Abstract: What are disclosed are embodiments of a saddle, cap, and adapter for use in an irrigation system. In a preferred embodiment, the disclosed inventive concepts utilize a dynamic seal that provides an improvement over prior known technology. In a preferred embodiment the adapter and cap are made to be removable so as to be easily changed or replaced.

Abstract: A fluid heating system may be installed for residential and commercial use, and may deliver fluid at consistent high temperatures for cooking, sterilizing tools or utensils, hot beverages and the like, without a limit on the number of consecutive discharges of fluid. The fluid heating system is installed with a tankless fluid heating device that includes an inlet port, an outlet port, at least one heat source connected with the inlet port, and a valve connecting the at least one heat source to the outlet port. A temperature sensor is downstream of the at least one heat source and connected to the valve. Another temperature sensor is on the heat source to enable it to be kept at an elevated temperature. The valve is operated so that an entire volume of a fluid discharge from the fluid heating system is delivered at a user-specified temperature on demand, for every demand.

Abstract: A system and method for operating a building heating system. The system includes a controller that operates the heating system in three modes of operation. The controller controls a valve that regulates the flow of steam to the building water loop. By maintaining a constant steam flow rate during peak demand periods, steam consumption during peak demand periods are reduced while maintaining a comfortable environment within the building.

Abstract: A hot water supply system includes a first tank for storing hot water for heating; a second tank for storing hot water to be supplied to a hot water tap; a heater circulation path for supplying the hot water of the first tank to a heater; a first path that includes a first heat transfer portion surrounding the exposed portion of the second tank to the inside of the first tank and that connects the first tank to a forward portion of the heater circulation path so that the hot water of the first tank can be supplied to the heater through the first heat transfer portion; and a second path that includes a second heat transfer portion disposed along the first heat transfer portion, and that allows heat exchange between the hot water of the second tank and the hot water flowing through the first heat transfer portion due to the flow, in the second heat transfer portion, of the hot water of the second tank.

Abstract: The present invention relates to a portable boiler for a hot mat, which comprises: a water reservoir, one side of which has an inlet pipe for introducing water circulating through the hot mat, and which stores the water; a heat transfer unit in which the water discharged from the water reservoir flows along a flow channel pipe to be heat exchanged, wherein the water is discharged to the hot mat via an outlet pipe formed at one side thereof; a heating unit which burns the fuel gas fed from a fuel tank to heat the water in the heat transfer unit; and a housing which forms the outer appearance of the boiler.

Abstract: An apparatus for heating water having three vertically aligned water heating process sections. The upper section includes an annular water storage tank disposed around a combustion chamber having a downward firing burner. The intermediate section, disposed vertically below the upper section receives flue gas from the combustion chamber, which flue gas is cooled and dehumidified, producing a hot condensate which collects in a passive condensate flow control device disposed proximate the bottom of the intermediate section. The lower section, disposed vertically below the intermediate and separated therefrom by the passive condensate flow control device receives hot condensate from the flow control device, which is used to preheat and humidify air, such as room air, which is then recycled to the combustion process of the upper section for use as combustion air.

Abstract: An apparatus for heating a hydronic heating fluid comprising a casing body having an inlet and an outlet adjacent to the inlet and a fluid flow path between the inlet and outlets. The flow path extends along first and second substantially straight sections with a return bend therebetween. The apparatus further includes a heating element located within one of the first or second sections of the flow path. The second end may include a threaded heater bore aligned with the second section wherein the heating element is threadably insertable into the second section through the heater bore. The first end may include a pump in fluidic communication with the inlet, the pump being operable to draw the heating fluid in through the inlet and to discharge the heating fluid through the first section of the casing body.

Abstract: Disclosed herein is a method of controlling a boiler. In the boiler control method, the boiler is controlled depending both on a room temperature and on a return water temperature, whereby, unnecessary operation of the boiler is minimized. Further, the boiler is controlled depending on a desired room temperature and a corresponding return water temperature in a non-sleeping time zone, and the boiler is variably controlled, in the sleeping time zone, within a variable sleeping-time room temperature range and a variable sleeping-time return water temperature range. Moreover, in the present invention, a temperature control deviation is within ±0.5° C. and a return water temperature control deviation is within ±1° C. so that the room temperature and the temperature of a floor of the room can be maintained constant. Thus, energy consumption can be markedly reduced.

