EP4636330A1

EP4636330A1 - Temperature control and safety in air handling unit configured with a supplemental heater assembly

Info

Publication number: EP4636330A1
Application number: EP25171109.9A
Authority: EP
Inventors: Dennis Blessing
Original assignee: Carrier Corp
Current assignee: Carrier Corp
Priority date: 2024-04-18
Filing date: 2025-04-16
Publication date: 2025-10-22

Abstract

A temperature control and safety system (100) for an air handling unit (102) is configured with a supplemental heater assembly (104). The system comprises one or more thermistors (112) configured at predefined positions around or adjacent to a heating element (204) associated with the heater assembly, and a controller (114) operatively connected to the thermistors (112), the heating element (204), and a blower (108) associated with the air handling unit (102), wherein the controller comprises one or more processors (114-1) coupled to a memory (114-2) storing instructions executable by the processors, which causes the controller to: monitor, using the thermistors (112), temperature of the heating element (204) and/or temperature of air leaving or flowing through the heating element (204), and control switching and/or adjust heating capacity of the heating element (204) based on the monitored temperatures, to maintain temperature of the heating element (204) at a first predefined temperature and/or the temperature of the air leaving the heater assembly at a second predefined temperature.

Description

BACKGROUND

The embodiments described herein relate to air handling units for HVAC systems.

SUMMARY

A first aspect of the invention provides a temperature control and safety system for an air handling unit configured with a supplemental heater assembly. The system comprises one or more thermistors configured at predefined positions around or adjacent to a heating element associated with the heater assembly, and a controller operatively connected to the one or more thermistors, the heating element, and a blower associated with the air handling unit, wherein the controller comprises one or more processors coupled to a memory storing instructions executable by the processors, which causes the controller to: monitor, using the one or more thermistors, temperature of the heating element and/or temperature of air leaving or flowing through the heating element, and control switching and/or adjust heating capacity of the heating element based on the monitored temperatures, to maintain temperature of the heating element at a first predefined temperature and/or the temperature of the air leaving the heater assembly at a second predefined temperature.
Optionally, the one or more thermistors are positioned adjacent to the heating element along a plane of the heating element.
Optionally, the one or more thermistors are positioned adjacent to the heating element along a plane downstream and at a predefined distance from a plane of the heating element.
Optionally, the heating element is associated with a heater module being coaxially disposed, upstream or downstream of the blower, in a housing duct associated with the air handling unit, wherein the one or more thermistors are configured at the predefined positions in the heating module.
Optionally, the heater module is one of a plurality of heater modules associated with the heater assembly, wherein the plurality of heater modules are coaxially stacked over each other along a direction of the airflow within the housing duct.
Optionally, the heating element is attached to and supported on a frame in the heater module, wherein the one or more thermistors are positioned, adjacent to the heating element, on the frame.
Optionally, the frame comprises a set of rods arranged parallelly, orthogonally, and/or diagonally to each other along a plane to form a mesh of rods defining the shape of the frame, wherein the one or more thermistors are positioned on at least one of the rods among the set of rods such that the thermistors remains adjacent to the heating element.
Optionally, the frame comprises one or more support plates connected to at least one end of the set of rods, the one or more support plates configured to be removably attached to an inner wall of the housing duct, wherein the one or more thermistors are positioned on at least one of the support plates among the one or more support plates.
Optionally, the heating element has a ring-shaped profile of a predefined inner radius and predefined thickness, wherein the one or more thermistors are positioned around an outer curved circumference of the ring-shaped heating element.
