WO2001079761A1

WO2001079761A1 - Central heating system for heat users provided with heat storage vessels

Info

Publication number: WO2001079761A1
Application number: PCT/EP2000/003443
Authority: WO
Inventors: Peter J. Collet
Original assignee: Collet Peter J
Priority date: 2000-04-18
Filing date: 2000-04-18
Publication date: 2001-10-25
Also published as: EP1277016B9; DE60032261D1; AU2000245507A1; EP1277016A1; EP1277016B1; DE60032261T2

Abstract

A central heating system for a plurality of separate heat users, for example houses or apartments, each of such users having a stratified heat storage vessel containing water of the circulation system as heat storage medium, characterized by means for concurrently charging heat storage vessels of a plurality of such users, and means for delivering, within a set time span after any user signals its storage vessel to approach depletion in between concurrent charging operations, primary water having a temperature that is higher than a set temperature to such user. Said means preferably include central control means and may optionally comprise bypass valve means such as (9,10) or (18,19) connecting main delivery to main return conduits.

Description

Central heating system for heat users provided with heat storage vessels

The present invention relates to a heating system for a plurality of seperate heat users, such as houses, apartments, and the like, comprising at least one heat source for heating a heat transfer liquid such as water (primary water), a circulation system for delivery o f hot primary water to said users, and each of said users provided with means that include a stratified heat storage vesse l containing primary water as heat storage medium.

Said circulation system comprises delivery conduits for supplying hot primary water to said users and return conduits for returning cooler primary water back to the heat source. Delivery and return conduits comprise main conduits and service conduits, said service conduits connecting main conduits to each of said heat users.

S uch heating systems are known from patent application EP A 0

168 084 and EUROHEAT & POWER - Fernwarme international 3/ 1 998 , pages 50 - 52. The advantages claimed for such systems particularly include a higher energy efficiency because of lower heat losses o f said service conduits. Hot primary water contained by said heat storage vessel is circulated through a through-flow heat exchanger for heating domestic water on demand and optionally through one or more heat emitters, such as radiators, for providing space heating on demand. Heat losses of service conduits are reduced because such conduits cool down during periods in between consecutive charging of a heat storage vessel, such reduction in heat lo sses being greater when the time intervals between charging are longer, particularly when the daily heat demand is re latively low and the water containment vo lume of the heat storage vessel is relative ly large. In said references mention is made of storage vessels having a vo lume of 200 liters.

A disadvantage o f such known heating systems is that although the heat losses of service conduits are reduced, the heat lo sses o f main delivery and return conduit s remain high. The temperature o f water flowing through main delivery conduits is continuously kept at a high level, so as to deliver on demand o f individual users, hot primary water having a temperature that is higher than a set minimum delivery temperature for heat storage. Such set minimum temperature, for example 75 degrees Celcius, is selected so as to be sufficiently high for heating domestic water to a relatively high temperature, for example 60 degrees Celcius, after the stored primary water has undergone a temperature drop because of heat lo sses during storage.

Because the heat losses of the main delivery conduits cause the temperature of primary water flowing through such conduits to decrease, such flow is continuously kept above a minimum leve l so as to prevent delivery temperatures from dropping below said minimum temperature for heat storage. During perio ds that little or no primary water is required for heating purposes, the flow through main delivery conduits is continuously maintained above said minimum level by conducting primary water through bypass conduits connecting main delivery conduits to main return conduits, such bypass conduits comprising thermo static valve means. Because hot primary water that is bypassed is not cooled by heat utilization, such bypass flow causes high temperatures o f water flowing through main return conduits, thereby increasing the heat losses of main return conduits. High temperatures of primary water returning to the heat source through main return conduits may further reduce energy effic iency because o f a lower efficiency of heat production , particularly when the heat source includes means o f heat production having an energy conversion efficiency and/or heat recovery effectiveness that is reduced when said return temperature is increased, for example heat pumps, condensing heat recovery heat exchangers, Rankine cycle cogeneration installations, intercooled gasturbine cogeneration installations, solar heat panels, and the like.

