U.S. patent application number 12/666585 was filed with the patent office on 2010-07-08 for water heating apparatus, especially for pools.
Invention is credited to Darren William Ford, Peter Ronald Wallace.
Application Number | 20100170452 12/666585 |
Document ID | / |
Family ID | 40225658 |
Filed Date | 2010-07-08 |
United States Patent
Application |
20100170452 |
Kind Code |
A1 |
Ford; Darren William ; et
al. |
July 8, 2010 |
WATER HEATING APPARATUS, ESPECIALLY FOR POOLS
Abstract
A water heater for heating water includes a burner assembly (54)
for generating a flow of hot gas. The burner assembly (54) includes
a gas burner (52) and means (64) adjustable to determine a heat
output of the burner assembly (54). The water heater further
includes a heat exchanger assembly (20) for transferring heat from
gas to water flowing therein. The heat exchanger assembly (20) has
a higher temperature zone (110) and a lower temperature zone (100).
The water heater is arranged to convey the flow of hot gas to the
higher temperature zone (110) and in turn to the lower temperature
zone (100). The water heater further includes ducting (22, 23) to
conduct said flowing water to and from said heat exchanger assembly
(20), means (40) to monitor the temperature of the hot gas
intermediate the higher temperature zone (110) and the lower
temperature zone (100), and control means (70) responsive to the
temperature monitoring means (40) to modulate the heat output of
the burner assembly (54) whereby to maintain the monitored
temperature within a predetermined range so as to substantially
prevent or minimise condensation of vapour from the hot gas in the
higher temperature zone (110). There is also disclosed a modular
heat exchanger apparatus (20) including like headers (34) for
redirecting fluid within respective modules (24) and for
interconnecting modules (24). There is also disclosed a water
heater having a condensate duct (84) to direct condensate into the
water for chemically treating the water.
Inventors: |
Ford; Darren William; (Noble
Park, AU) ; Wallace; Peter Ronald; (Noble Park,
AU) |
Correspondence
Address: |
WINSTEAD PC
P.O. BOX 50784
DALLAS
TX
75201
US
|
Family ID: |
40225658 |
Appl. No.: |
12/666585 |
Filed: |
July 4, 2008 |
PCT Filed: |
July 4, 2008 |
PCT NO: |
PCT/AU08/00987 |
371 Date: |
December 23, 2009 |
Current U.S.
Class: |
122/14.21 ;
122/18.1; 165/173 |
Current CPC
Class: |
Y02B 30/00 20130101;
F24H 1/445 20130101; F24H 9/2035 20130101; F24H 9/165 20130101;
F24H 9/0036 20130101; F28D 7/1607 20130101; Y02B 30/106 20130101;
F24H 8/006 20130101; F24H 1/40 20130101 |
Class at
Publication: |
122/14.21 ;
122/18.1; 165/173 |
International
Class: |
F24H 9/20 20060101
F24H009/20; F24H 1/00 20060101 F24H001/00; F28F 9/02 20060101
F28F009/02 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 4, 2007 |
AU |
2007903605 |
Claims
1. A water heater for heating water, including: a burner assembly
for generating a flow of hot gas, which burner assembly includes a
gas burner and means adjustable to determine a heat output of the
burner assembly; a heat exchanger assembly for transferring heat
from gas to water flowing therein, wherein the heat exchanger
assembly has a higher temperature zone and a lower temperature
zone, the water heater being arranged to convey the flow of hot gas
to the higher temperature zone and in turn to the lower temperature
zone; ducting to conduct said flowing water to and from said heat
exchanger assembly; means to monitor the temperature of the hot gas
intermediate the higher temperature zone and the lower temperature
zone; and control means responsive to said temperature monitoring
means to modulate the heat output of the burner assembly whereby to
maintain the monitored temperature within a predetermined range so
as to substantially prevent or minimise condensation of vapour from
the hot gas in the higher temperature zone.
