Appliance Group - Thermostat

From the Appliance Group,

Edits and test profiles for Thermostat.

AttachmentSize
6.16 Thermostat.docx339.92 KB

Proposed by Martin Perlot.

Proposed by Martin Perlot.

Replace the test profile described in the submission with these Test Profiles. The work from the Working Group is incomplete, and fails to account for a number of combinations and contexts.

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Profile 88B: Base Thermostat
This profile is the base for all thermostat profiles, and describes a passive thermostat – that is, a thermostat that holds the necessary settings for active air conditioning, fans, and furnaces, but does not actively direct their operation.

ID: 88B-S-01
Datum: THERMOSTAT_COMMAND_1, THERMOSTAT_STATUS_1
Test: THERMOSTAT_COMMAND_1 is sent, with arbitrary Operating Mode, Fan Mode, Fan Speed, Set Point Heat, and Set Point Cool.
Desired Response: THERMOSTAT_STATUS_1 is broadcast with the indicated values. The broadcast is repeated at least every 5000ms.

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Profile 88C: Base Thermostat with Scheduling
Prerequisite: 88B – Base Thermostat
This profile adds scheduling to the basic profile. The minimal requirement for scheduling is the support of instances 0 (Sleep), 1 (Wake) and 2 (Away).

ID: 88C-S-01
Datum: THERMOSTAT_SCHEDULE_COMMAND_1, THERMOSTAT_SCHEDULE_STATUS_1
Test: THERMOSTAT_SCHEDUKE_COMMAND_1 is sent with Schedule Mode 0 (Sleep) and arbitrary values for Start Hour, Start Minute, Set Point Heat and Set Point Cool. The test is repeated for Schedule Mode 1 (Wake) with distinct set points and start times; and 2 (Away) with distinct set points and FFh (No Data) values for start times.
Desired Response: THERMOSTAT_SCHEDULE_STATUS_1 is broadcast with the indicated values.

ID: 88C-S-02
Datum: THERMOSTAT_COMMAND_2, THERMOSTAT_STATUS_2
Test: After test 88C-S-01 is complete, THERMOSTAT_COMMAND_2 is sent with Schedule Mode 0 (Sleep). The test is repeated with values of 1 (Wake) and 2 (Away).
Desired Response: THERMOSTAT_STATUS_2 is broadcast with the indicated Schedule Mode Instance. THERMOSTAT_STATUS_1 is broadcast with the Set Points used in test 88C-S-01.
When entering Away mode, GENERIC_ALARM_STATUS is sent with Instance 2 (Entering Away Mode).

ID: 88C-S-03
Datum: THERMOSTAT_STATUS_1, Schedule Mode
Test: THERMOSTAT_COMMAND_1 is sent with Schedule Mode 1 (Enabled). The test is repeated with Schedule Mode 0 (Disabled).
Desired Response: THERMOSTAT_STATUS_1 is sent with the appropriate Schedule Mode value.

ID: 88C-S-04
Datum: DATE_TIME_STATUS
Test: After test 88C-S-02, and with Scheduling Mode 1 (Enabled) and Current Schedule 0 (Sleep), DATE_TIME_STATUS is sent over the course of three minutes, starting with values two minutes previous to the Wake starting time and incremented normally. The test is repeated with the time beginning three minutes before the Sleep start time.
Desired Response: Within one minute of the programmed Wake start time, the product broadcasts THERMOSTAT_STATUS_1 and THERMOSTAT_STATUS_2 with values consistent with being in Wake mode. Within one minute of the programmed Sleep start time, the same DGNs are broadcast with values consistent with Sleep mode. In both tests, GENERIC_ALARM_STATUS is sent with Instance 1 (Entering New Schedule Mode).

ID: 88C-S-05
Datum: Away Mode
Test: As in 88C-S-04, but beginning with Current Schedule 2 (Away).
Desired Response. The unit shall remain in Away mode throughout the test.

ID: 88C-S-06
Datum: THERMOSTAT_COMMAND_2, Reset to Current
Test: After test 88C-S-02, and with Scheduling Mode 1 (Enabled) and Current Schedule 2 (Away), THERMOSTAT_COMMAND_2 is sent with Current Schedule Instance 251 (Reset to Current).
Desired Response: The unit shall broadcast THERMOSTAT_STATUS_1 and THERMOSTAT_STATUS_2 with values consistent with the Schedule Mode appropriate to the current time. GENERIC_ALARM_STATUS is sent with Instance 3 (Leaving Away Mode).

