Electric Boiler

Abstract

A prewired, unit-handled electric water boiler having a boiler casting housing a plurality of immersible heater elements, a removable control panel on which all the circuit elements are mounted including sequentially activable heater control relays and individual pilot lights for indicating energization of each heater element.

Description

BACKGROUND OF THE INVENTION

This invention relates to an electric water boiler and more particularly to an improved, unit-handled, relatively light and compact boiler which is adapted to be used for residential, commercial and industrial space heating and hot water supply applications.

Hot water heaters of the known gas or oil types are generally very large and cumbersome. Electric hydronic heaters may be considerably smaller because of their greater efficiency due to the immersion of plural heater elements directly into the path of the flowing water. These smaller units are especially well adapted to supply residential hot water for central heating and domestic needs. Usually the boilers of this type include a series of heater elements which may be thermostatically energized through a control circuit. Often they are complicated structures which require a skilled electrician to install, maintain and service. With particular reference to residential applications where space is at a premium it is desirable to design a boiler unit with these limited space considerations in mind so that installation and servicing may be accomplished with minimum lateral space requirements and the boiler unit may be housed in a closet. Further, it would be highly desirable if the homeowner himself could periodically check the unit with a quick glance at a visible control panel to determine whether any malfunctions are present in the system. Also, with respect to the power supply company, it would be desirable if the plural heater elements were sequentially activated so as to eliminate the possibility of load surging on the generator power system.

SUMMARY OF THE INVENTION

Accordingly, it is the primary object of this invention to provide an electric water boiler designed for maximum simplicity of installation, service and maintenance which is in the form of a compact, unit-handled, prewired device which will provide complete comfort control to the homeowner and complete load peaking control to the electric power company.

Other objects are to provide an electric water boiler with several safety features including visible heater element pilot lights and individual heater line circuit breakers. Still another object is to provide a nonhazardous electric water boiler in which all exposed metal parts are safely grounded.

To accomplish the objects of my invention in one form I have provided a compact, prewired, unit-handled electric water boiler including: a heater casting having an inlet and an outlet end through which the water passes to be heated; heater elements positioned within the housing to be immersed in the water; a control panel upon which electric circuit elements and their wiring are carried, the control panel being removably mounted upon the housing in spaced relationship thereto; the electric circuit elements are of the plug-in type for ease of removal and replacement and include temperature sensing master control means and relay means for sequentially energizing the heater elements in response to a thermostatic call for heat .

BRIEF DESCRIPTION OF THE DRAWINGS

Other objects and further details of that which I believe to be novel and my invention will be clear from the following specification and claims taken with the accompanying drawings wherein:

FIG. 1 is a front elevational view of the electric boiler of my invention shown mounted upon a wall and connected to the usual plumbing and electric service;

FIG. 2 is a front elevational view of the electric boiler shown with the cover removed;

FIG. 3 is a left side elevational view of the electric boiler with the cover partially broken away to show the heater casting, the surrounding insulation and the heater units;

FIG. 4 is a sectional view taken substantially along line 4-4 of FIG. 3 showing the interior of the heater casting and the heater elements;

FIG. 5 is a schematic electrical wiring diagram showing one form of my control circuit;

FIG. 6 is a view similar to that of FIG. 2 showing a modified form of my invention incorporating two rows of pilot lights and auxiliary plug-in relays; and

FIG. 7 is a schematic electrical wiring diagram showing the modified form of my control circuit with the auxiliary relays.

DESCRIPTION OF THE PREFERRED EMBODIMENTS E

With particular reference to FIGS. 1 -- 3, there is illustrated the improved electric boiler unit 10 of my invention which is shown mounted upon a wall W. When drained of water the electric boiler weighs approximately seventy pounds and may be easily installed by one man on a wood or a concrete wall. Installation may be accomplished by placing two spaced upper anchor bolts 12 into the wall and lifting the unit so that the slanted hook slots 14 in the back straps 16 are guided over the exposed shank of the anchor bolts. The boiler unit 10 may then be released and its weight helps it to find its own center. Anchor bolts 12 may be tightened and supporting anchor bolts 18 may be driven into the wall W in the lower slots 20 of the back straps 16. When these supporting anchor bolts are tightened the boiler 10 is securely wall mounted.

