Method of and unit for recovery of waste energy

Transfer waste water from wash cycle of dishwasher to collection tank beneath heat exchanger surrounding hollow central space, pass waste water through dual tube heat exchanger in countercurrent relation to cool feed water for hot water heater in central space of heat exchanger, supply heat to water in heater, then hot water to dishwasher rinse. May circulate feed water downwardly through outer space of heater, formed by partition, to lower end of inner space, in which heat is supplied by electrical immersion heaters. Ends of tank of hot water may be semi-oval, semi-elliptical or the like, while partition may be sufficiently close to bottom of tank to produce a wire-drawing effect as inlet water flows from outer to inner space, thereby maintaining light or small particles which fall off electric heaters in circulation, so that such particles will be removed with hot water. Heavier particles will collect in bottom of tank and may be drained periodically.

This invention relates to a method of and unit for recovering waste energy. 
BACKGROUND OF THE INVENTION 
My aforesaid application Ser. No. 130,615 discloses a method of and 
apparatus for the recovery of waste energy which includes a heat exchanger 
which receives heated waste water discharged from a dishwasher or the like 
to preheat the cold water supply to a hot water heater which supplies the 
dishwasher with hot water for the wash and rinse cycles. Such application 
also discloses the desirability of controlling the flow of waste water to 
the heat exchanger at a time when the dishwasher or the like requires hot 
water from the hot water heater, so that preheated feed water will be 
supplied. This heat exchanger is mounted in the upper portion of a unit 
having a housing, while a lower portion of the unit contains a tank for 
receiving the waste dishwater which passes through a removable screen 
above the tank. The tank is bordered by an overflow partition which 
separates an outlet area therefrom. The collected waste water is pumped 
from a sump beneath the tank to one inlet of the heat exchanger above, 
while the used waste water, after heat exchange, is discharged into the 
outlet area. The unit is installed beneath the dish counter of the 
dishwasher, or a similar closely adjacent position, rather than at a 
remote location adjacent to the hot water heater, as in my prior 
application Ser. No. 920,660. Since a hot water heater is often located at 
some distance from the dishwasher, under which the unit is placed, and the 
hot water heater may supply other facilities, such as wash rooms, sinks 
and the like, insulation is usually necessary in order to prevent the 
preheated feed water from becoming unduly cooled by passage to the hot 
water heater. However, the expense of installing the piping and insulation 
may reduce the savings due to recovery of waste energy. 
There are two general types of dishwashers in use, one being referred to as 
a "high temperature" dishwasher and operates with water at about 
180.degree. F. for rinsing and the waste water at about 140.degree. F. 
Normally, the wash water is used rinse water which has been retained in a 
separate space in the dishwasher for that purpose and then saponified, so 
that hot water is drawn from the hot water heater during the rinse cycle 
only. Thus, the used wash water would be saved until the next rinse cycle, 
while the hot water heater would be capable of heating the water to 
190.degree. or 195.degree. F. to supply rinse water at 180.degree. F. The 
other is referred to as a "low temperature" type and utilizes a special 
detergent. This type operates with water at a temperature of about 
140.degree. F. for rinsing, with the waste water at about 125.degree. F. 
In each type, the amount of water used for rinsing is within the capacity 
of electric heaters to produce. 
Among the objects of this invention are to provide a novel method and unit 
for recovering waste energy, particularly from equipment such as a 
dishwasher; to provide a method and unit which involves a heat exchanger 
for preheating incoming water to be heated to an appropriate temperature 
for rinsing dishes through heat exchange with the waste water from the 
dishwasher, normally wash water; to provide such a unit which may be 
positioned adjacent or beneath a dishwasher and also supply hot water 
thereto, without the necessity for transferring the waste water or the hot 
water being supplied through pipes for any great distance; to provide such 
a unit in which special provision is made for avoiding overheating the 
electric heaters and thereby burning out the same, when hot water for 
rinsing is supplied to a high temperature dishwasher, but which special 
equipment may be omitted when hot water is supplied to a low temperature 
dishwasher; and to provide such a method and unit which are effective and 
efficient in use. 