Such means o f heat production have great energy savings potential because of a high ratio between useful heat production and prime energy (fuel) consumption. Such energy savings are also of great benefit in reducing emissions of fuel combustion. Because of the reduction in energy efficiency caused by high temperatures in main delivery and return conduits, it is generally mandatory for such conduits to have a high degree of heat insulation so as to avo id energy savings from becoming very low or even negative, particularly when the daily heat demand is low and/or the users are located in an area with low building density. Such high degree of insulation has the disadvantage o f increasing investment and (indirectly) maintenance costs. The causes of such cost increases include a higher price per meter o f conduit and higher costs of installation because a larger outer (j acket) diameter causes the flexibility and therefore the ease of handling during installation to be reduced.

Other disadvantages of such heating systems relate to the size of the heat storage vessel, a larger vessel causing higher heat lo sses and increased costs, and limiting the applicability of such systems when said heat users have limited space for installing such vessels in an otherwise advantageous location.

An object of the invention is to improve the energy effic iency of such heating systems by greatly reducing heat lo sses of main delivery and return conduits and by decreasing return temperatures to the heat source, particularly during periods o f the year when there is little or no demand for space heating. Another object of the invention is to decrease investment and maintenance costs by reducing the heat insulation o f main delivery and return conduits without reducing energy savings to undesirably low levels. Another object of the invention is to greatly reduce the size o f heat storage vesse ls so as to avo id or reduce said disadvantages of large heat storage vesse l s.

Accordingly the proposed heating system is characterized by having little or no continuous bypass flow downstream of main delivery conduits during times that no primary water is delivered to any heat user connected downstream of such main delivery conduits. During such times, the temperature of water contained by such main delivery conduit decreases, causing the heat losses of such conduit to decrease. According to the invention the duration of such cooling down times (cooling time spans), and therefore the reduction in heat losses, is increased by concurrently charging the heat storage vessels of said connected users, so as to have said heat storage vessels approximately fully charged at approximately the same time, thereby causing the time span before depletion o f any heat storage vessel of said connected users to be on average longer than when heat storage vessels are charged on individual demand. During times in between concurrent charging operations, any of said users may have a demand for domestic hot water that causes depletion of hot primary water contained by its heat storage vessel, particularly when such demand is for a hot shower or bath, and when the water containment volume of the storage vessel is relatively small. When the temperature o f water, contained by (a) main de livery conduit(s) upstream of such user, has dropped below a set minimum temperature for delivery of hot primary water to said user, then the vo lume of primary water that must be bypassed before delivery o f water having a sufficiently high temperature can take place, may be very large . During the time span of such bypass operation, referred to in the fo llowing as the bypass time span, the primary hot water for heating domestic water is drawn from the storage vessel. The (rest) vo lume of hot water contained by said storage vessel at the beginning o f the bypass flow is set so as to be sufficient for heating a maximum flow o f domestic hot water during said bypass time span, so as to ensure an uninterrupted supply o f domestic hot water during the perio d o f such demand. A problem of such mode of operation is that when the vo lume of water that must be bypassed is large, said bypass time span, and therefore said rest vo lume, may also be large, particularly when the magnitude o f the bypass flow is limited by the maximum bypass flow capability o f an individual user.

According to the invention means are provided for greatly increasing the bypass flow downstream of main delivery conduits in comparison with the maximum bypass capability of an individual user, so as to decrease said bypass time span, so as to decrease the rest vo lume of the storage vessel, thereby reducing the size of the storage vessel. Such means may include bypass valves connecting main delivery and return conduits and/or may include central control means for concurrently opening individual bypass valves of a plurality of users.

These and other features and advantages o f the present invention are described, with reference to the accompanying drawings, for an example of an embodiment of a heating system according to the invention.

Fig. l is a schematic representation of a heating system comprising a heat source and a c irculation system for supplying hot primary water to a plurality of heat users.

Fig 2 is a schematic representation o f apparatus for receiving and utilizing hot primary water by a heat user.