2. A water heater according to claim 1 wherein use the monitored
temperature is maintained within a pre-determined range without
reducing the volume of water flowing through the heat
exchanger.
3. A water heater according to claim 1 wherein said control means
is operable to minimize said monitored temperature.
4. A water heater according to claim 1 wherein said means to
monitor the temperature of the hot gas is mounted closer to the
lower temperature zone than to the higher temperature zone.
5. A water heater according to claim 1 wherein the lower
temperature zone and the higher temperature zone each have tubes
for carrying water through the flow of hot gas, the tubes of the
lower temperature zone and the higher temperature zone being formed
of materials that respectively suit lower temperature operation and
higher temperature operation.
6. A water heater according to claim 5 wherein the tubes of the
lower temperature zone are formed of aluminium sheathed stainless
steel and the tubes of the higher temperature zone are formed of
cupronickel.
7. A water heater according to claim 5 wherein the tubes of the
higher temperature zone are formed of copper.
8. A water heater according to claim 1 configured for the flow of
hot gas to travel downwardly from the burner assembly through the
higher temperature zone and in turn through the lower temperature
zone.
9. A water heater according to claim 1 having means to collect
condensate produced from condensation of gas in said lower
temperature zone.
10. A water heater according to claim 9 including a condensate duct
arranged to direct said condensate into the water for chemically
treating the water.
11. A water heater according to claim 10 wherein the condensate
duct is arranged to direct said condensate into the ducting from
the heat exchanger assembly.
12. A water heater according to claim 10 wherein the condensate
duct is arranged to direct condensate into the water upstream of a
pump arranged to drive water through the water heater.
13. A water heater according to claim 10 including a venturi to
draw said condensate into the water.
14. A water heater according to claim 10 including a suction tee to
draw the condensate into the water.
15. A water heater according to claim 10 including a pump arranged
to receive condensate from said means to collect condensate and
drive said condensate through said condensate duct.
16. A water heater according to claim 9 including a dosing
apparatus for storing and selectively directing metered amounts of
condensate into the water at any suitable location.
17. A heat exchanger apparatus, including: a heat exchange module
having a plurality of heat exchange elements extending across a
passage, the passage being arranged to convey a first fluid past
and about the heat exchanger elements; and one or more return
headers adapted to be selectively mounted to said module either for
directing a second fluid in turn through any adjacent pair of heat
exchange elements, or for directing a second fluid from one heat
exchange element of said module to a heat exchange element of a
similar module when said module is coupled to said similar
module.
18. A heat exchanger apparatus according to claim 17 wherein each
heat exchange element is a bank of tubes.
19. A heat exchanger apparatus according to claim 18 wherein the
return header has a separate sealing engagement with each tube.
20. A heat exchanger apparatus according to claim 18 wherein the
banks of tubes are relatively displaced along said passage.
21. A heat exchanger apparatus according to claim 18 wherein the
banks of tubes respectively form one or more lower temperature
banks of tubes and one or more higher temperature banks of tubes
having their tubes formed in differing materials that respectively
suit lower temperature operation and higher temperature
operation.
22. A heat exchanger apparatus according to claim 21 wherein the
tubes of the one or more lower temperature banks of tubes are
formed of aluminium sheathed stainless steel and the tubes of the
one or more higher temperature banks of tubes are formed of
cupronickel.
23. A heat exchanger apparatus according to claim 21 wherein the
tubes of the one or more higher temperature banks of tubes are
formed of copper.
24. A heat exchanger apparatus according to claim 18 having a
plurality of the modules in coupled relation and a plurality of
like return headers interconnecting banks of tubes within the
modules and interconnecting modules.
25. A heat exchanger apparatus according to claim 18 to wherein
each module has only two banks of tubes.
26. A heat exchanger apparatus according to claim 25 having two of
said modules and three of said return headers, two of the return
headers being respectively mounted for directing the second fluid
between the banks of tubes within a respective module, and a third
return header for directing the second fluid from a second bank of
one module to a first bank of the other module.
