CA2078984A1

CA2078984A1 - Electric, modular tankless fluids heater

Info

Publication number: CA2078984A1
Application number: CA002078984A
Authority: CA
Inventors: Navarro F. Guillermo
Original assignee: Ntw Enterprises Inc
Current assignee: Ntw Enterprises Inc
Priority date: 1990-11-27
Filing date: 1991-11-25
Publication date: 1992-05-28
Also published as: WO1992010071A1

Abstract

Abstract This heater is designed for the heating of a continuous flow of most type of fluids. However, for simplicity purposes of discussion of the embodiment of this invention, we will use water, probably the most commonly used of fluids, to discuss the uses and applications of this invention.
A tankless, flow-through electric water heater (7) whose housing is designed for modular application, where serially connected modules (8) define the path of the fluid being heated, in this case water, through the heater from inlet (10) to final outlet (14). Each module (8) contains two separate chambers and each chamber is provided with an electric immersion type heating element (40). The first and last chambers will also have a temperature sensor (55) which will signal an electronic temperature control system (106). The temperature in the first and last chambers energize each heating element (40) of each chamber for a period of time proportional to the temperature difference between first chamber and the desired set leaving temperature of the water, which is set by an adjustable temperature controller (potentiometer) (51), included in this control system. This control system also has a minimum setting point for a "no flow" condition or for the prevention of water freezing, where extreme weather conditions exist.

Description

~ ?; ` ~ ~ ~
WO 92/10071 PCr/US91tO8849 EL~ MODULAR ~ANICLESS FLV~DS HEA'rEl~
ACICGROUND OF INVEI~TXON
~n The present lnvention relates to ~n apparatus that ; heats water or other liqulds w~.thout the need of a RtOrage tank but rather heats instantaneously a aontinuou~ Elow of .. the fluid whan heating elements are energized. For simplicity purposes, I will use water as the Eluid to be heated, since water is one o~ the most commonly used Eluids to be he~ted. Water heaters are well known. They include, but are not limi-ted to, a s~torage tank, a thermostat, a heat source and inlet and outlet ports. The water in the tank is heated until it reaches the deslred temperature which ls preset through the thermostat.
De~cri~tion Of ~rior Ar-t Normally, the tank of the convsntional water he~ter is of fair siza and it is a slow process to heat all the water in the tank to a preset temperature. The water i~ not heated at the same rate that it i~ used, therefore, the rate of recovery for the water to reach agaln the de~ired temperature, is relatlvely ~low. Tha storaga tank provides a reserve of hot water which normally supplies short term needs. If more hot water i9 used than the amount o~ water stored ln tha tan~, the temperature of the water drastical- ;
ly drops due to the heater's low heat recovery rate, then the user must stop the flow and wait ~or the heater to heat : the water back to the desired tamperature. This type of heatar is usually installed in an environment where the ambient temperature is lowe~ than that of.the temperature of the watar in the tank. Thus, the loss of heat to the ambient air causes the heater to turn on and continuously reheat the water in the tank in order to maintain the desired water temperature. The energy used to raheat the water is wasted and no benefit is derived rom it.
Hereto:Eore, numarous attempts have been made to reduce the heat loss and wasted energy. This includes obvious ' :.
~' ~3UE3ST~ JTE SHEEl i.,3 i i~
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solutlon~ such ~s ln~ulation for the water heaters. ~rhis helped to re~uce the haat loss to ~ome extent but wa~ not completely effectlva and adver3ely incre3~ad the slze o~
tha heaters knowr~ in the prior art. Anvther solution to this problem has been the ~ntroduction o~ a vari~ty of tanklass water he~ters. ~hese heate~s reduced to ~ome extent the problem o~ energy lo~s, but were characterlzed by insufficient volume of hot water and sp~ce problems.
Ohviously, even these tankless type wat~r heaters brought on a new variety of problem~. Most units avallable were o~
small capacity and had severely limite~ ~low rates and temperatura rlse capability. The larger units at~empted maximum flow rates and temperature rlse but requl re~
excessival y l arge minimum flow rates to energlza the systems. Most depended on conventional flow detection devices to energize the heaters. Other shortcomlngs included were poor ma~ntenance capabillty, inability to replace individually worn parts without ~ubstantial componant replacement~ and the inability to get rid o~
entrapped air or gas2s in the systam. ~hi~ was at times due to use of water wells as a source of water supply and to pre~surized pump 5y~tems ~i.e., to get rld of air or ga3es).
S~3~,_ The prssent invention is directed to a tankless water heater characterizsd by a hlgh hot water flow capability that is greater than any known in the prior art. It also 501ve8 the problems of maintenance accessib~lity and capability of capacity growth. It has al~o solved one o~
the princip~e problems of conventional storage t~pe water heaters, namely tha high energy loss due to having to con~tantly reheat the water. Similarly, the heat loss to the atmosphere due to storlng the water is alleviated.

