US2312772A - Water heating system - Google Patents

Description

March 2, 1943- c. M. osTERHELD 2,312,772

WATER HEATING SYSTEM Filed June 14, 1941 A TT@ p/VEY Patented Mar. A2, 1943 WATER HEATING SYSTEM Clark M. Osterheld, Stoughton, Wis., assigner to McGraw Electric Company, Elgin, Ill., a corporation of Delaware Application June 14, 1941, Serial No. 398,094

4 Claims. (lCl. 21S-39) My invention relates to electric temperature control systems and particularly to water heating control Systems.

An object oi my invention is to provide a relatively simple all-day water heating system.

Another object of my invention is to provide a water heating control system embodying thermal means subject to tank water temperature at a predetermined point or height of the tank to vary the amount of electric energy translated into heat for the water in the tank.

Other objects of my invention will either be apparent from a description of my invention as embodied in several modifications or will be pointed out in the course of such description and set forth in the appended claims.

In the drawing:

Figure l is a schematic diagram of connections embodying my invention shown as applied to an ordinary domestic hot water tank, which is shown generally only, and,

` Fig. 2 is a view similar'to Fig. l showing a modified system of control.

Since the system embodying my invention is particularly applicable to and useful in the control of electric heaters used on ordinary domestic hot water tanks, have elected to show, schematically only, a hot water tank I l which is to be understood as being provided with a cold water inlet pipe, preferably at the bottom of the tank, and with a hot water outlet pipe at the top of the tank. The tank may also be provided with the usual layer of heat insulating material and with an outer protective casing for such material. However, since my invention has nothing to do with these details. I have shown the tank generally only.

Referring to Fig. 1, an electric heater comprises two sections I3 and I5 and I may make the resistance of these two sections the same or I may make the resistance of section I3 greater than that of section I5 so that when section I5 is energized separately, the amount of electrical energy translated into heat in section I5 will be greater than if section I3 were energized alone. I prefer to apply these two sections of the heater to the tank near the lower end thereof, as shown in Fig. l of the drawing.

I provide a lower main thermal heater control switch I1 here shown as embodying a tubular member i 9 so secured to the wall of tank II as to extend into the tank in a fluid-tight manner. An expansion rod 2i is positioned within the tubular member I9 and extends outwardly beyond the outer surface of the wall of tank II engaging a contact or switch arm 23. This contact arm is adapted to engage with or be disengaged from a fixed contact member 25. When tubular member I9 is subject to cold water, switch arm 23 will be in engagement with xed contact member 25 but if tubular member I8 is surrounded by and subject to hot water, the expanded rod ZI will have moved the switch arm 23 out of engagement with fixed contact member 25 to thereby interrupt a circuit controlled by this switch.

I provide an auxiliary thermal switch 21 which is preferably located at an intermediate point or height of the tank iI and for illustrative purposes it may be positioned at about one-half of the height of the tank or even at about twothirds of the height of the tank from the bottom. Switch 21 includes a tubular contact member 29 secured to the wall of the tank in a duid-tight manner to be positioned within the tank and has located therein an expansion rod 3| adapted to move a Contact or switch arm 33. The movable end of arm 33 is adapted to engage either one of two xed contact members 35 and 31, it being understood that the design, construction and ad- J'ustment of the thermal switch 21 is such that the free end of arm 33 is in engagement with either contact member 35 or with contact member 31, but has no intermediate position. I may use any of the present types of two-operative position switches now on the market to obtain this result but have not shown any details thereof since they do not form any part of my present invention.

I provide two supply circuit conductors 39 and 4I, supply circuit conductor 39 being connected to the plvotally mounted end oi switch arm 33. Fixed contact member 35 is connected by a conductor 43 with one terminal of each of the heater sections I3 and I5. The other end of heater section I3 is connected by a conductor 45 with the xed pivotal end of switch arm 23. Contact member 25 is connected by a conductor l1 with xed contact member 31. The other terminal of heater section i5 is connected by a conductor 49 with the other supply circuit conductor It.

Let it be assumed that the tank H has just been lled with cold water and that the supply circuit conductors 39 and 4I are connected to suitable supply circuit of electric energy. The two thermal switches I1 and 21 will be in substantially the position shown in Fig. 1 of the drawing, e. g., switch arm 23 will be in engage ment with fixed contact 25 and switch arm 33 will be in engagement with fixed contact 35. An energizing circuit through the heater will therefore be established substantially as follows: From supply circuitconductor 39 through engaged switch arm 33 and contact 35, through conductor 43 and through heater section I5 to and throughconductor 49 to the other supply circuit conductor 4I. energy will therefore be translated into heat depending upon the resistance of heater section I and since this heater section alone is connected in circuit, i'n this diagram of connections. it may be considered that a relatively large amount of electrical energy isr `translated into heat causing the temperature of the waterin the tank to increase at a relatively rapid rate.

