Heat recovery apparatus

Abstract

A heat recovery apparatus comprising a vessel having: a first liquid flow path such that a first liquid can pass through the vessel between a first liquid inlet and a first liquid outlet; a second liquid flow path in thermal contact with the first liquid flow path; and a heater for occasionally heating at least the liquid in the second liquid flow path on an occasional basis. This allows Legionella growth to be inhibited.

Description

[0001]The present invention relates to a heat recovery apparatus, and in particular to an apparatus suitable for recovering heat from “grey” water.BACKGROUND OF THE INVENTION[0002]Water after it has been used for washing or showing is often discharged directly to the waste water, i.e. sewerage, systems. However such water which is typically termed “grey” water may contain significant amounts of heat. For example most bathers get out of a bath while it is still relatively warm. Furthermore it is estimated that around 70 to 80% of the heat delivered into a shower leaves via the shower drain. Thus there is significant potential to collect heat from such grey water.SUMMARY OF THE INVENTION[0003]According to a first aspect of the present invention there is provided a heat recovery apparatus comprising a vessel having: a first liquid flow path such that a first liquid can pass through the vessel between a first liquid inlet and a first liquid outlet; a second liquid flow path in thermal c...

AI Technical Summary

Benefits of technology

[0004]It is thus possible to provide a heat recovery apparatus which can recover heat from grey water and deliver it to a further liquid such as a cold water supply. The cold water supply may be used as a cold water input to a boiler, thereby reducing the amount of work that needs to be done by the boiler and hence the amount of fuel it consumes. Alternatively the water supply may go to items such as washing machines and dishwashers thereby reducing their heating requirements.

[0005]However, having static volumes of previously warmed water can cause a health risk due to Legionella. It is therefore beneficial to provide a heater to occasionally heat at least the liquid in the second liquid flow path such that any Legionella in it is deactivated. The heater may, for example, be in the form of an electrical resistance heater embedded within or formed in or on the second liquid flow path. However, it is generally more convenient to have the heater heat a volume of water that is in contact with the second liquid flow path, thereby ensuring that that volume of water does not propose a Legionella risk either.

[0008]Advantageously a temperature operated valve, where the valve is either mechanically or electrically controlled, may be provided in order to inhibit the grey water from being in substantial thermal exchange with the second liquid flow path or the tank surrounding the second liquid flow path whilst the grey water is below a first threshold temperature. The first threshold temperature may be an absolute temperature, for example 25° C., or it may be determined relative to the temperature of the water in the tank or in the second liquid flow path. This provides a mechanism for preventing the passage of cold grey water through the heat recovery apparatus from depleting the heat store of heat that it had previously recovered and stored.

Problems solved by technology

However, having static volumes of previously warmed water can cause a health risk due to Legionella.

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