27. A heat exchanger apparatus according to claim 26 wherein the
successive spacings of the banks of tubes along said passage are
substantially equal, and the tubes one of the modules and the tubes
of the other of the module being formed in materials that
respectively suit a lower temperature operation and higher
temperature operation.
28. A heat exchanger apparatus according to claim 18 wherein the
first fluid is hot gas from a burner assembly and the second fluid
is water.
29. A water heater according to claim 1 wherein the heat exchanger
assembly includes: a heat exchange module having banks of tubes
extending across a passage, the passage being arranged to convey
the hot gas past and about the bank of tubes; and one or more
return headers adapted to be selectively mounted to said module
either for directing the water in turn through any adjacent pair of
tube banks, or for directing the water from one bank of tubes of
said module to a bank of tubes of a similar module when said module
is coupled to said similar module.
30. A water heater for heating water, including: a burner assembly
for generating a flow of hot gas; a heat exchanger assembly
arranged to receive said flow of hot gas for transferring heat from
the gas to water flowing therein; ducting to conduct said water to
and from said heat exchanger assembly; means to collect condensate
produced from condensation of said gas in said heat exchanger
assembly; and a condensate duct to direct said condensate into said
water for chemically treating said water.
31. A water heater according to claim 30 wherein the condensate
duct is arranged to direct said condensate into the ducting from
the heat exchanger assembly.
32. A water heater according to claim 30 wherein the condensate
duct is arranged to direct condensate into the flowing water
upstream of a pump arranged to drive water through said water
heater.
33. A water heater according to claim 30 including a venturi to
draw said condensate into said water.
34. A water heater according to claim 30 including a suction tee to
draw said condensate into said water.
35. A water heater according to claim 30 including a pump arranged
to receive condensate from said means to collect condensate and
drive said condensate through said condensate duct.
36. A water heater according to claim 30 including a dosing
apparatus along said condensate duct for storing and selectively
directing metered amounts of condensate into the water at any
suitable location.
37. A method of chemically treating water in a pool comprising
adding to the water condensate collected from a heat exchanger
assembly of a water heater through which the pool water is
circulated and heated.
38. A water heater according to claim 2 wherein said control means
is operable to minimize said monitored temperature.
39. A water heater according to claim 38 wherein the lower
temperature zone and the higher temperature zone each have tubes
for carrying water through the flow of hot gas, the tubes of the
lower temperature zone and the higher temperature zone being formed
of materials that respectively suit lower temperature operation and
higher temperature operation.
Description
FIELD OF THE INVENTION
[0001] This invention relates generally to water heating equipment,
but has particularly useful application to pool and spa heaters.
Respective aspects of the invention are concerned with a novel
configuration of water heater, with a heat exchanger arrangement
useful in pool and spa heaters, and with a practical use for the
condensate that is a by-product of certain types of water
heaters.
[0002] Throughout this specification, the term "pool" includes in
its ambit any kind of confined water body in which humans can be
immersed, including spas, swim spas and Japanese-style immersion
tubs.
BACKGROUND OF THE INVENTION
[0003] Pool heating is conventionally effected either by
circulating the pool water through solar panels, typically
roof-mounted, or by means of gas-fired water heaters. Water heaters
for this purpose are designed to heat a continuous flow of water
circulated from the pool to a target temperature in a range
comfortable for swimming, and so the requirements differ
considerably from, for example, hot water services, where a static
body of water is heated in a tank to a relatively high temperature,
and hydronic central heating systems, where a flow of water is
heated but the total volume of water is much less and the target
temperature significantly higher.
[0004] Conventional pool heaters typically have a gas burner
assembly that generates a hot gas flow employed to heat the water
as it traverses multiple tubes in a heat exchanger. Because of the
relatively high water volume and relatively low water temperature,
these systems must address the problem of condensation in the gas
stream as it passes among the heat exchanger tubes: the condensate
is slightly acidic because of the uptake of combustion products,
and is therefore a corrosive by-product. A popular material for the
heat exchanger tubes is cupronickel, which is especially
susceptible to corrosion by the condensate.