SUMMARY OF THE INVENTION 
The energy recovery method of this invention includes transferring waste 
water from the wash cycle of a dishwasher or the like to a collection tank 
located beneath a heat exchanger having a hollow central space, passing 
the waste water through the heat exchanger in countercurrent relation to 
cool feed water for a hot water heater which occupies the central space of 
the heat exchanger, supplying heat to the water in the heater and 
supplying hot water to the dishwasher or the like. Such method may also 
include circulating incoming feed water downwardly through an outer space 
of the hot water heater to a connection with the lower end of an inner 
space, in which heat is supplied by electrical immersion heaters. Such 
method may also include venting fluid at excess pressure and/or 
temperature from the hot water heater to the waste water collection tank, 
as well as recirculating water from the outlet to the inlet of the hot 
water heater to prevent overheating the electrical heaters through 
accumulation of higher temperature water or steam about the heaters, where 
generally upright and which does not move away due to lack of circulation 
when there is no withdrawal to the dishwasher. The energy recovery unit of 
this invention includes a housing enclosing a heat exchanger having coils 
disposed about a central space and a hot water heater in the central 
space. The hot water heater may include an upright tank in which immersion 
type electrical heaters are disposed, which has an inwardly spaced 
partition providing an outer space and a larger, inner heating space with 
the partition terminating above the lower end of the tank, while the inlet 
for preheated feed water is adapted to produce an annular circulation in 
the outer space. A recirculation pump may be connected between the inlet 
and outlet of the tank and a pressure relief valve may exhaust through a 
pipe leading through a corner of the housing to a collection tank for 
waste water beneath the heat exchanger. 
Additional objects and novel features of this invention will become 
apparent from the description which follows, taken in conjunction with the 
accompanying drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
The energy recovery unit illustrated in the drawings may be placed beneath 
a dish table of a conventional dishwasher, similar to the heat exchanger 
and holding tank unit of my aforesaid copending application Ser. No. 
130,615, or other position convenient to the dishwasher, or other 
equipment which supplies a liquid from which heat may be recovered, it 
being understood that reference to "water" herein encompasses any other 
liquid. Such embodiment includes an upper housing U which encloses a heat 
exchanger E of FIGS. 3 and 5, which surrounds a water heater W of FIG. 5. 
Heat exchanger E is similar to a corresponding heat exchanger of my 
aforesaid application Ser. No. 130,615 and is preferably constructed in 
accordance with my copending application Ser. No. 20,615 filed Mar. 15, 
1979, as indicated previously, while water heater W of FIG. 5, in 
accordance with this invention, occupies the area within the coils of heat 
exchanger E and is specially constructed. Water heater W conveniently 
rests on a pad 10 of insulating material in the lower end of upper housing 
U. A shorter, lower housing L, similar to a corresponding portion of a 
unit of my aforesaid copending application Ser. No. 130,615, encloses a 
holding tank T of FIGS. 5 and 7, into which the waste dishwater flows 
through a screen 11 from waste dishwasher inlet 12 of FIGS. 1 and 5. A 
sump 13 of FIG. 1 provides a supply of warm water, through an outlet 14 of 
FIG. 5 and a pipe 15 of FIG. 1, to a pump 16 which is driven by a motor 
17, while a level sensitive device 18 of FIG. 5, such as a float 
controlled switch, prevents the pump motor 17 from starting unless the 
sump is full. As in my aforesaid application Ser. No. 130,615, pump motor 
17 and consequently, pump 16, is controlled so as to pump warm waste water 
through the heat exchanger E when the dishwasher controls call for hot 
water to be supplied from water heater W, thereby insuring that preheating 
of the feed water for the water heater will take place at the same time as 
hot water is withdrawn from the water heater. From pump 16, the warm water 
is supplied through a hose 19 to an upper inlet connection 20 of FIG. 3 
for the heat exchanger. After passage through the heat exchanger, the 
preferred construction of which will be described later, the water 
exhausts from a lower outlet sleeve 21 of FIG. 5 and a pipe 22 which 
discharges directly into a cup 23 which depends from the lower housing 
beneath an outlet chamber 24, which adjoins tank T for a purpose described 
in my aforesaid application Ser. No. 130,615 and referred to herein later. 
