EUCHNER ESM-BT411 Safety Relay with Time-Delayed Contacts

One relay for stop category 0 and 1 outputs

The EUCHNER ESM-BT411 (order no. 090819) is a basic safety relay module for emergency stop circuits and safety switches that combines instantaneous and time-delayed outputs in one 24 V device. When the emergency stop or guard opens, two safety contacts drop out immediately while two more open after an adjustable delay of 1 to 30 seconds. Drives can therefore be braked under power before their supply is cut, as required for stop category 1, while other circuits are removed at once.

The module can be controlled through one or two channels and offers automatic start, manual start or monitored manual start, plus a feedback loop for monitoring downstream contactors. Short circuits between input lines and earth faults can be detected and lead to shutdown or prevent a restart.

Technical specifications

Data from the EUCHNER product data for order no. 090819.

Selecting within the ESM-BT4 family

If more delayed contacts are needed, ESM-TE3 time-delayed contact expansions can be added.

Installation and commissioning notes

The 24 V supply must come from a safety transformer to EN IEC 61558-2-6 or an equivalent isolated source. Control lines may be up to 1000 m at 0.75 mm2. With automatic start the relay energizes as soon as power is applied, so this mode should only be chosen where the risk assessment allows it. The stated safety values apply within the switching-cycle limits given by EUCHNER for 0.1, 1 and 2 A loads at 24 V DC. Several BT4 units mounted side by side under load need 5 mm spacing above 9 A total at 20 °C. The emergency stop function and delay should be tested monthly.

Documents and quotation

EUCHNER’s operating instructions cover wiring for each start mode and fault finding; they can be downloaded from the official product page linked in the Datasheet & Documentation section below. Quote order no. 090819 when requesting a price. More interlocks and relays are listed under Safety Switches and Guard Locking.

How the EUCHNER ESM-BT411 safety relay works

A safety relay monitors one or more safety devices, such as an emergency stop pushbutton or a guard interlock switch, and switches the power to hazardous machine functions through internally redundant, force-guided relay contacts. In the EUCHNER ESM-BT411, the input circuit is checked continuously. When the input opens, the two instantaneous safety contacts open within the stated response delay, and the two time-delayed contacts open after the time set on the front potentiometer, within the 1–30 s range.

This combination is typical for a stop category 1 function as described in EN 60204-1: the drive is first commanded to stop under control, for example by a frequency inverter braking ramp, while power remains available, and the power is removed by the delayed contacts once the set time has elapsed. The instantaneous contacts can be used for stop category 0 functions or to signal the stop command to the drive controller.

The feedback loop monitors the normally closed auxiliary contacts of downstream contactors. If a contactor welds or fails to drop out, the relay will not allow a restart, so a single fault in the output path is detected before the next cycle.

Selection & ordering guide

• ESM-BT411 (090819): 2 instantaneous and 2 time-delayed contacts, adjustable 1–30 s.
• ESM-BT411-20S: same contact arrangement with a fixed 2 s delay, for applications where the delay must not be altered on site.
• Other ESM-BT4 types give different splits between instantaneous and delayed contacts (see the table above).

Before selecting, check the required performance level from the machine risk assessment. Note that EUCHNER states different safety values for the delayed contacts (PL e, category 3) and the undelayed contacts (PL e, category 4). Quote order number 090819 when you request a quote, and our team can help confirm the correct ordering code.

Wiring and commissioning tips

• Mount the module on a TH 35 DIN rail inside a control cabinet with at least IP54 protection.
• Use wire sizes within the 0.14–2.5 mm² terminal range and protect the output contacts with fuses as specified in the operating instructions.
• Select the start mode (automatic, manual or monitored manual) by wiring as shown in the instructions, and choose monitored manual start where the risk assessment requires a deliberate reset action.
• Set the delay with the potentiometer to suit the actual braking time of the drive, then verify that the machine has come to rest before the delayed contacts open.
• After installation and after any change, perform a functional test of each safety device and confirm the instantaneous and delayed behaviour.

Typical applications in Oman & the GCC

Time-delay safety relays like the ESM-BT411 are used on packaging lines, conveyors, cranes and hoists, process pumps and mixers, machine tools, bottling plants and material handling systems in factories, food and beverage plants, oil and gas facilities and utilities throughout Oman and the GCC, wherever a controlled stop must precede removal of power.

Why source from Seven Star LLC

Seven Star LLC supplies EUCHNER safety relays, interlocks and related automation components across Oman and the GCC. Request a quote with the order numbers and quantities you need.