US2742881A - Water heater control - Google Patents

Description

April 24, 1956 Filed Aug. 8, 1950 J. C. RIDEOUT ET AL WATER HEATER CONTROL 3 Sheets-Sheet l NVENT R J C/P/ 6; 7

April 24, 1956 J. c. RIDEOUT ET AL 2,742,881

WATER HEATER CONTROL 3 Sheets-Sheet 2 Filed Aug. 8, 1950 INVENTORJ JCfi/aeoaf BY j d/e April 24, 1956 J. c. RIDEOUT 5- AL 2,742,881

WATER HEATER CONTROL Filed Aug. 8, 1950 3 Sheets-Sheet 3 IN V 7' 15. 007

BY KIA .57 a /e V siy @1551? Fig. 1. V

i 16 sho a hsmet sm tsi a tam titan f the r mt in en ion United States Patent- 2,742,881 ER HEA E CQ IRQ Jerry c. Rideout and John K.. Sidgile, colum us, o io,

T i invention rela es to alutomafis sontrolsy tems fo 'l eaters for hea ing a he t bzk 'haiige fli In SiI Qh 'pio ifi'e (11 11 2 115 fo .fety witch to stop the Is o ni-E; .circulatingp fip p t mperature {111 ig biistiop the iel has by stored fiai} tion'f he fluid circulatin pump mg h 'easd u iitid heat parts of th lim an "This invention, 'iijakes thes function w h 8 s pnovide a novellgmd sam e v ce r a e nsid. zio of'what w isye o e n v l and ou n sni mi fiiin cted t9 the io l w ng specifica i n audibl a ms b'p' vdl h e o- In' the acoiiipzinying' specifi.cation,

Fig 1 shows a press sectional yiew 9 2; water heater which the preseht'in eliti g is applied in it P eferred Fig-2 i l t tmtes on feiqments itfithe wait boil-fluid be ng heated, i i j -f e rer rm n 9f pment han he eto o e and pe haps alternat arrangeme t o thei'mal X ea .bf i V- fig- 3 s1: ,s vfs,- with ot e -I flawed, gombinati fsty Switch Us?! in Fi-s- 1 v -s n;=.' 10 the s m system illustrated-in Fig. :4. v i

Fisa S l i sqntml d a am s ppl ed to izi th wtiibi atien af ty e Pmi w Of s 1 l wit h 955%" v w i m edifisat n tth dia am of Fi 0 the mal lements 182? used niliw 2f the at s t m a co in to utiliz ng mqqnventional. I-time de1ay,s e. y.swith, .c mxn o nIy known as a warp switch.

- of he as mmnyi -diiaw ng a he l 38 Q1 outer sh ll 1!! Mo toxin an-annu a tlei the sl iell :11. An outer head ,foi r s with the ou ter Side of d aw ng oi i iw p h ti Ph -W 2? .nd YQ d coo ing the mb stion econ mi al sy tem or, h

#114 an tin-1192' V A thermostat 21 is disposed in the wgte system, shown wh xsb i m y ontrol th f l 71y t a burn r to main ain d s -md a e t mpe a- A som nat qn safe ycont w h 1 s hown in F g 1 w th it the ma s u -M1 930 Extending nto he coinbustion gas conduit 23 to a point Within the annular Wai t hambq With hthtna1elemsntfiqsploqa it is t pt iye to the amb' nt tem e ature of the water i n Lair Water cha of g ses -th u h-ih com ust n as QQIldHit 2?:- I w f soul be? und isw d tha s ne the wmbii tion 'climh t s ubstanti l y su ro t sledhy th an lar water lis m -fi' it w l no ma ly 26s th s y lq fimpfirature .4 asqs Pass n th o h he conmm 2.3 t i y BIQJithfl bat; ue to sqm s o of fuel, th reby :tfind g to fux hi he t he t erm l lement .39, orf old endi t9 9! 81 th rmal l m n 30 and. whoh air bi y ti'l b iiiss a ed o pi u l f om he .gb busfi hich a nbe r.