The boiler unit 10 includes an L-shaped member 22 made of heavy sheet metal which forms the rear and lower walls thereof. Elongated securing bolts 23 are provided to support the various members of the unit and to secure them together. These members include a heater casting 24 through which the water flows and a control panel 26 supporting the electrical circuit elements. The heater casting which will be described in greater detail hereinafter is formed with outwardly extending inlet and outlet pipe couplings 27 and 28 at the bottom and top thereof respectively, as viewed in FIGS. 1 and 2.

The plumbing installation includes a water inlet line generally designed by the numeral 29 comprising a water supply pipe 30, an automatic fill valve 32, a gate valve 34 and a water circulator comprising a motor 36 and pump 38. A hot water return pipe 40 including therein a gate valve 42 also forms part of the inlet line 29 and feeds to the circulator pump 38. A usual drain valve 44 is located at the lowermost point of the system. The heated water exiting the boiler flows through an outlet line 46 connected to the outlet coupling 28. The outlet line comprises a relief valve 48, a temperature/pressure indicator gauge 50, an air purger 52 which communicates with an expansion tank 54 and a gate valve 56. A drainage shunt pipe 58 connects the outlet line 46 with the inlet line 29 and also includes a gate valve 60 therein.

When the plumber has completed the plumbing installation as described above, an electrician may simply feed a three-wire 230 VAC service 62 through an opening 64 in the lower wall of the unit to wire the control panel 26. The two wires identified as L1 and L2 are electrically connected to the "hot" terminal clamps 66 and 68 and the third wire indicated by the letter N is electrically connected to the neutral terminal clamp 70. Then a two-wire 120 VAC circulator cable 72 is brought into the unit through a second opening 74 in the lower wall. A first wire C1 is electrically connected to the "hot" terminal 76 which comprises an eyelet receiving screw and a second wire C2 is electrically connected to a neutral terminal clamp 78. A second two-wire 120 VAC service 79 is connected to the thermostat terminal clamps 80 and 82. A grounding wire 83 is secured to a suitable terminal lug located on the lower wall of the L-shaped member 22 to fully electrically ground all exposed parts of the unit. While four separate cables are shown, it should be understood that a single cable may service the unit. Since the unit has been completely prewired at the factory as will become apparent, and the entire wiring is assembled behind the control panel 26 where it is not exposed to view or touch, the boiler unit is immediately ready for operation.

When the electrician has completed the wiring a single louvered cover 84 having side walls 86, a top wall 88, and front wall 90 is secured to the L-shaped member 22 by means of several large binding head screws 92. It should be noted that the front wall includes two elongated openings 94 and 96 on its left side, one to expose a bank of pilot lights 152 and the other to expose the automatic circuit breakers both of which will be fully described hereinafter.

Turning now to FIGS. 3 and 4 boiler unit 10 is illustrated in greater detail. It comprises the heater casting 24 which is of generally rectangular shape. The casting is formed with longitudinal internal baffles 98 defining individual heater cavities through which the water flows in a serpentine path to be heated to a maximum temperature at a maximum rate within a minimum volume. As set forth above, the heater casting 24 is formed with inlet and outlet pipe couplings 27 and 28. A coupling 100 plugged by a suitable plug member 102 is formed adjacent the outlet coupling 28 to flush the casting. A pipe fitting 104 (see FIG. 3) extends outwardly from one face of the heater casting including an immersion well 105 into which a temperature sensing probe 106 may extend into the last heater cavity adjacent the outlet pipe coupling 28. Bolt hole openings 108 are formed through enlarged formations 110 to receive the elongated securing bolts 23. At the left end of the heater casting (as viewed in FIG. 4) four openings 112 are provided in the end wall to receive the heater elements 114. Adjacent the openings are formations 116 having tapped holes therein to receive heater securing bolts 118. In this manner, both the elongated securing bolts 23 and the heater securing bolts 118 are isolated from the water compartment thereby minimizing rusting and freezing in place of the bolts and eliminating an interface for leakage to occur.

