WO2016126269A1

WO2016126269A1 - Redundant heating, ventilation, and air conditioning control system

Info

Publication number: WO2016126269A1
Application number: PCT/US2015/014891
Authority: WO
Inventors: Vamsi Krishna Komanduru; Ankith Makam; Yongxi ZHOU; Deenadayalan Karunakaran
Original assignee: Honeywell International Inc.
Priority date: 2015-02-06
Filing date: 2015-02-06
Publication date: 2016-08-11
Also published as: KR20170110144A; KR102347620B1

Abstract

Redundant heating, ventilation, and air conditioning (HVAC) control systems are described herein. One redundant HVAC control system includes an operator workstation and a first communication network connected thereto. The system also includes a first HVAC system controller and a second HVAC system controller each HVAC system controller connected to a second communication network and a third communication network, wherein the first HVAC system controller and a second HVAC system controller communicates with the operator workstation via the second communication network or third communication network via connections between the first communication network and the second and third communication networks, and wherein the second HVAC system controller can execute a set of instructions to monitor the health of the first controller to identify if the second HVAC system controller has to take over for the first HVAC system controller by initiating control of the HVAC system via the second control application.

Description

REDUNDANT HEATING, VENTILATION, AND AIR CONDITIONING

CONTROL SYSTEM

Technical Field

The present disclosure relates to redundant heating, ventilation, and air conditioning control systems.

Background

A heating, ventilation, and air conditioning (HVAC) system can be used to control the climate within a facility (e.g., building). For example, a control system (e.g., controller) of a HVAC system can be used to control the operation of the HVAC system (e.g., the operation of the components of the HVAC system) in order to control the air temperature, humidity, and/or air quality of the facility.

A HVAC system may include redundancies to maintain control over the operation of the HVAC system in the event of a failure of the HVAC system. For example, a HVAC system may include a specially designed redundant (e.g., backup) control system to ensure that the HVAC system continues to operate in the event of a controller failure in the HVAC system.

Previous redundant control systems may be designed to recover and continue the operation of the HVAC system within a very short time (e.g., a few milliseconds) from when the failure occurs. Such high speed redundant control systems, however, can be expensive, and may not be compatible with an existing HVAC system (e.g., as some HVAC systems are older, their legacy hardware and/or software may be incompatible with newer redundancy solutions). For example, such high speed redundant control systems may be designed from scratch, may include complex high speed processors, may need to be separately installed in the existing HVAC system, and/or may use a large amount of network bandwidth in the HVAC system. Brief Description of the Drawings

Figure 1 illustrates a redundant HVAC control system in accordance with one or more embodiments of the present disclosure.

Figure 2 illustrates the operational use of two ports in a HVAC controller according to one or more embodiments of the present disclosure.

Figure 3 illustrates a method of network redundancy in a HVAC controller according to one or more embodiments of the present disclosure.

Figure 4 illustrates a hardware failure scenario having network redundancy in a HVAC controller according to one or more embodiments of the present disclosure.

Figure 5 illustrates a commissioning scenario of network redundancy in a HVAC controller according to one or more embodiments of the present disclosure.

Detailed Description

Redundant heating, ventilation, and air conditioning (HVAC) control systems are described herein. One redundant HVAC control system includes an operator workstation and a first communication network connected thereto. The system also includes a first HVAC system controller and a second HVAC system controller each HVAC system controller connected to a second communication network and a third communication network, wherein the first HVAC system controller and a second HVAC system controller can communicate with the operator workstation via either of the second communication network or third communication network via connections between the first communication network and the second and third communication networks, and wherein the second HVAC system controller is configured to execute a set of instructions to monitor the health of the first controller to identify if the second HVAC system controller has to take over for the first HVAC system controller by initiating control of the HVAC system via the second control application.

Typical HVAC building management systems containing components such as an operator workstation, supervisory plant controller devices, unitary controller devices and/or input and/or output (10) modules, communicate with an operator workstation and/or with other devices using BACnet (a data communication protocol for building automation and control networks) over an Internet protocol (IP) network. The operator monitors and controls all devices and equipment using the workstation. The reliability of monitoring and/or controlling the devices and equipment depends on the availability of one or more supervisory plant controller devices over the BACnet IP network.