i e m n 30 subst ntia ly i Il a. the ma e emen :30 s hus e t nsivs t h emi arat c of as s in he hen ase m flow t th co i an is 5y 'tesmpsiv t9 th t mpexat t of .t heater, Qr'd 'livater vsat d whe gases t o owin the omiui i g 3 th eombi tat mz saf t qontno w ch n is shown with covs i t mo s out in rca er detail, Th fma e emen 39 qmpi s s a spi a el m nt 32. m1 ma 3. T e spix c em t 32 3 s cured it metnbs '35 hro gh a s ou d r 35 an 13 :36 Ih iti z of t e sp al e eme t :2 ay li'glian t t us u n n Q- and p ra y mo ed by rod Ju QQW -Ih' m ptest w th nne r sk the WS .7

i m d-t Ad ustme t 9 the ca b at on p sa yls i ch 4A i :aswmp sh through iu ting 411, Upon ea h sa ety switch, w on aifi at 41054151 m e e a id the a overrun rswi qh 4 op n-t e a a i e im e mis- Qi coolin itw he neg ssa y o the Q cmm wit tg ee-t ig for oyeiztrayei t9 ,aocgmmodaie .ope r at of the safety syyitg t 2 1 flirth r position or. arm 42. This overtray elrti 0,9 might, outsqb b I g; third" switch,

the am) 42Qgs e d vis ion oi able bolt 41' 'by t re; tsg i ng or the lix s w? a hrew w tes? mbe f'iml s t is af e ed by when 39 a es ar flow g ou h t in t s o s infimge switch 46 may also be attached to the frame member 34 to be actuated by the thermal element 30 through adjusting screw 39. This switch 46 will be adjusted to break contact above a maximum temperature such as 400 deg. F., acting as a safety switch and a positive fuel shut-off. Thus loss of water from the circulation system will not cause damage by subsequent overheating of the apparatus.

In Fig. 2 an alternate design is shown to that of Fig. 1 wherein the function of the combination safety control switch 31 is performed by two separate switches, a stack switch 22 located in the fiue gas exhaust conduit 231 and sensitive only to temperatures of combustion gases and a safety switch 24 disposed within the annular water chamber and extending into the combustion gas passage 23 whereby it is responsive to water temperatures unless it is adversely affected by gases in the gas passages. In this modification the thermal element 96 of the safety switch 24 responds to the same conditions as does the element 30 of the combination safety control switch 31 as shown in Fig. 1.

In Fig. 4 a control diagram is shown as adapted for the apparatus illustrated in Fig. 1, thermal element 30 being the same element as 30 of the combination switch 31, further illustrated in Fig. 3. Element 30 is adapted to operate fan overrun switch 43, safety switch 44 and overheat switch 46.

A master switch 51 is connected by a lead 52 to a battery 50 the other terminal of which is connected to ground. Master switch 51 connects by lead 53 to a push button starter switch 54, the contact 55 of which is directly connected by leads 56 and 57 to the thermostat 21. The thermostat 21 is designed to make contact at 150 deg. F. and to break at 165 deg. F., so when it is cold, below 150-165 deg. F., it is closed and calling for heat, making its contact 60. Lead 66 connects contact 60 to the cold contact 67 of the fan overrun switch 43. Cold contact 67 of the fan overrun switch 43 is connected to switch 46 by lead 68, and lead 63 connects switch 46 to a fuel pump 64 and ignition means 65 such as the spark plug 19 shown in Fig. l. The center, or pole, contact of the switch 43 is connected by lead 70 to the coil 71 of a relay 72 and thence to ground. The relay 72 is connected by lead 73 to the battery 50 and by lead 74 to a water pump 75 and a combustion air blower 76 whereby to operate the water pump 75 and the blower 76 when the relay coil is energized. The hot contact 80 of the fan overrun switch 43 is connected by lead 81 to the battery 50. Thus when the thermal element 30 of the combination switch 31 is colder than 210 deg. F., the adjustment temperature of the fan overrun switch 43, and the thermostat 21 calls for heat, i. e., is in the cold, closed position, the coil 71 of the relay 72 is energized. When the thermal element 30 moves the switch 43 to its hot position, a maintaining circuit is closed from the battery 50 directly to the coil 71, and the water pump 75 and the blower 76 will continue to operate independently of the thermostat 21.

At a fan overrun switch 43 setting of 210 deg. F., the fan operates long enough after the fuel is shut off by the thermostat 21 to purge unburned fuel from the combustion chamber and to avoid boiling the water by residual heat in the heater. The heat storage of the combustion chamber may be proportioned to the volume of surrounding water so that there is no danger of boiling. The control temperature of the fan overrun switch, 210 deg. F., gives about 2 minutes purging of the combustion chamber which is adequate for the apparatus of Fig. l.

The thermal element 30 is also adapted to operate the safety switch 44 at a relatively low temperature, 140 deg. F. A lead 79 connects the pole contact of the safety switch 44 to the master switch 51. The cold contact is connected by a lead 82 to a failure light 83.