SUBSrlTUTE SHE~Er . .

WO92~10071 i~ PCT/VS91/0~9 In th~ pre3ent lnventior1, the~e i~ shown, f or example, the heatar ~omprlslng a M~dul~ wlth two inner chamb~rs, each chamber containing a heating element. Several modules can be attached to each othar to form a heat~r of selective size that oan provide a grealt v~riety o~ ~low and tampera-ture rise requirements. For the purpose o~ example, the fluid chosan for explanatlon here ls water. It is the fluid *o be heated, but one E3hall know that thi8 heater is designed to be used to heat other ~luids other than water.
Cold watar enters the heater at an inlet port and then flows through the modu~e containing the two chambers or through a serias of modules sequentially lnstalled ln a manner defining the flow path of the water. The water lea~s through an outle~ port. The heating elements are contalned within each chamber o~ each module. I~ the temperature of the water leavlng the module's second chamber is lower than the desired pre~et temperatur2, the heatlng ele~ent will be energlzed to rai~e the departing water temperat~re to tha desired preget temperature.
Gen0rally, thi~ is true with rægpect to the departing ::
chamber o~ each module. T~e number o~ haating elements energized is made proportional to a number of factors ..
including the rate of flow, the enterlng temperature of the water, -the desired laavlng temperature of the water and the capac~ty of the heating elements~ ~he lower the rate of flow or temperature rise required, the few~r the number of heating elements that are enargized and the shorter the period o~ time that the heating elements must rsmain energized~

In ordar to achiave ths aforementioned operating . criterion, a heating element is locatad ~n eaah chamber of ~v~,~/.Uv/~ P~T~U~ X~9 each module. Al~o, a t~mp~rature ~en~lng device i~ in the ir~t and last chambers of a heater which wlll energlzs or de-ener~ize each element to maintain th~ desired water leaving temperature. The heater will include the nece~ary number of chambers and heating elaments to provlde the total heatlng capacity required ba~ad on the maximum desired temper~ture ri~e and rate o~ ~low, allowing ~he heat~r to maintain a continuous rate of flow at the de~lred water'leaving temperatura for an indefinite period o~ time.
It will be recognized that low flow rate~ are po~sible with thls heater design without an ovar-heatlng condltion due to the staged design of enargizlng the heating ele-ments. The unit is compaot in size due to ths ab~ence of a storage tank. The interlor surface of the chambars may be coated with an epoxy coating. This ooating is used to reduca the possibility o~ deterioration of the metallic walls of the chamber. It al~o provide~ a smooth, non-porous finish in the interior chamber surfa~e which reduces the amount of mineral deposits and other solid matter that will adhere to the lnterior walls o~ the chambers. The coatiny will also help ease the maintenance by keeping the chambers clean, thus also increasing the li~e of the heater.
~he module's exterior surface may be coated with a llquid ceramic coating. It i5 capable of provid1ny an equivalent insulating value o~ an R-7 ra~in~, more or less.
Even though the heat loss in this heater is very small due to its si~e, the ceramic coatlng will further reduce the heat lo~s to the atmosphere. The ceramic coating also renders the exter.~or æurfaces of the modules impermeable.

