AU610137B2 - Warm water supply - Google Patents

Description

A14A L

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AUSTRALIA

Patents Act 1952 COMPLETE SPECIFICATION

(ORIGINAL)

FOR OFFICE USE FORM Short Title: Int. C1: Application Number: goo Lodged: o 0 a o 0 Complete Specification Lodged: oooo. Accepted: 00 o0 Lapsed: o o Published: 000000 0 0 Priority: o o00 oooo Related Art: o 00 0 00 o oa o oo Tiis document contains the amcndmcnts made under l ScLion 49 and is correct for printing.

00 00 O O 0 0 0 0 0 TO BE COMPLETED BY APPLICANT 0 o000o Name of Applicant: o o 0 Address of Applicant: Rheem Australia Limited Brodie Street Rydalmere NSW 2116 Peter Thomas NICHOL Mr A W Tilley Rheem Australia Limited Brodie Street Rydalmere NSW 2116 Actual Inventor: Address for Service: Complete Specification for the Invention entitled: "WARM WATER SUPPLY" The following statement is a full description of this invention, including the best method of performing it known to me: BO11.F L I Ir I- 1 This invention relates to hot water systems and in particular to systems designed to supply warm as distinct from hot water. The applications for warm water hot water systems include installation in aged peoples' nursing homes where the availability of warm water, restricted to the temperature range of 40 degrees Celsius plus or minus 3 degrees, for showering and the like, is necessary to prevent the possibility of scalding due to mis-adjustment of conventional hot and cold taps feeding shower heads and the like.

A formerly widespread way of fulfilling the need for warm water systems was the provision of conventional storage type hot water systems modified by the use of thermostatic control of high precision which would enable the water stored to be kept at a precise temperature 0, around 40 degrees, but closely controlled in the narrow temperature Sooo 00 15 range which would ensure that it provided a comfortable temperature 000oooo0 able to be used directly without mixing with cold water at the outlet.

000000 0 0 This type of warm water system became unsatisfactory in concept when 0oo oo00 o 0 o Legionnaires' Disease became known and the optimum growth conditions of 0000 the pathogen Legionella became understood. It is believed that if Legionella were to be present in water coming from a mains supply then, upon being raised in temperature to about 40 degrees its multiplication 0 oo could be promoted such that the Legionella levels could then present a 0 0oo serious health risk to aged people at least.

oo oo 0 0 0 S 25 The next way of fulfilling the need for warm water systems was the provision of conventional hot water storage systems having storage temperatures at the commonplace 70 degees Celsius with each outlet 0 0OO°UO point provided with a so-called thermoscopic valve, which mixes hot and 0 oooooo cold water as close as possible to the point of use. These valves are 0 0 intended to ensure that the person using the water can only adjust the flow rate and not the temperature.

Such thermoscopic valves are the presently approved way of fulfilling the stated need, although they suffer the problem of being very expensive (for example, in 1987 the nominal three quarter inch valve cost $927) and are not fail-safe. In fact a six-monthly compliance check and service is mandatory under at least one Australian -2- State's Department of Works requirements. This Department is under- ood to be dissatisfied with the currently known and used system and would welcome an alternative arrangement. This need is understood to have existed for some years and has led to the response proposed by the present invention.

The invention relies upon first storing the water to be used in a first, mains-pressure type, storage tank or group of interconnected tanks, hereinafter referred to as the first storage, at a temperature effective in destroying Legionella which may have been admitted in the incoming mains water. A further provision is a heat exchanger in the hot water outlet of the first storage, the heat exchanger being selected from the types where at least one wall separates two flows of liquid exchanging o0o heat with one another while flowing through the exchanger. A subsequent provision of the system is a second storage tank or group of 00oo000O o 1 15 interconnected tanks, hereinafter referred to as the second storage, also 00oo oo00 o a of the mains pressure type, where water from the first storage, having 0 0ooooo been cooled to a temperature below that used for human bathing by passage through the heat exchanger, is stored for use in the second storage with no further mixing with cold water, nor with any admission of ambient air.

20 The second storage is provided with heating means controllable by ooo 0oooo thermostat means to raise the water in the second storage to a temperature 0000 o0 0 sufficient to provide a comfortable showering or bathing temperature at 00 the point of use. The water flowing from the first storage to the second 0 0° 0 °is cooled by exchange of heat with mains water flow entering the first storage to make up its volume on each withdrawal of warm water at the point of use.