In operation of the controls of Fig. 4, starting from cold, the master heater switch 51 is first closed. As the thermal element 30 is in a position colder than 140 deg. F., the failure light 33 is energized. The push-button starter switch 54 is depressed and makes a circuit through thermostat 21, overheat switch 46, and to fuel pump 64 and the ignition device 65. A circuit is then also closed through the thermostat 21, and the cold contact 67 of the fan overrun switch 43 to the energizing coil 71 of the relay 72 and thence to ground, closing the relay and thereby closing a circuit from the battery 50 to the water pump 75 and the combustion air blower 76. As ignition takes place and the fuel burns, the thermal element 30 will be warmed to above the 140 deg. F. point in 15 to 20 seconds by the combustion gases and the safety switch 44 will move to its hot contact, whereby the starter switch 54 is by-passed, maintaining the circuit to the thermostat 21. As the safety switch 44 leaves its cold contact the failure light 83 is extinguished. If the failure light is not extinguished within a few seconds, the operator will release the starter button 54, thus deenergizing the entire system except the failure light, in order that he may take the proper steps to correct the ignition troubles, such as cleaning and adjusting the ignition device, obtaining fuel, cleaning the fuel nozzle, replacing refective motors, and the like. The operator releases the starter switch 54 when the failure light is extinguished, after which the system operates automatically. When the temperature of the water as sensed by the thermostat 21 reaches 165 deg. F., the thermostat breaks the contact 60 and therefor breaks the circuit to the fuel pump, the ignition, and the cold contact 67 of the fan overrun switch 43, and thereby also to the coil 71 of the relay 72. Normally the thermal element 30 is above 210 deg. F. after combustion, and the fan overrun switch will be at its hot contact which maintains the circuit through the relay coil 72 and therefor to the water circulating pump and the combustion air blower. Thus the water pump and the blower continue to operate until the thermal element 30 drops to below 210 deg. F., at which point the fan overrun switch 43 moves to the cold contact and stops the water pump and the blower, provided the thermostat 21 is still in the hot position and not calling for heat. Alternatively, the water pump 75 may be controlled independently by a thermostat in the space heated by the heat exchanger 27.

When the system of Fig. 4 is operating and on control and the thermostat 21 cools to 150 deg. F. and closes the contact 60, calling for heat, if for some reason the fuel fails to ignite, the combustion air blower and the fuel pump deliver air and fuel to the combustion chamber and rapidly cool it, cooling the thremal element 30 to a failure position below 140 deg. F. in less than 90 seconds. The water circulating pump also circulates cooler water to the combustion chamber, tending to cool it.

In Fig. 5, a modification and simplification of Fig. 4, stack switch 2 and safety switch 24 each have their own operating thermal elements 95 and 96. These switches perform the same functions insatlled according to Fig. 2 as the combination switch 31 in Fig. l, and for that reason safety switch 24 in Fig. 2 is the equivalent of safety switch 44 and stack switch 22 is equivalent of fan overrun switch 43. Limit switch 62, normally closed, is substituted for overheat switch 46 and may be operated in any suitable manner.

In Fig. 6 a control is shown which utilizes a conventional time delay, or warp, switch instead of the safety switch and starter switch combination of Fig. 3. when the main heater switch 51 is closed, and the system is cold, a circuit is closed from the battery 50 through the heater 93 of the warp switch 85 and through the thermal element 30 to ground. At the same time a circuit is closed through the warp switch contact 87 and the thermostat 21 to limit switch 62 and thence to the ignition device 65 and the fuel pump 64, and also a circuit from the thermostat 21 which leads to the cold contact 90 of a fan overrun switch 91, which is operated by the thermal element 30. The pole contact 94 of the fan overrun switch 91 is connected to the energizing coil 71 of a relay 72 and thence to ground. The hot contact 92 of the fan overrun switch is connected directly to the battery 50. One contact of the relay 72 is connected to the battery and the other through a combustion air blower 76 to ground. If a failure light 83 is desired a second contact is built into the warp switch 85, normally open, which will close when the heater element 93 of the warp switch causes the main circuit through the thermostat 21 to break.

In operation of the system of Fig. 6, when the unit is started by closing the main switch 51 the heater starts switch 85 becomes hot enough to break the fuei and ignition circuit. Then further operation warms the unit until the thremostat 21 exceeds 165 deg. F., at which time it breaks the circuit to the ignition 65 and the fuel pump 64 and to the cold contact 90 of the fan overrun switch 91. When the thermal element St) rises to 210 deg. or above, the fan overrun switch is then in a hot position and closes a maintaining circuit through contact 92 and the relay coil 71, thus keeping the water pump and the air blower operating until the fan overrun switch 91 again moves to the tion, at which time the thermostat 21 again takes over control of the fan 76 and the water pump 75.