ID: 88C-S-07
Datum: DATE_TIME_STATUS
Test: DATE_TIME_STATUS is not broadcast for one minute.
Desired Response: A DM_RV is broadcast with Standardized SPN 8 (Node Date/Time).
This test is unnecessary if the device meets the requirements of an RV-C-compliant clock.

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Profile 88Z: Temperature Sensor

ID 88Z-S-01
Datum: AMBIENT_TEMPERATURE_STATUS, Ambient Temperature
Test: The unit is operated under normal conditions.
Required Response: AMBIENT_TEMPERATURE_STATUS is broadcast with a gap of no more than 5000ms, and Ambient Temperature equal to the current sensor reading. The accuracy must be reasonably appropriate for use as a room thermostat.

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Profile 88A: Active Thermostat w/ Internal Temperature Sensor

This profile applies to thermostats that actively manage a networked air conditioner and which have an internal temperature sensor. The air conditioner(s) is required to be compliant with Profile 103H (Slave Air Conditioner with Hysteresis).

Prerequisite: 88B Base Thermostat, 88Z Temperature Sensor

Test 88A-S-01
Datum: THERMOSTAT_COMMAND_1 - OpMode Cool/Auto/Off
1. THERMOSTAT_COMMAND_1 is sent with Operating Mode = 1 (Cool), Set Point Cool set 5 degF below the current temperature, Fan Speed 0 (Automatic).
2. After step 1 is complete, the test continues with Operating Mode = 0 (Off).
3. As step 1, but with Operating Mode = 3 (Auto)
4. After step 3 is complete, the test continues with Operating Mode = 0 (Off).
Required Response:
1. AIR_CONDITIONER_COMMAND is sent immediately with Operating Mode 1 (Manual), Output Level 200 (100%), Fan Speed 0 (Automatic).
2. AIR_CONDITIONER_COMMAND is sent immediately with Operating Mode 1 (Manual), Output Level 0 (0%).
3. Same as Step 1
4. Same as Step 2.

Test 88A-S-02
Datum: THERMOSTAT_COMMAND_1 – Set Point Cool
1. THERMOSTAT_COMMAND_1 is sent with Operating Mode = 1 (Cool), Set Point Cool 5 degF below the current temperature. The temperature sensor is slowly cooled until it reaches a point where cooling is no longer demanded.
2. After step 2 is complete, the temperature sensor is slowly warmed until it reaches a point where cooling is again demanded.
Required Response:
1. Same as 88A-S-01. When the temperature reaches a point below the Set Point Cool, AIR_CONDITIONER_COMMAND is sent immediately with Operating Mode 1 (Manual), Output Level 0 (0%).
2. When the temperature reaches a point above the Set Point Cool, AIR_CONDITIONER_COMMAND is sent immediately with Operating Mode 1 (Manual), Output Level 200 (100%).
The test does not specify the precise point where the command shall be sent, only that the point is below/above the Set Point Cool.

Test 88A-S-03
Datum: Fan Speed
Test:
1. THERMOSTAT_COMMAND_1 is sent with Operating Mode = 1 (Cool), Set Point Cool set 5 degF below the current temperature, Fan Speed 200 (100%).
2. After Step 1, the test continues with arbitrary values for Fan Speed.
3. After Step 2, the test continues with Fan Speed 0 (Automatic). The temperature sensor is then cooled until it reaches the point where air conditioning is no longer demanded.
Required Response:
1. AIR_CONDITIONER_COMMAND is sent immediately with Operating Mode 1 (Manual), Output Level 200 (100%), Fan Speed 200 (100%).
2. As Step 1, with the Fan Speed per the command.
3. As Step 1, with the Fan Speed initially at 200 (100%). As the temperature cools, the Fan Speed may be allowed to decrease, but implementation of a specific algorithm is not required.