Abstract: Disclosed is a boiler for providing hot water to a heating system of a building and for simultaneously producing hot domestic water. This boiler comprises a heating tank provided with a water inlet and a water outlet through which water for use in the heating system circulates and an adjacent chamber annexed to the heating tank. This adjacent chamber is in direct communication with the heating tank and containing means for heating the water. The boiler also comprises a heat exchanger provided with a water inlet and a water outlet through which circulates the domestic water. This heat exchanger is made of a plurality of tubular coils of helicoidal shape that are located within the heating tank in order to allow heat transfer between the hot water within the heating tank and the domestic water that circulates within the tubular coils.

Abstract: The invention relates to a device (1) for heating a fluid (9), with a housing (2) comprising a housing shell (3), a housing base (4) and a housing cover (5), with at least one inlet opening (11) and at least one outlet opening (13) for the fluid (9), and at least two electrodes are disposed in the housing (2) at a distance (25) apart from one another, which are each electrically conductively connected to a pole of at least one pulse generator (20). At least one other electrode (45 or 46) is provided or at least two other electrodes (45, 46) are provided in the reaction chamber (12), which is/are electrically conductively connected to a power source (47).

Abstract: An air elimination device with a hydraulic separator in a compact format that eliminates numerous separate field installed components and connections and can be cost effectively made by means of spun, bent, bored, milled sheet copper or brass sheet, copper or brass tube or rod utilizing brazing, soldering and threading of parts. The device can be made to include a manifold, particularly with compact end suction pumps and can serve as a transition adaptor to other modular mechanical components.

Abstract: A system and a method for controlling a pump in a recirculating hot water system is provided. In one embodiment, the invention relates to a method for controlling a temperature of water in a recirculating hot water system including a storage tank for storing heated water, a recirculation conduit including a supply conduit for supplying the heated water to users via a plurality of outlets having a first outlet and a last outlet and a return conduit for returning an unused portion the heated water to the storage tank, a pump for circulating the heated water, the pump disposed along the return conduit, the method including measuring, at a point along the recirculation conduit, a temperature of the heated water provided from the storage tank, and controlling a speed of the pump, disposed along the return conduit, based on the measured temperature.

Abstract: A car wash system for large vehicles, such as trucks and busses, in which the arrival of a vehicle initiates a process of directing hot water from a supply tank through a relatively long supply line to a spray system. Water standing in the supply line is prevented for a time from going to the spray nozzles and, instead, is directed back to the source. This allows the temperature in the line to reach a predetermined desired value before washing is started. Water is recirculated at a faster rater than it is dispensed once the desired temperature has been reached.

Abstract: Disclosed is an automatic switching two pipe hydronic system for conditioning a space. In one embodiment the two pipe hydronic system enables automatic switching from a first mode of operation to a second mode of operation or vice versa in a reduced span of time. The present invention saves fuel, energy and water, when there are lower load conditions that affect boilers, chillers, and cooling towers. In another embodiment, the present invention provides a system for simultaneously heating and cooling a first portion and a second portion of a space by utilizing a plurality of boilers, chillers, heat exchangers, condenser pumps and closed loop pumps by using a plurality of sensors indicating the temperatures inside and outside the space and a controlling module controlling the operation of the system. The present invention can be easily achieved by making minor configurational modifications to existing systems thereby increases system versatility.

Abstract: Provided is an apparatus for automatically controlling a constant flow by considering a heating load in which a necessary request heat amount necessary for optimum heating is calculated by considering a heating load per room to find a optimum flow in proportion to the heat amount and reduce a total constant flow of the household by the optimum flow corresponding to the heating-stopped room, and thereby to save fuel cost in proportion to the heating-stopped flow and decrease tube noise due to cavitation.

Abstract: In a hydronic heating/cooling system, liquid is led along a main supply pipe (1) to a supply manifold (2) and distributed into heating loops (3). The heating loops (3) return to a return manifold (4). At least one of the manifolds (2, 4) has actuators (6) for controlling the flow in the heating loops (3). Actuators with fast operating times are used and valves of the actuators are controlled to close at different times in different heating loops (3).

Abstract: The present invention relates to a prefabricated heat-insulation panel with two hot water flow paths. The prefabricated heat-insulation panel comprises a panel; primary and secondary hot water supply pipes which are installed separately inside the panel to provide at least two hot water flow paths; and primary and secondary connection parts which are provided in the panel and connected to a boiler or primary and secondary hot water supply pipes installed in another panel to allow hot water to circulate in the primary and secondary hot water supply pipes.

