Stem NC86 Operating Instructions

Operating instructions for safety control unit mod. NC86

Description

The NC86 safety relay is created for use in safety circuit intended by
EN 81-20, EN 81-50, EN 60204-1, EN ISO 13849-1.
This module is based upon the use of guided-contact safety relays.
! !

Safety Precautions

The manufacturer or the technician that install the machinery is responsible for
correct and safe overall function.
Auxiliary output Y1/Y2 is optoinsulated and gives informations about the state of the
device; it must not be used as a safety output.
The NC86 is not proper for the operation in presence of ionizing and not ionizing
radiations (rays X, microwaves, laser, ultraviolet rays)
(EN 60204-1:2018, §4.4.7).

Functioning

The NC86 Module can control the state of two contacts (Reed sensors,
emergency stop button, mechanical safety switches, interlocks for mobile guards):
the output is activated by pressing the START button only if the contacts of two
sensors are closed. The opening of even only one input contact (S1 and/or S2),
leads to a safety situation, by putting the safety outputs in open state and by
preventing the closing even after the re-closing of the contact and the pressure of the
START button.
WARNING: the start command does not fulfill the requirements of §5.2.2 of
EN ISO 13849:2015 standard because it works on the rising edge of the signal.
If the NC86 is used to control emergency stop button, after the intervention of the
device, the reset of the command shall not restart the machinery but only permit
restarting
(EN 60204-1:2018, §9.2.3.4.2, EN ISO 13850:2015, §4.1.4).
If the NC86 is used to control interlocks for mobile guards, the reclosing or
resetting of an interlock safeguard shall not initiate hazardous machine operation
(EN 60204-1:2006, §9.3.1).
If START button is not used (automatic rearmament), see the connection diagram in
the following page; the behavior of the machinery to the restart of the device - or the
not automatic restart of the dangerous elements of the machinery - depends on the
realization of the command circuit of the machinery according to the risk evaluation
effected by the user.
Input channels work on opposite potentials (S11,S31
It's available an input (X1-X2) for feedback with contactors or external relays
(see Ka and Kb on the connection diagram); if not used, X1-X2 have to be bridged.
Safety category 4 is granted only if (see connection diagram):
-to interrupt the load are used two relays, each connected to an input of the
safety unit;
-the contacts of the relays controlled by the safety unit are inserted into the
feedback loop.
The safety is ensured by using guided contacts, by the redundance and by the
interconnection schematic of the contacts.
The responsibility to choose the adequate components for safety applications, for
example guided contacts safety relays, falls to the user.

Assembly

Installation must be performed by authorized personnel only.
The NC86 control unit must be assembled in a suitable operating area
(switch cabinet, protective housing).
The unit is installed by clipping it to a standard 35 mm top-hat rail.

Electrical Connection

Electrical connection must be performed by authorized personnel only following the
indications of EN ISO 13849-1 and EN ISO 13849-2.
All the electrical inputs must either be isolated from the mains supply by a separate
coils safety transformer in accordance with EN IEC 61558-2-6 with limited output
voltage in the event of a defect or by another equivalent movable mechanism.
The outputs of the relays have a maximum current of 3 A; the supply connected to
the outputs must be protected from overcurrents by devices adequate to the loads
that have to be protected. All the output contacts must have an adequate protective
circuit for capacitive and inductive loads.
If a common power supply is used, all the inductive and capacitive loads (e.g. relay
contactors) connected to the power supply must be connected to appropriate
interference suppressors.

Service and Inspection

The correct functioning of the NC86 safety unit must be controlled by the operator
and/or by the control circuit of the machine in which it is used periodically (at the
beginning of every shift), by checking:
- Correct switching function of each sensor by checking:
a) that the opening of the single sensor / safety guard will cause the opening of the
safety outputs (13-14 / 23-24)
b) that the closure of the same sensor / safety guard will cause the closing of the
safety outputs (13-14 / 23-24) as a result of a startup command
- secure mounting of components
- correct connection fixing.
The monitoring function of the unit is done at every switching cycle.
If with all safety guards closed and following the eventual start command, the safety
device does not activate its safety outputs, do not turn off and turn on the device ,
then proceed to the checking of the possible safety guard open and perform the
above tests in point a) and b). In the event of damage or wear and tear, the
damaged system component must be replaced.
Liability coverage is void under the following circumstances:
- if instructions are not followed
- non-compliance with safety regulations
- installation and electrical connection not performed by authorized personnel
- non-implementation of functional checks.

Setup

If the control unit does not appear to function when operating voltage is applied
(PWR LED does not light up), the unit must be returned unopened to the
manufacturer.
Check whether the safety outputs are being switched (see LED display) by
activating the two inputs S1, S2 and START.

Operation according to EN 81-20:2014

The safety module ensures the opening of contacts within 15 ms from the opening
of the sensors S1 or S2.
It can be used as a detector, according to 5.6.7.7 EN 81-20:2014,to be integrated in
a A3 system.

Connections

→ →
- ; S21,S41
+).
- original instructions -
Main inputs
S21 S22 S11S12
-
+
A1 A2 Y1 Y2 S33S34 X1
Supply Signal
24 V ac/dc Output
Start
button
(reset)
Feedback loop of the
external contactor
(bridged if not used)
1) Lift applications 2) Machine safety applications
(EN 81-20, EN 81-50:2014): (cat.4 EN ISO 13849-1):
sensor (S1) with 2 normally open
Reed contact sensors S1 e S2
(N.O.) contacts
-
+
S21 S22 S11 S12
S2 S1
4) Emergency stop button in
3) Mobile guard interlock sensors
accordance with EN ISO13850
with normally closed (N.C. contacts)
(stop category 0, EN ISO 13850)
(EN ISO 14119;
with 2 N.C. contacts (S1)
cat.4 EN ISO 13849-1;
(cat 4 EN ISO 13849-1)
EN 60204-1:2018, §9.3)
-
+
S21 S22 S11 S12
S2 S1
5) Emergency stop button with 1 N.C. contacts (S1) in accordance with
EN ISO13850 (stop category 0, EN ISO 13850;
EN 60204-1:2018, §9.2.3.4; cat 4 EN ISO 13849-1 if one or no*
sensor is connected to the unit)
A1 A2
S1
*Short the inputs if not used for
L1 +
Alimentazione
24 V ac/dc -
L2

Automatic start connections

-1- Automatic start ONLY FOR use as lift safety unit
(EN 81-20, EN 81-50)
Reed switch sensors ID, IS and IZ.
In this configuration the inputs synchronization time among the closing
of IZ and one between IS and ID, it is endless, but a correct closing
sequence has to be respected: the first contact to be closed is IZ, then
IS or ID.
IS ID
IZ
S11 S12 S21 S22 S33 S34
GND +
-2- Short-circuit of S33 and S34; in this case there will be a
synchronism time between inputs of 600 ms.
K2 K2
K3 K3 K3
K1 K1
Safety
X2 13 14 23 24
outputs
L
L1L2 L3
Ka
Kb
N
M
3
-
+
S21 S22 S11 S12
S1
-
+
S21 S22 S11 S12
S1
S21 S22 S11 S12
2 NO contacts sensor
MD
MZ
MS
ID
IS
IZ
Feedback loop of the
external contactor
(short-circuit if not used)
NOT CONNECTED
+
S33 S34