Various controllers also communicate with each other using BACnet over IP network. These controllers share the data which are required to run various control algorithms.

In case of any failures in the IP network, the operator may be able to identify the failure but the system will be down until the issue is resolved. Also, the IP network failure detection happens only when operator identifies the status at the operator workstation.

If the IP network, wired or wireless (e.g., Wi-Fi, VLAN, etc.), fails, the system and/or user may face the following problems:

1 ) The operator cannot make any changes to the plant controllers or down the line connected equipment thereby running the system with old values which are not intended;

2) Monitoring the system is not possible due to missing alarms from the devices;

3) Control algorithms may drive unintended outputs due to nonavailability of data shared from various devices across the network;

4) The system may not be able to run effective schedules such pre- cooling or heating or exceptions that may need to run from the devices in regular schedules as writing to these devices may not be possible;

and/or

5) The user may choose to put the equipment to manual mode due to monitoring and controlling doesn't happen thereby potentially making the system inefficient.

The above issues can lead to system down time, as down time depends on the failure detection and rectification of the issue causing the failure. This downtime may cause a non-comfort environment for the building occupants and/or in critical applications where an environmental condition such as temperature, humidity, and/or air pressure needs to be maintained without any deviation and where a failure will potentially cause a production loss to the user.

Possible scenarios for network failures include:

1 ) IP Cable connected to device broken or faulty

2) Cable unplugged from the device

3) Failure at a switch, such as switching power off, malfunctioning, hanging, etc.

Redundant HVAC control systems in accordance with the present disclosure may be less expensive than previous (e.g., high speed) redundant HVAC control systems, and may be compatible with an existing HVAC system (e.g., with the existing/legacy controllers of the HVAC system). For example, redundant HVAC control systems in accordance with the present disclosure may not need to be separately installed in an existing HVAC system, may be compatible with the existing hardware and software of the existing HVAC system, and/or may use a lower amount of network bandwidth than previous redundant HVAC control systems.

In some situations, redundant HVAC control systems in accordance with the present disclosure may not be able to recover and continue the operation of a HVAC system as quickly as previous (e.g., high speed) redundant HVAC control systems. For example, redundant HVAC control systems in accordance with the present disclosure may recover and continue the operation of a HVAC system within a few seconds (e.g., less than five seconds) from when a failure (e.g., a controller failure) occurs in the HVAC system. Such a response time, however, may be appropriate for (e.g., within the acceptable limits of) non-critical (e.g., normal and/or standard) HVAC systems, such as HVAC systems of office buildings, hospitals, and shopping malls, among other facilities.

In the following detailed description, reference is made to the accompanying drawings that form a part hereof. The drawings show by way of illustration how one or more embodiments of the disclosure may be practiced.

These embodiments are described in sufficient detail to enable those of ordinary skill in the art to practice one or more embodiments of this disclosure. It is to be understood that other embodiments may be utilized and that mechanical, electrical, and/or process changes may be made without departing from the scope of the present disclosure.

As will be appreciated, elements shown in the various

embodiments herein can be added, exchanged, combined, and/or eliminated so as to provide a number of additional embodiments of the present disclosure. The proportion and the relative scale of the elements provided in the figures are intended to illustrate the embodiments of the present disclosure, and should not be taken in a limiting sense.

The figures herein follow a numbering convention in which the first digit or digits correspond to the drawing figure number and the remaining digits identify an element or component in the drawing. Similar elements or components between different figures may be identified by the use of similar digits.

As used herein, "a" or "a number of" something can refer to one or more such things. For example, "a number of controllers" can refer to one or more controllers.

Figure 1 illustrates a redundant heating, ventilation, and air conditioning (HVAC) control system 100 in accordance with one or more embodiments of the present disclosure. As shown in Figure 1 , redundant HVAC control system 100 can include a first (e.g., active) HVAC system controller 1 10, a second (e.g., standby) HVAC system controller 120, and an operator workstation 130.

Active controller 1 10 and standby controller 120 can be, for example, direct digital control (DDC) controllers. Operator workstation 130 can be, for example, a computing device, such as a laptop computer, desktop computer, or mobile device (e.g., smart phone, tablet, PDA, etc.). However, embodiments of the present disclosure are not limited to a particular type of controller or workstation.

