Heater assembly

Abstract

A termination assembly for a heater assembly includes a plurality of resistive heaters (26) configured in discrete power phases, each resistive heater including a resistive heating element surrounded by a dielectric material and a jacket. The termination assembly includes a plurality of non-conductive members (76). Each non-conductive member (76) includes a plurality of apertures configured to receive power pins (80) of the plurality of resistive heaters. The termination assembly includes a plurality of connectors (82) configured to connect the power pins to the non-conductive member. Each non-conductive member includes a number of the plurality of connectors corresponding to a number of terminated power pins. The termination assembly includes an electrical circuit (85) embedded in or disposed on at least one of the plurality of non-conductive members.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to and the benefit of U.S. Provisional Patent Application No. 63 / 130,084, filed on December 23, 2020. The disclosure of the above application is incorporated herein by reference in its entirety. Technical Field

[0003] The present disclosure relates to heat exchangers and, more particularly, to heat exchangers having a resistive heater and electrical termination structures for connecting the resistive heating element to a power supply. Background Art

[0004] The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.

[0005] Industrial electrical heaters generally heat materials such as solids, liquids, or gases with resistive heaters that convert electricity into heat. In some applications, the resistive heaters are immersed in a liquid or gas, where the liquid or gas flows between the resistive heaters (e.g., a heat exchanger). In some applications, a large amount of electricity is required to bring the material to a desired temperature. For example, some applications require more than 1 million watts of electricity, with some applications in the range of 5 million watts or more. Typical low-voltage electrical heaters operate at about 700 volts, but may require high currents (e.g., over 7,000 amps) to achieve the required power. High currents may require large and expensive electrical components, cabling, and grounding strategies. In addition, some industrial power supplies require step-down transformers to supply low voltages.

[0006] The present disclosure addresses issues related to connecting resistive heaters to power supplies in these industrial applications, including medium voltage heat exchanger applications, as well as other challenges associated with fluid heating vessels. Summary of the invention

[0007] This section provides a general summary of the disclosure, and is not a comprehensive disclosure of its full scope or all of its features.

[0008] In one form, a termination assembly for a heater assembly has a plurality of resistive heaters configured in discrete power phases, each resistive heater comprising a resistive heating element and a sleeve surrounded by a dielectric material, the termination assembly comprising: a plurality of non-conductive components, each non-conductive component comprising a plurality of openings assembled to receive power pins of the plurality of resistive heaters; a plurality of connectors assembled to connect the power pins to the non-conductive components, wherein each non-conductive component comprises a number of the plurality of connectors corresponding to the number of power pins being terminated; and a circuit embedded in or disposed on at least one of the plurality of non-conductive components.

[0009] In a variation of such a termination assembly that may be implemented individually or in any combination: the plurality of non-conductive components are spaced apart; the assembly further includes a dielectric enclosure that surrounds at least one of the power pins in at least one opening; the dielectric enclosure is partially removed adjacent to a remote face of the non-conductive component, and the termination assembly further includes an electrical connector secured to the remote face and in electrical contact with a power pin; the assembly further includes a conductive component disposed in at least one opening of one of the non-conductive components, the conductive component coupled to the power pin and coupled to the circuit; the assembly further includes an electrical isolator disposed around the conductive component and in electrical contact with the remote face. The non-conductive members are in dielectric sealed contact; the assembly further includes an electrical isolator, which is disposed in at least one opening and surrounds the power pin; the assembly further includes at least one electrical insulating plug, which is disposed in one of the openings; the assembly further includes a spare component isolator, which is disposed around the terminal of at least one power pin; each non-conductive member corresponds to one of the discrete power phases; at least one non-conductive member corresponds to one of the discrete power phases; multiple of the non-conductive members correspond to one of the discrete power phases; at least one of the non-conductive members corresponds to multiple power phases; and the non-conductive members are configured longitudinally.

[0010] In another form, a heater assembly includes a plurality of resistive heaters configured in discrete power phases, each resistive heater comprising a resistive heating element and a sleeve surrounded by a dielectric material, and a termination assembly comprising: a plurality of non-conductive components, each non-conductive component comprising a plurality of openings assembled to receive power pins of the plurality of resistive heaters; a plurality of connectors assembled to connect the power pins to the non-conductive components, wherein each non-conductive component comprises a number of the plurality of connectors corresponding to the number of power pins being terminated; and a circuit embedded in or disposed on at least one of the plurality of non-conductive components.

