Read and understand these instructions before installing, operating, or
maintaining the equipment.
Will cause death or serious injury.
Disconnect power before working
Reliable functioning of the equipment is only ensured with certified compon-
The safety relay must be installed in switchgear cubicles complying
with degree of protection IP32, IP43 or IP54, depending on the prevailing
The products described herein are designed to be components of a customized
machinery safety-oriented control system. A complete safety-oriented system
may include safety sensors, evaluators, actuators and signaling components. It
is the responsibility of each company to conduct its own evalution of the effecti-
veness of the safety system by trained individuals. Siemens AG, its subsidiaries
and affiliates (collectively "Siemens") are not in a position to evaluate all of the
characteristics of a given system or product or machine not designed by SIE-
Siemens accepts no liability for any recommendation that may be implied or
stated herein. The warranty contained in the contract of sale by Siemens is the
sole warranty of Siemens. Any statements contained herein do not create new
warranties or modify existing ones.
The 3TK2840 safety relay can be used in EMERGENCY STOP devices according to
EN 418 and in safety circuits according to EN 60 204-1 (11.98), e.g. for moving
covers and protective doors. Safety catetory 3 according to DIN EN 954-1 or SIL2
according to IEC 61508 can be achieved, depending on the external circuit ele-
Functional description and instructions for connection
The 3TK2840 safety relay has two solid-state outputs. Three LEDs indicate the
operating state and the function.
During operation, all internal circuit elements are cyclically monitored for faults.
Connect the EMERGENCY STOP button and the position switch to terminals Y11,
Y12 or Y21, Y22. Connect the ON button in series with the NC contacts of the
external actuators (feedback circuit) to terminals Y33, Y34 .
The 3TK2840 safety relay and the activated contactors K1 and K2 must have the
same frame potential.
Safety category 3 to EN 954-1 is achieved only in combination with 2 external
actuators with positively driven feedback contacts.
Use a power pack to IEC 60536 safety class III (SELV or PELV)
for power supply!
Outputs 14, 24
Cable lengths for 2 x 1.5 mm
Figures Fig. I:
Dimension drawings (dimensions in mm)
Fig. Ia: Terminal designation
Fig. II: Installation/Connection
Fig. III: Internal circuit: ¿ power pack, À control logic,
Á Output 1, Â Output 2
Fig. IV: Two-channel autostart for protective door monitoring,
Fig. V: EMERGENCY STOP, two-channel, with monitored start,
Channel 1 EMERGENCY STOP or
Channel 2 EMERGENCY STOP or
Changeover contact, single-channel
ON button, feedback circuit
max. 2000 m (total cable length for sensors)
Order No.: 3ZX1012-0TK28-4BA1
Figures Fig. VI: EMERGENCY STOP, single-channel, with monitored start,
Fig. VII: Single-channel autostart for protective door monitoring,
*) This wiring example only satisfies category 2 according to EN 954-1 if a warning is
automatically generated when the actuator fails or the machine control initiates a safe state.
Otherwise an alternative shut-down method is required.
• Defect in electronics
• Crossover in EMERGENCY STOP
Permissible ambient temperature T
Degree of protection to EN 60 529
Rated insulation voltage U
Rated impulse withstand voltage U
Rated control supply voltage U
Shock resistance (half-sine) as per IEC 60068 8 g/10 ms
Recovery time after EMERGENCY STOP
Release time after EMERGENCY STOP
Pickup time, monitored start
Pickup time, autostart
Release time after power failure
as per IEC 60947-5-1
For further data and accessories see Catalog.
DIN EN 60 947-5-1 (08.00)
No supply voltage
–25 to +60 °C / –40 to +80 °C
IP40, IP20 at terminals
24 V DC
0.9 to 1.15 x U
min. 20 ms
< 30 ms
< 125 ms
< 250 ms
< 25 ms
no fusing necessary!
Rated operational current I