Let it now be assumed that the amount` of hot water in the tank has increased, because of the fiow of current for some time through ,heater section I5 and attendant heating of the water', to such an extent that tubular member- 29 of the upper or auxiliary thermal switch is surrounded by hot water. When this occurs the expanded rod 3i will cause movement of switch arm 33 out of engagement with xed contact 35 and into engagement with fixed contact 31 whereby a new circuit through the heater is provided, substantially as follows: From supply circuit conductor 39 to and through engaged switch arm 33 and contact 3l, through conductor 41 to and through engaged contact 25 and switch arm 23, through conductor 45, through heater sections I3 and I5 connected in series circuit with each other and from there through conductor 49 to the other supply circuit conductor 4I. It will therefore be evident that when a certain fractional part of the amount of water imthe tank has been heated to a given temperatura the upper or auxiliary thermal switchwill cause a lchange-over in the heating circuit whereby the two sections of the electric tank heater are connected in series cire cuit with each other whereby the amount of electrical energy translated into heat is greatly reduced. y

It is therefore evident that when the tank, at any time, contains a relatively small amount of `hot water, which may be considered to be less than that required for normal household needs and purposes, the amount of electrical energy translated into heat is relatively large but as soon as an amount of water in the tank sumcient for normal household purposes has been heated, the amount of electrical energy translated into heat and applied to the water in the tank is greatly reduced.

Referring now to Fig. 2 of the drawing, I have there illustrated a modied system embodying myinvention. I have shown a two-section heater comprising sections 49 and 5i both sections being located near the lower end of the tank II. For purposes of illustration I have shown a main lower thermal switch 53 asincluding a ilexible bimetal bar 55 having one end thereof mounted on suitable electric and heat conducting means subject to the temperature of the water in the lower part of the tank and adapted to engage with and be disengaged from a fixed contact member 51. This main thermal heater control switch need not be of the two-operative position type since it is merely required to open the circuit when substantially all of the Water in the tank is hot and I have shown a bimetal switch to illustrate that such a type of switch may be used.

I provide an upper thermally actuable heater control switch 59 which includes a tubular member 3| substantially the same as tubular member An amount of electrical hot water.

29 and located at an intermediate height of the tank which may be either at one-half height or at two-thirds height from the bottom of the tank. An expansion rod or bar 53 is adapted to pivotally move a contact or switch arm 55 in accordance with the temperature of the water to which the tubular member 5I is subjected. An outer ilxed contact member 51 may be engaged by switch arm 55 when the tubular member 3i is subject to I provide two inner xed contact members 59 and 'II spaced apart from ,each other and adapted to be engaged by contact or switch arm 55 when tubular member 5l is subject to cold water. Switch 59 is designed. constructed `and adjusted so that arm ,'55 is 'in engagement l lower main thermal heatercontrol switch. Contact member 1I is connected by a conductor 15 fwith one terminal of heater section 5 I The other terminal of heater section 5I is connected to one terminal of heater 'section 49 which two tervminals are connected bya conductorI 11 with supply circuit conductor 4I.-- s

Let it be assumed that tank il as shown in Fig. 2 has justbeen filled with cold water and that supply circuit conductors 39 and 4I are connected to a suitable source of supply of electric energy. Bimetal bar 55 will be in engagement with fixed contact member 51 and contact arm 55 will be in engagement with xed contact members 58 and li.,y This establishes an energizing circuit through the twosection heater substantially as follows: From supply'- circuit conductor 39 to and through engaged contact arm 55 and fixed contact member 59, through conductor I3 to and through the engaged members of the lower main thermal switch 53 and from fixed contact li through conductor i5 through heater section 5I, and through heater section 49, through conductor I'I to the other supply circuit conductor i It is evident that the two heater sections are connected in parallel circuit relation with each other. It is therefore evident that when the upper thermal heater control switch 59 is subject to cold water, current will flow through both sections of the heater in parallel whereby a relatively large amount of electrical energy will be translated into heat causing a relatively rapid heating up of the water in the tank II and its collection at thellpper part of the tank, in a manner now Well known in the art.

