GB2237864A

GB2237864A - Hot water system

Info

Publication number: GB2237864A
Application number: GB8925071A
Authority: GB
Inventors: Peter Hollidge
Original assignee: Individual
Current assignee: Individual
Priority date: 1989-11-07
Filing date: 1989-11-07
Publication date: 1991-05-15
Also published as: GB8925071D0

Abstract

A domestic hot water system, with a primary circuit (10, 12, 14) heated by a boiler and a secondary circuit leading from a conventional hot water cylinder (16) to feed hot water outlets such as taps and showers, additionally incorporates a subsidiary electric heater (20) in the primary circuit. The subsidiary heater may be controlled by a thermostat (34) located near the bottom against the outer casing (18) of the cylinder (16). The location of the subsidiary heater allows indirect heating of the secondary water when the boiler is not in use and so avoids the build-up of hard water deposits on a conventional immersion heater in the secondary water. <IMAGE>

Description

Title: Hot Water System Field of the Invention This invention relates to hot water systems having a boiler and primary and secondary circuits. Such systems are generally called "indirect" because water in the secondary circuit is heated by water in the primary which is itself heated by the boiler.

Background to the Invention A conventional indirect hot water system has a hot water cylinder (or calorifier) with an inner coil disposed within the outer casing of the cylinder. Water in the primary circuit is passed through the coil and heats the secondary water in the secondary circuit in the casing.

The primary circuit frequently serves to provide space heating, eg by radiators, and the secondary circuit provides hot water to be drawn from the system at outlets such as taps, showers or the like.

In many cases the hot water cylinder is fitted with an electric immersion heater for providing hot water when the boiler is not used, such as during the summer. the immersion heater is fitted in the top of the cylinder casing and projects into the cylinder to heat secondary water in the upper part of the cylinder casing. This arrangement has a number of disadvantages: the volume of water heated is generally quite small and is frequently insufficient to meet a sudden demand for hot water, such as occurs when water is drawn for a hot bath; the immersion heater element, being in the secondary water circuit, rapidly becomes coated with hard water deposits (so-called fur), resulting in loss of efficiency, slowness in heating, corrosion and eventual failure, frequently requiring the replacement of the complete cylinder as well as the immersion heater.

The invention aims to provide a hot water system which does not suffer from these disadvantages.

Summary of the Invention According to the invention a hot water system comprises a primary water circuit with water heated by a boiler, and a secondary circuit with water which is heated by the water in the primary circuit and which serves to supply hot water to be drawn from the system, wherein a subsidiary electrical heater is provided in the primary circuit to heat the primary water and, indirectly, the secondary water.

The system preferably includes a hot water cylinder having an inner coil for the passage of primary circuit water, and an outer casing for enclosing secondary circuit water. The subsidiary electric water heater may be energised when the boiler is not used, eg during the summer, to provide a supply of hot water in the secondary circuit. Because the water in the secondary circuit is heated indirectly from water in the primary circuit, the disadvantages associated with the use of a conventional immersion heater (directly heating water in the secondary circuit) are avoided.

The subsidiary electric heater is preferably a unit separate from the hot water cylinder for ease of installation and maintenance of the unit, and in a preferred embodiment the subsidiary electric heater is connected between the flow and return pipes leading from the boiler to the inner coil of the hot water cylinder.

The subsidiary electric heater may be thermostatically controlled, the thermostat preferably being located on the outer casing of the hot water cylinder than the top.

A domestic hot water system according to the invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a perspective view of the novel part of the system, and Figure 2 is a from view of the part of the system shown in Figure 1, with the supporting flooring of a house being shown in section.

Detailed Description of the Drawings The system illustrated in the drawings comprises a boiler (not shown) which heats water in a primary circuit, the feed and return pipes of which are indicated at 10 and 12 in the drawings. The feed and return pipes 10 and 12 communicate with respective ends of an inner coil 14 (Figure 2) disposed within a conventional hot water cylinder 16. Water in the intervening space between the coil 14 and the outer casing 18 of the cylinder 16 is in the secondary circuit, and this water is available to be drawn off from the system at hot water outlets such as taps and showers.

In accordance with the invention, a subsidiary electric heater 20 is incorporated in the primary circuit, being connected by linking water pipes 22, 24 to the pipes 10, 12 respectively. A valve 26, with an adjusting hand wheel, is incorporated in the pipe 22, and the pipe 24 incorporates a drain cock 28. The heater has a cylindrical metal casing into which projects from one end the coil 30 of an electric immersion heater powered from an electrical mains socket 32. A thermostat 34 is mounted on the external wall of the cylinder casing 18 at substantially the same level as the return pipe leaving the cylinder (ie. nearer the bottom of the cylinder than the top) to sense the temperature of the secondary circuit water at this level in the cylinder, and is linked by a cable 36 to the socket 32. The thermostat 34 controls the energisation of the immersion heater and maintains the secondary water temperature between predetermined levels.

The heater 20 is used when the boiler is shut down, for example during the summer, to provide an indirectly heated supply of hot water in the secondary circuit. The heater 20 heats a larger volume of water than does a conventional immersion heater in the secondary circuit, and does not suffer from hard water deposits because it heats the continually recirculating primary circuit water. Moreover, the heater 20, being separate from the cylinder, is easy to services and maintain.

Claims

Claims:

1. A hot water system comprising a primary water circuit with water heated by a boiler, and a secondary circuit with water which is heated by the water in the primary circuit and which serves to supply hot water to be drawn from the system, wherein a subsidiary electric heater is provided in the primary circuit to heat the primary water and, indirectly, the secondary water.

2. A system according to claim 1 including a hot water cylinder having an inner coil for the passage of primary circuit water, and an outer casing for enclosing secondary circuit water.

3. A system according to claim 1 or 2 in which the subsidiary electric heater is energised when the boiler is not used (eg during the summer) to provide a supply of hot water in the secondary circuit.

4. A system according to claim 2 or claim 3 in which the subsidiary electric heater is a unit separate from the hot water cylinder, for ease of installation and maintenance of the unit.

5. A system according to any one of claims 2 to 4 in which the subsidiary electric heater is connected between the flow and return pipes leading from the boiler to the inner coil of the hot water cylinder.

6. A system according to any one preceding claim in which the subsidiary electric heater is thermostatically controlled.

7. A system according to any one of claims 2 to 6 and further comprising a thermostat located on the outer casing of the hot water cylinder at a position nearer the bottom of the cylinder than the top.

8. A hot water system substantially as herein described with reference to, and as shown in, the accompanying drawings.