US3780261A - Automatic control for electrode boilers - Google Patents

Automatic control for electrode boilers Download PDF

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US3780261A
US3780261A US3780261DA US3780261A US 3780261 A US3780261 A US 3780261A US 3780261D A US3780261D A US 3780261DA US 3780261 A US3780261 A US 3780261A
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boiler
water
feed
electrode
drain
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Williams R Eaton
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Eaton Williams Group Ltd
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F22—STEAM GENERATION
    • F22B—METHODS OF STEAM GENERATION; STEAM BOILERS
    • F22B1/00—Methods of steam generation characterised by form of heating method
    • F22B1/28—Methods of steam generation characterised by form of heating method in boilers heated electrically
    • F22B1/30—Electrode boilers
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F22—STEAM GENERATION
    • F22D—PREHEATING, OR ACCUMULATING PREHEATED, FEED-WATER FOR STEAM GENERATION; FEED-WATER SUPPLY FOR STEAM GENERATION; CONTROLLING WATER LEVEL FOR STEAM GENERATION; AUXILIARY DEVICES FOR PROMOTING WATER CIRCULATION WITHIN STEAM BOILERS
    • F22D5/00—Controlling water feed or water level; Automatic water feeding or water-level regulators
    • F22D5/24—Controlling water feed or water level; Automatic water feeding or water-level regulators with electric switches
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T137/00—Fluid handling
    • Y10T137/7287—Liquid level responsive or maintaining systems
    • Y10T137/7306—Electrical characteristic sensing