One of the chambar~ in each module may also have a port looated in an upper area so that an automatic air Sllr~STI i UTE SHr~T
.... ... . .

W092/1~071 PCT/US91J08~9 -~- 2 ~ ",? .,i float vsnt may be lnstalled to allow entrapped alr or gases in the syst0m to leave without havlng to manually do it.
A~ electrical circult which is part of th~ electronic control Syst~1~ preven~s ~he electric system from baing energized wlthout the pre~ence of water i~ all chambers.
This feature in the electronic control 8y8ta~, prevents the - all too common problem of "dr~-firing" a heat~r and thus burnlng the heating elements and poqslbly causlng extenslve damage, lf not destruction, to the heater, the electrical system and ad~acant property. These "dry firlng" sen~ors are installed in the ~irst and last chamber~ of aach water he~ter, in order to insure that water is pre~ent in all chambers. The preced~ng eatures and advantages of the invention will be more clearly understood upon a careful readi.ng of the ~ollowing cla~ms, speclfloation, and drawinys wherein like numerals denote liXe parts ln the various views and wherein:
BRI~F DESCRIPTION OF_DRAWI~S
Figurs l ls a front vlew of heater.
Flgure 2 is a cxos~ ~ec~ion of front elevation of heater.
Flgure 3 is a ~eotion A-A through Flgure l.
Figure 4 i8 a top v1ew of Figure 2.
Figure 5 i8 a section B-B view through Figure 2.
Figure 6 is a ectlon C-C view through Flgure 2.
Figure 7 is a OEeCtiOn D-D view through Flgure 2.
Figure 8 l~ an exploded perspective view of heater ~one module).
~igure 9 ls a f ront view of typical module.
Figure 10 i8 a front view o~ heater in a modular configuration. :~
Figure ll ls ~ seotion E-E view through ~igure 9.

IPCT/US91/O~U~

Pigwre 12 i8 a ~chematic co~ltrel dlagram o~ the control system loglc.
Figure 13a and 13h are ~chematic control diagram~ of the heater control system.
DESC~IPTION OF PP~EFERRED EMBODIMENT
Referring to Fig. l, Fig. 8 and Fig. lO, there i~
shown a water hsater 7 exemplary of the pre~ent invention.
The heater 7 contalns a heater lnlet pipe lO, a heater outlet' pipe 14" communiGat;lng with a module B which contain~ a fi~t chamber 60 and a secend chamber 70. Each contaln a heating elemant 40 and 41, respectively ~Fig. 8).
A multlple module (2) heater configuration is shown in Flg.
lO. Re~erring to Fig. l, Fig. B and Pig. 10, inlet pipe 10 is attached to triac mou~ting section 30 which ls per~orat-ed inside to allow the flow of water through it. This triac mounting section 30 i~ attached to a pipe nipple ll whlch in turn ~ attached to module 8 at po:rt 62 in ohambsr 60 (see Flg. 2, Fig. 7, and Fig. ll~. The above connec-tions may be made through threaded connectlons.
Referring to Figs. 2, 3, 6 and ll, chamber 60 is encased by chamber walls 66 and 67. At the upper area of - chamber wall 67 i~ a connecting port 65 which allows the flow of water from chamber 60 to chamber 70, which itself is encased by chamber walls 67 and 7~. Outlet pipe l~
(Flg. 1), attached to elbow 15, which is attached to pipe nipple 12. This, in turn, is attached to module 8 at outlet port 73 in chamber 70. All of the above may be connected through threaded connections. It is thus seen that the water flows f rom inl et pipe lO through module or modules 8 and out through outlet plpe 14.
Now, referring to Figs. 2, 7, and 9, there is shown, at the lower area of chamber 60 and chamber 70, openings 63 and 64, respectively. These openings exist ~or ths purpose .....