O0 0ooo 000 0L 0 The invention consists of apparatus to supply warmed water for human 0 0i washing and adapted to provide protection both against undesirably high levels of pathogenic organisms of the species Legionella in said water and against risk of scalding by said water, said apparatus comprising an enclosed water mains pressurised first flow path for cold water, a first storage connected to the first flow path, heating means adapted to heat the water in said first storage to a first, higher temperature effective in destroying said organisms, a temperature control means adapted to maintain said higher temperature, a second storage, a second R( -3 I flow path intercommunicating between said first and second storages, direct heat exchange means between said first and second flow paths, heating means adapted to heat the water in said second storage to a second, lower temperatu,'e and temperature control means adapted to maintain said lower temperature at a precise pre-determined value approximating that required for washing at an outlet provided and supplied from said second storage, said lower temperature being selected such that the water temperature at the outlet is within the range required for human comfort in the deliberate avoidance of any provision of a thermostatically controlled mixing or blending valve for mixing of the warm water with cold water either between the first and second storage or between the second storage and the point of use.

00 0 15 In order that the present ihvention may be more clearly understood a 0 0 particularly preferred embodiment and variations thereof of apparatus in 0 accordance with the invention will now be described. The ensuing o0000 0 description refers to non-limiting examples only, as illustrated in and 00 00 2 00 described with reference to the accompanying drawings, wherein: 0 Figure 1 is a schematic block diagram of the water circuits and storage tanks of the invention.

Figure 2 is a schematic block diagram of an alternative embodiment of 0000 00o0 the present invention.

000 00 0 o Referring to Figure 1 a storage tank 10 is shown having an inlet 0' 0 0 0o o0 oper;ng 11 and an outlet opening 12 both openings being for water flow.

Adjacent to the storage tank 10 is a heat exchanger 13 which may be of the flat plate type and constructed with wetted surfaces of stainless steel.

'3 7 A mains water supply is piped to an entry fitting 14 and after passing through the heat exchanger via a flow path referred to as a warming flow path emerges from outlet 15. The water then passes via pipe 16 to the water inlet 11 of the tank. In the tank 10 the water is heated to a temperature of at least 65 degrees C which is accepted as a temperature sufficient to effectively kill Legionella pathogens. The time needed at this temperature to effect death of Legionella is ~urrr~Dlraa)llCrr~nrr~srrra 1 believed to be substantially instantaneous.

Leading from the tank outlet 12 is a pipe 17 which leads to a solenoid valve 18 of known type. The valve is operable to automatically shut off flow in pipe 17 whenever temperature sensed by a temperature measuring probe (not shown) in, or in thermal contact with, the top of the tank indicates that the stored water temperature is below degrees C at the top of the tank. At this location is the hottest stored water in the tank due to the phenomenon of thermal stratification prevalent in hot water storage tanks of the type.

Pipe 19 is provided to convey water from the outlet of the solenoid valve 18 to a second inlet 20 of the heat exchanger 13. Water o entering the heat exchanger at 20 emerges from a second outlet 21 after oO 15 passing through the exchanger via a flow path referred to as a cooling flow path. Pipe 22 is provided to convey water from outlet 21 to inlet S 23 of second storage tank 24. Tank 24 is provided with at least one 0 00 0o o °0 heating element 25 and an associated thermostat (not shown) in order to 0 o0oooo control its temperature. The control of tank 24 has the intention to hold the temperature to a precise level fine tuned for each individual installation. This is to ensure that taking into account any relatively 0° 00constant small temperature drop occuring in piping to the point of use oa0o 0 results in water supply within the quite narrow range necessary for optimum human comfort.

o00 o Q 0 o Tank 24 is provided with water outlet 26 to which water for use is conveyed by pipe 27 toward delivery point 27. Preferably in pipe 27 a 0°00 a second solenoid valve 28 is inserted which is installed in conjunction 1o with a second temperature measuring probe (not shown) capable of measuring temperature of the water either in the top of tank 26 or in the pipe 27. Control means (not shown) is included to enable valve 28 to shut off if the sensed temperature of the water available to the point of delivery exceeds 45 degrees C.

The system is adjusted and set for use in such manner that the temperature of the water emerging from the heat exchanger at 21 can never exceed that required for comfort. The heat exchanger is selected Fa~paa~rr; -i I Y rr* 1 and initially balanced for the required temperature for the extreme case, assuming that the inlet mains water is at its highest temperature as in Summer; (ii) the tank 10 is at its full thermal capacity and, (iii) the water flow rate through the system is such as to result in the minimum temperature drop across the cooling flow path of the heat exchanger, that is between points 20 and 21. In an application where a number of warm water outlets are simultaneously turned on, the temperature change of the two liquid streams while passing through the heat exchanger will be different from that when only one of those outlets is turned on.

Referring to Figure 2 a cold water supply is provided to the following components described generally in the direction of normal flow through the system when in use. The system described is a mains pressurised type.

0 oo Cold water is provided to a 50 L water pre-heat holding tank 32 Cold water is provided to a 50 L water pre-heat holding tank 32 0o oo° having inlet and outlet openings 31 and 33 respectively. Tank 32 is equipped with 3 heating elements and a thermostat, not shown. After the outlet 33 is positioned a first pipe branch 35 and thereafter a plate heat exchanger 36 having a cold side inlet 37 and cold side outlet 38.