[0005] Modern pool heater controllers advantageously receive a
measurement of the pool water temperature, and thermostatically
control the operation of the heater, and as the pool water
temperature approaches a desired temperature, modulate the heater
down to a very low power level to maintain the pool water
temperature without noticeable stopping and starting of the heater.
It has been discovered that operation at this very low power level
results in low flue temperatures such that condensation and
corrosion is particularly problematic.
[0006] The common approach to corrosion prevention is to design the
heater so that at the maximum water flow condition, minimum water
temperature and a predetermined gas flow rate the temperature in
the heat exchanger remains above the dew point temperature at which
condensation begins to occur. Water flow is typically reduced
through the heat exchanger by diverting a proportion of the flow
via a bypass. This approach places limits on the efficiency
achievable with the overall heater configuration.
[0007] Two publications that illustrate known approaches to
corrosion prevention are European patent publication 0226534 and
Japanese published (Kokai) application 11351559.
[0008] It is an object of the invention, at least in one or more
aspects or applications, to improve the efficiency of pool heater
systems.
SUMMARY OF THE INVENTION
[0009] The invention involves, in a first aspect, a different
approach to temperature management in the heat exchanger, and, in a
second aspect, the adoption of a two-part heat exchanger whereby
condensate is an acceptable by-product. In a third aspect, the
invention proposes recycling of the condensate for usefully
treating the pool water.
[0010] The invention accordingly provides, in its first aspect, a
water heater for heating water, including: [0011] a burner assembly
for generating a flow of hot gas, which burner assembly includes a
gas burner and means adjustable to determine a heat output of the
burner assembly; [0012] a heat exchanger assembly for transferring
heat from gas to water flowing therein, wherein the heat exchanger
assembly has a higher temperature zone and a lower temperature
zone, the water heater being arranged to convey the flow of hot gas
to the higher temperature zone and in turn to the lower temperature
zone; [0013] ducting to conduct said flowing water to and from said
heat exchanger assembly; [0014] means to monitor the temperature of
the hot gas intermediate the higher temperature zone and the lower
temperature zone; and [0015] control means responsive to said
temperature monitoring means to modulate the heat output of the
burner assembly whereby to maintain the monitored temperature
within a predetermined range so as to substantially prevent or
minimise condensation of vapour from the hot gas in the higher
temperature zone.
[0016] By modulating the heat output of the burner the monitored
temperature can be maintained within a pre-determined range without
reducing the volume of water flowing through the heat exchanger
thereby improving efficiency. It is desirable to minimise said
monitored temperature in order to maximise efficiency.
[0017] Preferably said means to monitor the temperature of the hot
gas is mounted closer to the lower temperature zone than to the
higher temperature zone.
[0018] The configuration is preferably such that the hot gas is
directed downwardly from the burner assembly through the heat
exchanger assembly to traverse the higher temperature zone and then
the lower temperature zone. Means is advantageously provided under
the heat exchanger assembly for collecting condensate that forms in
said lower temperature zone.
[0019] In a second aspect, the invention provides a heat exchanger
apparatus, including: [0020] a heat exchange module having a
plurality of heat exchange elements, extending across a passage,
the passage being arranged to convey a first fluid past and about
the heat exchanger elements; and [0021] one or more return headers
adapted to be selectively mounted to said module either for
directing a second fluid in turn through any adjacent pair of heat
exchange elements, or for directing a second fluid from one heat
exchange element of said module to a heat exchange element of a
similar module when said module is coupled to said similar
module.
[0022] The return header can have a separate sealing engagement
with each bank of tubes. Most preferably, the return header has a
separate sealing engagement with each tube.