W092/10071 PCTtUS91/0~9 ~7~ t '. ~

o.f providing access to remova any accumulated particulate matter in tha chambers and also for draining the chambers.
These openings 63 and 74 ara closed when tha heater i3 on by mean~ of threaded plug~ lG and 17 attached to chamber 60 and chamber 70, r4spectively ( Sae Fig. 1 ) . Ref erring now tu Figs. 2, 4, 8 and 9, heating element 40 and heating elem~nt 41 extend down through openings 61 and 71 located at upper araa of chamber 60 alnd cham~er 70, respectively.
These may conneot by mean~3 o~ threaded connections.
Although tha preferred embodiment uses electric resl~tlve typa heating elements as the haating mean3r other m~ans are possible such as, or example, liquifiad petroleum, natural gas, heating oll, or any other sources of heat.
In Figs. l, 8, and lO, there i5 ~hown a relief vent 21 tied to an elbow ~0 wh~ch ln turn i5 connected to module 8 at chamber 70 through opening port 72, or in tha case o double module (Flg. lO), at chamber ~0 through same port.
The automatie relief air ~loat vent 21 ln chamber 70 is for the purpose o~ relea~lng to the atmosphere any entrapped air or gases in the systam.
In operation, the cold fluid entsrs heater 7 through inlet pipe lO and ~lows through trlac mounting ~ectisn 30.
This section serves at lea~t two matn purposes. First, it provides an area in which to mount triacs 51, 52, 53 and 54, and sacond, the low of cold water throu~h the triac mounting section 30 advantageously cools down the triacs while hea~er 7 iB in operation. This markedly reduces wear and snhances the lie of the unl-t. A heat ~ink compound may be installed between the sur~ace o~ the triac mountlng section 30 and the triacs 51, 52, 53 and 54. The cold water then anters chamber 60 at inlet port 62 in module 8 (aee Flgs. 2, 7 and 93 and travels past heating elemant 40.
The water is then heatad at thi~ point when heater 7 ls i~J `J~ IU~ Pcr/lJss1/o~
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an~rgi~ed. A~ter the water ~8 hea~ed by the heating element 40, it flows to chamber 70 through aonnectlng port 65 (Flgs. 2 and 5). The dimen~ions o~ ~he connecting port 65 is varled depending on flow rate requirements.
Referring to Fiys. l an~l 10, ~ iQ seen that when water lea~e~ chamber 60 and enters chamber 70, it i~ heated by haating element 41, if addil:ional heat i~ requlred. The same procedure follows through chamber 80 and chambar 90 in the multlple module model wlth heatlng elements 42 and 43, respectlvely (~ee Flg. 10). The actual number o modulss and~er chambar~ and heating element~ 18 varlable as initlally explained and depending on the ra~e of flow raquired, the temperature rlse and oapacity o~ the heating elaments. ~hl~ is accomplished expaditiou31y b~ the modu~ar dsslgn. In any event, the wa*ar ~inally leave~ the last ch~mber and exits tha heater 7 through the outlet plpe 14.
Referr~ng to Flg. 10, a temperature ~ensor 55 and 56 looated ln chambers 60, and 90 respe~tively is shown. Even if only two modules 8 are shown, there i8 illustrated the capability of multiple installation of modules 8 for different capacity heaters. Each addltlonal module 8 connects to the preceding module by means o~ pipe nlpple 13. Through use of temperature sensor 55 (Flgs. 8 and 9) connected to chamber 60 through sp~ning 64 and protrudes into cha~ber ona 60 for sensing the temperaturs o~ the water flowing in thi~ ~hamberO
Temp6rature sensor 56 is connected to chamber 90 through opsning 75 and protrudes into the in~erlor of that ehamber for sensing the temperature o~ the water flowing through this chamber. In Figs. 1, 8 and lO, there is shown terminal block 44 and ground terminal block 45 are mounted to a module 8 with screws, on a slngle module heater 7.