[0011] In variations of such heater assemblies which may be practiced alone or in any combination: the plurality of resistive heaters extend along a longitudinal axis of the heater assembly; and each non-conductive member corresponds to one of the discrete electrical phases.

[0012] In another form of the present disclosure, a fluid heat exchanger includes: a pipe including an inlet and an outlet; a plurality of resistive heaters configured in discrete power phases and disposed within the pipe; and a termination assembly including: a plurality of non-conductive components, each of which includes a plurality of openings configured to receive power pins of the plurality of resistive heaters; a plurality of connectors configured to connect the power pins to the non-conductive components, wherein each non-conductive component includes a number of the plurality of connectors corresponding to the number of power pins terminated; and a circuit embedded in or disposed on at least one of the plurality of non-conductive components.

[0013] In a variation of such a fluid heat exchanger that may be implemented alone or in any combination: the fluid heat exchanger operates at a medium voltage; the heat exchanger further includes a baffle disposed within the tube and extending along the plurality of resistive heaters; the baffle defines a spiral shape; and each non-conductive member corresponds to one of the discrete electrical phases.

[0014] Further areas of applicability will become apparent from the description provided herein.It should be understood that the description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order that the present disclosure may be well understood, its different forms will now be described by way of example and with reference to the accompanying drawings, in which:

[0016] Figure 1 is a perspective view of an electrical heater for use with a fluid heat exchanger and constructed in accordance with the teachings of the present disclosure;

[0017] Figure 2 for Figure 1 A side view of an electric heater;

[0018] Figure 3 is a schematic side view illustrating a termination assembly having a bus plate constructed according to the teachings of the present disclosure;

[0019] Figure 4A is a schematic side view of one form of a terminal having a dielectric encapsulation constructed in accordance with the teachings of the present disclosure;

[0020] Figure 4BAccording to the teachings of the present disclosure, a portion of the dielectric encapsulant is removed. Figure 4A A schematic side view of a terminal;

[0021] Figure 5-5D are schematic illustrations of various terminal connections constructed in accordance with the teachings of the present disclosure; and

[0022] Figure 6-6D Included are further schematic illustrations of various terminal connections constructed in accordance with the teachings of the present disclosure.

[0023] The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way. DETAILED DESCRIPTION

[0024] The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses. It should be understood that throughout the drawings, corresponding reference numerals indicate similar or corresponding components and features.

[0025] See also Figure 1 and 2 , illustrates an exemplary electric heater 10. The electric heater 10 includes a heating portion 14, a power supply portion 18, and a neutral terminal portion 22. The heating portion 14 includes a plurality of resistive heaters 26 extending between the power supply portion 18 and the neutral terminal portion 22 and parallel to a longitudinal axis 28 of the electric heater 10. In the example provided, each resistive heater 26 includes a resistive heating element and a casing surrounded by a dielectric material.

[0026] In the example provided, the electrical heater 10 is disposed within a tube 30 having a first port or first inlet / outlet 34 proximate the power supply portion 18, and a second port or second inlet / outlet 38 proximate the neutral terminal portion 22. The tube 30 is illustrated as transparent for clarity purposes to better illustrate the components within the tube 30. In the example provided, the tube 30 is metallic and opaque, but other configurations may be used. A fluid may be pumped into the tube 30 via one of the inlet / outlet 34, 38, and it flows through the tube 30, contacting the respective jacket of the resistive heater 26 until it exits via the other inlet / outlet 34, 38. In the example provided, it is a fluid heat exchanger, with the fluid flowing into the first inlet / outlet 34 and out of the second inlet / outlet 38, but the flows may be reversed. It should be understood that the term "fluid" may be interpreted to include solid, liquid, gas, and slurry, as well as other material states, while still falling within the scope of the present disclosure.

[0027] The pipe fitting 30 includes a first housing flange 42 and a second housing flange 46. The first housing flange 42 is disposed between the power supply portion 18 and the first inlet / outlet 34 and is assembled to couple the pipe fitting 30 to the power supply portion 18. The second housing flange 46 is disposed between the neutral terminal portion 22 and the second inlet / outlet 38 and is assembled to couple the pipe fitting 30 to the neutral terminal portion 22.