Optionally, the heating element has a linear shape comprising one or more passes and turns, wherein the one or more thermistors are positioned around an outer periphery of the corresponding heating element.
Optionally, the controller is positioned on the first or second support plate.
Optionally, the controller is configured to switch OFF the heating element upon detecting the temperature of the heating element to exceed the first predefined temperature and/or upon detecting the temperature of the air leaving the heater assembly to exceed the second predefined temperature.
Optionally, when the temperature of the heating element is below the first predefined temperature, the controller is configured to reduce the heating capacity of the heating element upon detecting the temperature of the air leaving the heater assembly to exceed the second predefined temperature.
Optionally, when the temperature of the heating element is below the first predefined temperature, the controller is configured to increase the heating capacity of the heating element upon detecting the temperature of the air leaving the heater assembly to be below the second predefined temperature.
Optionally, the controller is configured to control switching and/or speed of the blower to maintain temperature of the heating element at the first predefined temperature and/or the temperature the air leaving the heater assembly at the second predefined temperature.
A second aspect of the invention provides a method for enabling temperature control and safety in an air handling unit configured with a supplemental heater assembly. The method comprises monitoring, using the one or more thermistors configured at predefined positions around a heating element associated with the heater assembly, temperature of the heating element and/or temperature of air leaving or flowing through the heating element, and controlling switching and/or adjusting heating capacity of the heating element based on the monitored temperatures, to maintain the temperature of the heating element at a first predefined temperature and/or the temperature of the air leaving the heater assembly at a second predefined temperature
Optionally, the method comprises the steps of switching OFF the heating element when the temperature of the heating element exceeds the first predefined temperature and/or when the temperature of the air leaving the heater assembly exceeds the second predefined temperature.
Optionally, when the temperature of the heating element is below the first predefined temperature, the method comprises the steps of reducing the heating capacity of the heating element when the temperature of the air leaving the heater assembly exceeds the second predefined temperature.
Optionally, when the temperature of the heating element is below the first predefined temperature, the method comprises the steps of increasing the heating capacity of the heating element when the temperature of the air leaving the heater assembly goes below the second predefined temperature.
Optionally, the method comprises the steps of controlling switching and/or adjusting speed of a blower associated with the air handling unit to maintain temperature of the heating element at the first predefined temperature and/or the temperature the air leaving the heater assembly at the second predefined temperature.
The foregoing summary is illustrative only and is not intended to be in any way limiting. In addition to the illustrative aspects, embodiments, and features described above, further aspects, embodiments, features, and techniques of the invention will become more apparent from the following description taken in conjunction with the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification. The drawings illustrate non-limiting exemplary embodiments of the invention and, together with the description, serve to explain the principles of the invention.
In the drawings, similar components and/or features may have the same reference label. Further, various components of the same type may be distinguished by following the reference label with a second label that distinguishes among the similar components. If only the first reference label is used in the specification, the description is applicable to any one of the similar components having the same first reference label irrespective of the second reference label.