[0023] The banks of tubes are preferably relatively displaced along
said passage. Advantageously, first and second banks of tubes have
their tubes formed in materials that respectively suit a lower
temperature operation and higher temperature operation. A suitable
material for the tubes of the lower temperature bank is aluminium
sheathed stainless steel while a suitable material for the tubes of
the higher temperature bank is cupronickel. Copper is another
material suitable for the tubes of the higher temperature
bank(s).
[0024] Preferably there are a plurality of modules in coupled
relation and a plurality of like return headers for interconnecting
banks of tubes within the modules and interconnecting modules.
Advantageously each module has only two banks of tubes.
[0025] In an embodiment, there are two of said modules and three
return headers, two mounted for directing the second fluid from one
of the banks of tubes to the other in the respective pair, and a
third for directing the second fluid from a second bank of one
module to a first bank of the other module. Preferably, in this
embodiment, the successive spacings of the four banks of tubes
along said passage are substantially equal, and the tubes of the
respective pairs of banks are formed in materials that respectively
suit a lower temperature operation and higher temperature
operation.
[0026] In a particularly useful application, a heat exchanger
apparatus according to the second aspect of the invention is
employed as the heat exchanger assembly of the first aspect of the
invention.
[0027] A third aspect of the invention relates to the condensate
which is a by-product from some types of pool heater and indeed
from one or more embodiments of the first and second aspects of the
present invention. More particularly, in its third aspect, the
invention provides a water heater for heating water, including:
[0028] a burner assembly for generating a flow of hot gas; [0029] a
heat exchanger assembly arranged to receive said flow of hot gas
for transferring heat from the gas to water flowing therein; [0030]
ducting to conduct said water to and from said heat exchanger
assembly; [0031] means to collect condensate produced from
condensation of said gas in said heat exchanger assembly; and
[0032] a condensate duct to direct said condensate into said water
for chemically treating said water.
[0033] The condensate will typically be slightly acidic, i.e. have
a pH slightly less than 7, and said chemical treatment may comprise
pH adjustment. In one embodiment of the third aspect of the
invention, the condensate is directed into the heated stream of
water immediately downstream of the heat exchanger assembly, and
for this purpose said condensate duct may include a venturi at
which the condensate is drawn into the heated water stream. A pump
may be arranged to receive condensate from the means to collect
condensate and drive the condensate through the condensate duct. In
an alternative embodiment, the condensate is stored and said
condensate duct forms part of dosing apparatus for selectively
directing metered amounts of condensate into the pool water at any
suitable location.
[0034] In a further alternative embodiment condensate may be
directed into the water with the aid of a suction tee.
[0035] Advantageously the condensate duct may be arranged to direct
the condensate into the water upstream of a pump arranged to drive
said water through said water heater.
[0036] The means to collect condensate may comprise a tray or
housing base in a water heater according to the first aspect of the
invention or in or below a heat exchanger apparatus according to
the second aspect of the invention.
[0037] In its third aspect, the invention further provides a method
of chemically treating water in a pool comprising adding to the
water condensate collected from a heat exchanger assembly of a
water heater through which the pool water is circulated and
heated.