Definitions

  • ABSTRACT May19197l Great Britain u 1 5386/71 An electronic controller for an electrode boiler in Mar. 10, 1972- Great Britain 11,287/72 which the heating Current Passing through an electtode depends upon the water level in the boiler, in 52 us. 01 219/324, 122/382, 137/392, which circuitry eehtrels feed and drain valveS to carry 219 271 219 234 out an automatic repetitive cycle to feed water into [51 1m. F24h 1/00 the boiler to a predetermined level, to sense.
  • This invention relates generally to automatic controls for electrode boilers, and more particularly to a control for a boiler in which the water is boiled so that the steam given off may be used in an air conditioning systern.
  • Such boilers are sometimes referred to as humidifiers.
  • the type of boiler with which the invention is concerned may be of any shape but is conveniently cylindrical, with its axis vertical, and having a height greater than its diameter.
  • the boiler has a steam outlet pipe at the top and aconnection at the bottom, which may serve both as a water inlet and a water outlet. This has an advantage over separate inlet and outlet connections in that each inrush of supply water will clear'the passages of any lodged solids, thereby leaving these passages clear when the boiler is drained.
  • a filter may be incorporated in the boiler, so placedthat inlet and outlet water must pass through it.
  • the boiler contains water heating electrodes arranged vertically and extending over most of the height of the boiler. The arrangement of the electrodes may be varied in dependence upon whether the boiler is provided with electrodes for single-phase or three-phase operation.
  • the control valves normally comprise one electrically controled (that is, solenoid operated) feed water valve and one electrically controlled drain valve which when the boiler has a common inlet and outlet connection, may be connected to the two sides of a T-junction the central branch of which is connected to the boiler.
  • the electronic controller which is the subject of the invention is arranged to detect the magnitude of the electrode current and to operate the feed valve and drain valve in relation to predetermined sequences and in dependence upon the magnitudes of changes in electrode current.
  • the controller is also arranged to detect the point at which electrode maintenance is necessary.
  • an additional electrode which will be referred to as the boiler full sensing electrode is desirably installed in the boiler.
  • the invention consists of an electronic controller for an electrode boiler in which the heating current passing through an electrode depends upon the depth of im-' mersion of the electrode and hence upon the water level in the boiler, comprising circuitry to operate an electrically controlled feed valve to allow feed water to enter the boiler, first sensing means in the circuitry to detect when the electrode current has risen to a predetermined normal level, means responsive to the first sensing means to cause the feed valve to be closed, whereupon the water is allowed to boil, second sensing means to detect when the electrode current has fallen to another predetermined level due to loss of water boiled away, andmeans responsive to the second sensing means to initiate a desired sequence of steps includto cause an electrically controlled drain valve to be opened whereupon water is allowed to drain from the boiler, the circuitry also comprising third sensing means to detect when the electrode current falls to another predetermined level due to loss of water drained from the boiler, and means responsive to the third sensing means to cause the drain valve to be closed and the feed valve to be opened, whereupon feed water is again allowed
  • the means responsive to the second sensing means comprises means to re-open the feed valve
  • the circuitry comprising also further means responsive to the first sensing means to cause the feed valve to be closed and an electrically controlled drain valve to be opened when the electrode current has again reached the predetermined normal level, third sensing means to detect when the electrode current has fallen to a further predetermined point, and means responsive to the third sensing means to cause the drain valve to be closed and the feed valve to be re-opened, the first sensing means and the means responsive thereto causing the feed valve to be closed when the electrode current has again risen to the pre-- determined normal level so that boiling may recommence, the circuitry being arranged to carry out the feed, boil, feed, drain cycle repetitively.
  • Additional circuitry may be provided to sense whe the electrode current has risen by a predetermined amount above the predetermined normal level and to open the drain valve allowing water to drain from the boiler until the electrode current has fallen to a value near to the predetermined normal level when the additional circuitry closes the drain valve and permits the continued operation of repetitive cycles of feed, boil, drain as already described.
  • Additional circuitry may also be provided to sense when the boiler becomes overfilled and to close the feed valve and if required to initate an alarm signal.
  • Means may also be provided to vary the quantity of water drained away in relation to the amount boiled away during each cycle of operations so that this may be greater, equal or lesser as required.
  • the electric supply to the electrodes is switched on. Initially, since the boiler is empty, no electrode current flows and the controller opens the feed valve while the drain valve remains closed. Water therefore passes into the boiler and as the water level rises the electrodes become progressively more deeply immersed so that the electrode current progressively rises.
  • the controller causes the feed valve to close. The water is then heated due to the passage of current between the electrodes. As the water temperature rises the conductivity of the water may increase and in addition the level of the water in the boiler may rise due to expansion. Consequently the electrode current increases and when it rises to a predetermined level above the operating point current, usually about of the operating point'current, the controller opens the drain valve so that the water level in the boiler falls.