FIG. 1 illustrates an exemplary schematic representation of a temperature control and safety system 100 implemented in a heater assembly 104 of an air handling unit 102.
FIG. 2 illustrates an exemplary representation of an embodiment of one of the heating modules 106 associated with the AHU 102 of FIG. 1, where the heating element has circular shape and the thermistors are arranged around the heating element.
FIG. 3A and 3B illustrates exemplary representation of another embodiment of one of the heating modules 106 associated with the AHU 102 of FIG. 1, where the heating element has linear shape.
FIG. 4 illustrates an exemplary schematic representation of a method 400 for enabling temperature control and safety in a heater assembly of an air handling unit.

DETAILED DESCRIPTION

The following is a detailed description of embodiments of the invention depicted in the accompanying drawings. The embodiments are in such detail as to clearly communicate the invention. However, the amount of detail offered is not intended to limit the anticipated variations of embodiments; on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the scope of the invention as defined by the appended claims.
Various terms are used herein. To the extent a term used in a claim is not defined below, it should be given the broadest definition persons in the pertinent art have given that term as reflected in printed publications and issued patents at the time of filing.
In the specification, reference may be made to the spatial relationships between various components and to the spatial orientation of various aspects of components as the devices are depicted in the attached drawings. However, as will be recognized by those skilled in the art after a complete reading of the specification, the components of this invention described herein may be positioned in any desired orientation. Thus, the use of terms such as "above," "below," "upper," "lower," "first," "second" or other like terms to describe a spatial relationship between various components or to describe the spatial orientation of aspects of such components should be understood to describe a relative relationship between the components or a spatial orientation of aspects of such components.
Electric heating systems are widely used in residential, commercial, and industrial settings due to their efficiency, reliability, and ease of installation. A supplemental electric heater assembly is employed in an air handling unit (AHU) along with a heat exchanger to control the temperature of air supplied by the AHU.
The heater assembly converts electric energy into heat, which is then used for heating the air flowing through the AHU. The core component of the heater assembly is the electric heat element, which generates heat when an electrical current flows through it. Safety is an important concern in the design and operation of heater assemblies. Over-temperature conditions may occur in the heater assembly or AHU due to various reasons. These conditions may not only reduce the efficiency of the heater assembly and the AHU but may also pose significant safety risks, including the potential for fire hazards and damage to the nearby components. Besides, these conditions may also lead to an uncontrolled temperature rise or drop in the air leaving the AHU.
Existing safety mechanism employed in heater assemblies to prevent over-temperature conditions is a temperature-based bimetal switch. This switch may be designed to interrupt the electrical current to the heating element when the air temperature leaving the heater exceeds a pre-set limit. However, the application of temperature-based bimetal switches may present several challenges.
One of the primary limitations may be the need for customizing the size and application of each electric heating element. Given the diverse range of electric heater assembly designs and the specific requirements of different applications, each bimetal switch must be individually set for a unique temperature limit. This not only complicates the manufacturing process but also increases the cost and complexity of managing different bimetal switch configurations. Furthermore, the reliance on a fixed temperature limit may not account for the dynamic conditions under which the heater assembly operates.
There is, therefore, a need to overcome the above-mentioned limitations and drawbacks, by providing an improved and reliable temperature control and safety solution for heater assembly associated with the air handling unit which provides a more adaptable and reliable solution for preventing over-temperature conditions, ensuring the safety, efficiency, and longevity of the heater assembly and the AHU.
Referring to FIGs. 1 and 2, a temperature control and safety system 100 (referred to as a system, hereinafter) for an air handling unit (AHU) 102 configured with a supplemental heater assembly 104 is disclosed. The AHU 102 may generally include a housing duct (not shown) fluidically coupling an inlet and an outlet. Air may be moved through the housing duct from the inlet to the outlet along a direction of flow of air. In one or more embodiments, the AHU 102 may further include blower/fan 108, and a heat exchanger 110. The blower 108 and the heat exchanger 110 may be disposed within the housing duct along a direction of flow of the air, such that the air flowing through the housing duct further flows through the blower 108 and the heat exchanger 110.
The heater assembly 104 may be disposed within the housing duct, along the direction of flow of the air, such that the air flowing through the housing duct flows through the heater assembly 104, the blower 108, and the heat exchanger 110. The heater assembly 104 may include one or more heating modules 106 (collectively referred to as heating modules 106 and individually referred to as heating module 106, herein) that may be configured to heat the air passing through the housing duct. In some embodiments, the heater assembly 104 and the heat exchanger 110 may together be configured to heat the air and regulate the heated air temperature, respectively, that is flowing through the housing duct.