BRIEF DESCRIPTION OF THE DRAWINGS
[0038] The invention will now be further described, by way of
example only, with reference to the accompanying drawings, in
which:
[0039] FIG. 1 is a perspective view of a pool heater according to
an embodiment of the invention, as viewed without its exterior
decorative housing;
[0040] FIG. 2 is a rear view of the pool heater depicted in FIG. 1
with some parts omitted for a better view and with the condensate
venturi additionally shown in place;
[0041] FIG. 3 is a vertical, generally central cross-section of the
pool heater depicted in FIGS. 1 and 2, with most of the heat
exchanger tubes omitted for the purpose of illustration;
[0042] FIGS. 4 and 5 are different perspective views of the heat
exchanger assembly;
[0043] FIG. 6 is a view of the heat exchanger assembly, and with
many of the upper bank of tubes omitted;
[0044] FIG. 7 is a plan view of the heat exchanger assembly;
[0045] FIG. 8 is a cross-section on the line 8-8 in FIG. 7;
[0046] FIG. 9 is a simplified schematic diagram of the burner
control loop incorporating a temperature sensor in the heat
exchanger assembly;
[0047] FIGS. 10 and 11 are respectively a perspective view and an
end elevation of a larger heat exchanger assembly with four banks
of tubes;
[0048] FIG. 12 is a rear view one embodiment of the third aspect of
the invention entailing recycling of condensate collected from the
heat exchanger assembly;
[0049] FIG. 13 is a fragmentary axial cross-section view of the
condensate venturi forming part of the embodiment of FIG. 12;
[0050] FIG. 14 is a rear view of an alternative embodiment of the
condensate recycling concept;
[0051] FIG. 15A is a perspective view of an embodiment of the
return header;
[0052] FIGS. 15B and 15C are perspective cut away views of the
header of FIG. 15A;
[0053] FIG. 16 is a perspective view an embodiment of the tray;
[0054] FIG. 17 is a rear view of a further alternative embodiment
of the condensate recycling concept; and
[0055] FIG. 18 is a rear view of a further alternative embodiment
of the condensate recycling concept.
DETAILED DESCRIPTION OF THE EMBODIMENTS OF THE INVENTION
[0056] The illustrated pool heater 10 is a stacked assembly of four
principal components: a tray 80 over which is fitted a heat
exchanger assembly 20 on which is mounted a firebox 50, which is in
turn capped by a fan unit 60 that includes a controller 70 with an
external interface 72 and a lid 62 that is removable for access.
Tray 80 sits in plastic base 12.
[0057] Tray 80 is a unitary casting and, as will be further
explained below, serves as a condensate collection tray. Tray 80
sealingly communicates with a flue 82 that extends upwardly behind
the heat exchanger assembly 20, firebox 50 and fan unit 60 to a
flue outlet 83.
[0058] In situ and in operation, pool water is circulated by a
separate pump installation to a water intake port 22 and recovered
from outlet 23. A fan 64 within fan unit 60 draws in a correctly
proportioned combustible mixture of gas (delivered via line 65) and
air, and delivers the mixture to a gas burner 52 at the top of
firebox 50. The gas burner 52 and the fan unit 60 together form a
burner assembly 54 (FIG. 3) that generates a downwardly directed
flow of hot gas. This flow is received by the heat exchanger
assembly 20 where heat is transferred from the hot gas to pool
water flowing therein. The burner 52 is of the premix type and
includes a knitted mesh. Below the heat exchanger 20, the hot gas
is guided laterally by the shaped tray 80 to the base of flue 82
and thence up the flue.
[0059] Fan 64 constitutes a means that is adjustable to vary the
volume of gas and air directed to the burner 52 and so determines
the heat output of the burner. The fan 64 and gas burner 52
together constitute a burner assembly for generating a flow of hot
gas.
[0060] The construction of heat exchanger assembly 20 is detailed
in FIGS. 4 to 8. A simple box 24 of front, rear and side flanged
plates 24a, 24b, 24c provides a suitable chassis. Side plates 24b,
24c have two rows of apertures 25a and 25b that communicate with
the interior of heat exchange tubes 27, 29 arrange in respective
lower and upper banks 26, 28. At one side plate 24b, there are
fitted respective inlet and outlet headers 30, 32 that define a
manifold space respectively communicating the lower and upper
apertures 25 and therefore the lower tubes 27 and upper tubes 29 to
water inlet ports 22, 23. At the other side plate 24c, there is a
return header 34, a suitably profiled moulding that defines a
manifold space for communicating the lower of apertures 25a with
the upper row 25b. Vanes 31 are placed between the tubes 27, 29 to
deflect the gas flow and improve the heat transference to tubes 27,
29.
[0061] A convenient method for assembling the module like box 24
involves forming side plates 24b and 24c with apertures 25a, 25b
being slightly oversized, e.g. 0.1 mm, to receive the tubes 27, 29.
