Redirect Siemens Synco time switch to a BACnet Object Schedule – Wattsense Support Portal

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Due to structural differences between Synco and BACnet schedule representations, specific mapping rules have been established by Wattsense to ensure proper data translation between both systems. Sections 1 to 10 describe them before section 11 describes how to set the redirection.

Requires APPs >= 6.14.3

1. BACnet architecture

1.1 Object Structure

For each Synco circuit, the BACnet redirection is organized as follows:

One Schedule object per Synco circuit containing:
- The weekly schedule
- The exceptions (exception schedule)
One shared Multi-State object containing Synco mode values, for example:
- Comfort (value 1)
- Standby (value 2)
- Eco (value 3)
- Protection (value 4)
- Holiday (value 5)

1.2 Referencing

The Schedule object uses and references the value of the Multi-State object to define the modes to apply according to time slots.

2. BACnet schedule default value and first slot of the day

If the BACnet schedule default value is set, it is used as the source of truth to set the Synco time switch mode when a specific mode is not set.

Warning: the (BACnet) default value is mandatory if there is at least one time slot for which the mode is not set. If the BACnet client doesn’t specify the mode for a specific time slot, then the writing will fail on the Synco.

If the below is set for a specific day in the Synco:

After the first reading, the BACnet client will show:

00:00: null
08:00: 1
18:00: 3

Where null stands for the default value currently applied by the Synco and set in a specific data point.

Now, if the BACnet client edits the schedule to read "Apply Comfort (3) from 8am to 6pm" with a Schedule default value of 3, it will write:

Default: 3
00:00: null
08:00: 1
18:00: null

The BACnet default value now takes over and the Synco will read:

And if the BACnet client reads the same schedule again, it will read:

Default: 3
00:00: null
08:00: 1
18:00: null

3. Shared Exceptions Management

3.1 Exception Duplication

Rule: Exceptions shared between multiple Synco circuits are duplicated in each corresponding BACnet Schedule object.

Example:

If a "Christmas Holidays" exception applies to circuits 1 and 2 on Synco
It will be present in both BACnet Schedule objects (circuit 1 and circuit 2)

3.2 Bidirectional Synchronization

Rule: Modifying an exception on a BACnet Schedule object results in:

Modification of the shared exception on the Synco side
Automatic reflection on all corresponding BACnet Schedule objects

Impact: Modifying the exception on circuit 1 on the BACnet side will also modify the exception on circuit 2.

4. Exception mode distinction

4.1 Synco Exception Modes

Synco offers two modes for exceptions:

"8th day" mode (also called "special day"): applies a specific schedule during the exception (with multiple possible time slots)
"Reduced" mode (holiday): applies a single mode throughout the day

4.2 BACnet Differentiation Rule

Identification rule:

Exception in reduced mode:
- The exception starts at 00:00
- The value is 5 (Holiday) from the start
- Format: {"time": "00:00", "value": 5}
Exception in 8th day/special day mode:
- Any other case
- Contains one or more time slots with different modes
- Format: multiple timeValues with different modes (2, 3, 4)

Reduced mode example:

{ 
  "exceptionId": "2", 
  "calendarEntry": { 
    "dateRange": { 
      "startDate": "2025-08-01", 
      "endDate": "2025-08-31" 
    } 
  }, 
  "timeValues": [ 
    {"time": "00:00", "value": 5} 
  ], 
  "syncoReference": { 
    "type": "reduced" 
  } 
}

8th day/special day mode example:

{ 
  "exceptionId": "1", 
  "calendarEntry": { 
    "dateRange": { 
      "startDate": "2024-12-23", 
      "endDate": "2025-01-02" 
    } 
  }, 
  "timeValues": [ 
    {"time": "00:00", "value": 3}, 
    {"time": "18:00", "value": 2}, 
    {"time": "19:00", "value": 3} 
  ], 
  "syncoReference": { 
    "type": "8th_day" 
  } 
}

5. Reduced Mode Modification

5.1 Reduced Mode Configuration

Rule: To modify the reduced mode itself (e.g., switching from Eco to Protection):

This property must be redirected independently in the BACnet gateway
The modification is not done through Schedule objects
It is a separate configuration from the schedule system

Justification: The reduced mode is a global property of the Synco circuit, not a characteristic of the exception itself.

6. Multiple Exceptions Limitation

6.1 Synco Constraint

Rule: It is not possible to have two "8th day/special day" exceptions with different modes/time slots for the same circuit.

Explanation: This would correspond to having two different "8th days" (special days), which is not supported by Synco.

Consequence: If multiple exceptions in "8th day/special day" mode exist for the same circuit, they must all use the same schedule (same time slots and modes). If there are different schedude (time slots and/or mode) in mutliple exceptions, only the first one chronologically will be considered as the reference for Synco synchronization. Others will be replaced after Synco being updated then resynchronized with BACnet supervison.

