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manual operation
meets the minimum requirements in terms of local operation and
signalling, but can only be used if the substation is intact
local override device
(LOD)
enables direct intervention in the technical installation, even if the substation
is not available. Emergency operation mode is only used for maintaining
the operation of important systems and system components.
local operation
enables direct dialog with the technical installation via the substation,
provided it is operational
Operating modes in addition to automatic operation
Application Note DK9222-0810-0040
I/O, Building Automation
Interfaces for Local Override Operation
Keywords
KM1644
KM2614
KM2652
KM4602
Local override device (LOD)
operating level
local override
local indication
Local indication device (LID)
analog output
relay module
manual operating level
Building Automation
This application example covers complementary operating modes for building automation and describes
how local operation and local override operation can be realized with Beckhoff Bus Terminals. With local
operation, the individual system units are operated through manual user intervention; with local override
operation important system components can be kept operational in the event of a fault. The two operating
modes are usually combined. Manual operation requires system-compliant interfaces for the operation of
field devices and line components, independent of the central unit. The manual operating terminals from
Beckhoff are designed for this purpose and can be extended to form a local override operation system in
conjunction with an independent power supply.
1. Operating levels in building automation
Depending on the building control requirements, different operating levels are available within the building automation
system. Typically, the following operating modes are used in building automation in addition to automatic operation of systems
or system components:
Tab. 1 Complementary building automation operating modes
For application notes see disclaimer on the last page
Beckhoff
New Automation Technology
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Application Note DK9222-0810-0040
I/O, Building Automation
Local override operation
Local override operation enables the direct intervention in the building control system. Via this operating level important
system components can be controlled manually in order to maintain important functions, if the substation is not available, has
failed or is faulty. The operating elements at this level act directly without regard to the automation device.
Local override operation can be realized conventionally with switches and buttons, although it is important to ensure that all
elements are supplied via an independent power supply. To avoid manipulations, access to the local override operation control
elements must be secured, for example through integration in the control cabinet.
If a manual/local operating level or local override operating level is used, all safety functions should be triggered externally.
The local operation system must not be used for safety shutdown. The local override operations are executed directly in
accordance with ISO 16 484-2, section 3.110, without protection or interlock, so that the operator has full responsibility for all
interventions.
2. System-compliant interfaces for field devices and system components, independent of
the central unit
The Beckhoff product range includes the following Bus Terminals for full system integration of manual intervention within
the building control system. The manual operating terminals are system-compliant interfaces for field devices and system
components, which operate independent of the central unit:
KM1644 | 4-channel manual operation
KM2614 | 4-channel relay module, 230 V AC, 16 A, potential-free changeover contacts, with manual operation
KM2652 | 2-channel relay module, manual/automatic operation 6 A, 230 V AC
KM4602 | 2-channel analog output terminal 0…10 V, manual/automatic operation
The four switches and four LEDs in the front panel of the KM1644 are available as digital inputs or outputs in the control
system and they enable the direct input and display of process parameters at the terminal. The combination of four digital
inputs and outputs in a 24 mm terminal block reduces to a minimum the space requirement in the control cabinet as well as
the number of operating elements that have to be installed in the control cabinet door. The avoidance of additional external
operating elements at the door also reduces the personnel requirements, material use and possible error sources (incorrect
wiring).
Consumers from different rating classes can be connected directly to the KM2614 and KM2652 relay module terminals so that
they can be controlled via the changeover contact either by the controller or manually. The KM2614 enables manual control
of four high-power consumers with a current consumption of up to 16 A at 230 V AC. The KM2652 can be used to switch two
For application notes see disclaimer on the last page
Beckhoff
New Automation Technology
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0 V
5 V
0 V
COM
N/O
Auto
ON
OFF
N/C
K-Bus
Internal KM2652 circuit
10 V
ON
ADC
Internal KM4602 circuit
Ch x
GND
Auto
K-Bus
Application Note DK9222-0810-0040
I/O, Building Automation
lower-power consumers up to 6 A, 230 V AC to On/Off and auto mode. The priority function for manual interventions is realized
through the internal configuration (see Fig. 1).
Fig. 1 Internal circuit of the KM2652 relay module terminal
The KM4602 2-channel analog output terminal is the corresponding equivalent for analog signals from 0 to 10 V. The operating
mode (manual/auto) is selected via a toggle switch in the front panel and the analog value is set via a potentiometer.