Fig. l schematically shows a circulation system having delivery conduits that are represented by full lines and indicated by numerals having an affix D, and return conduits that are indicated by broken lines and like numerals having an affix R. Said circulation system comprises a main ring delivery conduit I D and a main ring return conduit I R connecting a heat source 2 to (examp les of) groups o f heat users G l , G2, G3 ,G4, each group comprising at least one main branch conduit that is connected by service conduits to each o f said users. Such users are provided with apparatus, not shown in Fig. 1 , for receiving and utilizing hot primary water. Circulation pump 4 provides circulation o f primary water through delivery and return conduits.

Main ring delivery conduit I D has at least two connections with heat source 2 . During periods that little or no primary water is delivered to said users, circulation pump 3 provides circulation of hot primary water through said main ring delivery conduit I D and heat source 2, said heat source heating such circulated water so as to compensate for heat lo sses of main ring delivery conduit I D, thereby continuously provid ing at each connection to a main branch delivery conduit, hot primary water having a temperature within a small band o f for example 3 degrees. Heating systems that inc lude such main ring conduits are known to also have the advantage of increasing the reliability of the heating system by maintaining the delivery of hot primary water to most or all heat users when a section of the main ring conduit is clo sed for maintenance or repairs.

Delivery of hot primary water for concurrently charging heat storage vesse ls of a plurality of users is preferably timed so as to have storage vesse ls contain sufficient hot primary water for meeting low volume demands during periods in between consecutive concurrent charging operations. Such low vo lume demands are for example for heating domestic water for washing hands or washing dishes, or for providing space heating for keeping room temperatures at an approximately constant level. On days without space heating demand, and when heat storage vessels have a relatively small water containment vo lume o f for examp le 40 liters, such timing may for example comprise 4 concurrent charging operations per day. On days with space heating demand, the number o f such charging operations may be increased up to more than 20 per day. The water containment volume of heat storage vesse ls may advantageously be increased up to for example 80 liters, for users having a greater total of low vo lume domestic water demands, and/or a greater space heat ing demand, and/or having service conduits o f greater length.

Concurrent charging o f storage vessels may be sequenced for adjacent users, so as to reduce flow losses in main delivery conduits during such charging operations. The timing of such operations is preferably controlled by one or more central electronic system contro l lers, not shown in Fig. l , connected by wireless and/or conduit-bound transmission means with users of a group or with all users of the heating system. Such communication means may advantageously be utilized for also centrally recording the energy usage of heat users.

When users have a high vo lume demand for primary hot water, for example for heating domestic water for a hot shower or bath, or for providing space heating during a warm up period after a night with decreased room thermo stat setting, it becomes very likely that the heat storage vessel, particularly a small vessel, becomes depleted during such demand. Additional hot primary water for meeting such demand and for individually recharging said heat storage vessel is then delivered in between two consecutive concurrent charging operations, thereby increasing the frequency and reducing the average duration of coo ling time spans, thereby increasing the heat losses o f such conduits. However, because such high vo lume demands occur predominately during limited periods of the day, particularly during early morning and late evenings, the average coo ling time spans during other periods of the day are little reduced, therefore the daily heat loss reduction remains high.

When such a high vo lume demand is for heating domestic water, it is mandatory for comfort reasons to provide an uninterrupted flow o f domestic hot water during the period o f such demand, particularly when such demand is for providing a hot shower. Means are provided for adapting the bypass flow so as to deliver hot primary water for heating domestic water before the heat storage vesse l o f such user is fully depleted of hot primary water. Such means are described in the fo llowing for examples of user groups shown in Fig 1 .