As shown in Figure 1 , operator workstation 130 can be coupled to (e.g., communicate with) active controller 1 10 and standby controller 120 via connections to networks 126-1 , 126-2, and 126-3 among potentially other networks.

Further, active controller 1 10 and standby controller 120 can be coupled (e.g., communicate) via a network 128, as illustrated in Figure 1 . The first HVAC system controller can be configured to execute a set of instructions to monitor the health of the second controller to identify if the first HVAC system controller has to take over for the second HVAC system controller by initiating control of the HVAC system via the first control application, for example, via network 128 or other suitable direct or indirect connection between the first and second controller.

Networks 126-1 , 126-2, 126-3, and 128 can be wired or wireless networks of HVAC control system 100. For instance, in the embodiment illustrated in Figure 1 , network 128 can be a master slave token passing (MSTP) network, and network 126-1 , 126-2, and 126-3 can be Internet protocol (IP) networks. However, embodiments of the present disclosure are not limited to a particular type of network or that each of the networks 126 be the same type of network as the other networks 126.

Embodiments of the redundant HVAC control system of the present disclosure can include embodiments wherein all devices connected to the second communication network, including the first and second HVAC system controllers, have the same subnet and wherein all devices connected to the first communication network, including the operator workstation, have a subnet that is different from that of the second communication network. Further, in some embodiments, the first HVAC system controller and a second HVAC system controller each have a unique, different MAC address. In various embodiments, the first HVAC system controller and a second HVAC system controller each have a unique, different Internet protocol address. The first HVAC system controller and a second HVAC system controller each have the same BACnet instance identifier (e.g., instance number), in some embodiments. In these manners, the chances of one failure affecting both sets of devices can be reduced or eliminated.

As used herein, a "network" (e.g., networks 126-1 , 126-2, 126-3, and 128) can provide a communication system that directly or indirectly links two or more computers and/or peripheral devices and allows users to access resources on other computing devices and exchange messages with other users.

A network can allow users to share resources on their own systems with other network users and to access information on centrally located systems or on systems that are located at remote locations. For example, networks 126-1 , 126-2, 126-3, and 128 can tie a number of computing devices together to form a distributed control network.

A network may provide connections to the Internet and/or to the networks of other entities (e.g., organizations, institutions, etc.). Users may interact with network-enabled software applications to make a network request, such as to get a file, print on a network printer, or actuate a device. Applications may also communicate with network management software, which can interact with network hardware to transmit information between devices on the network.

In embodiments of the present disclosure, failure protection can be provided through use of a number of redundant components. For example, in the embodiment of Figure 1 , the system 100 includes multiple networks 126-1 , 126-2, and 126-3. The active controller 1 10 and the standby controller 120 each have two ports that are each connected to a different network.

For instance, active controller 1 10 has a connection 1 18-1 from a port on the controller to network 126-2 and another connection 1 18-2 from a port on the controller to network 126-3. Standby controller 120 also has a connection 1 19-1 from a port on the controller to network 126- 2 and another connection 1 19-2 from a port on the controller to network 126-3.

These networks are also in communication with the operator workstation 130 (e.g., via one or more network routers 136 and connections 1 16-1 to network 126-1 (which can be used to allow communication between operator workstation 130 and network router 136), 1 16-2 to network 126-2, and 1 16-3 to network 126-3). In this manner, should one network have a failure, the other network may be able to continue communication. In addition to, or alternatively to, the system having redundant controllers and networks, the utilization of ports on the controllers can also be used in providing failure protection. Such an implementation will be discussed in more detail with respect to Figure 2 below.

As shown in Figure 1 , active controller 1 10 can include a processor 1 12 and a memory 1 14, and standby controller 120 can include a processor 122 and a memory 124. Memory locations 1 14 and 124 can be any type of storage medium that can be accessed by processors 1 12 and 122, respectively, to perform various examples of the present disclosure.

For example, memory locations 1 14 and 124 can be a non- transitory computer readable medium having computer readable instructions (e.g., computer program instructions) stored thereon that are executable by processors 1 12 and 122, respectively, to perform various examples of the present disclosure. That is, processors 1 12 and 122 can execute the executable instructions stored in memory locations 1 14 and 124, respectively, to perform various examples of the present disclosure.