  • the controller causes the drain valve to close.
  • the drain valve may be operated several times in order to keep the water level at approximately the desired point.
  • the boiling point is reached, boiling continues and the water level is progressively reduced as water is boiled away, resulting in a progressive reduction of the electrode current as the electrodes become less deeply immersed. This continues until the water level has fallen to the point where the electrode current is reduced to a magnitude which will be referred to as the boiling period lower limit currentto which is chosen to be at a value of approximately 80 percent of the operating point current.
  • the controller causes the drain valve to open and water drains from the boiler so that the electrode current falls as a result of the progressively decreasing immersion of the electrodes.
  • the controller closes the drain valve and opens the feed valve. Fresh water again enters the cylindeand the electrodes become progressively more deeply immersed until the operating point current is again reached, at which point the controller closes the feed valve and, with both feed and drain valves closed, another period of boiling takes place. The successive operating cycle of feed, boil, drain as described above is continued.
  • the operations of feeding and draining take place in a comparatively short time depending on feed water pressures and other conditions whilst the operation of boiling may take place in a comparatively longer time.
  • These three successive operations constitute the water purification cycle and the object of draining water away is to allow solids, previously dissolved in the water and precipitated as the water is boiled away, to be drained out.
  • the result is that, with a water supply containing a given amount of dissolved solids, the life of the boiler and electrodes, before they become so furred up as to'require major maintenance, is very considerably lengthened.
  • the amount of water normally drained away is equal to the amount of water which is boiled away during a boiling period but, as will appear later, the amount drained away may be considerably more or less than the amount boiled away depending upon the amount of purification which is desired.
  • the boiler actually used may be of a type which is constructed in a very inexpensive manner so that when it and the electrodes become thoroughly furred up the whole boiler may be thrown away and replaced by a new one.
  • the electrodes After a long period of normal operation the electrodes gradually become furred up or'coated with scale and this reduces the conductivity of the immersed parts of the electrodes so that a greater depth of immersion becomes necessary in order to reach the desired operation point current. This will continue until it eventually becomes impossible to achieve the operating point current even with the electrodes totally immersed and this would cause the feed valve to remain open and allow the boiler to fill itself completely and overflow through the steam outlet.
  • the boiler is preferably provided with a boiler full sensing electrode.” This electrode extends downwardly from the top of the boiler to a point which is selected as the highest permissible water level. When the water reaches this electrode the controller causes the feed valve to close and also illuminates a warning lamp to indicate that the electrodes require maintenance.
  • the boiler will continue to operate by preventing the water level from exceeding that set by the boiler full sensing electrode even if the normal operating point current is not reached. The operating cycle will then continue but with the maximum electrode current achieved becoming progressively less. The steam output will also be progressively reduced until electrode'maintenance (or replacement of the whole boiler) takes place.
  • FIG. 1 shows the circuit of a controller to operate the boiler automatically and repetitively in a feed, boil, drain cycle
  • FIG. 2 shows the circuit of a controller to operate the boiler automatically and repetitively in a feed, boil, feed, drain cycle.
  • FIG. 3 shows a part of the top of a boiler to be operated by a controller according to the invention, illustrating a current transformer having its primary winding connected in series with the power feed to one of the electrodes;
  • FIG. 4 shows an additional boiler full" sensing electrode inserted in the boiler.
  • circuits will be set out on printed circuit boards and the terminals of the boards are indicated at the left hand sides of thedrawings.
  • a transformer (not shown) having its primary winding connected to the supply mains and having a secondary winding to provide an output of 22 volts r.m.s., the secondary winding being connected to terminals 10 and 11.
  • the transformer secondary voltage is applied to a full wave rectitier MR1 and the output is fed through a'resistor R2 to a reservoir capacitor C2 and thence through a resistor R5 to a pair of Zener diodes ZD2 and ZD3 in series to provide stabilised, smoothed power supplies of 12 volts and 6 volts d.c.
  • a small capacitor C4 is connected in parallel with the Zener diodes for transient suppression purposes.
  • FIG. 3 shows a part of the top of a boiler casing 41 having two heating electrodes, respectively 42 and 43, connected respectively to power feed lines 44 and 46.
  • Line 44 is connected to one end of the primary winding 45 of a current transformer generally indicated at 47 the other end of the primary winding being connected to the power line feeding the electrode 42.
  • the current transformer 47 has a secondary winding 48 which is connected to terminals 7 and 8. A typical ratio for this current transformer would be -1, so that the secondary current passing the terminals 7 and 8 will be approximately one one hundred fiftieth of the electrode current.
  • variable resistor Also connected between terminals 7 and 8, but not shown on the drawing, is a series combination of a fixed resistor and a variable resistor which provide a load for the secondary winding of the current transformer.
