Writing the BACnet Out of Service Property Using CAS BACnet Explorer
CAS BACnet Explorer:
Available as a free tool for discovering, browsing, and testing BACnet devices.
The Out of Service property is a standard BACnet property used to logically remove an object from normal automatic control. When an object is set to Out of Service, its Present Value may be written manually without being overridden by the device’s internal control logic. This mechanism is commonly used during commissioning, troubleshooting, simulation, and point verification.
This article describes how to write to the Out of Service property using the CAS BACnet Explorer. The procedure applies to any BACnet device that exposes a writable Out of Service property and supports standard BACnet WriteProperty services.
Prerequisites and Behavior
Before attempting to write to the Out of Service property, the target device must be online, reachable, and successfully discovered by the CAS BACnet Explorer. The user must also have sufficient write access, as enforced by the device. Some devices restrict this property to specific object types or require elevated access levels.
Setting Out of Service to True typically disables the object’s interaction with physical I/O or internal control sequences. Setting it back to False returns the object to normal operation. The exact behavior is device-specific and defined by the device manufacturer.
Step-by-Step Procedure
Step 1 – Discover the device
Open the CAS BACnet Explorer and perform a device discovery. Locate and expand the device that contains
the object you intend to place Out of Service.
Step 2 – Select the Out of Service property
Navigate to the desired object and click on its Out of Service property to select it.
Step 3 – Open the WriteProperty dialog
Right-click on the Out of Service property to open the context menu. Select the
WriteProperty option.
Step 4 – Write the desired value
In the Write Property dialog, change the Data Value to True or False,
depending on whether you want to place the object Out of Service or return it to normal operation.
Step 5 – Verify the result
After the write completes, confirm that the Out of Service property reflects the new value. You may also
verify that the object’s Present Value can now be written manually if the object is Out of Service.
Access control note:
If the Out of Service property is not writable, the device may return a
Write Access Denied error. This indicates that the device does not permit writing this property
under the current conditions or credentials.
FAQ
What does the Out of Service property do?
It removes the object from automatic control, allowing manual manipulation of its Present Value
without interference from control logic.
Is Out of Service writable on all BACnet objects?
No. Writability and behavior depend on the device implementation and object type.
Why do I receive a Write Access Denied error?
The device may restrict write access, require higher privileges, or disallow Out of Service writes
for that object.
Does setting Out of Service affect physical outputs?
Often yes, but the exact effect is device-specific and defined by the manufacturer.