User group G l is representative o f a small number of heat users, for example houses such as 6 in a row of six houses, located clo se to main ring conduits I D, I R . Hot primary water flowing though main ring delivery conduit I D is supplied to such users through main branch delivery conduit 5D and service delivery conduits such as 7D. When the temperature of water contained by main branch delivery conduit 5D drops below a set minimum temperature for delivery to users, for examp le be low 70 degrees Celcius, the vo lume of water that must be bypassed, so as to deliver primary water having at least said temperature, to a user located farthest from said main ring delivery conduit I D, may for example be 1 5 liters. Such user is provided with an individual bypass valve 26, not shown in Fig 1 , which because of a limited maximum flow through service delivery conduit 8D may have a maximum flow capability o f only 10 liters per minute. The bypass time span is then one and half minutes. The rest vo lume o f the heat storage vessel is set so as to provide hot water for heating a maximum flow of domestic hot water during such time span, for example 9 liters.

User groups G2, G3 and G4 comprise larger numbers of users located farther from main ring conduits I D, I R. The volume o f water contained by main delivery conduits connecting users to main ring delivery conduit I D, and therefore the vo lume of primary water that is to be bypassed within said set bypass time span of one and half minutes, may be very much larger.

For users of group G2, comprising two rows of six houses such as 7, such bypass volume may for example be 50 liters. Bypass means that connect main delivery conduit 8D with main return conduit 8R, are provided at the downstream end o f de livery conduit 8D, so as to greatly increase the bypass flow capability in comparison with the bypass capability of an individual user, so as to keep the bypass time span below one and a half minutes. Said bypass means include bypass valve 9 and temperature sensor 10. Bypass valve 9 is governed to open when one o f the users o f G2 signals a demand for delivery of hot primary water and when temperature sensor 10 senses primary water contained by main delivery conduit 8D to be below a set minimum temperature for delivery o f hot primary water to users. The signal for such user demand may be transmitted through aforementioned communication means between central system contro ller and said user, or alternatively by pressure sensing means, not shown in Fig. 1 , signaling a sudden pressure change in main delivery conduit 8D . Bypass valve 9 is governed to close when temperature sensor 10 senses a temperature that is above said set minimum temperature.

User group G3 is representative of a still larger number o f heat users that may be located even farther from main ring conduits

1 D, 1 R . Because a temperature drop of all the water contained by delivery conduit 1 1 D may cause the required bypass vo lume to be very high, for example more than 100 liters, bypass valve 12 is provided for continuously bypassing primary water from delivery condu it 1 1 D to return conduit 1 1 R, so as to maintain high water temperatures in delivery conduit 1 1 D, so as to reduce the volume of primary water to be bypassed within said set time span of one and half minutes. Said bypass means 12 may be very simple and therefore cheap, comprising for example a fixed orifice.

Means for greatly increasing the bypass flow in comparison with the bypass capability of an individual user may, as an alternative to bypass means 9, 1 0 shown for G2, comprise aforementioned central system contro ller governing individual bypass valves of a plurality of users downstream o f main delivery conduit 13D, so as to open when one of such users signals a demand for delivery o f hot primary water, and when the coo ling time span since a preceding delivery to any o f said users exceeds a set limit. Such limit is set so as to correspond with the time that it takes for the temperature of water contained by main branch delivery conduit 1 3 D to drop below said set minimum delivery temperature. Such alternative means for greatly increasing the bypass flow provide the advantage of avo iding the need for bypass valve means 9, 1 0, which may, particularly when such means would need to be located outside of a bui lding, significantly reduce investment and maintenance costs.

User group G4 is representative of multistorey buildings comprising apartments such as 14. Hot primary water flowing through main ring delivery conduit I D is supplied to such users through main branch delivery conduit 1 5 D, connected downstream to a plurality of main branch delivery conduits such as 16D, each of which are connected by service delivery conduits such as 1 7D to heating apparatus inside each of said apartments. Means that are provided for greatly increasing the bypass flow in comparison with the bypass capability of an individual user connect main delivery conduit 15D with main return conduit 1 5R at the downstream end of delivery conduit 1 5 D. Said means include bypass valve 1 8 and temperature sensor 19 that operate in the manner as described in the forego ing for bypass means 9, 10.

Delivery and return conduits o f a heating system according to the invention may advantageously be adapted so as to provide high energy efficiency and low investment and maintenance costs. Service conduits such as 7D,7R , and main branch conduits such as 5D,5R and 8D, 8R and 1 3D, 13 R, preferably comprise insulated water carrying ( carrier) pipes that have little or no problems with frequent and large temperature changes, for examp le flexible conduits comprising plastic carrier p ipes.