The heater elements 114 are of the standard water heater type having an elongated doubled over heater member 120 of low watt density (75 -- 100 watts per square inch of heating surface). The heater members 120 are preferably made with a copper sheath and are tin plated to increase service life, reduce electrolytic action, reduce vibration and increase the heat transfer efficiency. Each member 120 is mounted on a closure plate 122, preferably made of brass. A rubber-asbestos gasket 124 is interposed between the generator casting 24 and each closure plate 122 to seal each opening 112. Centrally located on each closure plate 122 is a terminal block 126 made of a suitable insulating material such as plastic, which supports two terminal clamps 128 in electrical contact with the ends of the heater member 120. The terminal clamps 128 receive the current carrying heater element load wires 130.

I have completely surrounded the heater casting 24 with a suitable insulating material 132, for example, a glass fiber board type insulation, to reduce heat transfer losses to a negligible amount thereby preventing heat build up within the boiler unit which may have a deleterious effect on the electronic components. A metal heat reflector shield 134 is mounted on the elongated securing bolts 23 adjacent the insulating material 132, and spaced therefrom by means of spacers 136 is a fire wall 138 made of an asbestos-type material which cooperates with the insulating material and the heat reflector shield to prevent fire and excessive water and heat damage to the unit. Spacers 140 are disposed upon the elongated securing bolts 23 at the opposite face of the fire wall 138 to maintain the control panel 26 spaced from the fire wall to allow a sufficient area between these two planar members to house the internal circuit wiring.

The control panel is made of a rigid nonmetallic, dielectric material having spaced openings throughout, which receive usual plug-in type sockets secured thereto in a known manner and accept electrical components in a standard plug-in manner. I will now describe the electrical components utilized with reference to their position as viewed in FIG. 2.

The master control for the unit includes a dual function aquastat 142 having two scales located on its face relative to which adjustable temperature limit setting pointers are disposed. The temperature sensing probe 106 extends from the aquastat 142 into the immersion well 105 to sense the temperature of water near the outlet end of the casting (see FIG. 4). The master control further includes a low voltage transformer 144 and a control relay 146 which may be actuated in response to a call for heat from a room thermostat.

The four components shown aligned in the lower right hand quadrant of the control panel are power relays 148 of the double-pole, double-throw type which provide complete line isolation across the 230 VAC heater load line. The three components shown on an angle at the upper central portion of the control panel are thermal time delay relays 150a, 150b and 150c which are provided to sequentially close the power relays 148 at approximately 30 second intervals.

A bank of pilot lights 152 each connected in parallel with its respective heater element 114 is located in the upper left-hand corner of the control panel 26. Each pilot light is a neon type rated at 240 VAC. The bank of lights extends through the opening 94 in the cover 84 to be visible for quick inspection by the homeowner.

A large opening 154 has been formed through the control panel 26 to receive heater circuit breakers 156 rated at 240 VAC, 30 amp. which are mounted in a known manner upon a support plate 158 secured to the rear face of the control panel. The support plate includes a bar 160 extending along one end thereof in a direction parallel to the longitudinal dimension of the control panel, and terminal blocks mounted at its other end. The terminal blocks carry a first bus bar 162 in electrical contact with the wire L1, a second bus bar 164 in electrical contact with the wire L2, and a third bus bar 166 in electrical contact with the wire N. One end of each circuit breaker is snapped over the bar 160 and the other end clasps the respective bus bar extensions for electrical connection thereto. I have also provided control circuit breakers 168 rated at 115 VAC, 15 amps. to protect the circulator circuit from overload.