Test 88A-S-04
Datum: THERMOSTAT_COMMAND_1: OpMode 4 (Fan Only)
Test:
1. THERMOSTAT_COMMAND_1 is sent with Operating Mode = 4 (Fan Only), Set Point Cool 5 degF below the current temperature, Fan Speed 0 (Automatic).
2. After step 1 is complete, the test continues with Operating Mode = 0 (Off).
3. Step 1 is repeated with Set Point Cool 5 degF higher than the current temperature.
4. Step 1 is repeated with arbitrary non-zero values for THERMOSTAT_STATUS_1, Fan Speed,
Required Response:
5. Step 1 is repeated with Fan Speed 0 (Automatic). The temperature sensor is then slowly cooled until it reaches the point where no cooling is demanded.
1. AIR_CONDITIONER_COMMAND is sent immediately with Operating Mode 1 (Manual), Output Level 0 (0%), Fan Speed 200 (100%).
2. AIR_CONDITIONER_COMMAND is sent immediately with Operating Mode 1 (Manual), Output Level 0 (0%), Fan Speed 0 (0%).
3. Same.
4. As Step 1, with the Fan Speed per the command.
5. As Step 1, with the Fan Speed initially at 200 (100%). As the temperature cools, the Fan Speed may be allowed to decrease, but implementation of a specific algorithm is not required.

Test 88A-S-05
Datum: THERMOSTAT_COMMAND_1: Fan Mode = 1 (Forced)
Test:
1. THERMOSTAT_COMMAND_1 is sent with Operating Mode = 0 (Off), Fan Mode 1 (On), Fan Speed 0 (Auto).
2. After step 1 is complete, the test continues with THERMOSTAT_COMMAND_1 Fan Mode 0 (Off).
3. Step 1 is repeated with arbitrary non-zero values for Fan Speed.
4. Step 1 is repeated with arbitrary values for Set Point Cool.
Required Response:
1. AIR_CONDITIONER_COMMAND is sent with Operating Mode 1 (Manual), Fan Speed 200 (100%), and Output Level 0 (0%).
2. AIR_CONDITIONER_COMMAND is sent with Operating Mode 1 (Manual), Fan Speed 0 (100%), and Output Level 0 (0%).
3. AIR_CONDITIONER_COMMAND is sent with Operating Mode 1 (Manual), Fan Speed matching the value given, and Output Level 0 (0%).
4. Same. The unit shall ignore the Set Point.

Test 88A-S-06
Datum: SPN - Networked A/C Not Responding
Test:
1. An air conditioner is removed from the network.
2. The air conditioner is replaced on the network.
Required Response:
1. Within 20 seconds, a DM_RV with SPN Networked A/C , FMI 21 (Networked Device Not Responding), and Red Lamp 1 (On). The broadcast is repeated every 1000ms.
2. Within 20 seconds, DM_RV is broadcast with no SPN and Red Lamp 0 (Off).

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Profile 88X: Active Thermostat w/ Network Temperature Sensor
This profile applies to thermostats that actively manage a networked air conditioner and which use a remote (networked) temperature sensor. The air conditioner(s) is required to be compliant with Profile 103H (Slave Air Conditioner with Hysteresis).

Prerequisite: 88B Base Thermostat

Test 88X-S-01
Datum: THERMOSTAT_COMMAND_1 - OpMode Cool/Auto/Off
Test: Same as 88A-S-01, with the network temperature in place of the current temperature.

Test 88X-S-02
Datum: THERMOSTAT_COMMAND_1 – Set Point Cool
Test: Same as 88A-S-02, with the network temperature in place of the current temperature.

Test 88X-S-03
Datum: Fan Speed
Test: Same as 88A-S-03, with the network temperature in place of the current temperature.

Test 88X-S-04
Datum: THERMOSTAT_COMMAND_1: OpMode 4 (Fan Only)
Test: Same as 88A-S-04, with the network temperature in place of the current temperature.

Test 88X-S-05
Datum: THERMOSTAT_COMMAND_1: Fan Mode = 1 (Forced)
Test: Same as 88A-S-05

Test 88X-S-06
Datum: SPN - Networked A/C Not Responding
Test: Same as 88A-S-06

Test 88X-S-07
Datum: SPN - Temperature Not Received
Test:
1. The networked temperature source is removed from the network.
2. The temperature source is restored on the network.
Required Response:
1. Within 20 seconds, a DM_RV with SPN Ambient Temperature, FMI 21 (Networked Device Not Responding), and Red Lamp 1 (On). The broadcast is repeated every 1000ms.
2. DM_RV is broadcast with no SPN and Red Lamp 0 (Off).

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Profile 88H Hysteresis Capability

This profile is implemented in addition to Profile 88A or 88X. To be considered compliant with this profile, the product is tested for either 88A or 88X, but with the following change. In every test in which an air conditioner is turns on or off, logic must be present to prevent short-cycling the air conditioner. Delays based on time, temperature, or some combination are required any time the Output Level is changed repeatedly. Each test which changes the level from on to off or off to on shall be repeated at least twice, rapidly enough to require the operation to be delayed. The specific algorithm need not be specified.