When the amount of hot water heated by current flowing from the two sections of the electric heater has increased to such an extent that the upper auxiliary thermal switch 59 is subject to hot water, contact arm 55 will be moved out of engagement with fixed contact members 59 and 'il and into engagement with xed contact member 6l whereby another energizing circuit through the heater is established substantially to the other supply circuit conductor 4i. There-h fore, when the upper part of the tank is illed with hot water to such an extent that the upper auxiliary thermal switch 59 is surrounded by hot water, it will be effective to establish a new energizing circuit through only one of the sections of the electric heater. Let it be assumed that the ohmic resistances of heater sections 49 and 5I are the same. Then it is evident that when only heater section 49 is energized as just above described, the amount of energy translated into heat will be only one-half of that which is translated into heat when both heater sections are energized in parallel circuit with each other, as is the case when the thermal heater control switch 59 is subject to cold water.

It will be noted that the lower thermal heater control switch I1 or 53 is in circuit and in complete control when the tank is filled with hot water and causes complete deenergization of the heater as soon as Athe tank is full of hot water. In case of withdrawal of hot water, in small quantities, the lower thermal switch will reclose and cause reenergization of the heater at low watt input.

The two systems shown in the drawing and hereinbefore described will therefore be eifective to translate a greater amount of electrical energy into heat when the tank contains no or only a small amount of hot water and it is, of course, to be understood, as has already been hereinbefore stated, that this small amount of hot water is that which would be required to meet the normal demands or calls for hot water in the course of the daylight hours.

While I have not shown any means for recording the amount of energy used during the daytime as distinguished from that used during socalled off-peak hours, such means may be provided but are not shown since they constitute no part of my present invention.

Various other modifications may be made in the system embodying my invention without departing from the spirit and scope thereof :and

I therefore desire that all such modifications as are clearly covered by the appended claims shall be included as a part of my invention.

I claim as my invention:

1. A control system for a hot water tank having a plural-section electric heater applied thereto near the lower end of the tank and adapted to heat water in only the lower end of the tank, comprising a switching means having two operative positions, a thermal element subject to tank water temperature at a point substantially one-half of the height of the tank and adapted to move said switching means from one to the other of its operative positions in accordance with its ambient temperature, electric connections between the heater sections and the switching means to cause the generation of a greater amount of heat by said heater when the upper half of the tank is filled with cold water than when the upper half of the tank is iilled with hot water and a second thermally-operative switch subject to tank water temperature at the lower end ot the tank for deenergizing said heater when substantially all of the water in the tank is hot.

2. A control system for a hot water tank having a two-section electric heater applied thereto near the bottom end of the tank and adapted to heat water in only the lower end of the tank, said system comprising a thermally-actuable switch having two operative positions and subject to tank water temperature near the upper end of the tank, electric connections between the switch and the heater sections to bias the thermally-actuable switch into a first operative position to cause the generation of a predetermined amount of heat in the heater when the upper part of the tank is filled with cold water and to move the thermally-actuable switch into its second operative position to cause the generation of a smaller amount of heat in the heater when the upper part of the tank is filled with hot water.

3. A control system for a domestic hot water` tank having a greater height than diameter and having a plural-section electric heater applied thereto near the lower end of the tank adapted to heat water in only the lower end of the tank, comprising a switching means having two operative positions, a thermal element subject to tank water temperature in the upper part of the tank, electric connections between the switching means and the electric heater, the thermal element holding the switching means in one of its operative positions to cause the genera.. tion of a predetermined amount of heat when subject to cold water and causing the switching means to move into its other operative position to effect the generation of a lesser amount of heat when the thermal element is subject to hot water, a second switching Ameans comprising a thermal element subject to tank water temperature in the lower end of the tank and normally holding the second switching means in heater energizing position when subject to cold water and effective to move the second switching means to heater deenergizing position when the water in the lower end of the tank is hot.

4. A control systm for a domestic hot water tank having a greater height than diameter and having a plural-section electric heater applied thereto near the lower end of the tank adapted to heat water in only the lower end of the tank, comprising a switching means having two operative positions, a thermal element subject to tank water temperature in the upper part of the tank, electric connections between the switching means and the electric heater, the thermal element holding the switching means in one of its operative positions to energize one only of said heater sections when the thermal element is subject to cold water and causing the switching means to move into its other operative position to energize both said heater sections in series circuit with each other when the thermal element is subject to hot water. j

CLARK M. OSTERHELD.

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