Abstract: A primary-secondary loop piping system includes at least one boiler in fluid communication with a primary piping loop and at least one primary loop pump in the primary piping loop. At least one secondary piping loop branches away from the primary loop and returns downstream to the primary loop via a pair of closely spaced tees in a primary/secondary piping loop interface apparatus. The primary/secondary piping loop interface apparatus is of unitary construction and includes a secondary loop shut-off valve, drain valve and drain port in each branch of each secondary loop in which it is installed.

Abstract: A heating system and method includes a water circulation system for heating the interior of a building. The system further includes a boiler for storing and alternatively heating the water, and a fireplace jacket positioned in a fireplace of the building. The fireplace jacket includes a serpentine shaped length of pipe for circulating water. Fireplace jacket inlet and outlet ports communicate with the boiler for circulating the water in a closed system. A heating system control system manages the circulation of the water in the circulation system. The control system includes a safety unit having a thermometer, and the control system automatically circulates the water when the water is heated to a specified temperature. The control system automatically switches between using fossil fuel to heat the water in the boiler and using the fireplace jacket to heat the water in the boiler.

Abstract: The present invention relates to a heating system using a fireplace which includes a combustion room having a discharge hole installed at the wall body of a dwelling house comprises a water tank installed within the combustion room of the fireplace and having water therein; and a pipe with a predetermined length flatly placed with a zigzag type under the bottom surface with a constant area at the neighborhood of the fireplace, the inlet and outlet of the pipe communicated with a side of the water tank, which the water discharged from the water tank through the inlet is circulated along the pipe with a predetermined length, then returned to the water tank through the outlet of the pipe, whereby the warmth at the bottom surface of the room is maintained by the circulated warm water.

Abstract: A multi-layer heated floor includes insulating layer having a bottom surface positioned on a ground level and a top surface. Heating conduits are positioned above the top surface of the insulating layer and a base material layer is positioned on the insulating layer where the base material layer encases the conduits. The base material comprises a compactible material and wherein the base layer comprises a top surface. A concrete layer is positioned on the top surface of the base layer wherein heat from the heating conduit passes through the base layer and wherein the base layer distributes the heat. The heat enters the concrete slab through a bottom surface through a top surface of the concrete layer to heat the space above the floor.

Abstract: A tank for use with a liquid heating vessel of a hydronic radiant heating system to assist in the simultaneous sealing and venting of air from the system where the heating vessel has a flue for release of exhaust, the tank including a liquid holder that is exposed to the atmosphere and an aperture defined in the holder such that the flue of the vessel may extend upward through the aperture of the tank.

Abstract: A multiloop temperature-control system has a hydraulic bus connected to a plurality of loops for the temperature-control medium and respective hydraulic modules connected to the hydraulic bus, and through the hydraulic bus, to these loops. Plug connectors join each hydraulic module with an electrical supply and control module and the supply and control modules in turn are connected by plug and jack connectors to an electrical bus.

Abstract: The assisting in the evaporation of water from a surface impoundment or other impoundment that utilizes a closed heat pipe system that is partially submerged within the material of the surface impoundment. Water, or other heat transfer fluid, is circulated within the closed heat pipe system with this water being heated exteriorly of the surface impoundment prior to flowing within the portion of the heat pipe system that is located within the surface impoundment. The water is heated within the closed heat pipe system to an approximate temperature of one hundred seventy degrees Fahrenheit. The heating of the material in the surface impoundment is accomplished by the transfer of heat from the heat pipe system to the material in the surface impoundment. The rate of evaporation of water from the surface impoundment can be increased to more than thirty times the evaporation rate of a surface impoundment that doesn't utilize heat from an external source.

Abstract: A process and apparatus for heating gas in which a flow rate D0 of a warm fluid is caused in an input line, connected at its upstream portion to a source of warm fluid and at its downstream portion to the inlet of one of the passages of a heat exchanger; a portion of the flow D0 is diverted before it reaches the inlet of the first passage, into a branch line connected at its upstream portion to a so-called primary point of the inlet line located between the source of warm fluid and the inlet of the first passage; the gas to be heated is caused to circulate in another passage of the exchanger, so as to effect heat exchange between the gas to be heated and the warm fluid, thereby to obtain at the outlet of the second passage a warmed gas, and at the outlet of the first passage, a cooled warm fluid; the temperature of the warmed gas is controlled by the aid of a flow rate regulating valve located in a selected position in the inlet or outlet line.