Waste water collecting in outlet chamber 24 is discharged through an 
outlet 25 of FIGS. 1 and 5. A cold water inlet 27 of FIG. 1 is connected 
to a conventional supply pipe (not shown) and also to the lower ends of 
alternate tubes of the heat exchanger E for flow in an upward direction, 
countercurrent to the downward flow of the warm water from which heat is 
to be recovered, as in my aforesaid application Ser. No. 130,615. From the 
upper end of the heat exchanger, the preheated supply water passes through 
a U-fitting 28 which extends upwardly and forwardly, into the space above 
upper housing U and within a cover C, to a pipe 29 of FIG. 2 which 
supplies the water heater W. A hot water outlet pipe 30 extends rearwardly 
from the hot water heater and is connected to a conventional hot water 
supply pipe or flexible hose for supplying the dishwasher. 
The hot water heater W, as in FIG. 5, includes a cylindrical outer shell 31 
having a bottom disc 32 attached thereto, as by welding. Outer shell 31 is 
provided with an inwardly extending upper flange 33 for attachment to a 
heavier, top circular plate 34, with a gasket 35 between, as by studs 36 
spot welded to the flange. Within shell 31 and spaced inwardly therefrom 
is a partition, such as a cylindrical ring 37, attached to the underside 
of plate 34, as by welding, and open at the bottom, as well as spaced from 
disc 32 to provide a larger central space 38 in which heating takes place 
and a smaller, annular entrance space 39 through which incoming water will 
flow downwardly and around the lower edge of ring 37, as indicated by the 
arrows 40. Inlet pipe 29 extends through shell 31 and is provided with an 
ell 41 which causes the inlet water to flow circumferentially in the 
annular space 39, as indicated by arrow 42 of FIG. 6, so that the incoming 
cold feed water will flow, as indicated by arrows 40, smoothly and without 
turbulence around the lower edge of ring 37, so that the heated water will 
flow evenly from the central space through outlet pipe 30 and incoming 
cold feed water will not mix with previously heated water during discharge 
of hot water from the heater. Since the space 39 receives warmed water 
directly from the heat exchanger, the differential in temperature is small 
and insulation between outer shell 31 and heat exchanger E is normally 
unnecessary. 
The water in space 38 is conveniently heated by immersion type electrical 
resistance heaters, such as two sets of three U-shaped calrod heaters 44, 
each set of which depends from a mounting block 45 on plate 34 and 
receives current through wires in cables 46 and 46' which are connected to 
posts 47 of FIG. 5 and extend through an electrical conduit 48, which in 
turn extends rearwardly and then downwardly to an electrical control box 
49 mounted on the rear of upper housing U. Also extending through plate 34 
is a thermostat 50, having terminals 51 and a mounting plug 52, and 
depending from plate 34 centrally of the space 38. Thermostat 50 is 
connected by wires in a cable 53 with a control box 54 having a 
conventional temperature control setting device and a temperature 
indicator 55. Cable 53 also extends into conduit 48 for passage to main 
control box 49 of FIG. 1. 