In one or more embodiments, the heater assembly 104 may include a single heating module 106 that may be coaxially disposed within the housing duct, along the direction of flow of the air such that the air downstream of the blower 108 flows through the heater module 106. Further, in one or more embodiments, the heater assembly 104 may include a plurality of heating modules 106, where each of the heating modules 106 may be configured to be coaxially stacked over each other along a direction of the airflow within the housing duct.
In one or more embodiments, the blower 108 may be a mixed airflow blower 108 but is not limited to the like. In one or more embodiments, the blower 108 may be positioned downstream or upstream relative to the heat exchanger 110. Further, the blower 108 may be positioned upstream relative to the heater assembly 104.
The system 100 may include one or more thermistors 112 (collectively referred to as thermistors 112, herein) configured at predefined positions around or adjacent to a heating element 204 or one or more heating elements (designated as 204 in FIGs. 2 to 3B) associated with the heating module(s) 106 of the heater assembly 104. The thermistors 112 may be configured to monitor the temperature of the heating element 204 and/or the temperature of the air leaving or flowing through the heating element 204 or heating module(s) 106. In one or more embodiments, the thermistors 112 may be positioned adjacent to the heating element 204 along a plane of the heating element 204. However, in some embodiments, the thermistors 112 may be positioned adjacent to the heating element 204 along a plane downstream and at a predefined distance from the plane of the heating element 204.
The system 100 or AHU 102 may further include a controller 114 that may be in communication with different components of the AHU 102, including, without limitations, the thermistors 112, the heating module(s) 106, the blower 108, and the heat exchanger 110. The controller 114 may be configured to control the operations of the different components of the system 100 and the AHU 102. The controller 114 may include one or more processors 114-1 coupled to a memory 114-2 storing instructions executable by the processors 114-1, which may cause the controller 114 to perform the designated operations.
The controller 114 may be configured to monitor, using the thermistors 112, the temperature of the heating element 204 and/or the temperature of the air leaving or flowing through the heating element 204 associated with each of the or heating module(s) 106. The controller 114 may accordingly control switching of the or heating module(s) 106 and/or adjust the heating capacity of the heating element(s) 204 based on the monitored temperatures, to maintain the temperature of the heating element(s) 204 at a first predefined temperature and/or maintain the temperature of the air leaving the heating assembly 104 at a second predefined temperature.
In one or more embodiments, when the temperature of the heating element 204 of the or heating module(s) 106 is detected to be below the first predefined temperature, the controller 114 may be configured to reduce the heating capacity of the one or more heating element(s) 204 associated with the heater assembly 104 upon detecting the temperature of the air leaving the heater assembly 104 to exceed the second predefined temperature. Further, in one or more embodiments, when the temperature of the heating element 204 of the or heating module(s) 106 is detected to be below the first predefined temperature, the controller 114 may be configured to increase the heating capacity of the one or more heating element(s) 204 associated with the heater assembly 104 upon detecting the temperature of the air leaving the heater assembly 104 to be below the second predefined temperature.
Furthermore, in one or more embodiments, the controller 114 may be configured to switch-OFF the one or more heating element(s) 204 associated with the heater assembly 104 upon detecting the temperature of the corresponding heating element 204 to exceed the first predefined temperature and/or upon detecting the temperature of the air leaving the heater assembly 104 to exceed the second predefined temperature. In addition, in some embodiments, the controller 114 may additionally control the switching and/or speed of the blower 108 associated with the AHU 102 to maintain the temperature of the heating element 204 at the first predefined temperature and/or the temperature of the air leaving the heater assembly 104 at the second predefined temperature. Accordingly, these operations may facilitate the system 100 in bringing and maintaining the temperature of the air leaving the heater assembly 104 at the second predefined temperature, while keeping the temperature of the heating element 204 of the heating module 106(s) below the first predefined (safe) temperature.
In one or more embodiments, a dedicated controller 114 may be associated with heater assembly 104 where the controller 114 may be removably secured on any of the heating modules 106 as shown in FIGs. 2 to 3B. In other embodiments, each of the heating modules 106 may include a separate controller 114, where each of the controller 114s may be in communication with each other and/or a central control system 100 via a wired or wireless network. Further, in some embodiments, the controller 114 may be a part of the HVAC controls (central control system 100) of the air conditioning system 100 as well.
Referring to FIGs. 2 to 3B, in one or more embodiments, each of the heating modules 106 may include a frame 202 formed by a mesh of rods 202-1 to 202-3, where the heating element 204 is supported on the frame 202. In such embodiments, the thermistors 112 may be positioned on at least one of the rods 202-1 to 202-3 of the frame 202 such that the thermistors 112 remain around and adjacent to the heating element 204.
