Heating systems – Automatic control – Water
Patent
1990-11-12
1993-01-12
Bennet, Henry A.
Heating systems
Automatic control
Water
137455, F24D 300
Patent
active
051783240
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a method of regulating a central or district heating plant provided with a differential pressure valve for circulating a heat carrying liquid, such as water, in a building with several rooms, each of which has at least one radiator controlled by a thermostat valve, said differential pressure valve being placed after the radiators in the direction of flow and having a closing device controlled by a membrane for regulating the flow of the heat carrying liquid through a passage between an inlet and an outlet.
In central heating plants it is important that the water is distributed through the plant in a previously calculated proportion in such a way that the dimensioned heat requirements of the individual radiators are taken into consideration.
It is also important that the heat carrying liquid remains in the plant for long enough to allow an adequate amount of heat to be dissipated to the rooms in the building which is to be heated by the plant. This is enabled by means of a differential pressure valve placed in the individual branches of the plant, which valve can regulate the flow of the heat carrying liquid.
Furthermore, it is important that the differential pressure across the individual radiators is so small that noise is not generated in the valves, because such noise may cause inconvenience, directly or by transmission through the piping system.
In the individual rooms the flow of the heat carrying liquid through the radiator or through each radiator is controlled by means of thermostat valves which, depending upon the room temperature, can open more or less to permit flow through the radiator or radiators respectively in such a way that the emission of heat to the room can be kept within the limits, which are determined by the accuracy of the thermostat valves, and the temperature, which the user of the room has decided to maintain, by adjustment of the thermostat valve or valves.
In this normal function of the plant the thermostat valves control the system, and the differential pressure valve assumes its previously fixed setting, which is combined number of thermostat valves will cause an appropriate pressure drop across the plant.
However, in a plant like this a situation will often arise which will deviate from this predetermined normal function.
This may for example occur when early in the morning when the cleaning personnel open the windows in several rooms to air the rooms prior to the arrival of the users of the individual rooms at normal working hours.
When the window or the windows are opened in a room in which there are radiators provided with thermostat valves these ought to be turned off to the flow of the heat carrying liquid.
Experience shows that the radiators are rarely turned off, and therefore several hours may pass with the windows left open, whereby the thermostat valves open fully for each radiator, especially at low outdoor temperature.
In this situation it is the differential pressure valve which must control the combined flow through the plant, but this cannot be accomplished since the pressure difference between the two surfaces of the membranes is small, even with full flow through the valve.
Therefore in this abnormal but nevertheless often recurring situation, a disproportionately large amount of the heat carrying liquid will flow through the plant with a poor economy as a consequence.
The purpose of the invention is to counter the above mentioned drawback, and this purpose is achieved through the method in question, which method according to the invention is characterized in that the differential pressure valve is provided with an adjustable throttle between the inlet and the closing device, and that the throttle is adjusted to allow a maximum amount of liquid to pass, regardless of the state of distribution of the pressure in the plant.
By providing the differential pressure valve with the said adjustable throttle the total amount of heat carrying liquid through the plant can be limited even if all of the thermostat valves are opened at a maximum,
REFERENCES:
patent: 1558330 (1925-10-01), Bain
W. Hoffmann, "Hausanschlusse fur das Warmwasserfernheiznetz Stuttgart," Aug. 1956, Heiz.-Luft.-Haustechn. 7, No. 8, pp. 130-131.
Samson AG, Einbau- und Bedienungsanleitung, Ausgabe Jan., 1988.
Bennet Henry A.
Frese Armatur A/S
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