Memory locations 1 14 and 124 can be volatile or nonvolatile memory. Memory locations 1 14 and 124 can also be removable (e.g., portable) memory, or non-removable (e.g., internal) memory. For example, memory locations 1 14 and 124 can be random access memory (RAM) (e.g., dynamic random access memory (DRAM) and/or phase change random access memory (PCRAM)), read-only memory (ROM) (e.g., electrically erasable programmable read-only memory (EEPROM) and/or compact-disk read-only memory (CD-ROM)), flash memory, a laser disk, a digital versatile disk (DVD) or other optical disk storage, and/or a magnetic medium such as magnetic cassettes, tapes, or disks, among other types of memory.

Further, although memory locations 1 14 and 124 are illustrated as being located in active controller 1 10 and standby controller 120, respectively, embodiments of the present disclosure are not so limited. For example, memory locations 1 14 and 124 can also be located internal to another computing resource (e.g., enabling computer readable instructions to be downloaded over the Internet or another wired or wireless connection).

An operator (e.g., a field engineer or technician) of operator workstation 130 can use (e.g., via network 126) active controller 1 10 and/or standby controller 120 to control the HVAC system of a facility. That is, active controller 1 10 and/or standby controller 120 can be used by the operator of workstation 130 (e.g., via one or more of networks 126-1 , 126-2, and 126-3) to control the climate within the facility (e.g., building). The facility may be, for example, an office space, a hospital, or a shopping mall, among other types of facilities.

The HVAC system of the facility may include a number of components whose operating parameters can be controlled by active controller 1 10 and standby controller 120. For example, the HVAC system may include objects, control components, equipment, devices, networks, sensors, and/or actuators such as, for instance, valves such as a heating and/or cooling valves, chillers (e.g., chiller plant), boilers (e.g., boiler plant), pumps such as hot water and/or chilled water pumps, fans, compressors, air dampers such as a variable air volume (VAV) damper, air handling units (AHUs) (e.g., AHU plant), coils such as a heating and/or cooling coil, air filters, and/or cooling towers, among other components.

The HVAC system may also include connections (e.g., physical connections) between the components, such as a chain of equipment (e.g., duct work, pipes, ventilation, and/or electrical and/or gas

distribution equipment) that connects the components, among other connections. Further, the HVAC system may include (e.g., be divided into) a number of zones, which can correspond to different zones (e.g., rooms, areas, spaces, and/or floors) of the building.

For example, active controller 1 10 can execute a set of

instructions of a control application for controlling the HVAC system (e.g., for controlling the operating parameters of the components of the HVAC system). The control application (e.g., the set of instructions executed by active controller 1 10) can be executed in a particular sequence for an indefinite number of cycles over an indefinite amount of time in order to continuously maintain the desired control of the HVAC system. A cycle can be considered a complete execution of the entire set of instructions of the control application.

In some embodiments, active controller 1 10 may execute the set of instructions based on the status of active controller 1 10 and standby controller 120 (e.g., based on whether the status of the controllers is active, standby, error, or maintenance). For example, active controller 1 10 may use the status of active controller 1 10 and/or standby controller 120 to determine when and/or how to execute the set of instructions (e.g., when to log, what control actions to take, etc.).

Further, active controller 1 10 and standby controller 120 can send (e.g., via network 126) their respective status (e.g., active, standby, error, or maintenance) to operator workstation 130. That is, the status of active controller 1 10 and standby controller 120 can be monitored from operator workstation 130 (e.g., by the operator of operator workstation 130).

Upon executing the set of instructions of the control application, active controller 1 10 can send (e.g., via network 1 16) the output of only a subset of the executed instructions to standby controller 120, such that only the output of that subset of the executed instructions is synchronized between active controller 1 10 and standby controller 120. That is, the output of the other executed instructions may not be sent to standby controller 120 by active controller 1 10 (e.g., the output of the other executed instructions are not synchronized between active controller 1 10 and standby controller 120). Synchronizing the output of only a subset of the executed instructions in such a manner can significantly reduce the amount of data to be synchronized, and can make the amount of data synchronized independent of the quantity of instructions in the control application, in some implementations.

