted from the fluid buffer is then in a temperature range suitable for heating the first secondary heat conductive liquid via the first heat exchanger.

[0067] In a second mode the second secondary heat conductive liquid is flowing through the second secondary side of the second heat exchanger. The primary heat conductive fluid outputted from the fluid buffer is then in a temperature range suitable for heating the second secondary heat conductive liquid via the second heat exchanger. The flow of the first secondary heat conductive liquid may be controlled for maintaining the output of the first secondary heat conductive liquid from the second side of the first heat exchanger within a predefined temperature range. Controlling the flow of the first secondary heat conductive liquid may comprise switching off, decreasing or increasing this flow.

[0068] This embodiment has the advantage of that, with the right configuration of heater capacity, buffer volume size and heat exchangers capacities, that the first secondary liquid may continue to flow at a different rate while the second secondary liquid also flows.

[0069] Figure 4 schematically shows a fourth heating system 400 according to an embodiment of the current invention. In this embodiment the second heat exchanger is arranged inside the fluid buffer. This enhances the response time between the start of flowing of the second secondary heat conductive liquid and this liquid being in the predefined temperature range.

[0070] Furthermore, this embodiment may be arranged such that the output of the fluid buffer is in fluid communication with the input of the first heat exchanger without having a three-way valve arranged in between as shown in figure 4. This configuration provides the same advantages as presented for figure 3.

[0071] Furthermore, this embodiment may comprise a three-way valve, preferable a three-way thermostat valve or a three-way controllable valve or a three-way controllable thermostat valve, controlled by the controller. The three-way valve takes as input flow the output flow of the fluid buffer and the output flow of the first heat exchanger. The output of the three-way valve is presented to the input of the first heat exchanger. As the output of the first heat exchanger is fed back to the first heat exchanger via the three-way valve, the temperature input of the primary heat conductive liquid into the first primary side of the first heat exchanger may be controlled much more compared to the configuration in figure 3. This configuration provides the advantage of that the balance between heater capacity, buffer volume size and heat exchangers capacities for providing at the same time first and second secondary liquids within respective different and predefined temperature ranges.

[0072] The configuration of figure 4 with the use of a three-way valve may be applied to the configuration of figure 3 for providing the same advantages as described above.

[0073] In an alternative embodiment, the three-way valve, such as a controllable three-way valve, a three-way thermostat valve or a three-way controllable thermostat valve, comprises one input and two outputs. The input receives the primary heat conductive fluid exiting the second primary side of the second heat exchanger, one output is in fluid communication with the first primary side of the first heat exchanger and one output allows the primary heat conductive liquid to bypass the first heat exchanger. This embodiment provides the same advantages as described above for the embodiment in figure 4.

[0074] Figure 5 schematically shows a fifth heating system 500 according to an embodiment of the current invention. Both heat exchangers are placed inside the fluid buffer in this embodiment. This configuration provides the advantage of ease of installation as fewer components and piping have to be installed. If the temperature gradient across the buffer is large enough the fluid buffer may provide first and second secondary heat conductive liquids at the same time. Further, this configuration provides the same advantages as described for the figures 3 and 4.

[0075] Figure 6 schematically shows a method 200 for heating according to the current invention. The method comprises the step of circulating 210 a primary heat conductive fluid 111. The circulation may have a natural circulation, such as heated water rising due to convection, or may be stimulated by for example a pump or both. The method comprises the step of heating 220 the primary fluid with a flow-through electrical heater 120. The method comprises the step of buffering 230 the heated primary fluid. The method comprises the step of exchanging 240 heat between the primary fluid and a first secondary heat conductive liquid, wherein the heat exchange is downstream from where the primary heat conductive fluid is heated. The method comprises the step of exchanging 250 heat between the primary fluid and a second secondary heat conductive liquid 151, wherein the heat exchange is downstream of where the primary fluid is heated and upstream of the heat exchange between the primary fluid and the first secondary heat conductive liquid. The method comprises the step of controlling 260 the temperature of the first secondary heat conductive liquid exiting the first heat exchanger. Although the steps in the method are described sequentially, in practice the steps of the method will be performed at least partly in parallel.