7. Multiple time slot management for exceptions

7.1 Issue

Context:

Synco: an "8th day" (special day) can have multiple time slots within the same day
BACnet (as in Siemens Desigo Optic): an exception can only have one time slot (date range + time range)

7.2 Solution: Two Mapping Options

Option 1: "FLATTEN" Mode

Principle: A Synco exception with multiple time slots is split into several BACnet events.

Example:

Synco side:

1 "8th day" (special day) with 2 slots:
- 08:00-12:00: Eco
- 12:00-17:00: Comfort
2 exceptions using this special day:
- From 10/20/2025 to 10/26/2025
- From 12/24/2025 to 12/31/2025

BACnet side (FLATTEN mode):

4 events created:
- From 10/20/2025 to 10/26/2025, 08:00-12:00: Eco
- From 10/20/2025 to 10/26/2025, 12:00-17:00: Comfort
- From 12/24/2025 to 12/31/2025, 08:00-12:00: Eco
- From 12/24/2025 to 12/31/2025, 12:00-17:00: Comfort

Usage: Recommended for Siemens Desigo Optic which only supports one time slot per event.

Option 2: "AS_IS" Mode

Principle: The exception with "8th day/special day" is transmitted as a single BACnet event with multiple time slots (timeValues).

Example:

BACnet side (AS_IS mode):

2 events created:
- From 10/20/2025 to 10/26/2025 with multiple timeValues
- From 12/24/2025 to 12/31/2025 with multiple timeValues

Usage: For BACnet systems supporting multiple timeValues per event.

7.3 Modification Reconciliation

Rule: The system is capable of reconciling the 4 BACnet events (FLATTEN mode) with the 2 Synco exceptions.

Behavior when modifying on BACnet:

Date modification → modifies the exception on the Synco side
Time or mode modification → modifies the "8th day/special day" on the Synco side (impacts all exceptions using this special day). In this case, the first exception in special day mode chronologically acts as reference to modify the 8th day. Other exceptions in special day mode that start later will not be considered to modify the 8th day.

8. Supported Exceptions Types

8.1 Compatible Types

Only 2 exception types are supported:

Date-to-date exception without annual recurrence
1. Example: From 10/20/2025 to 10/26/2025 (one-time only)
Single day exception without annual recurrence
1. Example: On the 01/01/2026 (one-time only)

Warning: Annual recurrence exceptions are not supported

8.2 Unsupported Types

Other exception types available at least in Siemens Desigo Optic are not supported:

Exceptions by month
Exceptions by day of week
Recurrences

9. Complete Example

9.1 Synco Configuration

Circuit 1 (Boiler):

Monday-Friday: Comfort from 06:00 to 22:00
Rest of the time: Eco

Circuit 2 (Ventilation):

Monday-Friday: Comfort from 08:00 to 17:00
Rest of the time: Eco

Shared exceptions:

Christmas Holidays (12/23 to 01/02) - 8th day/special day mode
1. Comfort only from 18:00 to 19:00
2. Eco the rest of the time
July 14th - 8th day/special day mode
1. Same slots as Christmas (18:00-19:00 Comfort)
August (08/01 to 08/31) - Reduced mode
1. Holiday all day

9.2 BACnet Representation

Objects created:

1 Multi-State object (shared modes)
1 Schedule object for circuit 1
1 Schedule object for circuit 2

Each Schedule contains:

The circuit-specific weekly schedule
The 3 exceptions (duplicated from Synco)

In FLATTEN mode (Desigo Optic):

Christmas and July 14th: 1 event each (since only one time slot 18:00-19:00)
August: 1 event with value=5 at 00:00

10. Warnings

10.1 Shared Special Days Consistency

If multiple exceptions use the same Synco "8th day/special day", modifying the time slots of one exception will impact all exceptions sharing this special day.

10.2 Reduced Mode Identification

The system relies on the 00:00 + value=5 rule to identify reduced mode. Any exception starting this way will be interpreted as reduced mode.

10.3 Current or Present Schedule value and Effective period not supported

The BACnet Schedule Object Present Value is not reflecting the current state of the schedule. It is always set to 1 by default.

The effective period start date and end date are not supported (ndlr: that is the reason why the redirected schedule object can’t be writen from Yabe).

10.4 Time interval between two readings of the Synco schedule

When the box runs, the redirected BACnet schedule is calculated every 10 minutes. To trigger a new value, send a configuration to the box to restart the service.

10.5 Siemens Desigo Optic Limitations

Use FLATTEN mode to ensure compatibility with Siemens Desigo Optic which only supports one time slot per event.

10.6 KNX network configuration

We recommend the following configuration for the KNX network

Interframe delay: 200000
Response timeout: 500000
Retry number: 0

11. Set the redirection from the console

Under Configuration > Gateways > Add Property, select the option to redirect a controller's schedule to your BACnet gateway.

Then fill the form with as much details as possible

After submitting the form, the Wattsense staff will be notified and will enable the redirection in the background.

Once it is done, you will be notified and you will find two new data points in your BACnet gateway.