Abstract: A hydronic heating system having a source of hot supply water and a reservoir of cooler return water, a supply water line from the source, a return water line to the reservoir and a multitude of heating loops through which water flows to deliver heat, including: a main distribution station having a supply header, main heating loops, and a return header with a pump compelling circulation within the main station so that heat from the source flows to the main heating loops; and one or more satellite distribution stations, each with a supply header feeding water to satellite heating loops, and a satellite return header and pump compelling circulation within the satellite station; and a satellite injection water line and return water line for circulating some hot water from the main station to each satellite station so that heat from said main station flows to each satellite station.

Abstract: A passive injection system for a hydronic heating system having a primary loop and a secondary loop is described. The passive injection system establishes a secondary temperature in the secondary loop significantly different from the temperature of the primary or boiler loop. A Venturi tee passively induces flow from the primary loop to the secondary loop. A valve is provided in the flow path of the Venturi tee between the primary and secondary loops and allows some flow or no flow from the primary loop to enter and mix with the secondary loop, depending upon whether the valve is open, closed, or partially open. A return leg is provided at a tee connection for returning flow from the secondary loop to the primary loop. In this way, the temperature of the secondary loop can be set well below the temperature of the primary loop and can be controlled without changing the flow rate of the secondary loop.

Abstract: The apparatus of the present invention comprises a hydronic distribution system using prefabricated, flexible cable containing plastic tubing to provide liquid supply and return conduits for the hydronic system. The plastic conduits are enclosed in a foam thermal insulation material which is encased in a flexible, moisture impervious shell. In an alternate embodiment of the invention, the flexible cable includes electrical conductors for supplying power to a fan and for carrying an electrical control signal from a thermostat. The flexible cable thus described can be installed in a building easily and quickly in a manner similar to that currently used for electrical cable.

Abstract: In a domestic hot water supply system including at least one user terminal such as a shower head to which blended hot and cold water are supplied at a selected temperature, the cold water of the blend is supplied via a check valve which responds to changes in hydrodynamic pressure so as to regulate the volumetric flow of cold water and thereby compensate for changes of water demand in other parts of the system.

Abstract: A three-way modulated diverting valve is provided in the return line to the boiler of a hydronic heating system between the heating loop return and the boiler return, the valve having its input from the heating loop return, one output to the boiler return and the second output to the heating loop supply, so that the valve diverts some of the cooler return water to the boiler hot supply water, diluting the supply water to reduce the temperature of supply water that feeds the heating loop; and the valve is modulated by a feedback signal representative of the temperature of the diluted supply water. In a preferred embodiment, the feedback modulation is accomplished using a non-electric thermostatic actuator head that drives the valve stem and is controlled by a capillary temperature sensor, the sensor bulb being immersed in the diluted supply water or clamped to the supply line next to the heating loop supply so that it is at the temperature of the diluted supply water.

Abstract: Device for expansion transfer in liquid cycle systems, in particular for heating installations, comprising a heating boiler (1), a liquid line (2, 2'), radiators (3) and an expansion vessel (4) at atmospheric pressure. The expansion vessel (4) is connected to the liquid line (2) of the heating installation through an inlet line (5), an outlet line (6), an overflow valve (7) which can be adjusted according to the operating pressure of the installation, and a continuously operating circulating pump (9).

Abstract: A hot water circulating system capable of decreasing energy loss, increasing the amount of hot water to be circulated per unit time and reducing time required for each circulating cycle. The system includes a valve opened at the start of emptying of water out of a water boiler to supply water from an open tank to the water boiler. The water boiler is divided into a heated section and a hot water receiving section arranged above and communicated with the heated section.

Abstract: Water heating methods and apparatus feed a combustible mixture of gas and air to an axial inlet of a cylindrical radiant surface burner and conduct water to be heated through a heat exchanger encompassing that cylindrical radiant surface burner as a cylindrical structure having first passages for combustion gases therethrough substantially radially of the cylindrical radiant surface burner and the heat exchanger.

Abstract: A boiler has a gas burner assembly and a heat exchanger positioned in a combustion chamber for heating water circulated through the heat exchanger by heat exchange with the combustion products. The performance of the heat exchanger is improved by rotating the heat exchanger to prevent formation of a boundary layer of cooler combustion products and/or a surface film of condensed moisture on the heat exchange surface.