After receiving the output of the subset of the executed

instructions from active controller 1 10, and upon a failure of active controller 1 10, standby controller 120 can execute the set of instructions of the control application using the received output. For example, upon a failure of active controller 1 10, standby controller 120 can use the received output to initialize its control application runtime and continue the execution of the set of instructions from the point of failure. The failure of active controller 1 10 can be detected by standby controller 120 (e.g., via networks 126-1 , 126-2, 126-3, and/or 128).

In some embodiments, active controller 1 10 and standby controller 120 may be existing controllers of HVAC control system 100 (e.g., controllers that did not include the control application when they were installed in HVAC control system 100). In such embodiments, the control application can be installed in existing active controller 1 10 and existing standby controller 120 by downloading the control application to existing controllers 1 10 and 120 using the existing (e.g., previously engineered and commissioned) hardware and software of HVAC control system 100 and existing controllers 1 10 and 120. That is, the control application can be downloaded to existing active controller 1 10 and existing standby controller 120 from operator workstation 130 via network 126, and can be compatible with existing controllers 1 10 and 120 (e.g., compatible with the existing application format and algorithms of controllers 1 10 and 120).

In some embodiments, the control application can be installed in active controller 1 10 and standby controller 120 before they are installed in an existing HVAC control system such as HVAC control system 100 (e.g., the control application can be installed in controllers 1 10 and 120 "out of the box"). That is, the control application can be installed in active controller 1 10 and standby controller 120, and controllers 1 10 and 120 can then be installed in an existing HVAC control system (e.g., HVAC control system 100) subsequent to the installation of the control application.

In various embodiments, the system (e.g., system 100) can include one or more I/O modules 132. These modules can be used, for example, to communication instructions and/or actions to a device to accomplish a task and/or receive information from other devices, such as sensor and/or status information. The interaction with the I/O module can be accomplished via a wired or wireless direct or network connection 134.

Further, in some embodiments, the system components can have separate power supplies to enable them to keep power if there is a power failure to the facility or area therein containing the components. For example, the embodiment of Figure 1 can include a power supply for the first system controller, a power supply for the second system controller, and/or a power supply for I/O module.

In an example embodiment, a redundant heating, ventilation, and air conditioning (HVAC) control system can include an operator workstation and a first communication network connected thereto. The embodiment also includes, a HVAC system controller having a first port and a second port and the HVAC system controller connected via its first port to a second communication network and via its second port to a third communication network.

In such an embodiment, the HVAC system controller can communicate with the operator workstation via either of the second communication network or third communication network via connections between the first communication network and the second and third communication networks. The HVAC system controller is configured to execute a set of instructions to switch one or more of the communication ports of the HVAC system controller between active and standby states when a failure of one of the communication ports is detected.

Also, as discussed herein, in some embodiments, the system further includes a second HVAC system controller having first and second ports and wherein the second HVAC system controller is configured to execute a set of instructions to monitor the health of the first controller to identify if the second HVAC system controller has to take over for the first HVAC system controller by initiating control of the HVAC system via the second control application.

The system can further include a second HVAC system controller having first and second ports and wherein the first and second ports of the second HVAC system controller have a different MAC address from the MAC address of the first and second ports of the first HVAC system controller. Additionally, the first and second ports of the first HVAC system controller can have a different IP address from the first and second ports of the second HVAC system controller. Further, the first and second ports of the first HVAC system controller can be on a different subnet from the first and second ports of the second HVAC system controller. A BACnet protocol can also be used to communicate a status of at least one of the first and second controller, in some embodiments. Through use of one or more of the above techniques, the impact of a failure in the system can be reduced or eliminated.

Another example redundant heating, ventilation, and air conditioning (HVAC) control system includes an operator workstation and a first communication network and a first HVAC system controller and a second HVAC system controller each controller having a first port and a second port and each HVAC system controller connected via its first port to a second communication network and via its second port to a third communication network.

In such an embodiments, the first HVAC system controller and a second HVAC system controller can communicate with the operator workstation via either of the second communication network or third communication network via connections between the first communication network and the second and third communication networks.