During a delay which keeps the A/C off, AIR_CONDITIONER_COMMAND is sent with a non-zero Output Level and a Max Output Level 0 (0%). At the end of the delay, the same is sent with Max Output Level 200 (100%), or other appropriate non-zero value.

An active thermostat compliant with Profile 88H is compatible with Air Conditioners satisfying Profile 103A.

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Profile 88M Multi-Zone Coordination

This profile is implemented in addition to Profile 88A or 88X for devices which manage multiple thermostat instances.

Test 88M-S-01
Datum: THERMOSTAT_COMMAND_1 - OpMode
Test:
Note: No step begins until the previous step is fully completed.
1. Same as 88A-S-01 or 88X-S-01, Step 1, but with all instances set to OpMode Cool in immediate sequence with a 25ms gap.
2. Same as 88A-S-01 or 88X-S-01, Step 2, but with all instances commanded in immediate sequence.
3. Same as 88A-S-01 or 88X-S-01, Step 3, but with all instances commanded in immediate sequence.
4. Same as 88A-S-01 or 88X-S-01, Step 4, but with all instances commanded in immediate sequence.
Desired Response:
1. As in test 88A-S-01 or 88X-S-01, but initially with Max Output Level set to 0 (0%) for all but one instance. After a delay, AIR_CONDITIONER_COMMAND shall be sent with non-zero Max Output Level to a second instance, and the process repeated until all instances are running. The delay shall be reasonably sufficient to allow a generator to stabilize its AC output.
2. Same as 88A-S-01, Step 2.
3. Same as Step 1.
4. Same as Step 2.

Test 88M-S-02
Datum: THERMOSTAT_COMMAND_1 - Set Point Cool
Test:
. Same as 88A-S-02 or 88X-S-02, Step 1, but with all instances set in immediate sequence with a 25ms gap.
2. Same as 88A-S-01 or 88X-S-01, Step 2, but with all instances commanded in immediate sequence.
3. Same as 88A-S-01 or 88X-S-01, Step 3, but with all instances commanded in immediate sequence.
4. Same as 88A-S-01 or 88X-S-01, Step 4, but with all instances commanded in immediate sequence.
Desired Response:
1. As in test 88A-S-02 or 88X-S-02, but initially with Max Output Level set to 0 (0%) for all but one instance. After a delay, AIR_CONDITIONER_COMMAND shall be sent with non-zero Max Output Level to a second instance, and the process repeated until all instances are running. The delay shall be reasonably sufficient to allow a generator to stabilize its AC output.
2. Same as 88A-S-02, Step 2.
3. Same as Step 1.
4. Same as Step 2.

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Profile 88S : Integrated Thermostat / Air Conditioner with Internal Temperature Sensor

This profile applies to thermostats that are integrated with one or more air conditioners, and which have an internal temperature sensor(s).

Hysteresis to prevent short-cycling the compressor is required as part of this profile. In all tests, a delay to prevent short-cycling the compressor or preventing AC power sags is allowed. During the delay, AIR_CONDITIONER_STATUS should be sent with Max Output Level 0 (0%) and Output Level 0 (0%). At the end of the delay, AIR_CONDITIONER_STATUS should be sent with Max Output Level 200 (100%) and Output Level 200 (100%).

Prerequisite: 88B Base Thermostat, 88Z Temperature Sensor

ID: 88S-S-01
Datum: AIR_CONDITIONER_STATUS
Test: The unit is operated under normal conditions
Required Response: Every five seconds, and on change, AIR_CONDITIONER_STATUS is broadcast with correct values for Fan Speed, Max Fan Speed, Output Level, and Max Output Level. Note that Operating Mode is not required.

Test 88S-C-01
Datum: THERMOSTAT_COMMAND_1 - OpMode Cool/Auto/Off
1. Same THERMOSTAT_COMMAND_1 is sent with Operating Mode = 1 (Cool), Set Point Cool set 5 degF below the current temperature, Fan Speed 0 (Automatic).
2. After step 1 is complete, the test continues with Operating Mode = 0 (Off).
3. As step 1, but with Operating Mode = 3 (Auto)
4. After step 3 is complete, the test continues with Operating Mode = 0 (Off).
Required Response:
1. The air conditioner turns on. AIR_CONDITIONER_STATUS is sent immediately with Output Level 200 (100%), Fan Speed 200 (100%).
2. The air conditioner turns off. AIR_CONDITIONER_STATUS is sent immediately with Output Level 0 (0%), Fan Speed 0 (0%).
3. Same as Step 1
4. Same as Step 2.