  • the setting of the variable resistor therefore, determines the level of the electrode current at which certain predetermined control voltages are developed across the secondary winding of the current transformer.
  • the arrangement may be such that when the detecting circuitry detects that the operating point current has been reached the electrode current may be about 15 amperes when the variable resistor is 'set at minimum resistance.
  • the voltage applied to terminals 7 and 8 is passed to a full wave bridge rectifier MR2 and the output of this rectifier is fed through a resistor R1 to a smoothing capacitor C1 having a voltage divider R3 and R4 connected in parallel therewith. Also connected in parallel with capacitor C1 is a Zener diode ZDl.
  • Capacitor C1 and resistor R1 together with loading resistors R3 and R4 provide a smoothing circuit having a time constant sufficient to even out the short term fluctuations of the electrode current, such as may be caused by bubbling or water turbulence in the boiler. Such short term variations could result in random and erratic operation of the control circuits and consequently of the feed and drain valves.
  • the voltage developed across R3 and effectively applied as input voltage to the sensing circuitry would be two-fifths of this voltage, corresponding to 4 volts d.c.
  • the Zener diode ZDl is provided to limit the maximum voltage which-can be developed across this circuitry under fault conditions or any other condition of rapid change of electrode current, and it therefore prevents any possible damage to the control circuitry.
  • the control voltage as developed across R3 is applied to the inverting inputs of three differential comparator integrated circuits [C1, IC2 and 1C3.
  • the non-inverting inputs of these three integrated circuits are set at varying points on a chain of potential divider resistors between the +l2 and -6 voltage supplies, such that the outputs of these integrated circuits will change state at different values of input signal.
  • One form of such rectifier is known as a triac.
  • the flow of current from the gate GRl to the collector of 02 causes GRl to become triggered and consequently the live mains supply connected to terminal 6 is passed through OR! to terminal 2 which is connected to the feed valve (not shown) which now opens.
  • the output of 1C2 will be in the negative condition causing transistor n-p-n O3 to be switched off” and permitting base current to flow via resistors R39 and R40 into the base of n-p-n transistor ()4 which will become switched on”.
  • the collector current of Q4 will be drawn through the gate circuit of bi-directional gated rectifier GR2 which, when p-n-p transistor O7 is in the off" condition, would cause GR2 to be triggered and the mains supply connected to line 13 is passed through GR2 to terminal 1 which is connected to the drain valve and would cause this valve to open.
  • transistor 02 is in the on condition, causing base current to be drawn through resistors R31 and R33 from the base of transistor Q7 which causes O7 to be switched on, effectively short circuiting the gate circuit of gated rectifier GR2 and preventing GR2 from becoming triggered.
  • both feed and drain valves will be closed but the electrode current will rise due to the increasing conductivity of the water as its temperature rises and also due to expansion of the water causing deeper immersion of the electrodes.
  • Such rising electrode current above operating point current will cause the voltage developed across R3 to exceed that corresponding to the operating point current and typically at about 110% of the operating point current it is arranged that the voltage applied to the inverting input of integrated circuit [C3 will pass the biasing voltage applied to the noninverting input of lC3. This will cause the output of lC3 to change from the negative to the positive condition and hence base current will flow through R46 into the base of n-p-n transistor 05, causing O to be switched on.
  • R37 and R45 will be so chosen that as the current falls to approximately the operating point current, integrated circuit lC3 will again change state andits output will become negative, thus applying negative bias to transistor Q5. Transistor Q5 will therefore be switched off and gate current will cease to flow into the gate of gated rectifier GR2 which will cease to be triggered and permit the drain valve to close. During the heating period of cold water to boiling point several successive operations of the drain valve in this manner may take place.
  • the hysteresis circuit is also applied to integrated circuit lCl, comprising resistors R13, RVl and R16.
  • This hysteresis circuit will have caused the biasing voltage applied to the non-inverting input of [C1 to be changed to a value corresponding to typically between 40 percent and 70 percent of the operating point current according to the setting of potentiometer RVl.
  • the circuit values associated with [C2 will have been selected such that the drain valve opens on falling electrode current as described above at approximately 80 percent of the operating point current.
  • a second result of 02 becoming switched on will be that base current flows into the base of transsitor 07 through resistor R33 causing O7 to be switched on and effectively short circuiting the gate circuit of gated rectifier GR2 resulting in the drain valve becoming nonenergized and closing.
  • This varies the amount of water drained from the boiler on each cycle and with the typical values given, this may be arranged to be anything between half the quantity which is boiled away (corresponding to a 70 percent setting) or double the quantity boiled away (corresponding to a 40 percent setting).
  • an additional electrode known as the boiler full sensing electrode is provided.
  • FIG. 4 shows the upper part of a boiler casing 41, similar to that of FIG. 3, showing the electrodes 42 and 43 with their respective feed lines 44 and 46.
  • the additional boiler full" sensing electrode is shown at 49 connected by a line 51 to terminal 12 of FIG. 1.
  • the electrode 49 is of such length that its lower end is at a level indicated in dotted lines at 50, which is the maxi mum level to which the boiler is to be filled; when the water rises to this level it comes into contact with the electrode, which then receives a potential lying between the neutral and live mains potentials.