Located at approximately the center of the control panel 26 is a protective cover 170 effectively closing four openings in the control panel which openings may receive optional auxiliary relays which are to be described hereinafter in the discussion of the modified form of my invention.

All of the electric circuit components which have been described are visible when the cover is removed as illustrated in FIG. 2 and can be easily replaced by direct in-line removal and plugging in of new components. The unit is completely prewired at the factory, the entire wiring being located behind the control panel and therefore not exposed to view or touch. It is possible to remove the entire control panel after (1) disconnecting the four sets of heater element load wires 130, (2) removing the four mounting nuts and washers which secure the control panel 26 upon the elongated bolts 23 (only three of which are shown in FIG. 2) and (3) loosening of the set screw (not shown) which holds the aquastat probe 106 in the immersion well 105. This may be necessary to rewire the unit if serious failure should occur. However, there is generally no need to remove the control panel since all electrical servicing and repairs may be accomplished by replacing the plug-in components.

With particular reference to the schematic electrical wiring diagram of FIG. 5 the electric boiler circuitry will now be discussed. Assuming that all the circuit breakers 156 and 168 are closed, the primary winding of the low voltage, stepdown, control transformer 144 will be energized. When one of the room thermostats (not shown) closes due to low temperature, the low voltage circuit of the low voltage stepdown transformer 144 is closed and a reduced voltage of approximately 24 volts is applied to the solenoid of the control relay 146 to close its double-pole, single-throw switch having contacts 146a and 146b. It must also be assumed that the dual function aquastat 142 is in a condition in which the two open-on-rise limit switches 172 and 174, which are wired in series, are closed, in order to energize the circulator 36, 38. The two switches of the aquastat are closed when (1) the boiler water operating temperature is preferably in the 185.degree. to 195.degree. F. range and (2) preferably below 230.degree. F., thus operating both as a failsafe device and a thermal overload above 230.degree. F. It should be noted that closing of the switch contact 146a energizes the circulator motor 36 and that closing of the switch contact 146b closes the circuit through the power relay 148a and the heater circuits of the time delay relays 150a -- c.

When the solenoid of the first power relay 148a is energized across the 120 VAC line its double-pole, single-throw switch is closed to energize the first heater member 120a and its pilot light 152 across the 240 VAC circuit. Simultaneously the heaters in the thermal time delay relays 150a -- c are energized so that approximately twenty seconds later the circuit is closed across the solenoid of the second power relay 148b by the positive action warp switch activated by the heater in the thermal time delay relay 150a. In this manner, the second heater member 120b is energized along with its pilot light 152b. Similarly, 25 seconds later the third heater member 120c and its pilot light 152c are energized and after a further 45 second delay the fourth heater member 120d and its pilot light 152d are energized, assuming, of course, that the system is set for maximum heat and the energization of all four heater elements.

Visual indication of electrical overload as well as automatic circuit protection is provided for each heater element by means of the circuit breakers 156 whose control levers protrude through the opening 96 in front wall 90 of the cover 84. This provides visual indication and easy accessibility to the user. It should be noted that every circuit is protected. Moreover, the user may use the circuit breakers as switches to reduce the number of energizable heater elements from four to perhaps two in the period from late spring to early fall.

In FIGS. 6 and 7 I have illustrated a modified form of my electric water boiler indicated by the numeral 10' comprising an auxiliary safety feature which will indicate deterioration of the individual heater members 120. The protective cover 170 is removed and suitable sockets are secured in the openings of the control panel 26 to receive plug-in type single-pole, double-throw relays 176a -- d (note FIG. 6) which are wired in series with the heater elements as illustrated in FIG. 7. A second bank of pilot lights 178 is provided and may be of a different color for ease of recognition. The auxiliary relays 176 operate in an inverse manner to the usual relay application using a low amperage indicating circuit on the contacts and a high amperage load circuit on the coil. The coil 180 of each relay 176 is wound with only a few turns of stranded wire capable of carrying the full current required by the heater element and is placed in series with the heaters. A first set of contacts 182 is maintained normally closed by the solenoid when the heater circuit is closed and the heater member is functioning properly. This set of contacts allows a first pilot light 152 (preferably green) to be energized to indicate normal operation. The second pilot light 178 (preferably red to indicate malfunction) connected across a second set of contacts 184 is normally open. When the heater member 120 has degraded or deteriorated to approximately twice its resistance or is broken or shorted, the heater current and the current through the coil 180 will decrease to at least fifty percent or less of its full load value. This causes the normally open contacts 182 to be released and closes the second set of contacts 184, deenergizing the green pilot light 152 and energizing the red pilot light 178 to indicate malfunction. In all other respects the boiler unit operates in a manner similar to the FIGS. 1 -- 5 form of my invention.