[0076] Figure 7 schematically shows a method 300 for adapting the electrical conductivity of a heat conductive fluid in a heating circuit 110 according to the current invention. The heating circuit comprises a flow-through electrical heater 120. The method comprises the step of detecting 310 the electrical conductivity of the heat conductive fluid. The method comprises the step of receiving 320 electrical conductivity measurements. The method comprises the step of receiving 330 an electrical conductivity setpoint. The method comprises the step of comparing 340 the received measurements with the electrical conductivity setpoint. The method comprises the step of based on the comparison dispensing 350 a fluid for changing the electrical conductivity of the heat conductive fluid such that the electrical conductivity of the heat conductive fluid approaches the electrical conductivity setpoint. Although the steps in the method are described sequentially, in practice the steps of the method will be performed at least partly in parallel.

[0077] Figure 8 schematically shows an embodiment of a computer program product, computer readable medium and/or non-transitory computer readable storage medium 1000 having a writable part 1010 including a computer program 1020, the computer program including instructions for causing a processor system to perform a method according to the current invention.

[0078] Combion is a registered trademark. Embodiments falling within the claims and embodiments mentioned throughout the text are traded under the Combion trademark.

[0079] Examples, embodiments or optional features, whether indicated as nonlimiting or not, are not to be understood as limiting the invention as claimed.

[0080] It should be noted that the figures are purely diagrammatic and not drawn to scale. In the figures, elements which correspond to elements already described may have the same reference numerals.

[0081] It will be appreciated that the invention also applies to computer programs, particularly computer programs on or in a carrier, adapted to put the invention into practice. The program may be in the form of a source code, a code intermediate source and an object code such as in a partially compiled form, or in any other form suitable for use in the implementation of the method according to the invention. It will also be appreciated that such a program may have many different architectural designs. For example, a program code implementing the functionality of the method or system according to the invention may be sub-divided into one or more sub-routines. Many different ways of distributing the functionality among these sub-routines will be apparent to the skilled person. The sub-routines may be stored together in one executable file to form a self-contained program. Such an executable file may comprise computer-executable instructions, for example, processor instructions and/or interpreter instructions (e.g. Java interpreter instructions). Alternatively, one or more or all of the sub-routines may be stored in at least one external library file and linked with a main program either statically or dynamically, e.g. at run-time. The main program contains at least one call to at least one of the sub-routines. The sub-routines may also comprise function calls to each other. An embodiment relating to a computer program product comprises computer-executable instructions corresponding to each processing stage of at least one of the methods set forth herein. These instructions may be sub-divided into sub-routines and/or stored in one or more files that may be linked statically or dynamically. Another embodiment relating to a computer program product comprises computer-executable instructions corresponding to each means of at least one of the systems and/or products set forth herein. These instructions may be sub-divided into sub-routines and/or stored in one or more files that may be linked statically or dynamically.

[0082] The carrier of a computer program may be any entity or device capable of carrying the program. For example, the carrier may include a data storage, such as a ROM, for example, a CD ROM or a semiconductor ROM, or a magnetic recording medium, for example, a hard disk. Furthermore, the carrier may be a transmissible carrier such as an electric or optical signal, which may be conveyed via electric or optical cable or by radio or other means. When the program is embodied in such a signal, the carrier may be constituted by such a cable or other device or means. Alternatively, the carrier may be an integrated circuit in which the program is embedded, the integrated circuit being adapted to perform, or used in the performance of, the relevant method.