[0028] A baffle 50 may also be optionally disposed within the tube 30. In the example provided, the baffle 50 is in a continuous spiral shape and directs fluid flow along a spiral flow path 54 between the two inlet / outlet ports 34, 38, although other configurations may be used. The baffle 50 may also function as a support member that supports the heater 26 relative to each other and relative to the tube 30. In one configuration, the baffle 50 and the tube 30 may be similar to those shown and described in U.S. Publication No. 2019 / 0063853, which is commonly owned with the present invention and the entire disclosure of which is incorporated herein by reference. Although illustrated and described with reference to heating a fluid flowing through the tube 30, the electric heater 10 may be used without the tube 30 in other applications such as immersion heating. Further optional construction details may be found in co-application Ser. No. 17 / 087,032, entitled “Three-Phase Medium Voltage Heater,” filed Nov. 2, 2020, U.S. Publication No. 2021 / 0136876, which is also commonly owned with the present invention and the entire disclosure of which is incorporated herein by reference. As used herein, the term “medium voltage” should be interpreted to mean between about 2,000 V and 20,000 V. However, it should be understood that the teachings of the present disclosure are not limited to medium voltage heaters.

[0029] In one form, the electrical heater 10 includes a housing tube 60, a tube segment 62 having a flange portion 64, and an end cap 66 and a mating flange 68 secured together by mechanical fasteners 70. From this, a terminal housing 72 is formed which defines an interior cavity 74.

[0030] View now Figure 3, within the inner cavity 74 of the terminal housing 72 as shown above, an innovative termination assembly is provided and generally indicated by the reference numeral 100. The termination assembly 100 in one form includes a plurality of longitudinally arranged non-conductive components 76. These non-conductive components 76 generally serve as electrical bussing elements, and are therefore also referred to herein as "bus boards" or "layered bus boards". The term "component" used in the context of this form is generally a plate or disk, or any suitable structure that functions as an electrical bussing element. The geometry can be flat or curved, and can further define circular, square, rectangular and polygonal geometries, among other shapes. In Figure 3 In the non-limiting example of FIG. 7 , the three non-conductive members 76 are shown as plates. In another non-limiting form not shown in the figure, the non-conductive members 76 have a convex curved surface in a hemispherical shape.

[0031] As shown, each non-conductive member 76 includes a plurality of openings 78 configured to receive power pins 80 of a plurality of resistive heaters 26. In one form, each non-conductive member 76 corresponds to one of the discrete power phases. However, it should be appreciated that one non-conductive member 76 may accommodate more than one discrete power phase, and more than one non-conductive member 76 may correspond to one of the discrete power phases while remaining within the scope of the present disclosure.

[0032] As further shown, a plurality of connectors 82 are disposed on the remote face 87 of the non-conductive members 76, wherein each non-conductive member 76 includes a number of the plurality of connectors 82 corresponding to the number of power pins 80 to be terminated. Advantageously, a circuit 85 is embedded in at least one of the plurality of longitudinally arranged conductive members 76. This circuit is similar to a printed circuit board construction, wherein the circuit provides electrical connections and control for the electrical heater 10 during operation. The circuit 85 may also be applied (e.g., deposited, bonded) to the remote face 87 of the non-conductive member 76, rather than embedded, while remaining within the scope of the present disclosure. One or more circuits 85 may be used for each non-conductive member 76. In addition, the circuit 85 may include multiple layers ( Figure 4A and 4B ), and / or configured to reduce the harmful effects of electric fields by having shielding (not shown). These and other features of the circuit 85 should be interpreted as being within the scope of the present disclosure.

[0033] In one form, the non-conductive members 76 are longitudinally arranged and spaced apart, as shown. However, the non-conductive members 76 may be joined together to form a composite assembly (not shown). In another form, the teachings of the present disclosure contemplate a single non-conductive member 76 having an embedded bus connection and / or a bus connection applied to any external face of the non-conductive member 76.

[0034] like Figure 3 As further shown, a dielectric element 86 may be employed that reduces the electric field strength at the end of the resistive heater 26 where the power pins 80 exit the housing as shown. Figure 3 In addition to the illustrated components, various mechanical and electrical connectors are described in more detail below, which are assembled to provide the necessary electrical connections while maintaining the structural integrity, serviceability, and dielectric isolation of the termination assembly 100, as well as other functional features. These various forms of mechanical and electrical connectors should not be construed as limiting the scope of the present disclosure.