T51^1 JTI~ HF~T
.

W09~/10071 ' PCr/US91/0~
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slock 44 i8 normally mounted at chamber 70 on a double motlule ( 8 ) h~3at~r ( 7 ) and would be mounted at chamber 90.
In the same manner, th~ high limlt ~wi*ch 59 18 mounted on the 3econd chamber 70 a~d 90 of each module 8 of each heater 7.
Figure 12 is a low diagram showing the path of water flow and related sahamatic electricals. Figurs 13, howevar, shows in greater datail a de~criptlon of the control ~y8tem o~ the wate~/flu~d heater. A conventional power supply (PS) whi~h may supply ~40 volts incoming current to the control board 50 is reduced to lO volt~ AC
by means o~ a trans~ormer (Tl). A recti~ier (~l~ furnishes lO volts DC which is used to ~lre tha optitriacs U5l, U61, U71 and U8l, and a voltag~ regulator (U) then furnish0s 5 volts DC which i~ u~ed for the logic sy~em of control board 50.
~ ~L~NG ~E ENERGIZING AND

As best ~hown in Fi~ . l, 8 and lO, there are t~o temperature ~en~ors 55 ~nd 5~ which are conneeted to terminals 3 and 4 at connector IP2) (see Fig. 13). The sen-~ors provid3 compari~on voltage i~put wlth Sot Point volta~e furni~hed by potentiome-ter 51. The voltage input ~rom firæt temperature aensor (55) goes to the operational amplifier U7 through terminals 9 and lO. The s~gnal that leaves the amplifier U7, "i~" the temperatuxe sensor 55 is lower than the Set Polnt Te~perature of potentlometer 51, will ire the logic to energize the heating elements 40, 41 (Fig l). The second temperature ~ensor 56 detects the tempe~atura o~ the fluid at the last chamber 70 of the heatar (Fig. lj and compare~ the referenoe voltage after sensor 55 ascertains the changa in temperature. Once lt determines the voltage chan~e, lt fir~s thæ voltage coming ' ~'' ,:

~ PCT/U5~l/08M9 --1 0 ~ "1 from the operatlonal a~pli~ier U3 to ~re th0 modulator U4 which gi~es a pulsatlng output through ~erminal ~ the voltage co~es clo~e to belng equal, the output will ~top.
The modulated output goe~ thrc~ugh the "door~" at Ul ~iring opti~riacs U51, U61, U71 and U81 in a modulating mannar.
If the temper~ture or voltage coming ~rom temperature sensor 56 is lowar than the " ~iring" voltage, then the logic will compare thl~ difference in ~tep~ glven by the volta~e raference of Inkegrat:ed Circuits U5 and U6 (Fig.
13) firing in sequence, cvoparing those voltage.~ wlth ampllfier U3 which gavH the output to tha optitriac~ U51, U61, U71 and UBl, ~iring the elements ~n sequenae. In thls manner, it will have a propoxtional an~ modulat~d QUtpUt to the heatlng elements 40 and 41.
If the water temperature (F~gs~ 12 and 13) is lower than the predatexmlned t0~perature ~potenticmeter 51), all o~ the heating alements 40 and 41 wlll be energized. In th~ case of a ~our chsmber unlt (~ee Fig. 10), the No. 4 haating element 43 will begln modulatlng until it flnally shuts duwn (when temperature set~ln~ i~ satisfied).
Otherwise, the temperature continue~ to ri Re, and the third heating element 42 will ~tart modulating until it inally shuts off. Tha second heating elem0nt 41 and first heating element 40 will also do tha Bame, i.e. ~ they will start modulating until they flnally shut down a~ the temperature reaches the set point.
If the temperature is lower than the predetermlned (i.e., Set Point ~emp~rature) l~ea 103, Fig. lZ), the ~irst heating element 40 will enargize in a modulating manner until it stays fully on. If tha temperature continue~ to fall, then the ~econd heatiny element 41 will be energized and ~tart modulatlng al~o until it ~tays fully on. I~ the temparature still contlnues to fall, then the third heatlng ~lJB~:TlT1 ITF ~ IF~T
.