It should be understood that the present disclosure has been made only by way of example and that numerous changes in details of construction and the combination and arrangement of parts may be resorted to without departing from the true spirit and scope of the invention as hereinafter claimed.

Claims

I claim:

1. A prewired, unit handled electric water boiler unit comprising: a heater housing having an inlet end and an outlet end through which water passes to be heated; heater elements positioned within said housing to be immersed in the water; means for carrying electric circuit elements and their wiring, said means being removably mounted upon said housing in spaced relationship thereto; a temperature sensing probe positionable within said heater housing adjacent the outlet end thereof; and dual adjustable controls comprising a first selector means for defining a range of acceptable operating temperatures and a second selector means for limiting the maximum operating temperature, said first selector means being operationally connected to a first line switch to open said first switch to prevent operation of said boiler unit when said probe senses a temperature outside of the range defined by said first selector means, and said second selector means being operationally connected to a second line switch to open said second switch to prevent operation of said boiler unit when said probe senses a temperature above the maximum temperature as set on said second selector means.

2. A prewired, unit handled electric water boiler unit comprising: a heater housing having an inlet end and an outlet end through which water passes to be heated; heater elements positioned within said housing to be immersed in the water; means for carrying electric circuit elements and their wiring, said means being removably mounted upon said housing in spaced relationship thereto; and electric circuit elements of the plug-in type mounted on said means; said electric circuit elements including temperature sensing master control means for controlling the supplying of power to said heater elements; individual power relays operationally connected to each of said heater elements to energize said heater elements when said power relays are energized; and thermal time delay relays which sequentially energize said power relays.

3. The electric water boiler unit defined in claim 2 wherein said heater elements are protected with individual line circuit breakers mounted on said carrying means and wherein pilot lights for indicating the condition of said heater elements are mounted on said carrying means.

4. The electric water boiler unit defined in claim 2 wherein a cover is positioned over said housing and said carrying means and has openings therein for exposing the faces of said circuit breakers and said pilot lights whereby the condition of said heaters may be easily visually checked.

5. The electric water boiler defined in claim 2 wherein said heater housing is a cast metal body having internal baffles positioned to cause the water to flow through said housing in a serpentine path and defining parallel heater chambers in which said heater elements are disposed.

6. The electric water boiler unit defined in claim 2 wherein: said carrying means includes a planar control panel made of a dielectric material having said electric circuit elements mounted on one face thereof and said circuit wiring mounted on the opposite face thereof; and a plurality of plug-in type sockets are secured to said control panel to receive said plug-in type electric circuit elements.

7. The electric water boiler unit defined in claim 2 further including individual auxiliary relay means electrically connected to each of said heater elements controlling the energization of safety pilot lights to indicate the deterioration of said heater elements.

8. The electric water boiler unit defined in claim 7 wherein each of said auxiliary relay means comprises an operating coil connected in electrical series relationship with its associated heater element, and switch means operable by said coil to control said pilot lights.

9. The electric water boiler unit defined in claim 7 wherein said pilot lights include two banks thereof, the pilot lights of one bank being energized when said heater elements are operating normally and the pilot lights of the second bank being individually energizable in response to the deterioration of said individual heater elements.