[0035] View now Figure 4A and 4B In one form, the termination assembly 100 includes an elastomeric dielectric encapsulant 88 surrounding the power pin 80 within the opening 78 ( Figure 4A ). This encapsulation 88 is primarily used when the resistance heater 26 has no electrical connection or "no circuit", such as Figure 4A When it is desired to electrically connect the resistive heater 26, a portion of the elastomeric dielectric encapsulant 88 is removed proximate the remote face of the non-conductive member 76, as shown in FIG. Figure 4B The termination assembly 100 thus further includes an electrical connector 90 (in this example in the form of a conductive (e.g., copper) washer) that is affixed to the remote face 85 of the non-conductive member 76 and in electrical contact with the power pin 80 of the resistive heater 26. Accordingly, electrical connections may be made as desired by removing a portion of the elastomeric dielectric encapsulant 88. However, it should be understood that other forms of dielectric materials may be employed with this variation and that the elastomeric encapsulant as shown is merely exemplary.

[0036] View now Figure 5 and 5A -5D, Figure 3 A form of mechanical / electrical connector 82 is illustrated in more detail. Specifically, Figure 5Three resistive heaters 26 are illustrated, along with two connectors 82: an isolator plug 102 for an active resistive heater 26 and an alternate isolator plug 104 for an inactive resistive heater 26. When connected to a power source, the isolator plug 102 connects the resistive heater 26. When disconnected from a power source, the alternate isolator plug 104 isolates the resistive heater.

[0037] exist Figure 5 and Figures 5A-5C In one form shown, the connector base 106 of the isolator plug 102 is disposed at the end of the resistive heater 26 and around the power pin 80. The connector base 106 includes a lower flange 108, which is used to position the connector base 106 against the resistive heater 26; together with an extension 110, which is assembled to make contact with the circuit 85 within the non-conductive component 76 ("bus board"), as shown. The connector base 106 may include a threaded internal hole 112, which is used to secure the connector base 106 to the power pin 80 (the power pin is externally threaded in this form). A connector top 114 is then disposed above the power pin 80, and the connector top may also include a threaded internal hole 116 for receiving the threaded power pin 80. The dielectric isolator 118 is then as shown. Figure 5 The dielectric isolator 118 is shown disposed above the connector top 114 for use with the active resistive heater 26. The dielectric isolator 118 defines a cavity 120 therein configured to receive the connector top 114.

[0038] Figure 5D In one form, when the resistive heater 26 is not active, or connected to a power source, a replacement isolator plug 104 may be disposed within the opening 78 and enclose the power pin 80 ("cold pin" due to the low resistivity of the material) within a cavity 122 defined therein. The isolator plug 104 includes a flange 124 to secure the isolator plug 104 to the remote end of the bus member 76. The isolator plug 104 is electrically insulated and implemented as a "spare" and is used for a "cold" pin 80 or a power pin 80 that is not electrically connected and receiving power. In one form, the isolator plug 104 is molded.

[0039] View now Figure 6 and 6A -6D, display for Figure 31 and 1 . Another configuration of the mechanical / electrical connector 82 of the present invention. In this form, the connector assembly 126 includes a main connector 128, which is a dielectric isolator. Various materials may be used for this main connector 128, and in one form, the material may be compressed to fill any voids / gaps and suppress arcing. A socket connector 130 is disposed about the power pins 80 and within a central portion of the main connector 128, as shown. In addition, a conductive adapter 132 is secured to the socket connector 130 and is configured for connection to a power source, as shown. A removable terminal cap / plug 134 may be placed over the conductive adapter 132 until electrical connections are ready to be made. As shown Fig.6D As shown, an alternative form may employ a "spare" cap 136 (electrically insulating) that extends around the power pins 80 of the resistive heater 26 when the resistive heater 26 is not functional.

[0040] Thus, the present disclosure provides improved durability and reduced installation labor for heaters having termination connection structures such as described herein. In addition, the present disclosure allows bus connection circuits to be packed tightly together and provides a means for mechanically supporting the circuits, which reduces the forces that may be applied to the heater during installation and service. The manufacturing process of the present disclosure can allow different circuit designs to be assembled without special tools, allowing for more customized designs with less investment and shorter lead time.