In order to prevent localized overheating and damage to the heaters 44, 
particularly when the hot water heater is supplying hot water at a higher 
temperature, such as approaching the boiling point, for a so-called high 
temperature dishwasher, a portion of the hot water from outlet pipe 30 is 
recirculated to inlet pipe 29 by a pump 57 which pumps in the direction of 
the arrow thereon and is driven by a motor 58 having a control box 59. The 
inlet of pump 57 is connected to a reducing tee 60 installed in pipe 30 
and the outlet thereof is connected to a similar reducing tee 61 installed 
in pipe 29. Pump 57 is operated only when heaters 44 are turned on and 
merely prevents localized overheating of the heaters. However, operation 
of the pump 57 normally results in a larger amount of hot water being 
available, since recirculation through inlet pipe 29 tends to cause the 
entire space 38 to be filled with hot water and warmer water to fill space 
39. Recirculation by pump 57 does not interfere with the non-turbulent 
flow of water from passage 39 around the lower edge of ring 37, since 
recirculation produces a flow but ell 41 reduces the turbulence of that 
flow. Also, the heaters 44 should be designed so that there will be enough 
hot water in the heater when the dishwasher requires it, so that the 
heaters should be turned off, with pump 57 also turned off, before or when 
the hot water is required. Consideration should be given to the omission 
of pump 57 and associated parts, including recirculation tees 60 and 61, 
when the hot water heater supplies a so-called low temperature dishwasher. 
A pressure relief pipe 62, extending through plate 34 to space 38 in the 
same manner as pipe 30, as in FIG. 5, but at a different position, as in 
FIG. 2, connects with a pressure relief valve 63 having a handle, as 
shown, for manual actuation, as well as being adjustable to open at a 
desired pressure. When pressure relief valve 63 is activated, flow is 
through a pipe 64 which extends downwardly in a corner of upper housing U, 
as in FIGS. 3 and 4, for discharge into tank T. The lower end of pipe 64 
is shown in dotted lines in FIG. 5 to indicate its relative lateral 
position, although it is actually in the front rather than the rear of the 
lower housing L. 
In the heat exchanger E, similar to the unit of my aforesaid application 
Ser. No. 130,615, from inlet fitting 20 of FIG. 3, the incoming warm water 
is supplied through a tube 65, an ell 66 and a sleeve 67 to a series of 
coiled tubes 68, 69, 70, 71, 72, and 73, the inlet ends of which are 
sealed to the inside of the sleeve 67 and to each other. The opposite ends 
of tubes 68 to 73, inclusive, are connected to sleeve 21 of FIG. 5. Cold 
water outlet 28 of FIG. 1 is connected to a sleeve 74 similar to sleeve 67 
but connected to the upper ends of coiled tubes 75, 76, 77, 78, 79 and 80 
which are wound into coils simultaneously with tubes 68 to 73, 
respectively, so that, as in FIG. 5, tubes 68 and 75 will alternate in the 
first inside coil, tubes 69 and 76 will alternate in the second coil, and 
tubes 70, 77, tubes 71, 78, tubes 72, 79 and tubes 73, 80 will alternate 
in the succeeding coils. The tubes of each coil are wound in the groove 
between two tubes of the preceding coil, while a heat conduct mastic is 
squeezed between the tubes during winding. The lower ends of tubes 75 to 
80, inclusive, are received by a sleeve similar to sleeve 74 of FIG. 3 but 
which is connected to a cold water inlet pipe at inlet 27 of FIG. 1 in a 
conventional manner. Insulation 81 may be placed around the heat exchanger 
E, such as a plastic foam which is injected into the space around the heat 
exchanger and up to the open top of upper housing H. Such insulation also 
provides support for the heat exchanger during transportation. Insulation 
may also be placed around pipes 29 and 30, as well as in the space within 
cover C which encloses the parts extending above the upper housing and is 
provided with slots 82, 83, 84 and 85 for outward extension of parts. 
The front wall 87 of lower housing L, as in my aforesaid application Ser. 
No. 130,615, is provided with a generally rectangular opening 88 of FIGS. 