Fig. 2 Internal circuit of the analog KM4602 output terminal
To protect from improper operation by unauthorized or unqualified persons, the implementation of local operation and local
override operation with components from Beckhoff assumes that access to the elements within the control cabinet is restricted
to qualified personnel. If this requirement is met, local override operation can be implemented within the control cabinet.
For application notes see disclaimer on the last page
Beckhoff
New Automation Technology
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Application Note DK9222-0810-0040
M
HRmixed air
heater cooler
heat recovery
flap
fan
pump
valve
3-way valve
KM2652
3-pt. drives
KM4602
analog drives
KM2652
relay contacts
HR
M
M
M
caption
M
M
M
M
M
M
M
M
M
I/O, Building Automation
4. Practical example for local override: commissioning of a ventilation system
To start the following ventilation system, the individual units are operated manually.
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Fig. 3 Local override
Depending on the performance class of the connected consumers, the manual operating terminals with relay contacts
KM2614 (230 V AC, 16 A) and KM2652 (230 V AC, 6 A) are used. The KM4602 manual operating terminal for analog set value
specification is used for controlling the analog valves. The KM2652 can be used for controlling 3-point valves based on the
following configuration:
For application notes see disclaimer on the last page
Beckhoff
New Automation Technology
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Application Note DK9222-0810-0040
Substation (any automation device)
any fieldbus
KL9400
Power supply unit terminal for the K-bus
KM4602
manual operation, analog output 0...10 V
KM2652
manual operation, relay 230 V AC, 6 A
Power supply
Bus Coupler
Power supply
local override
=
Connection to BACS (Ethernet)
T
M
heating circuitSystem controller
Failure
Bus Couplers and Terminals
I/O, Building Automation
5. Practical example for local override operation: activation of a heating circuit
Since the focus in the event of malfunctions/failures is more on finding the source of error than on permanent availability,
targeted, limited operation of important building functions through manual interventions is required. This is where local
override operation comes in, explained here using the example of a heating circuit:
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Fig. 5 In the event of a failure of the communication, the controller or the power at the Bus Coupler, local override operation can
occur through the separate power supply of the manual operating terminals.
Despite failure of the communication to the building management system or the automation device, failure of the controller
or a power failure at the Bus Coupler, the configuration shown in Fig. 5 enables local override operation through the separate
power supply of the manual operating terminals. The KM2652 relay terminal activates the pump for the heating circuit. The
analog value specification of the KM4602 specifies the valve position. Since the terminal switch positions are submitted to
the controller (and therefore the building management system), the status of the switches can be queried once the fault has
been rectified. In the event of a failure of the 230 V AC power supply within the heating circuit, local override operation can no
longer be ensured.
For application notes see disclaimer on the last page
Beckhoff
New Automation Technology
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Application Note DK9222-0810-0040
I/O, Building Automation
– 4-channel manual operation www.beckhoff.com/KM1644
– 4-channel relay module, 230 V AC, 16 A www.beckhoff.com/KM2614
– 2-channel relay module, manual/automatic operation 6 A, 230 V AC www.beckhoff.com/KM2652
– 2-channel analog output terminal 0…10 V, manual/automatic operation www.beckhoff.com/KM4602
– Beckhoff Building Automation www.beckhoff.com/building
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This publication contains statements about the suitability of our products for certain areas of application. These statements are based on typical features of our products. The examples shown in this publication are for demonstration purposes only. The information provided herein should not be regarded as specific operation characteristics. It is incumbent on the
customer to check and decide whether a product is suit-able for use in a particular application. We do not give any warranty that the source code which is made available with this
publication is complete or accurate. This publication may be changed at any time with-out prior notice. No liability is assumed for errors and/or omissions. Our products are described
in detail in our data sheets and documentations. Product-specific warnings and cautions must be observed. For the latest version of our data sheets and documentations please visit
our website (www.beckhoff.com).
© Beckhoff Automation GmbH, August 2010
The reproduction, distribution and utilisation of this document as well as the communication of its contents to others without express authorisation is prohibited. Offenders will be
held liable for the payment of damages. All rights reserved in the event of the grant of a patent, utility model or design.
Beckhoff
New Automation Technology
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