Abstract: Conduits jointly define a fluid and vapor occupied annular chamber which when the conduits are heated emits bubbles which propel a quantity of fluid along a conduit. A fluid imbalanced condition in fluid heads is achieved by the bubble propulsion of fluid to cause fluid circulation in a heating system exposed to a heat source. A heat exchanger is also disclosed.

Abstract: The heating system includes water-radiators, a heat source as a boiler and/or one or more water-accumulators, an expansion vessel and a pipe-circulation system interconnecting the radiators and the source through which the water is pumped. The system is intended for one-family-houses with normally at most two floors above a cellar or a basement in which the source is situated. The expansion vessel is contrary to conventional open expansion systems arranged below the levels of the radiators in the boiler room and thus frost-free and immediately above or beside the top of the heat source. Its own top is provided with an open outlet to the atmospheric air in the boiler room. Thus the heat source is exposed approximately only for the very low water-pressure from its own water. Contrary to the heat source the radiators with belonging riser- and return-pipes are exposed to the same high water-pressure as at conventional radiator-systems with the expansion vessel situated above the topmost radiators.

Abstract: A heat-exchanging system for an enclosed space having wall-forming members, pipes provided on said members, and being adapted for discharging water for flow along the surfaces of the same, a source of water, a pump connecting said source and said pipes, ducts for returning water to said source, and a temperature sensor controlling the operation of said pump whereby said members serve as a heat exchanger for both heating and cooling purposes in response to predetermined temperatures.

Abstract: A hot water heating system is disclosed in which the convectors or radiators are provided with thermostatic valves capable of shutting off the supply water to all radiators. In order to prevent damage to the pump some circulation is permitted at all times by means of a bypass opening in a manifold which directs water to and from the radiators.

Abstract: In a method for the regulated transfer of heat from a primary steam network to a heat consumer, the supply flow of which is at a predetermined overpressure and the return flow of which is at a relatively lower pressure, the steam withdrawn from the steam network in accordance with the heat consumption on the part of the consumer is cooled down to the point of condensation by the withdrawal of heat by means of a secondary medium, while a predetermined overpressure relative to the supply pressure of the heat consumer is maintained. The overpressure in a jet pump is then reduced to the supply pressure of the heat consumer, generating a corresponding driving force for the supply flow, and secondary medium heated up in the course of the cooling down of the steam is mixed with the supply flow.

Abstract: A pulsing combustion device is disclosed including a combustion chamber with a poppet valve mounted for reciprocation in the combustion chamber. A pressurized combustible mixture is supplied to the poppet valve with the combustion gases ignited in the combustion chamber. The poppet valve is reciprocated in the combustion chamber by the pressure of the pressurized combustible mixture and the pressure of the combustion gases. The poppet valve regulates the flow of the combustible mixture into the combustible chamber. The pulsing combustion device may be utilized in a steam cleaning device wherein the pulsing combustion device is surrounded by a flow of liquid.The pulsing combustion device may also be utilized for home heating with a fluid heated by the combustion device.

Abstract: In a method for the regulated transfer of heat from a primary steam network (010), the flow (04) of the heat consumer (2) is supplied at a predetermined excess pressure, while the return flow (02) is at a relatively lower pressure.

Abstract: A wood burning heating system comprises a large hot water storage tank and a furnace or boiler with a water jacket and a vaulted ceiling over a firebox with a refractory bottom and a refractory lining partially up the side walls of the firebox. The volume of the tank is about ten to twenty times larger than the volume of the water jacket, whereby the large hot water volume acts as a heat storage and as a buffer or heat output equalizer counteracting any intermittent heat input inherent in a solid fuel system especially a wood burning system. The firebox is elongated and the door is so arranged that wood pieces of random and substantial size may be charged into the firebox so that the wood is burning while it is in a horizontal position. The large hot water storage tank may receive additional heat input, for example from an electrical heater operated by a wind driven generator. If desired, the furnace may be installed inside the large hot water storage tank.

Abstract: A heating system comprising a closed conduit containing a liquid which is continuously circulated through the conduit by a pump. An electrical resistance heating unit serves to heat the liquid in the conduit and heat is transferred from the liquid through a heat exchanger to a medium to be heated. A proportional timer is operably connected in the electrical circuit with the heating unit. The timer has a cycle of fixed duration composed of an "on" interval and an "off" interval, with the duration of the "on" interval being variable within the cycle. A temperature sensor senses the temperature of the liquid in the conduit and if the temperture falls below a set value, the sensor acts to operate the timer and energize the heating unit. A second temperature sensor acts to adjust the "on" interval of the timing cycle in proportion to the deviation of the liquid temperature from the temperature setting.