[0041] In summary, the present disclosure includes one or more bus-connected circuits that distribute current among multiple resistive heaters used, for example, in a fluid heating vessel. The bus-connected circuits are attached to one or more supporting substrates and encapsulated by a dielectric material, which may or may not be a material different from the substrate material. The circuits may include multiple layers separated by dielectric material to achieve sufficient cross-sectional area (that is, dielectric strength) and appropriate circuit heater connections. The assembly may include integrated connection features to facilitate connection to the heater terminals and connection to a power source.

[0042] Circuit materials can be selected to have desired electrical, thermal, mechanical, and chemical properties. In most cases, a highly conductive material such as copper will be used, but nickel, nickel alloys, aluminum, or other materials may be used depending on the application requirements.

[0043] The non-conductive member 76 is electrically insulating or dielectric and provides mechanical structure to the circuit. The non-conductive member 76 may be a polymer material such as polyimide, silicone or Teflon. It can be an epoxy material or a fiber (glass or aramid) reinforced epoxy matrix; it can be a ceramic material including engineered ceramics and glass; or it can be a composite material. The dielectric material that encapsulates and isolates the circuit can also be a polymer, epoxy, ceramic or composite material. It can be applied by bonding, gluing, mechanical fastening, dipping, spraying, potting and others.

[0044] The circuits may be fabricated using conventional metal building processes and then bonded to the substrate; or the circuits may be deposited by additive manufacturing processes such as thermal spray, thick film, thin film, electroless plating, among others; or the circuits may be made from foil / sheets that are attached to the substrate and then patterned using etching, stripping, or machining processes.

[0045] Options for connecting the bus circuit to the heater cold pin include, for example, diffusion bonding, welding, and mechanical fastening (e.g., threaded or push-on connectors). Some of these options, including mechanical fastening and welding, have the advantage of being removable in a field repair scenario.

[0046] For medium voltage applications, the entirety of the circuitry and connections are encapsulated or sealed within or on the non-conductive member 76. The present disclosure may have recessed features or protruding tubes that engage / overlap insulating features (not shown) at the ends of the heater element. These features may (but need not) be composed of the same polymer, ceramic, or epoxy material as the other dielectric features of the assembly.

[0047] Various forms of this disclosure include:

[0048] PCB style copper circuits on a circuit board substrate, encapsulated by a laminate sheet or potting insulating material;

[0049] A layered assembly of etched foil circuits sandwiched between sheets of polyimide or silicone rubber insulation;

[0050] a bus circuit completely encapsulated by a potting / molding material, wherein the dielectric material and the base material are the same material; and

[0051] Circuits are attached / deposited to a ceramic substrate and encapsulated (and bonded or pressed together) by more of the same ceramic material, or by a different material such as glass or polymer.

[0052] The present disclosure includes, in one form, at least three circuits to connect the resistance heaters 26 into a three-phase circuit. Depending on the application, there may be additional circuits to connect the resistance heaters 26 in parallel or series. In the extreme case, there may be n / 2 circuits, where n = the number of resistance heaters 26 in the assembly.

[0053] The assembly may include mounting holes for mechanically securing the assembly to a support structure. It may also contain one or more features for sensing and monitoring systems, including but not limited to temperature sensors, current sensors, shunt resistors, and others.

[0054] In some variations, the assembly may also contain a microprocessor and other integrated electronic components that enable control or monitoring of the heater bundle, such as temperature of the heater bundle, high temperature limit, power switch control, power / current / voltage limit, and others. In this case, the assembly may contain communication inputs or outputs (analog, digital, or fieldbus).

[0055] Unless otherwise expressly indicated herein, all numerical values ​​indicating mechanical / thermal properties, composition percentages, dimensions and / or tolerances or other characteristics in describing the scope of the present disclosure are to be understood as modified by the word "about" or "approximately". Such modifications are necessary for a variety of reasons, including: industrial practice; material, manufacturing and assembly tolerances; and testing capabilities.

[0056] As used herein, the phrase at least one of A, B, and C should be construed to mean a logical (A or B or C), using a non-exclusive logical "or", and should not be construed to mean "at least one A, at least one B, and at least one C."