The first HVAC system controller can be configured to execute a set of instructions to run a control application that can control a HVAC system and switch one or more of the communication ports of the first HVAC system controller between active and standby states when a failure of one of the communication ports is detected. The second HVAC system controller can be configured to execute a set of instructions to run a control application that can control a HVAC system and monitor the health of the first controller to identify if the second HVAC system controller has to take over for the first HVAC system controller by initiating control of the HVAC system via the second control application.

In some embodiments, the second HVAC system controller is further configured to execute a set of instructions to switch one or more of the communication ports of the second HVAC system controller between active and standby states when a failure of one or the communication ports of the second HVAC system controller is detected.

The system can further include a network router that connects the first communication network, second communication network, and third communication network, and allows communication between the first HVAC system controller and a second HVAC system controller and the operator workstation, as illustrated in the embodiment of Figure 1 .

In some embodiments, the computer readable instructions are executable by the processor to execute, by the second HVAC system controller upon the failure of the first HVAC system controller, the set of instructions of the control application using state information (the active or standby state of one or both controllers) from one or both controllers. In various embodiments, the computer readable instructions are executable by the processor to send a status of the first and second HVAC system controllers to an operator workstation of the HVAC system.

Figure 2 illustrates the operational use of multiple (e.g., two) ports in a HVAC controller according to one or more embodiments of the present disclosure. In various embodiments, the HVAC controller 210 can include multiple ports 240-1 and 240-2.

For example, in HVAC controller 210, only one of the ports 240-1 and 240-2 will be enabled and other port will be disabled, for example, through the software and/or firmware running in the controller. This allows the HVAC controller to communicate over the network using port 240-1 and to not communicate using port 240-2, as it is disabled.

This can be beneficial in some applications where, if the network status of HVAC controller 210 is down (e.g., due, for example, to a cable being unplugged, physical failure, a communication switch that port is connected to is down, or hardware failure of port 240-1 ) then the controller port 240-1 can be disabled and port 240-2 can be enabled. This allows communication to continue during a period when a portion of the system has failed.

This transition from port 240-1 to port 240-2 is shown in the Figure 2. Thereon, the HVAC controller 210 that has been communicating over port 240-1 will start communicating via port 240-2 over the network.

In some embodiments, the first and second ports can, for example, carry out this communication via the same MAC address. If the failure detected with respect to communication on port 240-1 on the HVAC controller 210 is resolved, the controller 210 will have the option to still communicate on port 240-2 without disturbing the states of the ports or to make the switch back to port 240-1 by enabling port 240-1 and disabling port 240-2. As discussed above, embodiments of the redundant HVAC control system can include wherein the second HVAC system controller is further configured to execute a set of instructions to switch one or more communication ports of the second HVAC system controller between active and standby states (enabled/disabled) when a failure of one or more communication ports of the second HVAC system controller is detected. Also, in some embodiments, the second HVAC system controller can be configured to execute a set of instructions to switch one or more communication ports of the second HVAC system controller between active and standby states when a failure of one of the communication ports is detected. In these manners, the impact of a failure in the system can be reduced or eliminated.

Figure 3 illustrates a method of network redundancy in a HVAC controller according to one or more embodiments of the present disclosure. The HVAC controller includes multiple ports and is connected to network 1 via port 1 (e.g., a port) and to network 2 via port 2, at block 340.

In the HVAC controller, one port can be enabled and other port shall be disabled through the software and/or firmware running in the controller, at block 342. The HVAC controller can communicate over the network 1 using port 1 , at block 344, and does not communicate using port 2, as it is disabled.

In some instances, if the network status of the HVAC controller is down due, for example, to a cable being unplugged, physical failure, the switch this cable is connected is down or hardware failure of port 1 , at block 346, the controller port 1 can be disabled and port 2 can be enabled, at block 348. Thereon, the HVAC controller can start communicating via port 2 over the network 2, at block 350. If the failure detected over port 1 on the HVAC controller is resolved, at block 352, the controller can continue communicating on port 2 without disturbing their states, at block 354. Figure 4 illustrates a hardware failure scenario having network redundancy in a HVAC controller according to one or more embodiments of the present disclosure. The first HVAC controller, being the active controller, is communicating with a workstation over IP, and the second HVAC controller, being the standby controller, at block 460 and not communicating with the workstation, as it is not active. In some such embodiments, the standby controller continuously checks the health of the active controller (e.g., using Ethernet communication), at block 462.