The frame 202 may be configured to be removably disposed inside the housing duct. The heating module 106 may further include the heating element 204 of a predefined shape and a predefined heating capacity, removably attached to and supported on the frame 202 such that the heating element 204 remains coaxially disposed inside the housing duct upon coaxially positioning the heating module 106 within the housing duct.
In one or more embodiments, as shown in FIG. 2, the heating element 204 of the heating module 106 may have a substantially circular ring-shaped profile. Further, the ring-shaped heating element 204 may have a predefined inner radius and predefined thickness based on the airflow pattern of the air flowing through the respective heating module 106, such that the air (downstream of the blower 108) flows through the heating element 204. In such embodiments, the thermistors 112 may be positioned on the rods 202-1 to 202-3 of the frame 202 such that the thermistors 112 remain positioned circumferentially around and adjacent to an outer curved circumference of the ring-shaped heating element 204 and/or in a central hollow region of the ring-shaped heating element 204.
In one or more embodiments, as shown in FIGs. 3A and 3B, the heating element 204 of the heating modules 106 may have a linear shape having one or more passes or turns. For instance, the heating element 204 may have six passes as shown in FIG. 3A or four passes as shown in FIG. 3B. This heating element 204 may be formed by an angular spiral wound electrical wire of a predefined resistance having a typically linear shape, which may be turned or folded to define the passes and turns. Further, in one or more embodiments, an overall area of such heating element 204 may have a circular profile or other profile based on the airflow pattern of the air flowing through the respective heating module 106, such that the air (downstream of the blower 108) flows through the heating element 204. In one or more embodiments, the thermistors 112 may be positioned on the rods of the frame 202 such that the thermistors 112 remains positioned around and adjacent to an outer periphery of the corresponding heating element 204.
In one or more embodiments, the heating element 204 may be supported on the frame 202 using one or more thermally and electrically insulative devices 206 to electrically and thermally isolate the frame 202 from the heating element 204. In one or more embodiments, the heating element 204 may be supported on the frame 202 using one or more ceramic holders (206 also referred to as ceramic guides 206, herein) to electrically and thermally isolate the frame 202 from the heating element 204. Further, in some embodiments, the frame 202 may also be made of an electrically and thermally insulative material.
In one or more embodiments, the frame 202 may include the rods 202-1 to 202-3 being arranged parallelly, orthogonally, and/or diagonally to each other along a plane to form the mesh of rods defining the shape of the frame 202. The rods 202-1 to 202-3 may be arranged to define the frame 202 based on an inner profile of the housing duct such that an outer profile of the frame 202 allows the frame 202 or the heating modules 106 to be coaxially fitted within the housing duct without any hindrance.
In one or more embodiments, the frame 202 may include a first set of rods 202-1 arranged parallelly to each other along a plane, a second set of rods 202-2 arranged orthogonally to the first set of rods 202-1, and a third set of rods 202-3 arranged diagonally with respect to the first and second set of rods 202-1, 202-2 to form the mesh of rods defining the shape of the frame 202. Further, these rods 202-1 may remain in contact via the ceramic holders or ceramic guides. Accordingly, the formed mesh or the frame 202 may have an outer profile based on the inner profile of the housing duct, allowing the frame 202 or the heating modules 106 to be coaxially fitted within the housing duct without any hindrance. However, in other embodiments, the rods may be arranged in other fashions as well without any limitations to define the frame 202, as long as the frame 202 allows installation of the heating element 204 thereon and further allows installation of the frame 202 or heating modules 106 coaxially within the duct without any hindrance. Further, the parallelly arranged set of rods (or the first set of rods 202-1) may extend between opposite inner walls of the housing duct to support and help secure the frame 202 or heating modules 106 within the housing duct.
In one or more embodiments, the frame 202 may include one or more 208-1, 208-2 connected to at least one end of the set of rods 202-1 to 202-3. The support plate(s) may 208-1, 208-2 be configured to be removably attached to an inner wall of the housing duct to secure the heating module 106 within the housing duct. Further, the thermistors 112 may be positioned on at least one of the support plates among the support plates 208-1, 208-2, such that the thermistors 112 remain adjacent to the heating element 204 for monitoring the temperature of the corresponding heating element 204 and the air leaving or flowing through the heating element 204.
In one or more embodiments, the frame 202 may include a first support plate 208-1 connecting the first end of each of the first set of rods 202-1 and a second support plate 208-2 connecting the second end of each of the first set of rods 202-1. The first support plate 208-1 and the second support plate 208-2 may be configured to be removably attached to opposite inner walls of the housing duct, allowing the heating modules 106 to be secured within the housing duct. However, in some embodiments, the frame 202 may only include the first support plate 208-1 connecting the first end of each of the first set of rods 202-1. In such embodiments, the first support plate 208-1 may be configured to be removably attached to an inner wall of the housing duct and the second end of each of the first set of rods 202-1 may be configured to be removably attached to another wall, opposite to the first support plate 208-1, of the housing duct. Furthermore, in other embodiments (not shown), the frame 202 may include four support plates being connected in a substantially square or rectangular shape, with the rods extending between opposite plates and the heating element 204 supported on the rods. In such embodiments, the support plates may be configured to be removably attached to the inner walls of the housing duct.