W092/10071 ' P~r/US91/0~

element 42 and th~ ~ourth h~ating ~lement 43 will do the ~ame. As they ~re anergiz~d, th~y will ~tart modulating until they ~tay fully on.
Re~errlng to Fig. 12, the logic ~ystem ha~ two clraults 108 an~ 10~ to protect again3t dr~ iring, i.e., when no water i9 in the chamberg. Thi~ msy not unusually occur due te shut down of the water ~upply ~y~tam it~el~, or new in tallatlons or repairs where the w~ter ~upply h~s never baen turned on or lt has been turned of~ temporarlly.
These logic circuit~, called dry ~ire circuits, are created by liquid leYel senYor3 on ~erminals 1 and 2 in conneator ( P2 ) ( see ~ig . 13~ In ~ig~. 1, 8 and 10, one may see li~uid level ~ensors S7 and S~ which are to be located as hlgh as possihle in tha ~irst and la~t chamber~ of esch module~ They trigger the integrated circult U8 (Fig. 13a and 13b) which shuts off the loglc over OP~MP U3. In the ~Iflring~ input (see Fig. 13a and 13b), voltage goes to "0", preventing heater ~rom ~oming on in the even that "no"
water is sen~ed by the liquld level ~ensor~ 1 and 2 o~ P2.
Tha operatiol~ of thi~ heatlng ~y~tem requlres that enou~h heat be applied in the fir~ chamber 60 ~Fiy. 1), in order to malntain that chamber w~ter temperature at or above lnitial ~et temperature. Th~s control sy3tem u9e8 in t~is example, a first tempsrature sensor 5~ locatad in the first chamber 60 to maasure tempera~ure, while the second temperature sensor 56 lo~ated in the second chsmber 70 i9 used to mea~ure the temperature there, thus establlshing a temperature di~ference betwaen the chambar~ one and two.
When there is no water flow, heat is added to water ~n the ~irst chamber 60 by heater element 4n ~n order to :~
maintain water *emparature at or above the initial set - te~perature, thereby maintainlng the temperature higher than the second chamber 70 temperature. When the ~lrst . ~' ' ' ~'.

P~7~/U~91/0 chamber temperature tand~ to drift and approaches the temperature in the s~cond chamb4r, which 18 monltored by the second temperature sen~or 56, the control system evaluates the reading a~ a "flow" condltion. This condi-tion i9 on~y momentary ~or as the fi~st heating element 40 ~8 ~nergized, the temperature increa~a~ quickly ~ince th0re is no "real flow" and tha value oP the first chamber temperature becomes higher than the ~econd chambsr tempera-ture.
The control system again evaluates thl~ temperature di~ersnce between the ahambers and datermines there i~ no flow and the inltial set temperature polnt i9 re~toredO
The foregoing disclo~ure ~nd descrlptlon of the inventlon are illustrative and explanatory thereof, and various chan~e~ in the size, shape and materials used, as well as the detail3 of the illustrated constructlon, including lmprove~ents, may ba made without dsparting ~rom the spirit of the invention and are contemplated as following within ths scope of the appended clalms.