A major co st reductio n may be provided by reducing the heat insulation and thereby the outer diameter o f such conduits. Because the time-averaged temperature of water contained by such conduits is low, such adaptation causes little increase in heat lo sses. A first co st reduction is provided by the reduced weight and increased flexibility o f such conduits. A second cost reduction, and a much improved reliability, may be provided by prefabricating the connections between such a main conduit and a plurality o f service conduits, and adapting such connections so as to transport such prefabricated combination of conduits as a ro ll, particularly by connecting such a main conduit and service conduits in parallel. Prefabricated connections are particularly advantageous when said conduits comprise wiring for electronic communicatio n between users and aforementioned central system controller(s) .

Said circulation system may advantageously comprise return conduits with carrier pipes having inner diameters that are larger than inner diameters o f carrier pipes of delivery conduits having like numerals, for examp le between one and a half and twice times as large, and to have less heat insulation, thereby reducing the costs of such conduits. Because the time-averaged temperature of primary water contained by return conduits is very low, such decreased insulation causes only a small increase in heat lo sse s. Other advantages provided by such increase in inner diameter of return conduits are related to greatly decreased flow pressure lo sses in return conduits.

Heat source 2 includes heat production means 20 for heating primary water returning to the heat source at a low temperature, for example 25 degrees Celc ius. Such heat production means preferably haye an energy efficiency and/or effectiveness that yie lds greater energy savings when the (averaged) heat production temperature is decreased, for example a plurality o f electric heat pumps that are placed in series for stepwise heating of primary water, such heat pumps subtracting heat from a low temperature heat source, not shown in Fig. l , such as ground water, surface water, waste effluent and/or the like. Other examples for heat production means 20 include condenser means of Rankine cycle cogeneration installations, solar heat panels having a heat recovery effectiveness that increases as the temperature of the heat transfer liquid is reduced , and the like.

Preferably heat source 2 also includes production means 21 for further heating primary water to the temperature of the heat transfer liquid exiting heat source 2 and flowing through main ring delivery conduit I D. Such means may advantageously comprise heat production processes for which the energy effic iency hardly decreases when such exit temperature is raised, for example gasmotor cogeneratio n installations, fue l fired bo i lers, and the like.

Heat source 2 may alternatively comprise heat production means that combine said effects of first and second heat production in a single installation, for example a cogeneration installation or a fuel fired bo i ler comprising an integrated condensing heat exchanger for heat recovery from exhaust gases, or a cogeneration installation comprising an intercooled gasturbine .

Not shown in Fig 1 are auxiliary apparatus, wel l known to persons skilled in the art, such as heat storage reservo irs, pumps, valves, and the like.

Alternative embodiments of heating systems according to the invention may comprise a heat source supplying a smaller number of building units, for example a heat source for supplying apartments 14 of a multistorey apartment block, and having such heat source located inside the apartment block. Alternatively the embodiment shown in Fig 1 may form part of a larger heating system, heat source 2 being for example connected by delivery and return conduits to a remotely located heat source, for example waste heat recovery means o f an industrial plant or a central electricity generating station.

Fig. 2 schematically shows apparatus for receiving and utilizing hot primary water by a heat user, including a heat storage vessel 22 and a through flow heat exchanger 23 for heating domestic water, that are preferably contained within a common shell of heat insulating material 24 , so as to keep the temperature of domestic water heater 23 high during periods in between withdrawals of domestic hot water , thereby providing the advantages of instant availability o f domestic hot water and reduced standstill heat lo sses of said heater in between withdrawals of domestic hot water.

Heat storage vesse l 22 contains primary water preferably having a stratified temperature distribution, whereby an upper zone of hot water is separated from a lower zone of coo ler water by a layer o f water 25 having a steep vertical temperature gradient, such separating layer moving downward when the heat storage vessel is charged, and moving upward when hot heat transfer liquid is withdrawn for heating domestic water and/or for providing space heating.