7 and 8 having a lower portion of lesser width which provides ledges to 
accommodate angular slide flanges 89 of screen 11, shown in FIGS. 4, 5 and 
7. Screen 11 has holes of an appropriate diameter to permit the waste 
water to flow through but catch any food refuse or material larger than a 
predetermined size. A cover 90, to which screen 11 is attached, is in turn 
removably attached to the front wall by a latch 91 at each side, as in 
FIG. 4. The screen is, of course, removable by unhooking the latches 91 
and removing the front cover and the screen with it, then replacing the 
cover and screen, after the screen has been cleaned off. An improvement, 
in accordance with this invention, in the screen sealing and mounting, 
includes its attachment, as by welding, to a front plate 92, by which the 
screen may be removably attached to a mounting plate 93 in a conventional 
manner, as by a series of bolts 94 of FIG. 8 which also clamp a molded 
gasket 95 between front plate 92 and mounting plate 93, which has spring 
edges 96 which engage the inside of the top, bottom and ends of cover 90. 
Gasket 95 is rectangular and provided with a convex lip 97 on all four 
sides, which is compressed between housing front plate 87 and mounting 
plate 93 around but spaced from all edges of the opening 88. Gasket 95 may 
be formed of any suitable compressible material, such as rubber or 
plastic, to provide the desired seal. 
As the screen is inserted, one of the screen flanges 89 will slide along 
the top flange of an angular guide bar 98 of FIG. 5, similar to the screen 
of my aforesaid application Ser. No. 130,615, and the opposite flange 89 
will slide along a flange 99 at the lower edge of a plate 100 which 
depends from and is attached to the top wall 101 of the lower housing L. 
Guide bar 98, as in FIG. 7, extends between and is attached to front wall 
87 and rear wall 102 of the lower housing. A baffle 105 beneath the outer, 
lower edge of guide angle 98, as in FIG. 5 and also as in my aforesaid 
application Ser. No. 130,615, extends alongside the cup 23 and permits 
overflow of excess waste liquid from the tank beneath screen 11 to flow 
into outlet area 24 and thence flow through outlet 25 and through a hose 
or pipe to the sewer, or to another piece of equipment. Baffle 105 extends 
between and is attached to front wall 87 and rear wall 102, as well as to 
bottom wall 106 of the lower housing, to the underside of which supporting 
legs 107 are attached. Legs 107 are of a height which permits depending 
sump 13 to clear the floor 108. 
One advantage of the outlet area 24 is that it tends to render the screen 
11 self-cleaning, since the waste dishwater inlet 12 is at the opposite 
side of the screen from the outlet area 24. Thus, if the screen becomes 
clogged, the waste water will flow across the screen and over side flange 
89 into the outlet or discharge area and tend to carry with it material 
which clogs the screen. A similar result occurs in the event that there is 
a malfunction of the float or level indicator 18 or the pump 16, so that 
the waste water is not removed from the tank on one cycle and the level of 
water in the tank rises over the top of the baffle 105. In such an event, 
water which continues to pass through the screen will tend to overflow the 
baffle, but for complete discharge of the waste water, this overflow would 
be insufficient, so that the excess will flow across the screen and into 
the discharge area 24, tending to carry with it any material collected on 
the screen. 
An alternative water heater W' of FIGS. 10-13 includes a tubular shell 31 
which is attached, as by welding, to a generally semi-elliptical upper 
head 118 which extends through an appropriate opening in a partition 119 
above the heat exchanger, which includes tubes 68, 69, 70 and 75, 76, 77 
arranged in the manner described previously. Plates 120 and a flanged 
plate 121 of upper housing U' extend above partition 119, while a top 
plate (not shown) is attached across the upper ends of plates 120 and 121. 
The lower end of shell 31 is closed by a semi-elliptical lower head 122 of 
FIG. 11, which is also welded to the sleeve. The semi-elliptical heads 
permit a thinner material to be used and thus decrease the cost of 
producing the water heaters. The water heater is supported from partition 
118 by a series of removable brackets 123. In addition to the heat 
exchanger tubes, insulation 124, as of fiberglass, may surround the water 
heater and similar insulation 125 surround the heat exchange tubes. 