  • the electrode In the three phase boiler it is convenient to arrange the electrode at a position equally spaced from the three phase electrodes and in this way its potential is close to that of the neutral line of the mains supply. In a single phase boiler it is convenient to arrange this electrode near to the neutral end of the heating electrode.
  • n-p-n transistors Q8 and Q9 are arranged in a circuit commonly referred to as a Schmitt trigger, together with associated resistors R21, R22, R27, R47 and R30.
  • the Schmitt trigger In the absence of input signals from C7 the Schmitt trigger is in the condition in which Q8 conducts and O9 is non-conducting.
  • the cylinder fullensing electrode becomes immersed a voltage is developed across capacitor C7 changing the state of the Schmitt trigger such that Q8 becomes non-conducting and 09 conducts.
  • Q9 conducts, gate current -'is drawn through the gate of bi-directional gated rectifier GR3, causing GR3 to become triggered and a mains live alarm signal to be passed to the boiler full output terminal 9.
  • Transistor Q6 then effectively short circuits the gate circuit of gated rectififer GRl, preventing GRl from being triggered and, therefore,.preventing opening of the feed valve.
  • the feed valve can be switched off" and boiling in the boiler continues until the water level has fallen to a point at which the boiler full sensing electrode is no longer immersed-At this point the Schmitt trigger comprising 08 and Q9 reverts to its original condition, with O8 conducting, and the feed valve is permitted to open. The boiler then refills until the boiler full sensing electrode again become immersed and this process continues repetitively.
  • the boiler full sensing circuit comprising C7, R14 and R15 is arranged to have an overall time constant such that when the feed valve is permitted to open slight-over-filling takes place, with the result that successive openingsof the feed valve take place at reasonable intervals of time, for example one to five minutes.
  • a manual control means is provided for this purpose.
  • a double pole single throw switch is provided and is connected to terminals 3, 4 and 5. When this switch is closed to connect terminal to terminal 4 line 13 is connected to the gate of CR1, thereby short circuiting the gate and preventing operation of GR], so that the feed valve is prevented from opening.
  • Line 13. is also connected via terminal 3 directly to the drain valve terminal 1 so that the drain valve is opened and the boiler is allowed to empty completely.
  • FIG. 2 shows the circuit of a controller which is arranged to carry out a slightly more elaborate cycle con-. sisting in four steps in the sequence feed, boil, feed, drain. The additional feed step provides extra purification since it is then possible to drain a larger quantity of water from the boiler, thereby removing a large quantity of solids with the drained water.
  • a transformer in conjunction with a rectifier MRI 1, resistor R54, capacitors C24 and C25 and Zener diode ZDl 1, provides a smoothed and stabilized dc. power supply equivalent to that described in connection with FIG. 1, except that it provides a single output at volts.
  • Terminals 23 and 24, equivalent to terminals 7 and 8 of FIG. 1, receive the output of the secondary winding of the current transformer, which is rectified and smoothed by MR12, R51, R52, C22, C23 and ZD12.
  • Terminals 25 and 26 are for connection of a variable resistor which, when connected, is in series with R21 across terminals 23 and 24 to provide a load as descriform of such rectifier is known as a traic.”
  • a traic The flow of current from the gate of GRll to the collector of Q12 causes GRll to become triggered and consequently the live mains supply connected to a terminal 27 and a line 29 is passed through GRll to a terminal 28 which is connected to the feed valve.
  • bistable multivibrator circuit which includes resistors R80, R79, R77, R78 and capacitors C30 and C31. Due to the pulse steering circuit constituted by capacitor C28 and diodes D17 and D18, this circuit changes its state each time the pulse steering circuit receives a pulse via capacitor C28. That is to say, the bistable multivibrator changes its state each time the electrode current rises to the operating point current.
  • the bistable circuit Since the bistable circuit is in the state in which Q19 is conductive the drain valve would also remain open and this condition is unacceptable, as the resulting water flowv into and out of the boiler would depend upon water pressures and water valve characteristics.
  • An additional circuit is therefore provided comprising a transistor 020 which will be referred to as the drain valve inhibitor transistor.
  • the collector of 012 is connected via R84 to the gate of CR1! and thence to the line 29.
  • the collector current When 012 is non-conductive the collector current is negligible and the voltage at the collector of Q12 is substantially at the same level as line 29, so that the current into the base of Q20 is minute and Q30 is nonconductive.
  • the circuitry so far described provides automatically the successive functions of feed, drain, feed, boil, feed, etc. which is desired.
  • the difference between the operating point current and the boiling period lower limit current depends upon the difference in voltage level at which the Schmitt trigger 012/013 triggers and reverts to its prevous state and is determined by the component values in circuit.
  • the difference between the operating point current and the drainperiod lower limit current is determined in the same way, the latter being approximately the same as the boiling period lower limit current. It follows that the amount of water boiled away during the boiling period is substantially equal to that drained away during the draining period.
  • a special circuit is provided for this purpose and is brought into operation when a connection is made by means of an on-off switch between two terminals 31 and 32.
  • the electrode current may rise above the operating point current during the warming-up period, when the conductivity of the water may incrase due to increasing temperature and its level may rise due to expansion. Circuitry is therefore provided to ensure that the increase in electrode current is not excessiv'e.