It will be observed that in Figs. 4 and 6, the thermal element 30 is sensitiveto flue gas temperature, or when there is no flue gas, to the temperature of the water wall" of the annular water chamber. It is therefore able to do a multiple job. In Fig. 4 it eliminates the warp switch and the stack switch (using a push button starter switch) and it performs their functions, also serving as a fan overrun, or purge, switch and as an overheat switch. In Fig. 6 the thermal element serves as a stack switch, operating with a warp switch, and'also serves as a fan overrun, or purge, switch.

In Fig. 5 two thermal elements are used instead of the one as shown in Fig. 4, and one of them, that of the safety switch 24, is placed in such a manner as to make it sensitive to water temperature when no gases are af fecting it. This provides a basis for using the minimum water temperature as a control point in a burner safety circuit rather than a conventional warp switch. Since the water temperature is controlled from the thermostat, when it cools below the control point, such as 150 deg. F., it calls for heat from the burner and starts the combustion air blower and the water pump. If ignition fails, the air or the fuel rapidly cools, or water lessv rapidly cools, the thermal element 96 of the safety switch 24 and moves the switch to a failure position.

This safety feature in the circuits of Figs. 4 and 5 which shuts down the unit upon failure of ignition during operation is the equivalent of the disconnect operation of the warp switch 85 of Fig. 6 when the heating element 30 is cooled and closes the circuit to the warp switch heater element 93.

Upon starting from cold when ignition does take place the combustion gases will heat the thermal element of the safety switch very rapidly, while the water is just getting warm, and the resulting maintaining circuit will hold until the water temperature rises above the setting of the safety switch to that of the thermostat. This is a more rapid and positive control than a time delay, or warp switch, and for this reason the circuits of Figs. 4 and S are preferred over that of Fig. 6.

What is claimed as new is: V

1. In a liquid heater, in combination, outer and inner concentric circular walls and spaced end walls at one end of said concentric walls forming between them a liquid chamber including an annular portion and an end portion, and forming within said inner wall a combustion chamber for heating the liquid, means comprising a cold posi- V inner wall, duct means next adjacent the burner end of the flue gas discharge passage forming an exhaust port for flue gas from the annular flue gas discharge passage, means comprising a fuel pipe for supplying fuel to the burner, blower means for supplying a stream of combustion air to the burner, a liquid inlet and a liquid outlet for the liquid chamber, means for recirculating a stream of liquid to be heated through the liquid inlet, liquid chamber, and liquid outlet, a first thermostat in the liquid stream operably-connected to start or stop the liquid circulating means, the blower means and the fuel supply means when the first thermostat is below or above a control temperature, respectively, a thermostat well in the liquid chamber and facing the dry wall, a second thermostat in the well and extending into the annular flue gas discharge passage whereby it is responsive to the temperature of gas when gas is flowing in the discharge passage, and is responsive to the temperature of liquid in the liquid chamber when no gas is flowing in said discharge passage, the second thermostat being operably connected to the fuel supply means to prevent supply of fuel to the burner thereby when it is colder than a first temperature below the control temperature, and being operably connected to the liquid recirculating means and to the blower means to maintain operation thereof when it is hotter than a second temperature which is higher than the control temperature.

2. In a liquid heater, in combination, outer and inner concentric circular walls forming between them an annular liquid chamber for liquid to be heated and forming within said inner Wall a combustion chamber for heating the liquid, means comprising a burner for c1osing one end of the combustion chamber and burning fuel therein, a closure for the other end of the combustion chamber; a circular dry wall extending from the burner end of the combustion chamber to short of the closure and dividing the combustion chamber into a central combustion zone and an annular flue gas discharge passage between the dry wall and the inner wall, duct means next adjacent the burner end of said annular passage forming an exhaust port for flue gas from said annular flue gas discharge passage, means comprising a fuel pipe for supplying fuel to the burner, blower means for supplying a stream of combustion air to the burner, a liquid inlet and a liquid outlet for the liquid chamber, means for recirculating a stream of liquid to be heated through the liquid inlet, liquid chamber, and liquid outlet, a first thermostat operably connected to start or stop the liquid circulating means, the blower means andthe fuel supply means when the first thermostat is below or above a control temperature, respectively, a thermostat well in the liquid chamber and facing the dry wall, a second thermostat in the thermostat well and extending into the annular flue gas discharge passage whereby it is responsive to temperature of gas in the discharge passage when gas is flowing, and is responsive to the temperature of the liquid in the liquid chamber when gases are not Howing in the discharge passage, the second thermostat being operably connected to the fuel supply means to normally prevent supply of fuel to the burner thereby when it is colder than a first temperature below the control temperature and being operably connected to the liquid recirculating means and to the blower means to maintain operation thereof when it is hotter than a second temperature higher than the control temperature.

3. The combination according to claim 2 wherein the second thermostat is operably connected to the fuel supply means to prevent supply of fuel to the burner when

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