Insulation 81', as of urethane foam, may also be placed between insulation 
125 and the outer shell of upper housing U'. As before, an inlet pipe 29 
for fresh water, preheated by the heat exchanger, enters the top of the 
tank adjacent the outer edge of upper head 118, while an outlet pipe 30, 
for supplying water heated in the water heater to the dishwasher, connects 
with the upper head 118 at approximately the center thereof. Also, a 
pressure relief pipe 62' connects with the central portion of the heater 
tank, extending to a pressure relief valve 63' and an exhaust pipe 64' 
which may extend downwardly in a corner of upper housing U' for discharge 
into a waste water tank corresponding to tank T of FIG. 5. Three electric 
heating elements or heaters 127 extend into the central portion of the 
tank, similar to the central portion of FIG. 5, with each engaging a 
threaded ring fitting 128. Each heater is provided with threads on the 
outside for engagement with cooperating threads on the inside of the 
corresponding ring 128, which is tubular and extends through an axially 
aligned, circular hole in upper head 118 and is welded to the top of the 
head by an encircling weld, while maintained in an upright position. 
A temperature regular control 129 for heaters 127 may be connected by a 
cable 130 with a sensor 131, extending downwardly into the central portion 
of the tank and engaging an interiorly threaded ring fitting 132 which is 
installed in a manner similar to ring fitting 128. Also, a high 
temperature regulator 133 may be connected by a cable 134 with a sensor 
135 extending into the tank and similarly threaded into an interiorly 
threaded ring fitting 128. High temperature regulator 133 may be connected 
with the controls for heaters 127, and/or the relief valve 63'. The lower 
head 122, as in FIG. 11, which extends downwardly to top wall 101' of 
lower housing L', may be provided at the center with a depending nipple 
138 provided with a threaded plug 139, which may be removed for draining 
any sediment which may collect in the bottom of the tank, such as falling 
off the electric heaters. For accommodating the various parts which extend 
into the tank, a series of holes, as in FIGS. 12 and 13, may be provided 
in upper head 118, including holes 141 for the ring fittings 128 for 
heaters 127, a hole 142 for the inlet pipe 29, a hole 143 for the outlet 
pipe 30 and holes 145 and 146 for the respective ring fittings 132 and 136 
for the sensors. 
An alternative upper head 150 of FIG. 14 is particularly adapted to 
accommodate a single electric heater for a water heater which does not 
require three heaters. Upper head 150 is generally semi-elliptical but has 
a flat area 151 at the top, in which a hole 152 may be produced for the 
heater, with studs or the like for bolting a heater flange in position 
against flat 151. Such a construction permits a heater having a flat 
mounting flange to be used, rather than requiring a threaded fitting to be 
welded to a curved surface of the upper head, as when installed in holes 
141 in the upper head, shown in FIGS. 12 and 13. Alternative head 150 may 
be provided with smaller holes 153 and 154, as for one or more sensor 
fittings or an outlet pipe. A hole for the inlet pipe is, of course, 
closer to the edge of the head than the holes shown in FIG. 14, such as 
corresponding to hole 142 of FIG. 12. 