Abstract: A water heating system comprises a lower energy storage tank connected with a source of energy and an upper tank mounted on top of the lower. The upper tank may be a conventional water heater or a water storage tank connected at an outlet therefrom with an instantaneous type water heater, and the tanks are interconnected through a valve. The valve operates to direct incoming cold water through a heat exchanger in the lower tank for being preheated prior to introduction into the upper tank and accommodates a thermal syphon effect between the tanks when fresh water is not being supplied, whereby heat energy is automatically transferred from the lower to the upper tank. The lower tank may advantageously and economically comprise a conventional drum, for example a 55 gallon drum, and all system components are mounted in a cover assembly for the lower tank, so that the upper tank need not be specially fabricated, with the cover assembly also serving to support the upper tank.

Abstract: The invention relates to a control unit comprising two bodies, one of which is located in a main fluid-distributing section, such as a hot water heating system. A shunt valve in this main section body provides for shunting the hot water, of a boiler in the main section, between different channels which are enclosed within the two bodies. The second body section is located in a group flow-distributing section, and may be used in conjunction with a circulating pump. The two bodies are connected to each other via a mechanical heat-blocking device, made of a material having a heat conductivity figure which is lower than .lambda.=1.00 kcal/m h .degree.C. This heat-blocking device also establishes a communication for fluid flow between the channels, enclosed in the two bodies.

Abstract: The present invention relates to a heat pump for the circulation of a heat carrier fluid in a closed circuit in order to transfer calories from a hot source towards a cold source. This pump comprises two closed tanks which communicate, one with the hot source, and the other with the cold source, a pipe which connects the upper parts of the two tanks and which is equipped with an automatic valve controlled by two level sensors sensing the high and low level of the liquid in one of the two tanks and a circuit which connects the lower part of the first tank to the second tank through the cold source.

Abstract: A heating device for supplying hot water to home heating systems and hot water faucet outlets in the home includes a combustion chamber which is adapted to burn wood fuel for supplying the necessary heat. The heating device comprises a base member containing an ash bin and ash door for the removal of burnt fuel, a water tank positioned on the base and sealed thereto, the water tank containing therein the combustion chamber which includes a grate which rests over the ash bin, the water in the water tank substantially completely surrounding the combustion chamber, the combustion chamber further including an exhaust pipe for removing exhaust combustion gases from the combustion chamber out of the heating device, the water tank being fully enclosed by an insulating shell which fits over the top thereof.

Abstract: A heat distribution system is disclosed for transferring heat, such as is generated by a burner device of conventional construction, to a remote location, with circulation away from the burner in a horizontal or downward direction. The distribution system of the invention is particularly useful whenever a building heating arrangement requires the furnace or other equivalent heating means to be located above or level with the point at which heat is to be withdrawn from a circulating fluid.

Abstract: A fluid friction heater is disclosed. The heater includes a housing having a cylindrical inner surface. At least nearly circumferential, closely spaced grooves are formed in the inner surface of the housing, the depth of the grooves being small relative to the diameter of the surface itself. A drum is mounted within the housing and has a cylindrical outer surface in close proximity to the inner surface of the housing. The outer surface of the drum has at least nearly circumferential, closely spaced grooves formed in it as well. The pitch of the grooves in the respective surfaces are different from one another. A liquid is injected into the space between the inner surface of the housing and the outer surface of the drum. The housing and the drum rotate relative to one another so that the liquid passing between their respective surfaces is sheared and agitated by the respective grooves in the surfaces.

Abstract: A very well heat insulated water storage or accumulator tank of relatively large capacity as compared to the capacity of the hot water heating unit is interposed between the unit and the radiator system and is interconnected with the unit. Heated water from the top portion of the tank is used to preheat the unit prior to actuation thereof, and mixed water above a given temperature is fed to the unit from the tank during actuation, such that the corrosive condensation on the heating surfaces of the heating unit, caused by heating a cold surface, is eliminated thereby extending the useful life of the unit. When the unit is actuated, heated water from the unit fills the tank from the top side until a volume of non-heated return water from the radiator system, approximately equal to the capacity of the unit, remains in the bottom of the tank.