NO346322B1

NO346322B1 - A water heater

Info

Publication number: NO346322B1
Application number: NO20191315A
Authority: NO
Inventors: Sigurd Braathen
Original assignee: Oso Tech As
Priority date: 2019-11-04
Filing date: 2019-11-04
Publication date: 2022-06-07
Also published as: NO20191315A1

Description

A WATER HEATER

Technical Field

[0001] The present invention relates to a water heater, especially a water heater for heating domestic water to be used as hot tap water and/or for building heating systems, such as hot water radiator heating.

Background Art

[0002] Domestic water heaters are common in virtually any building that is equipped with a water supply. The most common type of heater comprises a large tank, that can contain from 30 to 400 liters of water. For industrial purposes the tank can contain up to 1000 liters or more. The tank has an inlet for supply of cold water from a water distribution system or from a local well. The inlet can be either at the top of the tank with a pipe leading the cold water down to the bottom of the tank, at the side of the tank with a pipe extending to the bottom or at the bottom of the tank.

[0003] The tank contains one or more heating elements, that can be in the form of an electric element, a heating coil or a heat exchanger. As the water in the tank is heated, the hot water will raise to the top of the tank, as hot water has a lower density than cold water. Consequently, a layer of hot water will accumulate in the upper region of the tank. A hot water outlet draws hot water from this region. The hot water outlet may be at the top of the tank, at the side of the tank with a pipe extending into the hot water region or at the bottom of the tank with a pipe extending upwards into the hot water region.

[0004] Because of the risk of bacterial infection, such as the risk of legionella in the water tank, the hot water must be heated to a temperature above 55 degrees Celsius, preferably well over this temperature. In addition, a higher storage temperature will enable the use of a smaller hot water tank, as stored energy will be higher. Temperatures up to 80 degrees Celsius are common storage temperatures in a water heater. However, this hot temperature may pose a scolding risk if led to the tap. It is therefore common to mix the hot water with cold water before it is led to the tap, in order to bring the temperature down. The hot water tap temperature should preferably be below 55 degrees. In buildings for old or disabled people the tap temperature should not exceed 38 degrees.

[0005] To facilitate this mixing of hot and cold water, it is well-known to arrange a mixing valve at the outlet of tap water from the tank. The valve is coupled to the hot water pipe that extends into the hot water region and to a cold water pipe that extends into the cold region at the bottom of the tank. Alternatively, the cold water may be supplied directly from the cold water supply.

[0006] The valve may or may not be adjustable to adjust the mixing of hot and cold water.

[0007] EP 1840481 and EP 1840482 show a solution for a water heater where the inlet pipe has openings at different levels along the height of the tank. This is done to avoid stratification of the water in the tank. However, the downside of this is that the water in the tank will gradually get colder at water is tapped from the tank. This means that the water often will be colder than the 55 degrees that prevents bacterial growth.

[0008] US 2007077043 shows a water heater where the outlet pipe extends upwards from the middle of the tank and has several openings to let in water at different levels. This means that the coldest water is drawn from a zone where it may be too hot to prevent scolding. This is especially a risk if the water has been heated in the tank for a long time without any tapping.

[0009] US 4409958 shows a water heater where the outlet pipe that extends aliong the height of the tank, has a plurality of temperature controlled valves along its length to let in water at different levels. There is a high risk of one or more of the valves getting stuck during the lifetime of the water heater. If this happens, the mixing of water to the right temperature will not work. It will also be difficult or impossible to change the valves as a water tank usually only have small openings to let a slick pipe therethrough.

Summary of invention

[0010] The mixing valves are both complicated and relatively expensive. There is also a risk of calcification over time, which could prevent proper function of the valve. There is a risk that the mixing of hot and cold water will be insufficient, resulting in too hot tap water from the tap. In addition, there is a leak risk due to the connections at the valve.

[0011] Consequently, there is a desire to simplify the construction. In the present invention this is solved by omitting the mixing valve as such and instead perform the mixing within the tank by a fixed aperture hole to let cold water into the pipe supplying hot water from the hot water region of the tank. As defined in the subsequent independent claim 1, the outlet pipe extends continuously and uninterrupted from the hot water zone to the cold water zone.

Brief description of drawings

[0012] The invention will now be described in greater detail, referring to the enclosed drawing, showing an exemplary embodiment of the invention, in which:

[0013] Figure 1 shows a cross section through a water heater according to the present invention.

Detailed description of the invention

[0014] Figure 1 shows a water heater 1 in cross section. The water heater 1 comprises a tank 2, which consists of a generally cylindrical middle portion 3 and upper and lower end caps 4, 5. These three parts 3, 4, 5 together form an enclosure with rounded ends. Outside of the tank 2 there is insulation (not shown).