A further alternative water heater W" of FIGS. 15 and 16 includes a tubular 
shell 31 which is attached, as by welding, to a generally semi-elliptical 
upper head 157 which extends through an appropriate opening in a 
partition, corresponding to partition 119 of FIG. 10, being provided with 
brackets 123 for attachment of the water heater to the partition. The 
lower end of shell 31 is attached, as by welding, to a lower 
semi-elliptical head 126 provided with a depending, threaded nipple 138 
having a drain plug 139. In order to support the heaters, such as three in 
number and corresponding to heaters 127 of FIG. 10, except for a lateral, 
planar flange having holes for engaging studs, rather than exterior 
threads, three predominantly annular flats 158, 159 and 160, except for a 
greater radius arc 161 at the outer edge, are provided with a central hole 
162 and a ring of studs 163, the flats being at equally spaced positions 
around upper head 157. Each flat is formed by the bottom of a well 164 
provided by cold or hot forming prior to drilling holes 161 or 
installation of studs 163, while the ring of studs 163 is positioned to 
engage a series of bolt holes in the planar attachment flange of the 
respective heater. Such attachment flanges are conventionally formed on a 
heater, so that the formation of the flats 158, 159 and 160 and the ring 
of studs 163 eliminate the requirement for welding a large special fitting 
for each heater. The heaters extend within the tank in a conventional 
manner, although due to the depression of the wells in which the flats are 
formed, the length of the heaters may be somewhat less than those provided 
for the heater W' of FIGS. 10 and 11. Also attached to head 157 are a 
threaded nipple 165 for a pressure relief valve, such as corresponding to 
valve 63' of FIG. 10, and a pair of threaded nipples 166 for a pair of 
sensors, such as corresponding to sensors 132 and 135 of FIG. 10. A 
partition or ring 168 having an upper edge 169 and a lower edge 170 is 
mounted inside the tank to provide an annular inlet space 171 around the 
inside of the shell 31, which inlet space is appropriately considerably 
less in thickness and volume than the space 172 within the ring. 
Inlet pipe 29 extends downwardly at a position between the outer edge of 
upper head 157 and ring 168, as in FIG. 17, and is welded to the head, 
while upper edge 169 of ring 168 engages the inside of upper shell 157 and 
is attached thereto, as by welding, at a position just inside inlet pipe 
29. As in FIG. 16, each arc 161 at the outer edge of a flat 158, 159 and 
160 is formed to correspond to the diameter at the outer edge of partition 
ring 168, so that the upper edge 169 of the ring engages the underside of 
each flat just within the arc 161. A continuous weld may not be necessary 
for attachment of partition 168 to the inside of head 157, since a series 
of tack welds, as attaching the upper edge 169 of partition 168 to the 
underside of each flat 158, 159 and 160, as well as a tack weld between 
each pair of flats, may be sufficient, since a small amount of leakage 
between inner space 172 and outer space 171 may be tolerated, inasmuch as 
heat leaked to the outer space 171 will be returned to the inner space as 
incoming water flows from the outer space to the inner space. 
A deflector 174 is disposed between the ring 168 and the upper head 157, 
directly beneath the lower end of inlet pipe 29, as indicated in dotted 
lines in FIG. 20, while the lower edge 175 of pipe 29, shaped to 
correspond to the inside of head 157, as in FIG. 17, extends through a 
hole in the head and may be welded to the head on the outside. Deflector 
174, as in FIG. 18, is provided with an upright flange 176 which may be 
tack welded along its outer edge, as in FIG. 20, to the inside of head 157 
prior to installation of ring 168 and attachment of shell 31 to the head. 
The outer edge 177 of flange 176, as in FIG. 18, is shaped to fit the 
inside of head 157. A curved portion 178 of the deflector, as in FIG. 19, 
may join the horizontal portion with upright flange 176, to insure that 
incoming cold water discharged from pipe 29 will be directed horizontally, 
while a notch 179 in the edge of deflector 175 fits against the outer edge 
of ring 168, as in FIG. 20. As will be evident, the deflector 174 causes 
the inlet liquid to flow in an annular path around the space 171 between 
ring 168 and shell 31 in a manner described previously in connection with 
ell 41 of FIG. 6. One purpose of the annular flow of the incoming water, 
which thus circulates around the ring 168, is that the incoming 
circulating water will be preheated by the heated water inside ring 168, 
but will also be insulated from the temperature outside the unit by the 
heat exchanger corresponding to the heat exchanger having tubes 68, etc. 
of FIG. 11. 