[0083] It should be noted that the above-mentioned embodiments illustrate rather than limit the invention, and that those skilled in the art will be able to design many alternative embodiments without departing from the scope of the appended claims. In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim. Use of the verb "comprise" and its conjugations does not exclude the presence of elements or stages other than those stated in a claim. The article "a" or "an" preceding an element does not exclude the presence of a plurality of such elements. The invention may be implemented by means of hardware comprising several distinct elements, and by means of a suitably programmed computer. In the device claim enumerating several means, several of these means may be embodied by one and the same item of hardware. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.

Claims

1. Heating system (100) comprising:

- a flow-through electrical heater (120) for heating a primary heat conductive fluid;

- a fluid buffer (130) for buffering the primary heat conductive fluid, wherein the fluid buffer comprises:

- a buffer input (135) in fluid communication with the flow-through electrical heater for receiving the heated primary heat conductive fluid;

- a first heat exchanger (140) having a first primary side for flow through of the primary heat conductive fluid and a first secondary side for flow through of a first secondary heat conductive liquid and being arranged for exchanging heat between the primary heat conductive fluid and the first secondary heat conductive liquid, wherein the first primary side is arranged downstream of the buffer input;

- a second heat exchanger (150) having a second primary side for flow through of the primary heat conductive fluid and a second secondary side for flow through of a second secondary heat conductive liquid and being arranged for exchanging heat between the primary heat conductive fluid and the second secondary heat conductive liquid, wherein the second primary side is arranged downstream of the buffer input and wherein the second secondary heat conductive liquid is separated from the first secondary heat conductive liquid; and

- control means (160) arranged for controlling the temperature of the first secondary heat conductive liquid exiting the first heat exchanger and/or the second secondary heat conductive liquid exiting the second heat exchanger, wherein the control means comprise:

- a flow sensor (161) for detecting flow of the second secondary heat conductive liquid through the second secondary side of the second heat exchanger; and

- flow control means (163) arranged for controlling flow of the first secondary heat conductive liquid through the first heat exchanger based on measurements of the flow sensor.

2. Heating system according to any of the preceding claims, wherein the control means comprise a three-way thermostat valve comprising:

- a valve-controlled hot input downstream of the second heat exchanger;

- a valve cold input downstream of the first heat exchanger;

- a valve output upstream of the first heat exchanger; and

- a thermostat arranged for controlling the amount of flow for the valve-controlled hot input based on the primary heat conductive fluid exiting the second primary side of the second heat exchanger; or wherein the control means comprise a three-way thermostat valve comprising:

- a valve-controlled hot output upstream of the second heat exchanger;

- a valve cold output upstream of the first heat exchanger;

- a valve input downstream of the second heat exchanger; and

- a thermostat arranged for controlling the amount of flow for the valve-controlled hot output based on the primary heat conductive fluid exiting the primary side of the second heat exchanger.

3. Heating system according to any of the preceding claims, wherein the control means comprise a three-way controllable valve comprising:

- a valve-controlled hot input downstream of the second heat exchanger;

- a valve cold input downstream of the first heat exchanger;

- a valve output upstream of the first heat exchanger; and

- a valve control arranged for controlling the amount of flow for the valve-controlled hot input based on based on measurements of the flow sensor; or wherein the control means comprise a three-way contorllable valve comprising:

- a valve-controlled hot output upstream of the second heat exchanger;

- a valve cold output upstream of the first heat exchanger;

- a valve input downstream of the second heat exchanger; and

- a valve control arranged for controlling the amount of flow for the valve-controlled hot output based on measurements of the flow sensor.

4. Heating system according to any of the preceding claims, wherein the fluid buffer comprises a buffer output, wherein the first heat exchanger and/or the second heat exchanger are arranged downstream of the buffer output.

5. Heating system according to claim 3, wherein the first heat exchanger and the second heat exchanger are arranged in parallel and downstream of buffer output.

6. Heating system according to claim 3-4, wherein the heat exchanger arranged downstream of buffer output is a tube heat exchanger.

7. Heating system according to any of the preceding claims, wherein the first and/or second heat exchanger are an integral part of the fluid buffer, preferably wherein the heat exchanger arranged as integral part of the fluid buffer is a plate heat exchanger.