Upon receiving a signal from aforementioned contro l means for beginning o f a concurrent charging operation, bypass contro l valve 26 is activated so as to open and cause a flow o f primary water through . bypass conduit 27, such flow preferably being as high as is allowable for reasons that limit the maximum flow through service delivery conduit 7D, such reasons being for example flow pressure lo sses or so as to avo id high noise levels. Flow limiter 28 in bypass conduit 27 is optionally inc luded so as to provide such flow limitation. When temperature sensor 29 signals the temperature of the bypassed liquid to be higher than a set temperature, bypass control valve 26 is activated so as to clo se and control valve 30 is activated so as to open, causing hot primary water to flow through service delivery conduit 7D and through conduit 3 1 into heat storage vessel 22, and causing coo ler primary water to flow out of said storage vessel through conduit 32 and through service return conduit 7R, thereby causing the heat storage vessel to be charged. The flow rate during charging is preferably kept within a relative ly narrow band by flow limiter 33 , and by operating circulation pump 4 at heat source 2 so as to keep the pressure difference over said flow limiter above a set level during such charging operation. The charging operation is terminated by contro l means, inc luding temperature sensor 34 in the lower part of storage vessel 22, activating valve 30 so as to clo se.

A signal for individual charging o f a heat storage vessel operation is given by temperature sensor 35 sensing an upward movement o f separating layer 25 , thereby indicating the hot primary water contained by storage vessel 22 to have decreased below a set minimum vo lume. S uch set vo lume is selected so as to provide hot primary water for heating a high(est) flow o f do mestic water during aforementioned bypass time span o f one and a half minutes, so as to avo id an undesirable drop in temperature o f domestic hot water exiting from domestic water heater 23 during a period o f domestic hot water withdrawal, particularly when such withdrawal is for a hot shower.

Upon the beginning o f a withdrawal of domestic hot water from an outlet such as tap 36 or douche head 37, flow sensor means 38 in the secondary circuit of dome stic water heater 23 , preferably a compact counter flow heat exchanger, activates control valve 39 and circulation pump 40 so as to circulate hot primary water from the upper part of storage vessel 22 through the primary side o f domestic water heater 23. Control valve 39 is thermo statically controlled by temperature sensor 47 so as to keep the temperature of heated domestic water approximate ly constant within a narrow temperature band. Domestic water heating may alternatively be controlled by means that are known to persons skilled in the art.

Space heating is provided by a direct system comprising at least one radiator heat emitter such as 4 1 through which primary water is circulated. Alternatively an indirect system may be provided inc lud ing a heat exchanger for transfer of heat from primary water to secondary water circulating through said radiator(s) . Space heating may alternatively be provided by other known systems, for example an air circulation system or a floor heating system.

Control means for providing space heating may for example inc lude a central room thermostat 42 activating contro l valve 43 and circulation pump 40 so as to circulate hot primary water through at least one radiator 41 . Such control means may also or alternatively include thermostatic valves, not shown in Fig. 2, for the or each radiator. Circulated primary water for space heating is generally withdrawn from the upper part of heat storage vessel 22 and coo ler primary water is returned to the lower part of said vessel. When a space heating demand occurs during charging o f said heat storage vessel, circulation o f primary water through space heating emitters may be parallel to circulation of primary water for charging of heat storage vessel 22, or priority contro ls may be provided for clo sing control valve 43. Priority control means may also be provided for clo sing said control valve during a withdrawal of domestic hot water.

By adapting flow limiter 33 and pressure levels in the circulation system so as to keep the flow rate during delivery of primary water to a user within a relatively narrow band, the heat meter o f a user may advantageously comprise a simple cheap water meter 44 registering the accumulated vo lume o f primary water delivered to a user, and an electronic meter 45 registering during delivery periods the time integrated temperature difference sensed by temperature sensors 29 and 46 . Such heat meter, providing high measuring accuracy, may be much cheaper than known heat meters comprising a flow meter for registering the time integrated product of flow and temperature.