Test 88S-C-02
Datum: THERMOSTAT_COMMAND_1 – Set Point Cool
1. THERMOSTAT_COMMAND_1 is sent with Operating Mode = 1 (Cool), Set Point Cool 5 degF below the current temperature. The temperature sensor is slowly cooled until it reaches a point where cooling is no longer demanded.
2. After step 2 is complete, the temperature sensor is slowly warmed until it reaches a point where cooling is again demanded.
Required Response:
1. Same as 88A-S-01. When the temperature reaches a point below the Set Point Cool, AIR_CONDITIONER_STATUS is sent immediately with Output Level 0 (0%).
2. The air conditioner turns on. When the temperature reaches a point above the Set Point Cool, AIR_CONDITIONER_STATUS is sent immediately with Output Level 200 (100%).
The test does not specify the precise point where the command shall be sent, only that the point is below/above the Set Point Cool.

Test 88S-C-03
Datum: Fan Speed
Test:
1. THERMOSTAT_COMMAND_1 is sent with Operating Mode = 1 (Cool), Set Point Cool set 5 degF below the current temperature, Fan Speed 200 (100%).
2. After Step 1, the test continues with arbitrary values for Fan Speed.
3. After Step 2, the test continues with Fan Speed 0 (Automatic). The temperature sensor is then cooled until it reaches the point where air conditioning is no longer demanded.
Required Response:
1. AIR_CONDITIONER_STATUS is sent with Output Level 200 (100%), Fan Speed 200 (100%).
2. As Step 1, with the Fan Speed per the command.
3. As Step 1, with the Fan Speed initially at 200 (100%). As the temperature cools, the Fan Speed may be allowed to decrease, but implementation of a specific algorithm is not required. Note that THERMOSTAT_STATUS_1 Fan Speed shall be 0 (Automatic).

Test 88S-C-04
Datum: THERMOSTAT_COMMAND_1: OpMode 4 (Fan Only)
Test:
1. THERMOSTAT_COMMAND_1 is sent with Operating Mode = 4 (Fan Only), Set Point Cool 5 degF below the current temperature, Fan Speed 0 (Automatic).
2. After step 1 is complete, the test continues with Operating Mode = 0 (Off).
3. Step 1 is repeated with Set Point Cool 5 degF higher than the current temperature.
4. Step 1 is repeated with arbitrary non-zero values for THERMOSTAT_STATUS_1, Fan Speed,
Required Response:
5. Step 1 is repeated with Fan Speed 0 (Automatic). The temperature sensor is then slowly cooled until it reaches the point where no cooling is demanded.
1. AIR_CONDITIONER_ STATUS is sent immediately with Output Level 0 (0%), Fan Speed 200 (100%).
2. AIR_CONDITIONER_ STATUS is sent immediately with Output Level 0 (0%), Fan Speed 0 (0%).
3. Same.
4. As Step 1, with the Fan Speed per the command.
5. As Step 1, with the Fan Speed initially at 200 (100%). As the temperature cools, the Fan Speed may be allowed to decrease, but implementation of a specific algorithm is not required. Note that THERMOSTAT_STATUS_1 Fan Speed shall be 0 (Automatic).

Test 88S-C-05
Datum: THERMOSTAT_COMMAND_1: Fan Mode = 1 (Forced)
Test:
1. THERMOSTAT_COMMAND_1 is sent with Operating Mode = 0 (Off), Fan Mode 1 (On), Fan Speed 0 (Auto).
2. After step 1 is complete, the test continues with THERMOSTAT_COMMAND_1 Fan Mode 0 (Off).
3. Step 1 is repeated with arbitrary non-zero values for Fan Speed.
4. Step 1 is repeated with arbitrary values for Set Point Cool.
Required Response:
1. AIR_CONDITIONER_STATUS is sent with Fan Speed 200 (100%), and Output Level 0 (0%).
2. AIR_CONDITIONER_STATUS is sent with Fan Speed 0 (100%), and Output Level 0 (0%).
3. AIR_CONDITIONER_STATUS is sent with Fan Speed matching the value given, and Output Level 0 (0%).
4. Same. The unit shall ignore the Set Point.

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Profile 88T : Integrated Thermostat / Air Conditioner with Network Temperature Sensor

This profile applies to thermostats that are integrated with one or more air conditioners, and which obtain a temperature reading from a network temperature sensor(s).