  • This comprises a further Schmitt trigger 014 and 015 with its associated components R69, R70, R66 and R56.
  • the component values of the 014/015 Schmitt trigger are arranged so that when the electrode current is within the normal operating range 014 is conductive and this condition is secured by base current flowing through resistor R66 into the base of 014.
  • a negative feed is provided to the base of 014 via a diode D4,
  • the Schmitt trigger 014/015 causes the Schmitt trigger 014/015 to change state so that 015 is conductive.
  • the collector current of 015 then flows through resistor R65 from the gate of GR12 so that GR12 is trig gered and the drain valve is opened.
  • the water level in the boiler is thus reduced to the level at which the Schmitt trigger 014/015 reverts to its normal state, when 014 conducts and 015 is non-conductive.
  • the GR12 trigger current is consequently cut off and the drain valve is closed.
  • the component values associated with the Schmitt trigger 014/015 are so selected that at the point at which the drain valve is closed the voltage across C23 corresponds substantially to that at which the electrode current is equal to the normal operating point current.
  • an additional electrode konwn as the boiler full sensing electrode is provided and is so placed that it only becomes immersed when the water level in the boiler has reached the maximum permissible level.
  • This electrode is so positioned in the boiler that when the water comes into contact with it the electrode receives a potential which lies between the neutral and the live mains potential. ln a threephase boiler it is convenient to arrange the electrode at a position equally spaced from the three-phase electrodes and in this way its potential is close to the neutral of the mains supply.
  • the collector current of 022 is drawn via a resistor R60 from the gate of a further gated rectifier GR13, so that GR13 is triggered and the live main line 29 is connected to a terminal 34 to energize a boiler full lamp or any other desired external warning device.
  • As 022 becomes conductive its collector goes negative with respect to the line 29 and current flows through a resistor R92 to the base of a p-n-p transistor 011 so that 011 becomes conductive.
  • the collector and emitter of 011 effectively short circuits the gate of GRll to the line 29, thereby preventing GRll from triggering so that opening of the feed valve is prevented.
  • Qll is referred to as the feed valve inhibiting transistor.
  • the boiler full sensing circuit comprising C31, R57, ZD13, C32 and R63 is arranged tohave an overall time constant such that when the feed valve is permitted to open slight overfilling takes place, with the result that successive openings of the feed valve take place at reasonable intervals of time, for example-1 to 5 minutes.
  • a double pole single throw switch is provided and is connected to terminals 35, 36 and 37.
  • line 29 is connected to the gate of GRl 1, thereby short circuiting the gate to line 29 and preventing operation of GRl 1, so that the feed valve is prevented from opening.
  • Line 29 is also connected directly to the drain valve terminal 30 so that the drain valve is opened and the boiler is allowed to empty completely.
  • An electronic controller for controlling, in accordance with a repetitive cycle, an electrode boiler in which the heating current passing through an electrode depends upon the depth of immersion of the electrode and hence upon the water level in the boiler, the controller comprising circuitry for initially operating an electrically controlled feed valve to allow feed water to enter the boiler, first sensing means in the circuitry to detect when the electrode current has risen to a level corresponding to a desired normal water level, means responsive to the first sensing means to cause the feed valve to be closed, whereupon the water is allowed to boil, second sensing means to detect when the electrode current falls to a level corresponding to a water level lower than the said normal water level due to loss of water boiled away, and means responsive to the second sensing means to initiate a desired sequence of steps including the opening of a drain valve to allow a quantity of water to drain from the boiler and the subsequent closure of the drain valve and the re-opening of the feed valve to allow the boiler to re-fill to the said normal level.
  • ahd means responsive to the third sensing means to cause the drain valve to be closed and the feed valve to be re-opened, the first sensing means and the means responsive thereto causing the feed valve to be closed when the electrode current has again risen to a level corresponding to the said normal water level so that boiling may recommence, the circuitry being arranged to carry out the feed-boil, feed, drain cycle repetitively.
  • a controller as claimed in claim 1 comprising additional sensing means to sense when the electrode current has risen to a level corresponding to a maximum water level, and means responsive to the additional sensing means to cause the drain valve to open, thereby draining water from the boiler and bringing about a reduction in the electrode current.
  • a controller as claimed in claim 1 comprising a current transformer having a primary winding for con nection in series with a boiler heating electrode, and a secondary winding, the controller including means to sense the voltage developed in the transformer secondary winding.
  • sensing means comprise two-state circuits which change state when the voltage of the transformer secondary winding reaches predetermined levels.
  • a controller as claimed in claim 1 a boiler full electrode for insertion in the boiler, the controller including circuit elements which cause the feed valve to be closed when the boiler full electrode becomes immersed, to prevent overfilling of the boiler.
  • a controller as claimed in claim 8 comprising circuitry to activate warning means when the boiler full electrode becomes immersed.
  • a controller as claimed in claim 1 comprising means to enable the drain valve to be opened and kept open in order to drain the boiler.