Tubes 27, 29 are inserted into apertures 25a, 25b and a rotary
swage used to expand the tubes to form an interference with
sideplates 24b, 24c. An advantage of certain embodiments of the
second aspect of the invention is that large heat exchangers can be
economically built up of several modules each having two rows. The
tubes of a two row module are easily gripped to prevent rotation
during the rotary swaging operation.
[0062] Although modules having two rows defining U-shaped flow
paths are illustrated, other arrangements are possible. For
example, a module having three rows defining an S-shape flow path
is an option.
[0063] Return header 34 is shown in more detail in FIGS. 15A to
15C. Apertures 35 are connected by cavity 37 and include a recess
to receive a sealing washer (not shown) to sealingly engage with
individual tubes 27, 29. The regular spacing of bolt locations 36
allows the header to securely press the sealing washers with less
risk of leakage due to warping of the header. This advantageously
allows for a cheaper moulded plastic (instead of cast metal)
construction.
[0064] It will be seen that because the cooler water traverses the
lower bank of tubes 27 and then the upper bank of tubes 29, the
lower bank 26 constitutes a lower temperature zone 100 of the heat
exchanger assembly and the upper bank 28 constitutes a higher
temperature zone 110. Accordingly, the respective banks of tubes
are formed of differing materials: the lower tubes 27 are
aluminium-sheathed stainless steel tubes, while the upper tubes 29
are of cupronickel alloy. It will be seen that the descending flow
of hot gas will pass through and about tubes 29 first and then, in
a cooler state, through and about tubes 27.
[0065] The cupronickel tubes 29 are effective heat exchange
elements at higher temperatures but are highly susceptible to
corrosion by any condensate that forms on them in the gas flow,
while the aluminium/stainless steel tubes 27 are resistant to
condensate corrosion but degrade at relatively low elevated
temperatures. Accordingly, in accordance with the first aspect of
the invention, the temperature profile in the gas stream across the
heat exchanger is managed to accommodate these characteristics.
Temperature sensor 40 (FIG. 8) is located on the vertically centred
plane of the heat exchanger assembly inwardly from side panel 24c
between the respective banks 26, 28 of heat exchange tubes. The
sensor output is delivered to controller 70 which adjusts the fan
64 to determine the heat output of burner 52 in response to various
inputs including sensor 40. Other inputs may include a desired
water temperature manually entered at interface 72, and actual
water temperature measured by sensor 73 on inlet header 32. A
suitable controller is a Genus PCB controller.
[0066] A diagram of the main elements of the burner control loop is
presented in FIG. 9.
[0067] In particular, controller 70 is responsive to temperature
sensor 40 (monitoring the temperature at its location in the heat
exchanger assembly), to operate fan 64 so as to modulate the heat
output of burner 52, whereby to maintain the monitored temperature
at sensor 40 within a predetermined set point range. This range is
between a minimum selected so that the gas temperature in the
higher temperature zone 110 remains above the dew point
condensation temperature, and a maximum is determined so that,
inter alia, the temperature of the gas delivered into the lower
temperature zone 100 is not so high as to damage
aluminium/stainless steel tubes 27. In the former case,
condensation of vapour from the gas is substantially prevented or
minimised in the higher temperature zone 110 of the heat exchanger
assembly.
[0068] FIGS. 10 and 11 illustrate the manner in which the heat
exchanger construction is readily adaptable to provide higher
capacity heat exchangers. In the heat exchanger of FIGS. 4 to 8,
the side plates 24b, 24c and tubes 27, 29 constitute a heat
exchange module 105. By forming the box chassis 24 from two of
these modules 105a, 105b fixed between front and rear plates 24a of
double height, comprising four banks 126, 128 of tubes 127, 129 can
be provided. In this case, the lower and higher temperature zones
are defined by the respective modules 105a, 105b.