In one or more embodiments, electrical terminals 204-1 of the heating element(s) 204 may extend through the first support plate 208-1 and/or the support second plate 208-2 to allow the electrical connection of the heating module(s) 106 to the controller 114 and a power source associated with the AHU 102. In such embodiments, slots may be formed in any of the support plates to allow extension of the terminals therethrough. Further, in one or more embodiments, the controller 114 may be part of each of the heating modules 106 where the controller 114 may be removably secured on any of the support plates 208-1, 208-2 associated with the heating module 106, thereby forming a stackable heating module 106 that may be stacked and easily removably configured within the housing duct of any AHU 102.
Referring to FIG. 4, method 400 for enabling temperature control and safety in a heater assembly or heating modules associated with an air handling unit is disclosed. Method 400 may involve the thermistors 112, the controller 114, and various other components associated with the system 100 and AHU 102 of FIG. 1. In one or more embodiments, method 400 may include step 402 of monitoring, using the one or more thermistors configured at predefined positions around a heating element associated with the heater assembly, the temperature of the heating element and/or temperature of the air leaving or flowing through the heating element. Method 400 may further include step 404 of controlling switching and/or adjusting the heating capacity of the heating element based on the monitored temperatures, to maintain the temperature of the heating element at a first predefined temperature and/or the temperature of the air leaving the heater assembly at a second predefined temperature.
In one or more embodiments, method 400 may include step 406 of switching OFF the heating element(s) when the temperature of the heating element(s) exceeds the first predefined temperature and/or when the temperature of the air leaving the heater assembly exceeds the second predefined temperature.
Further, in one or more embodiments, when the temperature of the heating element remains below the first predefined temperature, method 400 may include the steps of reducing the heating capacity of the heating element when the temperature of the air leaving the heater assembly exceeds the second predefined temperature. Furthermore, when the temperature of the heating element remains below the first predefined temperature, method 400 may include the steps of increasing the heating capacity of the heating element when the temperature of the air leaving the heater assembly goes below the second predefined temperature. Furthermore, in one or more embodiments, method 400 may include the steps of controlling switching and/or adjusting the speed of the blower associated with the air handling unit to maintain the temperature of the heating element at the first predefined temperature and/or the temperature the air leaving the heater assembly at the second predefined temperature. Accordingly, these operations may facilitate bringing and maintaining the temperature of the air leaving the heater assembly at the second predefined temperature, while keeping the temperature of the heating element of the heating module(s) below the first predefined (safe) temperature.
Thus, this invention overcomes the limitations and drawbacks associated with existing bimetallic strip-based temperature control systems, by providing an improved and reliable temperature control and safety system and method that provides a more adaptable and reliable solution for preventing over-temperature conditions, ensuring the safety, efficiency, and longevity of the heater assembly and the AHU. This system may help control the temperature of the corresponding heating elements and/or further control and vary the temperature of the air leaving the heating elements.
In addition, the heating modules have a modular, stackable, shock-proof, and thermally safe design that may allow technicians to easily stack and install the heating modules within or remove the heating modules from the housing duct associated with existing AHUs. Moreover, the shock-proof and thermally safe design allows the heating modules to safely operate within the AHU without affecting the other components of the AHU.
While the invention has been described with reference to exemplary embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention as defined by the appended claims. Modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed, but that the invention includes all embodiments falling within the scope of the invention as defined by the appended claims.
In interpreting the specification, all terms should be interpreted in the broadest possible manner consistent with the context. In particular, the terms "comprises" and "comprising" should be interpreted as referring to elements, components, or steps in a non-exclusive manner, indicating that the referenced elements, components, or steps may be present, or utilized, or combined with other elements, components, or steps that are not expressly referenced. Where the specification claims refer to at least one of something selected from the group consisting of A, B, C ....and N, the text should be interpreted as requiring only one element from the group, not A plus N, or B plus N, etc.

