Edwards Signaling 301-BT User Manual

GuardSwitch Series 300
Switches 301-BT and 303-BT Installation Sheet

Figure 1: Dimensions

Description

The 301-BT Series 300 DPST safety interlock switch is
designed for use with safety monitored relays or monitored
circuits. To achieve the optimum Series 300 defeat resistant
feature of the 301-BT, both the switch circuit (Circuit 1) and the
tamper circuit (Circuit 2) must be connected. An optional third
circuit can be provided to indicate at the panel which guard is
open.

Notes

• Environmental: Pollution Degree II

• Correct use of this control device is an essential part of
proper machine cycle control.

• Failure to follow all instructions could lead to serious bodily
injury or death.

• Maintenance to be done by qualified personnel only

• The connecting cables between the INT devices and the
switches must be located in an IP 23 type enclosure
(minimum).

• The mounting for the switch and the actuator magnet must
be accomplished per this specification.

• Non-removable hardware must be used for installation.

• The housing of the 300-BT must be connected to the PE
(Primary Earth) ground circuit via a lock washer on the
mounting screw. The PE ground symbol must be placed
adjacent to the screw.

To verify switch operation with an ohmmeter:

Set range at 20 mega ohms (switches with triac output, set
ohm range at 20 kilo ohms). For a normally open switch, the
meter will read a high impedance with the actuator away. It will
read very high to infinity range (triac switches will read high kilo
ohm to infinity range) with the actuator within sense range. You
will see the opposite reading for a normally closed switch.

Installation

Use non-removable screws, bolts, or nuts to mount the switch
and actuator. Do not over-torque mounting hardware.

1. Position the switch and actuator so the labels are reading
in the same direction (see Figure 2).

2. Mount the switch on the stationary frame of the machine
and mount the actuator on the moveable guard, door or
gate. Keep the switch and actuator within the listed sense
range. (See Ordering Information.) See Figure 3 for
recommended mounting configurations.

3. Mounting on a ferrous material will affect the sense range
a minimum of 50%. However, a 1/4" non-ferrous spacer
positioned under the magnet and/or switch should restore
most of the lost sense range.

4. For best protection against operator defeat, mount with
non-removable screws, bolts or nuts. See ordering
information for details.

© 2013 UTC Fire & Security. All rights reserved. 1 / 6 P/N 13924 • REV D • REB 27FEB13

Caution: When not used with a Sentrol INT relay particular

care must be taken to determine the actual load of the switch
circuit. High voltage transients from coils, motors, contactors
and solenoids must be considered. Transient protection, such
as back-to-back zener diodes (TransZorb®) or an RC network,
is recommended for such loads to ensure that maximum
ratings of the switch are not exceeded. Not recommended to
be used with tungsten filament loads because of high current
inrush surges. Line capacitance and load capacitance must be
considered.

Excessive line capacitance can be caused by cable lengths
over 50' when using a maximum 48 VAC. A resistor can be
added in series to limit the inrush current (at least 48 ohms for
24 Volt applications).

The resistor can be added in series just before the load.
The voltage drop and the power rating of the resistor must be

considered.
Voltage drop = I•R;
Watts = I2•R (I = maximum continuous current of the load).

6. When mounting the switch on an ungrounded machine,
ground the switch housing by connecting your ground lead to
one of the switch mounting screws.

Figure 2: Switch/Actuator position

Figure 4: Circuits

*Circuits shown with magnet actuator away from switch.
S1,S5 Normally open reed switch, closed when actuator is within

0.6"

S2, S3 Normally open reed switches, will close if misaligned or

tampered with a standard magnet

S4 Biased closed reed switch, open when actuator is between

0.3" and 0.6"

N.O. circuit: Black and white wires.
N.C. biased tamper circuit: Red and blue wires.
N.O. monitor circuit: Orange and brown wires.

Figure 3: Mounting configurations

2 / 6 P/N 13924 • REV D • REB 27FEB13