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Sustainable Development (AREA)
  • Sustainable Energy (AREA)
  • Cookers (AREA)
  • Control Of Steam Boilers And Waste-Gas Boilers (AREA)
  • Water Treatment By Electricity Or Magnetism (AREA)
US3780261D 1971-05-19 1972-05-19 Automatic control for electrode boilers Expired - Lifetime US3780261A (en)

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GB1588671 1971-05-19
GB1128772A GB1381113A (en) 1971-05-19 1972-03-10 Automatic control for electrode boilers

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US (1) US3780261A (enrdf_load_stackoverflow)
CA (1) CA981357A (enrdf_load_stackoverflow)
CH (1) CH534328A (enrdf_load_stackoverflow)
DE (1) DE2225398C3 (enrdf_load_stackoverflow)
FR (1) FR2138075B1 (enrdf_load_stackoverflow)
GB (1) GB1381113A (enrdf_load_stackoverflow)
NL (1) NL166318C (enrdf_load_stackoverflow)

Cited By (13)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3937920A (en) * 1973-03-09 1976-02-10 Plascon Ag. Method of operating an electrode-type water-vapor generator
US3944785A (en) * 1973-02-16 1976-03-16 Eaton Williams Raymond H Electrode boiler with automatic control
US4070992A (en) * 1976-04-23 1978-01-31 Chemed Corporation Boiler blow down controller
US4146775A (en) * 1976-09-16 1979-03-27 Armstrong Machine Works Automatic control system for an electrode-type air humidifier
US4308889A (en) * 1980-04-30 1982-01-05 Lin Jih Shyan Electric conductive type steam trap
US4347430A (en) * 1980-02-14 1982-08-31 Michael Howard-Leicester Vapor generator with cycling monitoring of conductivity
US4491146A (en) * 1982-09-22 1985-01-01 Groen Division/Dover Corporation Liquid level control
US4705936A (en) * 1985-01-17 1987-11-10 Masco Corporation Electronically controlled electric steam humidifier
US4841122A (en) * 1984-03-02 1989-06-20 Atlas Air (Australia) Pty, Limited Humidifier having a heating chamber with a continuously open drain and flushing outlet
US5440668A (en) * 1993-02-23 1995-08-08 Eaton-Williams Group Limited Electrode boiler with automatic drain control responsive to measured electrode current
US5932937A (en) * 1998-03-31 1999-08-03 Lancer Partnership, Ltd. Power control system
US20130322860A1 (en) * 2010-08-09 2013-12-05 International Green Boilers LLC Device for heating liquid and generating steam
US10700369B2 (en) * 2018-02-02 2020-06-30 Hyundai Motor Company Method of diagnosing level sensor failure in fuel cell water trap and control unit using the same

Families Citing this family (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4084547A (en) * 1976-03-24 1978-04-18 Honeywell Inc. Safe start checking liquid processing system
US4418269A (en) * 1980-03-24 1983-11-29 Eaton Williams Raymond H Multi-electrode boiler
JPH0732903B2 (ja) * 1985-11-21 1995-04-12 ノ−ウテイカル サ−ビスイズ ピ−テイ−ワイ リミテツド 脱塩器のための給水レベル制御装置
USPP12228P2 (en) 1999-06-01 2001-11-27 Florfis Ag Geranium plant named ‘Fislulu’

Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2006631A (en) * 1931-04-09 1935-07-02 Eaton Milton Means for regulating electric steam generators
US3209125A (en) * 1962-11-01 1965-09-28 Keeney Mfg Company Humidifier
US3269364A (en) * 1964-03-03 1966-08-30 Bradley C Higgins Automatic adjustable electric control of mineral contents for blowdown in a boiler
US3408941A (en) * 1967-04-13 1968-11-05 Kenneth G. Sorensen Tank filling control circuit
US3446937A (en) * 1965-10-23 1969-05-27 Max Hugentobler Water heater for coffee machines
US3523175A (en) * 1968-05-27 1970-08-04 Ernest F Gygax Humidifier
US3605798A (en) * 1970-04-02 1971-09-20 Carl P Green Water level controls for steam tables and the like
US3671142A (en) * 1970-06-22 1972-06-20 Lumenite Electronic Co Liquid level control

Patent Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2006631A (en) * 1931-04-09 1935-07-02 Eaton Milton Means for regulating electric steam generators
US3209125A (en) * 1962-11-01 1965-09-28 Keeney Mfg Company Humidifier
US3269364A (en) * 1964-03-03 1966-08-30 Bradley C Higgins Automatic adjustable electric control of mineral contents for blowdown in a boiler
US3446937A (en) * 1965-10-23 1969-05-27 Max Hugentobler Water heater for coffee machines
US3408941A (en) * 1967-04-13 1968-11-05 Kenneth G. Sorensen Tank filling control circuit
US3523175A (en) * 1968-05-27 1970-08-04 Ernest F Gygax Humidifier
US3605798A (en) * 1970-04-02 1971-09-20 Carl P Green Water level controls for steam tables and the like
US3671142A (en) * 1970-06-22 1972-06-20 Lumenite Electronic Co Liquid level control

Cited By (16)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3944785A (en) * 1973-02-16 1976-03-16 Eaton Williams Raymond H Electrode boiler with automatic control
US3937920A (en) * 1973-03-09 1976-02-10 Plascon Ag. Method of operating an electrode-type water-vapor generator
US4070992A (en) * 1976-04-23 1978-01-31 Chemed Corporation Boiler blow down controller
US4146775A (en) * 1976-09-16 1979-03-27 Armstrong Machine Works Automatic control system for an electrode-type air humidifier
US4347430A (en) * 1980-02-14 1982-08-31 Michael Howard-Leicester Vapor generator with cycling monitoring of conductivity
US4308889A (en) * 1980-04-30 1982-01-05 Lin Jih Shyan Electric conductive type steam trap
US4491146A (en) * 1982-09-22 1985-01-01 Groen Division/Dover Corporation Liquid level control
US4841122A (en) * 1984-03-02 1989-06-20 Atlas Air (Australia) Pty, Limited Humidifier having a heating chamber with a continuously open drain and flushing outlet
US4705936A (en) * 1985-01-17 1987-11-10 Masco Corporation Electronically controlled electric steam humidifier
US5440668A (en) * 1993-02-23 1995-08-08 Eaton-Williams Group Limited Electrode boiler with automatic drain control responsive to measured electrode current
US5932937A (en) * 1998-03-31 1999-08-03 Lancer Partnership, Ltd. Power control system
WO1999050870A1 (en) * 1998-03-31 1999-10-07 Lancer Partnership, Ltd. Power control system
AU735971B2 (en) * 1998-03-31 2001-07-19 Lancer Partnership, Ltd. Power control system
US20130322860A1 (en) * 2010-08-09 2013-12-05 International Green Boilers LLC Device for heating liquid and generating steam
US8750695B2 (en) * 2010-08-09 2014-06-10 International Green Boilers, Llc Device for heating liquid and generating steam
US10700369B2 (en) * 2018-02-02 2020-06-30 Hyundai Motor Company Method of diagnosing level sensor failure in fuel cell water trap and control unit using the same

Also Published As

Publication number Publication date
GB1381113A (en) 1975-01-22
DE2225398B2 (de) 1980-05-29
DE2225398A1 (de) 1972-12-28
DE2225398C3 (de) 1981-02-12
NL166318C (nl) 1981-07-15
CA981357A (en) 1976-01-06
FR2138075B1 (enrdf_load_stackoverflow) 1973-07-13
CH534328A (de) 1973-02-28
NL7206863A (enrdf_load_stackoverflow) 1972-11-21
FR2138075A1 (enrdf_load_stackoverflow) 1972-12-29

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