SU2~TI I L3TE S~EET
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Claims

WHAT IS CLAIMED

1. A heater apparatus designed for heating of a continuous flow of fluids therethrough comprising one or more modular housings disposed in serial fashion, each of said housings constituting a modular apparatus comprising:
(a) a first chamber and a second chamber each for the receipt of a flow of fluid therethrough and wherein the flow of fluid enters the first chamber at one end and exits it at the other end whereupon it enters the second chamber at one end and exits at the other end;
(b) a first temperature sensing means operably disposed in the first chamber for measuring the temperature of fluid therethrough and a second temperature tensing means operably disposed in the second chamber for measuring the temperature of the flow of fluid therethrough, and means for comparing the temperature of fluid flow in the first chamber against the temperature of fluid flow in the second chamber;
(c) a heating element disposed in each of said chambers operably keynoted to said means for measuring the temperature of the flow of fluid through each said chamber and for comparing the differences in temperature therein;
(d) means for energizing each of said healing ele-ments selectively;
(e) temperature set means operatively connected to each of said heating elements for the separate actuation thereof; and (d) electronic means coupling each said temperature measuring means to said temperature set means so that each of said heating elements are selective-? PCT/US91/08849 ly energized when the temperature of the flow of fluid in either of the chambers is lower than the temperature set means.

2. The heater apparatus of claim 1, wherein the number of said modular housings is determined by the predicted volume of fluid flow such that a larger quantita-tive fluid flow requires a theater apparatus having more modules than a predicted lower volume of fluid flow, each of said modules connected serially to the preceding modules and wherein each of said modules comprises first and second chambers having healing elements therein operably connected to temperature sensing and energizing means.

3. The heater apparatus of claim 2, wherein at least one of said chambers is characterized by venting means for releasing entrapped air or gases there within.

4. The heater apparatus of claim 3, wherein each of said chambers is characterized by an interior epoxy coating for minimizing deterioration therein resulting from contact with the fluid and an exterior coating for reducing the loss of heat from within and thereby enhancing the imperme-able character of the module.

5. The heater apparatus of claim 4, in which at least one of said chambers is characterized by a drain means in the bottom thereon which includes a removable plug for facilitating cleansing of the interior chamber.

6. The heater apparatus of claim 1, wherein the means for energizing the heating elements comprises means for energizing the heating element immediately proximate fluid departing the last module when the temperature of the fluid is below that which is desired and wherein said means for energizing aid healing element proximate the departing fluid in the last module continues to heat the fluid until a preset predetermined temperature is reached.

7. The heater apparatus of claim 1, wherein the means for energizing the heating elements comprises means for energizing the heating element immediately proximate the fluid entering the first module when the temperature of the fluid is below that which is desired and wherein said means for energizing said heating element proximate the entering fluid in the last module continues to heat the fluid until a preset predetermined temperature is reached.

8. A heating apparatus for healing a flow of fluid while it continuously travels therethrough one or more modules, each of said modules being characterized by a first and second chamber in which a heating element is disposed, the improvement comprising:
(a) electronic control means operatively coupled to each heating means in each chamber and to a temperature sensing means disposed at the entry to the first chamfer and the exit of the fluid from the healing apparatus soas to sense the temperature of the fluid passing thereby at each location and for energizing each of said healing means selectively when the temperature of the fluid at the entry to the first chamber is less than a predetermined temperature or for energiz-ing the heating means at the exit of the fluid from the heating apparatus when the temperature thereof is less than the predetermined tempera-ture.

9. The heater apparatus of claim 8, wherein a flow volume detection means is operatively connected to the heater apparatus for measuring the fluid volume flow therethrough and including temperature sensor means at each of two positions in the heater apparatus for detecting a differential in temperature therebetween to thereby ? PCT/US91/08849 a certain the existence of flow within the apparatus.

10. The heater apparatus of claim 8 wherein the heater apparatus includes temperature sensing means of the fluid departing each chamber and in which the temperature sensing means is operatively coupled to a temperature set means such that the temperature sensing means energizes the heating clement in the departing chamfer until the fluid departing the chamber reaches a temperature equivalent to the temperature required by the temperature set means.