Claims

A temperature control and safety system (100) for an air handling unit (102) configured with a supplemental heater assembly (104), the system comprising:
one or more thermistors (112) configured at predefined positions around or adjacent to a heating element (204) associated with the heater assembly; and

a controller (114) operatively connected to the one or more thermistors, the heating element, and a blower (108) associated with the air handling unit, wherein the controller comprises one or more processors (114-1) coupled to a memory (114-2) storing instructions executable by the processors, which causes the controller to:
monitor, using the one or more thermistors, temperature of the heating element and/or temperature of air leaving or flowing through the heating element; and

control switching and/or adjust heating capacity of the heating element based on the monitored temperatures, to maintain temperature of the heating element at a first predefined temperature and/or the temperature of the air leaving the heater assembly at a second predefined temperature.
The system (100) of claim 1, wherein the one or more thermistors (112) are positioned adjacent to the heating element (204) along a plane of the heating element,
or, wherein the one or more thermistors are positioned adjacent to the heating element along a plane downstream and at a predefined distance from a plane of the heating element.
The system (100) of any preceding claim, wherein the heating element (204) is associated with a heater module (106) being coaxially disposed, upstream or downstream of the blower (108), in a housing duct associated with the air handling unit (102), wherein the one or more thermistors (112) are configured at the predefined positions in the heating module, or, wherein the heater module is one of a plurality of heater modules associated with the heater assembly (104), wherein the plurality of heater modules are coaxially stacked over each other along a direction of the airflow within the housing duct.
The system (100) of any preceding claim, wherein the heating element (204) is attached to and supported on a frame (202) in the heater module (106), wherein the one or more thermistors (112) are positioned, adjacent to the heating element, on the frame.
The system (100) of claim 4, wherein the frame (202) comprises a set of rods (202-1, 202-2, 202-3) arranged parallelly, orthogonally, and/or diagonally to each other along a plane to form a mesh of rods defining the shape of the frame, wherein the one or more thermistors (112) are positioned on at least one of the rods among the set of rods such that the thermistors remain adjacent to the heating element (204).
The system (100) of claim 5, wherein the frame (202) comprises one or more support plates (208-1, 208-2) connected to at least one end of the set of rods (202-1, 202-2, 202-3), the one or more support plates configured to be removably attached to an inner wall of the housing duct, wherein the one or more thermistors (112) are positioned on at least one of the support plates among the one or more support plates.
The system (100) of any preceding claim, wherein the heating element (204) has a ring-shaped profile of a predefined inner radius and predefined thickness, wherein the one or more thermistors (112) are positioned around an outer curved circumference of the ring-shaped heating element,
and/or, wherein the heating element has a linear shape comprising one or more passes and turns, wherein the one or more thermistors are positioned around an outer periphery of the corresponding heating element.
The system (100) of claim 6 or claim 7 when dependent from claim 6, wherein the controller (114) is positioned on the first or second support plate (208-1, 208-2).
The system (100) of any preceding claim, wherein the controller (114) is configured to switch OFF the heating element (204) upon detecting the temperature of the heating element to exceed the first predefined temperature and/or upon detecting the temperature of the air leaving the heater assembly (104) to exceed the second predefined temperature.
The system (100) of any preceding claim, wherein when the temperature of the heating element (204) is below the first predefined temperature, the controller (114) is configured to reduce the heating capacity of the heating element upon detecting the temperature of the air leaving the heater assembly (104) to exceed the second predefined temperature,
or, wherein when the temperature of the heating element is below the first predefined temperature, the controller is configured to increase the heating capacity of the heating element upon detecting the temperature of the air leaving the heater assembly to be below the second predefined temperature.
The system (100) of any preceding claim, wherein the controller (114) is configured to control switching and/or speed of the blower (108) to maintain temperature of the heating element (204) at the first predefined temperature and/or the temperature the air leaving the heater assembly (104) at the second predefined temperature.
A method for enabling temperature control and safety in an air handling unit (102) configured with a supplemental heater assembly (104), the method comprising:
monitoring, using the one or more thermistors (112) configured at predefined positions around a heating element (204) associated with the heater assembly, temperature of the heating element and/or temperature of air leaving or flowing through the heating element; and

controlling switching and/or adjusting heating capacity of the heating element based on the monitored temperatures, to maintain the temperature of the heating element at a first predefined temperature and/or the temperature of the air leaving the heater assembly at a second predefined temperature.
The method of claim 12, wherein the method comprises the steps of switching OFF the heating element (204) when the temperature of the heating element exceeds the first predefined temperature and/or when the temperature of the air leaving the heater assembly (104) exceeds the second predefined temperature.
The method of claim 12 or 13, wherein when the temperature of the heating element (204) is below the first predefined temperature, the method comprises the steps of reducing the heating capacity of the heating element when the temperature of the air leaving the heater assembly (104) exceeds the second predefined temperature,
or, wherein when the temperature of the heating element is below the first predefined temperature, the method comprises the steps of increasing the heating capacity of the heating element when the temperature of the air leaving the heater assembly goes below the second predefined temperature.
The method of any one of claims 12 to 14, wherein the method comprises the steps of controlling switching and/or adjusting speed of a blower (108) associated with the air handling unit (102) to maintain temperature of the heating element (204) at the first predefined temperature and/or the temperature the air leaving the heater assembly (104) at the second predefined temperature.