[0069] This modular approach to enlarging the capacity of the heat
exchanger means that three identical return headers 34 can be
utilised as illustrated to direct water between the tubes of the
two lower banks and between the tubes of the two upper banks, and
also, on the other side of the box chassis 24, from the tubes of
the lower, aluminium/stainless steel tubes to the upper cupronickel
tubes. The inlet and outlet headers 30, 32 are identical to the
inlet headers 30, 32 depicted in FIGS. 4 to 6.
[0070] The illustrated configuration of water heater, including the
two-stage heat exchanger configuration and the control of burner
heat output in response to monitoring of the temperature in the
heat exchanger, together result in a pool heater system of
significantly higher efficiency than the earlier described
conventional arrangements. Full volume water flow, say up to 400
L/min is maintained without periodic bypassing and burner output is
matched with the desired set point gas temperature range in the
heat exchanger. Condensation is accepted and properly managed by
employing a two-stage heat exchanger in which the materials of the
heat exchange elements are selected to suit the respective higher
and lower temperature zones.
[0071] The third aspect of the invention is concerned with the
novel usage for the condensate collected in tray 80 which is
depicted in more detail in FIG. 16. The concept is that this
condensate, which contains traces of combustion by-products and is
thereby slightly acidic, is recycled to the pool water as an
effective chemical treatment. There are various ways in which this
can be done. In the first (illustrated in FIGS. 12 and 13), a
suitably dimensioned conduit 84 communicates the sump 81 via outlet
89 of tray 80 (see FIG. 16) with the feed port 86 of a venturi
suction device 87 fitted within water outlet port 23. Conduit 84
includes solenoid valve 85 for selectively determining when
condensate can flow to the venturi. The solenoid valve 85 is used
to close conduit 84 when the heater 10 and pump are not in use to
prevent water flowing through conduit 84 to tray 80. A suitable
construction for the venturi 87 is illustrated in FIG. 13: it will
be seen that the feed port 86 at the end of conduit 84 communicates
with a chamber 87 from which an aperture 88 opens into the neck of
the venturi.
[0072] A float sensor (not shown) may be associated with the sump
81 to detect blockage of the outlet 89 or conduit 84.
[0073] In the alternative condensate recycling arrangement depicted
in FIG. 14, a drain hose 90 from sump 81 conveys the condensate to
a storage reservoir 92 from which the condensate is selectively
drawn via a tube 93 by a dosing unit 94 for delivery at an
insertion point 98 in the pool water return pipe 96 downstream of
water heater 10.
[0074] In a further alternative embodiment illustrated in FIG. 17
the drain hose 90 is selectively closed by the solenoid valve 201.
Downstream along the drain hose 90 from the solenoid valve 201 is
the condensate pump 202. The condensate pump 202 may be activated
and the solenoid valve 201 opened to drive condensate collected in
the tray 80 through the pump discharge line 203. The pump discharge
line 203 extends from the pump 202 to a suction tee 204 positioned
along the return pipe 96 downstream of water heater 10. The use of
the solenoid valve 201 prevents water back feeding from the return
pipe 96 to the tray 80.
[0075] FIG. 18 illustrates a further alternative embodiment which
includes a collector reservoir 210 interposed between the tray 80
and the solenoid valve 201 along the drain hose 90 to store
condensate. A condensate suction line 211 extends from the solenoid
valve 201 to a suction tee 212. The suction tee 212 is fitted to an
inlet line 214 for supplying water to the water intake port 22. A
pump 213 is positioned along the inlet line 214 to draw water from
the swimming pool and drive the water through the heat exchanger 20
(the water is in turn returned to the pool via the return pipe 96).
The suction tee 212 is thereby in a low pressure region upstream of
the pump 213 and in addition is configured to create some venturi
effect so that condensate may be drawn into the inlet pipe 214 when
the solenoid valve 201 is open.
[0076] It will be understood that the invention disclosed and
defined in this specification extends to all alternative
combinations of two or more of the individual features mentioned or
evident from the text or drawings. All of these different
combinations constitute various alternative aspects of the
invention.
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