0 00 0ooO Further piping from outlet 38 proceeds via shut off valve 39 to storage oO water heater tanks 40 with inlets and outlets parallel connected. Each tank 40 is provided with heating elements and thermostats in the usual O D t 0 1 0( S 25 manner, not shown. After the outlets of the tanks 40 a second pipe branch 41 is provided, one path therefrom leading to a second, back-up plate heat exchanger 42, having a hot side inlet 43 and a hot side °0°C outlet 44. Following the hot 5ide outlet 44 is provided a shut off valve 45 and further piping from one branch leading to a 50 L water re-heater 46.

Back-up heat exchanger 42 has cold side inlet 48, hot side inlet 49 and hot side outlet 50. Either plate heat exchanger 36 or 42 is selected for use in the circuit by use of shut off valves 39, 45, 51 and 52 as appropriate, the back up heat exchanger is provided for enabling maintenance of the other heat exchanger without the need to interrupt the supply of warm water.

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1 The 50 L water reheater 46 has a water inlet 53 and one or more heating elements and a thermostat (not shown).

Reheater 46 has an outlet 54 leading to a circulation loop which includes a pump 55 running continuously. The circulation loop contains as many washing outlet points 57 as required. A return entry from the circulation loop to the reheater tank 46 is provided.

Provision is made in two ways for rejecting excessive heat should the usage and control means result in too high a temperature for optimum comfort to the users. Either or both provisions may be employed. In the first, branch connections 59 and 60 are provided before each hot side inlet to the plate heat exchangers, the branched 15 outlet leading to a second circulation loop (not shown) having in the loop heat rejection means preferably in the form of a coil with extended surface heat transfer fins. Instead of the loop heat can be rejected by draining off hot water in the same way as conventional hot water system temperature and pressure relief valves operate.

In the second, branch connections 61 and 62 are provided in the first circulation loop with a third circulation loop starting and finishing at those branches. The third loop is brought into circulation by a temperature sensor 56 in the first loop operating automatically to 25 open and close valves 65 and 66 as required. The third circulation loop is equipped with a heat rejection apparatus such as a finned coil (not shown).

Intended temperatures in degrees C around the circuit are as follows:- Inlet cold water Storage tank 32 Storage water heaters Entering storage tank 46 8 to 57 to 62 32 to 44 -7- 1 First circulation loop and outlets 57 42 to Having described the invention in terms of the above preferred embodiment and variations thereof it will be apparent to those skilled in the relevant arts that many minor variations may be made in the preferred embodiment described by way of example, including the substitution of a different number of storage tanks than the number described and illustrated.

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Claims (4)

1. Apparatus to supply warmed water for human washing and adapted to provide protection both against undesirably high levels of pathogenic organisms of the species Legionella in said water and against risk of scalding by said water, said apparatus comprising an enclosed water mains pressurised first flow path for cold water, a first storage connected to the first flow path, heating means adapted to heat the water in said first storage to a first, higher temperature effective in destroying said organisms, a temperature control means adapted to maintain said higher temperature, a second storage, a second flow path intercommunicating between said first and second storages, indirect heat exchange meansbetween said first and second flow 0 paths, heating means adapted to heat the water in said second storage to a second, lower temperature and temperature control means adapted to maintain said lower temperature at a precise pre-determined value a 0,, approximating that required for washing at an outlet provided and 00 00 2 20 supplied from said second storage, said lower temperature being 0 0 o selected such that the water temperature at the outlet is within the 000000 0 0 range required for human comfort in the deliberate avoidance of any provision of a thermostatically controlled mixing or blending valve for mixing of the warm water with cold water either between the first 0 °0aand second storage or between the second storage and the point of 0 0use. o00020 use. 00 0 o 000

2. Apparatus to supply warmed water as claimed in Claim 1 further including temperature sensing means and solenoid valve positioned in 0 said second flow path and operative to shut off flow from first 0o0 i storage if the temperature of the water leaving the first storage o° 30 falls below a pre-determined temperature effective in destroying 0 a~ pathogenic organisms of the species legionella.

3. Apparatus to supply warmed water as claimed either one of Claims 1 or 2 further including a second temperature sensing means and second solenoid valve positioned between said second storage and the point of use operative to shut off flow from the second storage if the temperature of water leaving the second storage is higher than that pre-determined temperature likely to cause over-temperature discomfort during human washing at said point of use. -9- c~

4. Apparatus to supply warmed water as claimed in any one of the previous claims further including heat rejection means positioned in either or both of the second flow path or between the second storage and the point of use. Apparatus to supply warmed water for human washing substantially as herein described and illustrated. DATED this 3rd day of December IC'0 RHEEM AUSTRALIA LIMITED C c C C cc~ CCC C Cc CC CC CC C a C C rc C CC 050910 i .1