Hysteresis to prevent short-cycling the compressor is required as part of this profile. In all tests, a delay to prevent short-cycling the compressor or preventing AC power sags is allowed. During the delay, AIR_CONDITIONER_STATUS should be sent with Max Output Level 0 (0%) and Output Level 0 (0%). At the end of the delay, AIR_CONDITIONER_STATUS should be sent with Max Output Level 200 (100%) and Output Level 200 (100%).

Prerequisite: 88B Base Thermostat

ID: 88T-S-01
Datum: AIR_CONDITIONER_STATUS
Test: Same as 88S-S-01.

Test 88T-S-02
Datum: SPN - Temperature Not Received
Test: Same as 88X-S-07

Test 88T-C-01
Datum: THERMOSTAT_COMMAND_1 - OpMode Cool/Auto/Off
Test: Same as 88S-C-01, with the network temperature in place of the current temperature.

Test 88T-C-02
Datum: THERMOSTAT_COMMAND_1 – Set Point Cool
Test: Same as 88S-C-02, with the network temperature in place of the current temperature.

Test 88T-C-03
Datum: Fan Speed
Test: Same as 88S-C-03, with the network temperature in place of the current temperature.

Test 88T-C-04
Datum: THERMOSTAT_COMMAND_1: OpMode 4 (Fan Only)
Test: Same as 88S-C-04, with the network temperature in place of the current temperature.

Test 88T-C-05
Datum: THERMOSTAT_COMMAND_1: Fan Mode = 1 (Forced)
Test: Same as 88S-C-05

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Profile 88U Integrated Thermostat / Air Conditioner with Multi-Zone Coordination

ID: 88U-S-01
Datum: AIR_CONDITIONER_STATUS
Test: Same as 88S-S-01. AIR_CONDITIONER_STATUS message must be sent as described for each air conditioner instance.

Test 88U-C-01
Datum: THERMOSTAT_COMMAND_1 - OpMode
Test: Same as 88M-S-01, with the requirements for AIR_CONDITIONER_COMMAND replaced by AIR_CONDITIONER_STATUS in a manner consistent with profiles 88S or 88T.

Test 88U-S-02
Datum: THERMOSTAT_COMMAND_1 - Set Point Cool
Test: Same as 88M-S-02, with the requirements for AIR_CONDITIONER_COMMAND replaced by AIR_CONDITIONER_STATUS in a manner consistent with profiles 88S or 88T.

Proposed by Martin

Proposed by Martin Perlot

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Change to description of THERMOSTAT_COMMAND_1 - Fan Speed

Currently Reads: see Table 5.3. One-speed fans shall interpret any nonzero value as “On”.

Proposed: see Table 5.3. A value of 0 indicates that the fan speed shall be set automatically according to the demand for cooling. A non-zero value indicates that the speed shall be manually overridden.

Justification: As written, no distinction is made between the manual and automatic fan speed. A similar distinction is to be added to AIR_CONDITIONER_STATUS/COMMAND_1.

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New Alarms

1 – Entering New Scheduled Mode.
2 – Entering Away Mode
3 – Leaving Away Mode
4 – Entering Storage Mode
5 – Leaving Storage Mode

Justification: Such alarms are useful for tracking user activity and RV usage.

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New SPNS

2-Instance-5 Networked A/C
2-Instance-6 Networked Furnace

Justification: Required for thermostats that actively control networked devices.

Proposed by Martin Perlot:

Proposed by Martin Perlot: Rewrite Introduction. Replace all introductory text with:

A thermostat may or may not be a standalone device. It is often integrated into a climate control device such as an air conditioner, and even if it is a standalone device, it may be a completely passive device that exists solely to store information regarding the desires of the operator.

A thermostat typically has a temperature sensor attached, and a thermostat device may have no other function than to report a temperature. However, it is possible for a thermostat to rely on a second thermostat for the temperature reading, in which case it shall echo the remote reading as though the reading came from an integrated sensor.

Note that a single physical thermostat may implement multiple thermostat Instances.

Although it may be convenient for the Instances of the thermostat to match the Instances of the Air Conditioners and Furnaces that it may control, this is not an absolute requirement. It is entirely possible - though confusing - for a climate control system to have completely different Instance numbers for every component - temperature sensors (which are treated as thermostats with only one function), thermostats, air conditioners, furnaces, etc..

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Justification

The current introduction is confusing and does not fully describe the possible ways in which a thermostat may be implemented.