In the example scenario of Figure 4, the first HVAC controller fails due to hardware failure and is unrecoverable, at block 464. The second HVAC controller then detects the failure and becomes active, at block 466.

In some embodiments, when the user acts to replace the first HVAC controller with new hardware at block 468, the second HVAC controller puts this new first HVAC controller into a maintenance state at block 470. Then, the second HVAC controller can synchronize the firmware, control application, and all the data being passed to the second controller to the first HVAC controller, at block 472.

Once the synchronization is complete, the first HVAC controller becomes the standby controller, at block 474. Now, the first HVAC controller can monitor the health of the active controller, for example, by using Ethernet communication between the two controllers (e.g., via a connection, such as connection 128 of the embodiment of Figure 1 ).

In such an embodiment, the redundancy of the active and standby controllers provides the failure protection to the system. Some embodiments can combine both, redundant controllers and the redundant ports to provide more robust failure protection.

Figure 5 illustrates a commissioning scenario of network redundancy in a HVAC controller according to one or more embodiments of the present disclosure. In such a scenario, the first HVAC controller is commissioned and is put into operation, at block 580. It starts communicating with the workstation, at block 582. The second HVAC controller, which is not configured, is connected to the network by assigning an IP address, at block 584. It is set as a redundant controller to the first HVAC controller, at block 586. The first HVAC controller puts the second HVAC controller in maintenance status, at block 588, and synchronizes all the required data, at block 590. Once the synchronization is complete, the second HVAC controller acts as a standby controller, at block 592, and can monitor the healthy status of first HVAC controller.

Although specific embodiments have been illustrated and described herein, those of ordinary skill in the art will appreciate that any arrangement calculated to achieve the same techniques can be substituted for the specific embodiments shown. This disclosure is intended to cover any and all adaptations or variations of various embodiments of the disclosure.

It is to be understood that the above description has been made in an illustrative fashion, and not a restrictive one. Combination of the above embodiments, and other embodiments not specifically described herein will be apparent to those of skill in the art upon reviewing the above description.

The scope of the various embodiments of the disclosure includes any other applications in which the above structures and methods are used. Therefore, the scope of various embodiments of the disclosure should be determined with reference to the appended claims, along with the full range of equivalents to which such claims are entitled.

In the foregoing Detailed Description, various features are grouped together in example embodiments illustrated in the figures for the purpose of streamlining the disclosure. This method of disclosure is not to be interpreted as reflecting an intention that the embodiments of the disclosure require more features than are expressly recited in each claim. Rather, as the following claims reflect, inventive subject matter lies in less than all features of a single disclosed embodiment. Thus, the following claims are hereby incorporated into the Detailed Description, with each claim standing on its own as a separate embodiment.

Claims

Claims What is claimed:

1 . A redundant heating, ventilation, and air conditioning (HVAC) control system, comprising:

an operator workstation and a first communication network connected thereto;

a first HVAC system controller running a first control program and a second HVAC system controller each HVAC system controller connected to a second communication network and a third

communication network;

wherein the first HVAC system controller and a second HVAC system controller can communicate with the operator workstation via either of the second communication network or third communication network via connections between the first communication network and the second and third communication networks; and

wherein the second HVAC system controller is configured to execute a set of instructions to monitor the health of the first controller to identify if the second HVAC system controller has to take over for the first HVAC system controller by initiating control of the HVAC system via a second control application.

2. The redundant HVAC control system of claim 1 , wherein the second HVAC system controller is further configured to execute a set of instructions to switch one or more communication ports of the second HVAC system controller between active and standby states when a failure of one or more communication ports of the second HVAC system controller is detected.

3. The redundant HVAC control system of claim 1 , wherein all devices connected to the second communication network, including the first and second HVAC system controllers, have the same subnet and wherein all devices connected to the first communication network, including the operator workstation, have a subnet that is different from that of the second communication network .

4. The redundant HVAC control system of claim 1 , wherein the first HVAC system controller is configured to execute a set of instructions to monitor the health of the second controller to identify if the first HVAC system controller has to take over for the second HVAC system controller by initiating control of the HVAC system via the first control application.