Preferably users comprise an individual electronic controller unit, not shown in Fig. 2, that is in communication with some or all o f the aforementioned sensors end contro l means, and that is in communication with aforementioned central system controller(s) .

Claims

1 A heating system for a plurality of heat users, comprising at least one heat source for heating a heat transfer liquid such as water (primary water), a circulation system for delivery of hot primary water to each of such users, and each of such users having a heat storage vessel containing primary water as heat storage medium, c haract e r ize d by:

-means for concurrently charging heat storage vessels of a plurality of heat users;

-means for delivering, within a set time span after a unit signals a demand for delivery of hot primary water, such water having a temperature that is higher than a set temperature to such user._.

2 A heating system according to claim 1, c h ar ac t e r ize d by said means including at least one central electronic system controller in communication with a plurality of said users.

3 A heating system according to claim 2, c har act e r i ze d by said means including wireless transmission means for providing said communication.

4 A heating system according to claim 2, c har a c t e r i z e d by said means including conduit-bound transmission means for providing said communication.

5 A heating system according to claim 2, c har ac t e ri z e d by said central electronic system controller(s) being programmed for increasing the number of concurrent charging operations on days with higher space heating demand. 6 A heating system according to claim 2, c h ar ac t e r i z e d by said central electronic system controller(s) being programmed for opening individual bypass valves of a plurality of users downstream of a main branch delivery conduit, when one of such users signals a demand for delivery of hot primary water and more than a set time has elapsed since a preceding delivery to any of such users.

7 A heating system according to claim 2, c har ac t e r i z e d by said means for delivering, within a set time span after a user signals a demand for delivery of hot primary water having a temperature higher than a set temperature, including bypass valve means connecting a main delivery conduit with a like main return conduit.

8 A heating system according to claim 7, c har ac t e r iz e d by said bypass means including a temperature sensor for controlling a bypass valve to open when one of the users downstream of said main delivery conduit signals a demand for hot primary water and the temperature of water contained by said conduit is sensed to be lower than a set temperature, and for such bypass valve to close when such temperature is sensed to be higher than a set temperature.

9 A heating system according to claim 1, c harac t e r i ze d by said circulation system comprising main ring delivery conduits.

10 A heating system according to claim 1, c h ar ac t e r i z e d by return conduits comprising carrier pipes having a larger inner diameter and less heat insulation than like delivery conduits. 11 A heating system according to claim 1, c h a r a c t e r i z e d by said circulation system including flexible main conduits and service conduits.

12 A heating system according to claim 11, c h a r a c t e r i z e d by said main conduits and service conduits having prefabricated connections.

13 A heating system according to claim 12, c h a r a c t e r i z e d by said prefabricated connections comprising main conduits and service conduits connected in parallel.

14 A heating system according to claim 11, 12 or 13, c h a r a c t e r i z e d by said conduits comprising plastic carrier pipes.

15 A heating system according to claim 1, c h a r a c t e r i z e d by said heat storage vessel containing primary water having a stratified temperature distribution.

16 A heating system according to claim 1, c h a r a c t e r i z e d by said users comprising a through flow domestic water heater.

17 A heating system according to claim 15 and 16 , c h a r a c t e r i z e d by said heat storage vessel and said through flow domestic water heater having a common encasing of heat insulating material.

18 A heating system according to claim 15, c h a r a c t e r i z e d by said stratified heat storage vessel having a water containment volume between 40 and 80 liters. 19 A heating system according to claim 1, c har a c t e r i z e d by said heat users comprising means for keeping the flow during delivery of hot primary water to such a user within a set band, and comprising a heat meter that includes an accumulative water meter and means for registering the integrated difference between delivery and return temperature over the time of delivery.

20 A heating system according to any of the preceding claims , c h ar ac t e r i z e d by said heat source comprising at least one form of heat production means that is selected from the group that includes heat pumps, solar heat panels, (intercooled) gasturbine cogeneration installations, gasmotor cogeneration installations or fuel fired boilers.