8. Method (200) for heating comprising the steps of:

- circulating (210) a primary heat conductive fluid (111);

- heating (220) the primary heat conductive fluid with a flow-through electrical heater (120);

- buffering (230) the heated primary heat conductive fluid;

- exchanging (240) heat between the primary heat conductive fluid and a first secondary heat conductive liquid (141), wherein the heat exchange is downstream from where the primary heat conductive fluid is heated;

- exchanging (250) heat between the primary heat conductive fluid and a second secondary heat conductive liquid (151), wherein the heat exchange is downstream from where the primary heat conductive fluid is heated; and

- controlling (260) the temperature of the first secondary heat conductive liquid exiting the first heat exchanger and/or the second secondary heat conductive liquid exiting the second heat exchanger - detecting flow of the second secondary heat conductive liquid through the second secondary side of the second heat exchanger; and

- controlling flow of the first secondary heat conductive liquid through the first heat exchanger based on measurements of the flow sensor.

9. Computer program product (1000) comprising a computer readable medium (1010) having computer readable code (1020) embodied therein, the computer readable code being configured such that, on execution by a suitable computer or processor, the computer or processor, when connected to a heating system according to any of the claims 1-7, is caused to perform the step of:

- controlling the temperature of the first secondary heat conductive liquid exiting the first heat exchanger and/or the second secondary heat conductive liquid exiting the second heat exchanger.

10. Conductivity adaptor for adapting the electrical conductivity of a heat conductive fluid (111) in a heating circuit (110) having a flow-through electrical heater (120), comprising:

- a dispenser (170) for dispensing a fluid for changing the electrical conductivity of the heat conductive fluid;

- a sensor (192) for detecting the electrical conductivity of the heat conductive fluid;

- a controller (169) configured for receiving electrical conductivity measurements from the sensor, for receiving an electrical conductivity setpoint, for comparing the received measurements with the electrical conductivity setpoint and for controlling the dispenser based on the comparison such that the electrical conductivity of the heat conductive fluid approaches the electrical conductivity setpoint.

11. Conductivity adaptor according to claim 10, wherein the dispenser comprises 1 reservoir.

12. Conductivity adaptor according to claim 10, wherein the dispenser comprises 2 reservoirs for holding a conductivity increasing fluid and for holding a conductivity decreasing fluid.

13. Conductivity adaptor according to claim 12, wherein one reservoir is arranged for comprising unadapted primary heat conducting fluid for diluting the primary heat conductive fluid in the heating circuit.

14. Method (300) for adapting the electrical conductivity of a heat conductive fluid (111) in a heating circuit (110) having a flow-through electrical heater (120), comprising the steps of:

- detecting (310) the electrical conductivity of the heat conductive fluid;

- receiving (320) electrical conductivity measurements;

- receiving (330) an electrical conductivity setpoint;

- comparing (340) the received measurements with the electrical conductivity setpoint; and

- based on the comparison dispensing (350) a fluid for changing the electrical conductivity of the heat conductive fluid such that the electrical conductivity of the heat conductive fluid approaches the electrical conductivity setpoint.

15. Computer program product (1000) comprising a computer readable medium (1010) having computer readable code (1020) embodied therein, the computer readable code being configured such that, on execution by a suitable computer or processor, the computer or processor is caused to perform a method for adapting the electrical conductivity of a heat conductive fluid (111) in a heating circuit (110) having a flow-through electrical heater (120), comprising the steps of:

- receiving electrical conductivity measurements of the heat conductive fluid;

- receiving an electrical conductivity setpoint;

- comparing the received measurements with the electrical conductivity setpoint; and

- based on the comparison controlling dispensing of a fluid for changing the electrical conductivity of the heat conductive fluid such that the electrical conductivity of the heat conductive fluid approaches the electrical conductivity setpoint.

Drawing