[0015] An electric heating element 6 is arranged within the tank 2, in the lower portion thereof.

[0016] A cold water inlet 7 is arranged through the bottom of the tank 2. This inlet can also be arranged through the side of the tank or the top of the tank, with a pipe extending down to the bottom of the tank 2.

[0017] A mixed hot and cold water outlet 8 for tap water is arranged through the bottom of the tank 2. The outlet connects with a hot water pipe 9 extending from the outlet 8 to an upper region of the tank 2. The upper region is the region in which heated water accumulates.

[0018] At the top of the pipe 9, the pipe has an opening 10 to let hot water into the pipe 9.

[0019] At a lower portion of the pipe 9, the pipe has one or more holes 11 through the wall of the pipe 9. These holes will let cold water from the lower region of the tank 2 into the pipe.

[0020] A short distance above the hole(s) 11 there is a baffle 12 attached to the cold water inlet 7. The baffle is situated vertically above the cold water inlet 7 to prevent the cold water flowing into the tank 2 from continuing upwards and mix with the hot water. The baffle 12 ensures that the cold water disperses into the lower region of the tank 2.

[0021] In the top of the tank is an alternative hot water outlet 13. This outlet can be used for drawing hot water out of the tank without mixing it with cold water. Such unmixed hot water can be used for purposes where scolding risks are not present, such as building heating in a closed circuit.

[0022] As an alternative to having a mixed hot and cold water outlet in the bottom of the tank, the outlet can be arranged in the top of the tank. In this case a pipe extends to the bottom region of the tank. The pipe has an open end in this region. Close to the mixed outlet at the top of the tank, the pipe has one or more holes to let hot water into the pipe.

[0023] When opening a hot water tap, water within the tank will be forced out through the hot and cold mixed water outlet 8. Hot water will from the upper region of the tank 2 into the open end 10 of the pipe 9. At the same time cold water will flow into the hole(s) 11 through the pipe 9 in the lower region of the tank 2. The ratio between the cold and hot water, and hence the temperature of the mixed water, is determined by the aperture of the open end 10 and the hole(s) 11, as well as the flow resistance for the hot water along the pipe 9. With a pipe of relatively large diameter, the flow resistance can be neglected. Consequently, the ratio is largely determined by the ratio of aperture between the open end 10 and hole(s) 11.

[0024] If the hot water in the upper region of the tank 2 is at a constant temperature, a fixed ratio between the apertures will result in approximately the same temperature of mixed water every time a hot water tap is opened. If the temperature in the upper region varies, the temperature of the mixed water will vary correspondingly. However, by selecting an aperture ratio that gives a resulting mixture of water that is less than the recommended tap water temperature, such as 55 degrees, when the hot water is at its maximum temperature, such as 75 degrees, the tap water temperature will never exceed the recommended tap water temperature, such as 55 degrees.

[0025] It has been found that for a pipe with a diameter of approximately 15 mm a single hole through the wall of the pipe of a diameter between 2 and 6 mm is suitable.

[0026] By this simple design is ensured a safe mixing of hot and cold water at a relatively constant temperature.

Claims

1. A water heater (1) for hot tap water, comprising a tank (2), and inlet (7) for cold water supply to a cold water region in a lower part of said tank (2), and a hot water outlet (8), said hot water outlet drawing water from a hot water region in an upper region of said tank (2), characterised in that said hot water outlet (8) is coupled to a pipe (9) extending between said hot water region and said cold water region of said tank (2), said pipe (9) having at least one opening (10) in said hot water region and at least one opening (11) in said cold water region, to draw water from both regions into said pipe (9) and out of said hot water outlet (8), and that said pipe (9) extending continuously and uninterrupted between the hot water region and the cold water region.

2. The water heater according to claim 1, characterised in that a ratio between the apertures of the at least one opening (10) in the hot water region and the at least one opening (11) in the cold water region is selected to mix hot water with cold water from a maximum set heated water temperature of the water in the hot water region to a temperature below a predetermined maximum tap water temperature.

3. The water heater of claim 1 or 2, characterised in that said hot water outlet (8) is in the bottom of said tank (2), and that said pipe (9) has an open end (10) in the hot water region and at least one opening (11) through the wall of the pipe (9) in the cold water region.

4. The water heater of claim 1 or 2, characterised in that said hot water outlet (13) is in the top of said tank (2), and that said pipe (9) has an open end in the cold water region and at least one opening through the wall of the pipe in the hot water region.