GB2355518A

GB2355518A - Thermal storage heaters

Info

Publication number: GB2355518A
Application number: GB9925087A
Authority: GB
Inventors: William Paul Cowling
Original assignee: Individual
Current assignee: Individual
Priority date: 1999-10-22
Filing date: 1999-10-22
Publication date: 2001-04-25
Also published as: GB9925087D0

Abstract

A storage heater comprises a refractory core, thermal insulation, a casing, electrical heating elements, a fan for heat extraction a <WC 1>control system and mounting brackets. Intake and discharge grilles extract and return air from an occupied space. The storage heater heats this air by passing it over the refractory core which is positioned under a floor or in a ceiling void. The refractory core is heated over-night using 'off-peak' electricity. A room temperature sensing thermistor probe senses the room temperature. The fan speed is then regulated. A bimetallic air-mixing control flap mixes hot air from the core with bypass air flowing over the top of the storage heater.

Description

2355518 STORAGE HEATER This invention relates to a storaCre heater, which

can be installed under a floor or in a ceiling void.

Contemporary designs of storage heater generally comprise of a core made from high density refractory bricks with form such that air passage is possible over this material; a surrounding layer of insulation, electrical heatino, elements of a sheathed construction (generally positioned central to the refractory core), an outer skin of io sheet steel to contain these components and to allow room ambient air to circulate such that external surfaces are maintained at an acceptable temperature.

In addition the stora(ze heater will contain thermostatic devices to limit the core temperature and to over-ride the supply in case of malfunction. A bimetallic damper may also be included to allow regulation of the rate of energy dissipation from the core during the discharge cycle.

The function of the storaae heater is the storing of cheap rate 'offpeak' energy from the heating elements in the refractory core such that it can be utilised in periods when the price of electricity is higher.

These charge periods are generally over seven hours, criving a discharge period of 17 Z 17 - hours before the start of the next 'top up' period. The use of fans to force air over the core coupled with case designs that prohibit natural convection has enabled further control the energy discharge.

Current designs of storage heater have tended to be slim, making their aspect ratios as close as is possible to a wet radiator. This tendency does however have a major drawback as the greater the surface area of the storage heater, the greater its tendency towards uncontrolled heat discharge.

Fan assisted storaee heaters are able to find a market position through their ability to control heat dissipation. These products generally have a higher degree of insulation resulting in a greater product cost, and a less aesthetically pleasing, 'fatter' aspect rati6.

j5 A problem inherent in current storage heater designs that depend on natural air convection for their heat discharcge is that maximum dissipation is frequently in the early hours of the day when the core is at its maximum temperature. By 1he evening, when the heating requirement, certainly for most of the working population is highest, the performance is restricted by the lower core temperature due to wasteful discharge during the day.

The problems faced by the invention are how to make an energy efficient and controllable storage heating product without the expense of a great deal of ('microporous') insulation material and to overcome the aesthetic / space utilisation problems encountered when large amounts of insulation are employed. In addition to provide a solution to the large set up and production costs associated with the manufacture of a product which can be accepted as a domestic appliance.

The solution provided by this invention is to make a storage heater with a cross 01 sectional aspect ratio as close to 1:1 as possible, to use a fan assisted means of heat dissipation coupled with insulation of an appropriate depth and cost / thermal resistivity, to case the heater in plane galvanised sheet steel with dimension to suit the application and to mount the heater either under the floor or in the ceilinL7 void with air outlet and return grilles to allow passage of supply and return air streams.

Unless cabling for a storage heater system is to be placed in surface mounted 1 0 trunking, it is normal for floorboards to be removed to allow the laying of cables.

I The installation cost benefits offered by electrical stora e heating systems over wet g 11 systems are therefore largely due to the fact that it is easier to manipulate electrical cable than it is to install copper pipe (Assuming that the cost of the storaze heaters roughly equate to the cost of the fossil fuel boiler).

It is during this stage that the underfloor storage heater is fitted between the floor ceiling beams, or recessed in to a shuttered space in a concrete floor.

Fig 1 shows a section through half of the storage heater, and the mountinz beam on one side with associated bracketry. The mounting system is such that the core box c'be positioned- in the available void, resting on the mounting brackets shown in an figure I such that the installation process is rapid and uncomplicated. The space 'A' at the top of the heater is used for bypass air from the core pressurisation fan. This is controlled by the bimetallic air-mixing control flap shown in figure 2. The purpose of this control flap is to mix hot air from the core and bypass air in the discharge plenum, and to prevent the outlet air, outlet grille and surround from reaching excessive 0 temperatures.

Figure 2 shows the passage of bypass air whereas figure 3 shows the passage of air through the core of the storage heater. These airflows are encouraged to mix in the outlet plenum chamber by the positioning of the bypass control flap.

Figure 4 shows how the supply air is to be drawn through a grille placed in the floor I and will travel under the floor to the storage heater. The heater is positioned near the discharge grille at the opposite end of the room so that the discharge air is straight from the heater.

Figure 4 shows the movement of air within the room, and position of system components for a system where the storage heater is installed under the floor. Figure 5 shows the movement of air within two rooms,- and position of system components for a system where the storage heater is installed in the void between the rooms.

A room temperature sensing, thermistor probe senses the room temperature, which is controlled by the consumer through the adjustment of a potentiometer to the desired temperature setting The fan speed is then regulated during the pre-set / timed discharge periods by a 0 1:1 thyristor speed control. Hence room temperature can be maintained at a precise predetermined level. A timer control will allow setback temperatures for periods if required.

The alternative installation shown in figure 5 where the storage heateris used for-the temperature regulation of two rooms, and is sited in the void between the two rooms could be of use in a number of applications:

If a concrete floor is present in the lower room during a retro fit exercise or if disruption in the lower room is to be minimised. If a sinale heater / control is to be used to heat both the upper and lower room (for commercial applications- where 105 temperature requirements of rooms are the same). Overhead mounting of the product, coupled with the use of a more powerful fan such that the extracted heat from the core can be delivered to the occupied space within the room; makes the invention suitable for applications where low surface temperature (L.S.T.) limits apply.

4

Claims

A storage heater (comprising of a refractory core, thermal insulation, a casing, electrical heating elements, a fan for heat extraction a control system and mounting brackets, intake and discharge grilles) that extracts air from the occupied space, heats this air by passing it over a refractory core positioned under a floor or in a ceiling void, and returns this heated air to the occupied space.

A storage heater which does not impinge on a room's usable area.

A storage heater that offers controllable and energy efficient heat output without the need to occupy any space within the living area. Having an intake grille for the extraction of air from the room positioned remotely from the heater, and a discharge grille attached to the heater casing for returning air following it's heating by passing 15 through the hot refractory core.

A storage heater designed for under-floor or ceiling void installation by virtue of the bricks being laid such that their vertical dimension is kept small compared with their longitudinal and lateral dimensions, and by virtue of a mounting system to facilitate 20 suspension between constructional timbers.

A storage heater that when mounted in a ceiling void presents no reachable hot surfaces to the living area, and is therefore safe for use where low surface temperature (L.S.T.) requirements apply.

A storage heater incorporating a thyristor controlled method of forced convective heat discharge such that the rotational speed of the fan is adjusted automatically according to room temperature and the control's setting.

A storage heater incorporating an electronic control that regulates the heat energy stored in the core during the charge period by means of two sensors linked to the electronic control. The first measuring the room ambient temperature during the charge period, and the second measuring the temperature of the refractory core.