[0057] The description of the present disclosure is merely exemplary in nature, and therefore, variations that do not depart from the essence of the present disclosure are intended to fall within the scope of the present disclosure. Such variations should not be regarded as departing from the spirit and scope of the present disclosure.

Claims

1. A heater assembly, characterized in that: The heater assembly has a termination assembly and a plurality of resistive heaters arranged in discrete power phases, each resistive heater comprising a resistive heating element, a dielectric material, a casing, and a power pin, wherein the resistive heating element is surrounded by the dielectric material and the casing, and the power pin is connected to the resistive heating element and extends from the casing, and the termination assembly comprises: a plurality of non-conductive members, each non-conductive member comprising a plurality of openings, each opening configured to receive a corresponding power pin of the power pins of the plurality of resistive heaters; an electrical circuit supported by and in contact with a first non-conductive member of the plurality of non-conductive members; as well as A plurality of connectors, each connector is configured to be coupled to a corresponding one of the power pins and to the circuit, thereby forming electrical communication between the power pin and the circuit.

2. The heater assembly according to claim 1, characterized in that: The plurality of non-conductive members are spaced apart.

3. The heater assembly according to claim 1, characterized in that: A power pin among the plurality of power pins is surrounded by a dielectric encapsulant, and the dielectric encapsulant is located in an opening for receiving the power pin.

4. The heater assembly according to claim 3, characterized in that: The power pin surrounded by the dielectric enclosure extends beyond a remote face of the non-conductive member defining the opening for receiving the power pin, and the termination assembly further includes an electrical connector fixedly connected to the remote face and in electrical contact with the power pin.

5. The heater assembly according to claim 1, characterized in that: Further included is an electrical isolator disposed about one of the plurality of connectors and in dielectrically sealing contact with the first non-conductive member.

6. The heater assembly according to claim 1, characterized in that: Further included is an electrical isolator disposed within one of the plurality of openings and surrounding a power pin that is not coupled to one of the plurality of connectors.

7. The heater assembly according to claim 6, characterized in that: The electrical isolator is disposed around the terminals of the power pins.

8. The heater assembly according to claim 1, characterized in that: Each non-conductive member corresponds to one of the discrete power phases.

9. The heater assembly according to claim 1, characterized in that: A plurality of the non-conductive members corresponds to one of the discrete power phases.

10. The heater assembly according to claim 1, characterized in that: At least one of the non-conductive members corresponds to a plurality of power phases.

11. The heater assembly according to claim 1, characterized in that: The non-conductive member is arranged longitudinally.

12. The heater assembly according to claim 1, characterized in that Further including: a pipe fitting, which includes an inlet and an outlet; Wherein the plurality of resistance heaters are arranged in the pipe.

13. The heater assembly according to claim 12, characterized in that The heater assembly operates at medium voltage.

14. The heater assembly according to claim 12, characterized in that Further included is a baffle disposed within the tube and extending along the plurality of resistive heaters, wherein the baffle defines a spiral shape.

15. The heater assembly according to claim 1, characterized in that Each connector includes a connector base that connects the circuit and engages the corresponding power pins on a first side of the circuit and a connector top that connects the circuit and engages the corresponding power pins on an opposite side of the circuit.

16. The heater assembly according to claim 1, characterized in that Further comprising an isolator plug, wherein the isolator plug is coupled to a power pin of the plurality of resistive heaters that is not connected to the circuit through one of the connectors, the isolator plug extending into an opening corresponding to the power pin and electrically isolating the power pin from the circuit.

17. The heater assembly according to claim 1, characterized in that Each connector includes a dielectric isolator, a conductive adapter and a socket connector, wherein the socket connector is disposed in the dielectric isolator and screws the corresponding power pin to the conductive adapter for electrical communication between the corresponding power pin and the conductive adapter, wherein the conductive adapter is coupled to the circuit for electrical communication between the conductive adapter and the circuit.

18. The heater assembly according to claim 17, characterized in that Further included is an electrically insulating cap coupled to a power pin of the plurality of resistive heaters that is not connected to the circuit through one of the connectors, the electrically insulating cap extending around the power pin.

19. The heater assembly according to claim 17, characterized in that Further included is a terminal cap removably coupled to an end of a conductive adapter of at least one of the connectors.

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