Watlow TLM-8 User Manual

TLM-8
User’s Guide

Features and Description

The TLM-8 is a multi-zone temperature limit switch.
For thermal system safety, the TLM-8 can satisfy the
requirement for independent temperature monitoring.
The TLM-8’s alarm outputs interface with visual and
audible alarm devices, or they can initiate safe shut­down of equipment.

The TLM-8 has the following features:

• Multi-channel temperature monitoring

• Latching alarms

• Isolated sensor inputs

• Support for various thermocouples, RTDs, and
thermostats

• Diagnostic test mode

• Open-sensor fail-safe

• Compact and easy to install

• LED indicator lights

Up to eight temperature zones may be monitored. If
any temperature exceeds a trip point, the TLM-8 gen­erates an alarm output. The alarm output may be used
for safety shutdown or annunciation. Alarm outputs
remain active until two conditions are met in sequence:
the temperature drops below the trip point and alarms
are acknowledged. Built-in indicator lights show power
and alarm states.

The TLM-8 accepts up to eight thermocouple, RTD or
thermostatic switch temperature sensors. There are
two global alarm relay outputs. The TLM-8 is also
available with eight channel-alarm relays in addition
to the two global relay outputs. If all temperatures are
below the trip point, the TLM-8’s relay outputs are
closed. When alarms activate, the relay contacts open.

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Relays that open on alarm are consistent with fail safe
designs and practices. Alarms are acknowledged with
an optically isolated, digital input. Another isolated
digital input is used for testing, by simulating alarms
on all channels.

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Warranty

The TLM-8 is manufactured by ISO 9001-registered
processes and is backed by a three-year warranty to
the first purchaser for use, providing that the units
have not been misapplied. Since Watlow has no control
over their use, and sometimes misuse, we cannot guar­antee against failure. Watlow’s obligations hereunder,
at Watlow’s option, are limited to replacement, repair,
or refund of purchase price, and parts which upon
examination prove to be defective within the warranty
period specified. This warranty does not apply to dam­age resulting from transportation, alteration, misuse or
abuse. The purchaser must use Watlow parts to main­tain all listed ratings.

Part No. 0600-2150-2000 Rev. D
Revised: October 2007

© 2004, 2007 Watlow Electric and Manufacturing Company. All
rights reserved.

WATLOW TLM-8 User’s Guide 1

Mounting the TLM-8

SENSOR

J6

1 2

3

4

5

6

7

8

TST-

V-

J5

ACK-

The TLM-8 mounts directly to a panel or on a DIN rail
depending on the mounting style ordered.

DIN Rail Mounting

The TLM-8 simply snaps onto a standard 35 mm DIN
rail. Place the hook side of the mounting mechanisms
over one of the DIN rail edges and snap the assembly
over the other edge.

DIN Rail Removal

Remove the TLM-8 from the DIN rail by placing a flat
blade screw driver through the slot in the end plate,
hook the blade into the snap latch and pry the snap
latch away from the DIN rail edge. Repeat for the other
side.

92 mm (3.61 in)

48 mm
(1.87 in)

20 mm
(0.75 in)

End View

Wiring Recommendations

TB5 Sensor Inputs

Sensor

Input

1 12

2 34

3 56

4 7 8

5 9 10

6 11 12

7 13 14

8 15 16

Sensor
Inputs

DC Power

Terminals

+-

Positive Terminals
Negative Terminals

+

Isolated

supply

_

TB6 Power and Digital
Inputs

Function

Test

Acknowledge

Power

Terminals

+-

12

34

56

Channel 1
Channel 2
.
.
.
.
Channel 7
Channel 8

TST
ACK
Powe r

236 mm (9.30 in)

Side View

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Mounting Hole Dimensions

Panel Mounting

The four mounting holes will accommodate up to 3.8
mm (#6) screws or bolts.

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Test and
Acknowledge Circuits

Input Wiring

DC Power Supply

The TLM-8 accepts 12 to 24VÎ (dc) power input from a
class 2 power supply.

Test Input

The test input, TST, is a level-triggered digital input. It
is activated after the input signal is applied for at least
1 second (filter). The input signal may be generated by
a contact closure or controller output. The input accepts
a 5 to 30VÎ (dc) signal. The circuit contains a resistor
and optical isolator.

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2 WATLOW TLM-8 User’s Guide

Acknowledge Input

J1

CH1CH2

CH3

CH4CH5CH6CH7 CH8 NOG1 NOG2

J2

OUTPUTS

The acknowledge input, ACK is an edge-triggered digi­tal input. The input accepts a 5 to 30V
The circuit contains a resistor and optical isolator. If
you are using a push button to generate the input sig­nal, momentary contacts are recommended because the
input is edge-triggered.

DC

Powe r

Supply

User Supplied

Contact

+

_

TLM-8 Internal Circuit

ACK+

ACK–

Î (dc) signal.

Ó

WARNING:

You must connect the thermocouple to the input terminal
blocks correctly. If the inputs are reversed, the sensor
may be unable to generate an alarm. This could result
in a fire or other accident leading to loss of property or
lives.

Ó

CAUTION:

To protect the alarm relay contacts when connected to an
inductive load, use catch diodes for dc loads and snub­bers on ac or dc loads. For dc applications select a diode
with a reverse breakdown voltage 10 times the applied
voltage and forward load current.

Acknowledge Input

Thermocouple and RTD Inputs

Be sure to use the type of sensor that matches your
TLM-8; the input type is noted on the label.

Thermostatic Switch Inputs

When using thermostatic switch (thermostat) inputs,
TLM-8 trip points can be set externally. The TLM-8
should be configured for thermostatic switches. Use
normally-closed thermostats that open at or above the
trip point.

Unused Inputs

If a sensor input is not used, short the positive and
negative input terminals.

TB1 Channel Relay Outputs

Relay Output Terminals

1 1, 2

2 3, 4

3 5, 6

4 7, 8

5 9, 10

6 11, 12

7 13, 14 1 1, 2

8 15, 16 2 3, 4

TB2 Global Relay Outputs

Global Alarm

Output

Terminals

Load

Back EMF Clamp

Load

Back EMF Clamp

Wiring Recommendations for relay outputs

Ó

CAUTION:

To minimize the power dissipated by the internal circuits
and ensure temperature accuracy, apply voltage to the
ACK and TST inputs only when intending to test the TLM-8
or acknowledge alarms. At other times the applied signal
should be 0VÎ (dc).

NOTE: To avoid interference with sensor readings, sepa­rate sensor and power wiring.

NOTE: This device is designed for indoor use only.

NOTE: Use only copper conductors for power and signals
other than thermocouples.

NOTE: Previous versions of the TLM-8 recommended
earth grounding the unit’s case, but the current version
does not require the case to be earth grounded.

NOTE: Alarm outputs and indicators are latched until the
condition is corrected and the alarm is acknowledged, as
long as the TLM-8 remains powered. If power is cycled to
the unit, it will evaluate the limits again.

WATLOW TLM-8 User’s Guide 3