ClimateTalk

ClimateTalk is an open communications protocol developed by Emerson Climate Technologies principally for the HVAC sector. The protocol is designed to be simple to use and low cost while providing control and diagnostic capabilities for residential applications. ClimateTalk is standards-based and focused on the data to simplify implementation. It also allows for each device to make its own decisions, providing flexibility, customization, and interoperability within a common framework.
Typical high-efficiency HVAC control systems are complex and involve pulling additional wires as well as tedious setting of many dip switches. The demand in the market for energy savings and comfort associated with these systems is growing but often high end equipment is not quoted or installed. This is typically because of the variability in the installation, additional training required to get the job done and potential costs of a bad installation. The initial deployment of the ClimateTalk protocol allows for easy control of heating, ventilation, or air-conditioning (HVAC) devices. Initial installation goes more smoothly; maintenance and upgrades are less complicated.
Overview
The ClimateTalk specification defines an open communications protocol, the language used to convey information between devices in a residential environment. ClimateTalk has been developed for either full functionality at a system level or reduced functionality (and reduced overhead) at a component level. The protocol then allows communication between the devices on the network by automatically recognizing components on the system.
The ClimateTalk 1.0 physical layer is based on the RS485 standard with additional requirements for protection against incorrect wiring, common in a residential installation. A network coordinator manages the network and coordinates the communication between devices. The network coordinator functions dynamically, allowing for upgradability and redundancy in the network. Application layer messages carry data and commands between devices on the network.
The ClimateTalk protocol has been developed to allow device manufacturers to readily code communications software. Because the protocol is open and reference sets are available, adoption is simple for manufacturers. Even though it is an open protocol, device manufacturers can embed proprietary messages within the ClimateTalk protocol, protecting their own intellectual property.
Because the communication intelligence is coded into the device, installation of compatible devices is much simpler. ClimateTalk includes auto-configuration capability; no field settings are required. The devices designed with ClimateTalk protocol are then easily installed by technicians without the need for specialized training, reducing complexity for HVAC contractors. ClimateTalk provides “plug-and-play” capability for HVAC controls. Once installed, the communication environment under this protocol provides operational and diagnostic information about the devices in the network. The information protects the homeowner’s investment; the system can monitor for faults and prevent operation under damaging conditions. Available diagnostics also help the contractor accurately troubleshoot for problems and repair them quickly. Finally, the ClimateTalk protocol enables use of generic controls in field replacement as critical operational parameters are stored with - and can be retrieved from - the nodes on the network. The contractor can reduce the inventory of replacement parts to a few key components, simplifying inventory and field replacement.
Uses of the Specification - Intended Applications and Devices
ClimateTalk has been designed initially around the heating, ventilating, and air conditioning (HVAC) application in a residential environment. In this application, communication occurs between many kinds of HVAC devices, such as:
• a thermostat,
• a furnace or air handler
• an air conditioner or heat pump
Each device communicates with every other device in the network through the network coordinator. Communication is around a few very basic queries which can be simplified to:
• This is who I am (what kind of device)
• This is what information I need
• Who are you?
• What information do you need?
ClimateTalk streamlines communications so that each device only sees information it needs and does not get overloaded with data from unrelated tasks.
Field Installation, Troubleshooting and Repair

The ClimateTalk protocol features auto-configuration of the devices in the network. As such, no programming of addresses or functions in the field is required. Installation involves simply connecting the 4 wires typically available in an HVAC system. Installers do not need to be communication systems experts to establish a network of ClimateTalk devices.
Since configuration data is stored in multiple nodes in the network, field replacement of a failed component also does not require field programming. Also, diagnostics of a failure point can be accomplished from anywhere in the network.
Device Types Accommodated by ClimateTalk Protocols
The ClimateTalk protocol has been initially designed around the elements of an HVAC system used in a residential environment. ClimateTalk message sets can be expanded to accommodate many other control applications such as air quality equipment, energy management systems and an unlimited number of applications that can benefit from advanced control and diagnostics capabilities. Easy adaptability, through the use of the reference sets, is one of the protocol's strengths.
Devices can be designed and optimized to operate at one of two levels in the system protocol. A Tier 1 device is fully functional; it has a direct connection to the network, it utilizes the full data packet and can access all of the information within a system. A Tier 2 device trades reduced functionality for a lower overhead; it has an indirect connection to the network, it utilizes a partial data packet, and it cannot directly access system information.
ClimateTalk Open Protocol Design
ClimateTalk has been developed as an open
protocol so that equipment from several manufacturers can communicate on a single network. As an open protocol, ClimateTalk has been designed for broad markets and acceptance of the protocol while enabling supplier competition.
As the protocol is managed by the ClimateTalk Alliance, an open community, stakeholders have access to the underlying specifications, can develop applications that run on the network, and can adapt the protocol to new situations and new uses as the protocol evolves. Being an open protocol drives stability and ensures the ClimateTalk roadmap is not guided by any one single-source solution.
Even though it is an open protocol, ClimateTalk can also permit proprietary messages and commands within the open architecture to protect intellectual property and provide feature advantages.
The HVAC market already recognizes some benefits of an open protocol through the adoption of common wiring schemes. Color-coding whereby green fan, yellow cool, and white = heat has created an open HVAC protocol concerning the 24VAC wiring. ClimateTalk has been designed to continue this legacy of plug and play connectivity.
Generally, only the simplest protocols are used alone. Most protocols, especially in the context of communications or networking, are layered together into protocol stacks. ClimateTalk has followed this convention, using the classic 7-layer Open Systems Interconnection (OSI) Reference Model for the fully configured Tier 1 device.
ClimateTalk is a data-centric model, with the system intelligence residing in the routing of the information, not in a computer. There is a common, routable packet of information transmitted, regardless of the profile or devices. The information travels on 2-wires and when used in a 4-wire bundle, both data and power are provided to take advantage of standard HVAC wiring practices. The data flows through standard interfaces to the application.

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