The lower edge 170 of ring 168 is placed fairly close to the inside of 
lower head 126 for the purpose of producing an increased rate of flow of 
water, similar to "wire drawing" as it passes from the annular space 171 
outside ring 168 to the space 172 inside the ring. This flow will tend to 
maintain in circulation small flakes which may fall off the heaters, so 
that such small flakes will pass on with the water supplied by the heater 
to the dishwasher and the like. However, larger flakes or particles will 
collect as sediment in the bottom of the lower head 122, from which they 
may be removed periodically through the drain plug 139. 
The alternative water heater W' of FIGS. 16 and 17 may be used in a unit 
corresponding to the unit U' of FIGS. 10 and 11, i.e. with corresponding 
inlet pipe 29 and outlet pipe 30, as well as heaters corresponding to 
heaters 130 whose flanges are installed against the respective flats 158, 
159 and 160, as well as a pressure relief valve pipe attached to nipple 
165 and a sensor extending through each of nipples 166 into the tank, with 
one sensor controlling the operation of the heaters and the other sensor 
being a high temperature sensor which will actuate the relief valve if the 
pressure responsive feature thereof fails to operate when an undue 
pressure is produced. Or, the high temperature sensor may be set for a 
temperature which corresponds to a slightly lower pressure than the 
pressure responsive mechanism of the relief valve, so that the high 
temperature sensor will normally operate to open the relief valve, but the 
latter will operate automatically if the pressure corresponding to the 
temperature for which the high temperature sensor is set is exceeded. 
The head shown in FIG. 14, as previously described, may be substituted for 
upper head 157 of FIGS. 15 and 16, when a smaller capacity heater is 
desired, in which only one electric heater becomes necessary. As indicated 
previously, a single flat 151 is placed at the center of the head 150, 
since it is more readily produced at that position. In addition, a series 
of studs corresponding to studs 163 of FIGS. 15 and 16 may be mounted on 
flat 151 of FIG. 14, surrounding hole 152. Head 150 of FIG. 14 may be 
attached to a shorter shell than shell 31 of FIG. 16, or the head 150 may 
be smaller in diameter and the shell correspondingly smaller, to provide 
the volume necessary for a smaller heater, for which only one electric 
heater is necessary. 
The tank of the water heater W' of FIGS. 10 and 11 may be provided with an 
interior ring corresponding to ring 168 of FIG. 16, while the lower edge 
may extend to a point closely adjacent the lower head 122 so as to produce 
an increase in velocity of incoming water, again in order to obtain a 
circulation of smaller flakes and particles. Again, larger flakes and 
particles will tend to collect in the bottom of the lower head 126 of FIG. 
11 and may be drained therefrom periodically by removing plug 139. Since 
the heater tank is centered over the screen 11 of FIG. 5, any water 
drained from the heater tank will pass into tank T and then through the 
heat exchanger, thereby avoiding loss of the heat held by this water. As 
will be evident, any larger flakes and particles drained into waste water 
tank T will, after passage through the heat exchanger, be discharged into 
the outlet cup and thence discarded. The operation of the alternative 
water heater W' of FIGS. 10 and 11 and the further alternative water 
heater W" of FIGS. 15 and 16 will be essentially as before, although the 
wire-drawing effect of the slight spacing between the lower edge of the 
ring 168 of FIG. 16 and the lower head 122, as well as the spacing of the 
corresponding ring of the alternative water heater W' of FIGS. 10 and 11, 
coupled with the concave shape of the lower head 122 of FIGS. 11 and 16, 
will circulate smaller particles but permit larger particles to collect 
without impeding the flow of the incoming water into the heating space. 
This is an additional advantage of the water heater constructions of FIGS. 
10-14 and 15-19. 
Although more than one preferred embodiment of this invention has been 
illustrated and described. it will be understood that other embodiments 
may exist and that various changes may be made without departing from the 
spirit and scope of this invention.