5. The redundant HVAC control system of claim 1 , wherein the second HVAC system controller is configured to execute a set of instructions to switch one or more communication ports of the second HVAC system controller between active and standby states when a failure of one of the communication ports is detected.

6. The redundant HVAC control system of claim 1 , wherein the first HVAC system controller and a second HVAC system controller each have a unique, different MAC address.

7. The redundant HVAC control system of claim 6, wherein the first HVAC system controller and a second HVAC system controller each have a unique, different Internet protocol address.

8. The redundant HVAC control system of claim 1 , wherein the first HVAC system controller and a second HVAC system controller each have the same BACnet instance identifier.

9. A redundant heating, ventilation, and air conditioning (HVAC) control system, comprising:

an operator workstation and a first communication network connected thereto; a HVAC system controller having a first port and a second port and the HVAC system controller connected via its first port to a second communication network and via its second port to a third communication network;

wherein the HVAC system controller can communicate with the operator workstation via either of the second communication network or third communication network via connections between the first communication network and the second and third communication networks;

wherein the HVAC system controller is configured to execute a set of instructions to switch one or more of the communication ports of the HVAC system controller between active and standby states when a failure of one of the communication ports is detected.

10. The redundant HVAC control system of claim 9, wherein the first and second ports have the same MAC address.

1 1 . The redundant HVAC control system of claim 9, wherein the system further includes a second HVAC system controller having first and second ports and wherein the second HVAC system controller is configured to execute a set of instructions to monitor the health of the first controller to identify if the second HVAC system controller has to take over for the first HVAC system controller by initiating control of the HVAC system via the second control application.

12. The redundant HVAC control system of claim 9, wherein the system further includes a second HVAC system controller having first and second ports and wherein the first and second ports of the second HVAC system controller have a different MAC address from the MAC address of the first and second ports of the first HVAC system controller.

13. The redundant HVAC control system of claim 1 1 , wherein the first and second ports of the first HVAC system controller have a different IP address from the first and second ports of the second HVAC system controller.

14. The redundant HVAC control system of claim 1 1 , wherein the first and second ports of the first HVAC system controller are on a different subnet from the first and second ports of the second HVAC system controller.

15. The redundant HVAC control system of claim 1 1 , wherein a BACnet protocol is used to communicate a status of at least one of the first and second controller.

16. A redundant heating, ventilation, and air conditioning (HVAC) control system, comprising:

an operator workstation and a first communication network;

a first HVAC system controller and a second HVAC system controller each having a first port and a second port and each HVAC system controller connected via its first port to a second communication network and via its second port to a third communication network;

wherein the first HVAC system controller and a second HVAC system controller can communicate with the operator workstation via either of the second communication network or third communication network via connections between the first communication network and the second and third communication networks;

wherein the first HVAC system controller is configured to execute a set of instructions to:

run a control application that can control a HVAC system; and

switch one or more of the communication ports of the first HVAC system controller between active and standby states when a failure of one of the communication ports is detected;

wherein the second HVAC system controller is configured to execute a set of instructions to: run a control application that can control a HVAC system; monitor the health of the first controller to identify if the second HVAC system controller has to take over for the first HVAC system controller by initiating control of the HVAC system via the second control application.

17. The redundant HVAC control system of claim 16, wherein the second HVAC system controller is further configured to execute a set of instructions to switch one or more of the communication ports of the second HVAC system controller between active and standby states when a failure of one or the communication ports of the second HVAC system controller is detected.

18. The redundant HVAC control system of claim 16, wherein the system further includes a network router that connects the first communication network, second communication network, and third communication network, and allows communication between the first HVAC system controller and a second HVAC system controller and the operator workstation.

19. The redundant HVAC control system of claim 18, wherein the computer readable instructions are executable by the processor to execute, by the second HVAC system controller upon the failure of the first HVAC system controller, the set of instructions of the control application using state information obtained from the first or second HVAC system controllers.

20. The computer readable medium of claim 16, wherein the computer readable instructions are executable by the processor to send a status of the first and second HVAC system controllers to an operator workstation of the HVAC system.