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Thermcraft XST-3-0-36-3V User Manual

Page 178

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Installation

Installation and Operation Handbook

1-6

2416 Controller

1.2.3

Plug-in module connections

In Figure 1-4, Modules 1, 2 and 3, and Comms are plug-in modules.

1.2.3.1 Modules 1, 2 and 3

Module positions 1, 2 and 3 each have two terminals. They will accept four types of module:
Relay, Logic (non-isolated), Triac, and DC (non-isolated) output.

Collectively, these can be configured to operate in six different ways:

Heating control
Cooling control
Alarm output
Program event output
PDS mode 1*, which provides logic heating using a Eurotherm TE10S solid state relay
with feedback of a load failure alarm.
PDSIO mode 2*, which provides logic heating using a Eurotherm TE10S solid state relay,
with feedback of the load current reading and two alarms: solid state relay failure and
heater circuit failure.


* PDS stands for ‘Pulse Density Signalling Input/Output’. This is a proprietary technique
developed by Eurotherm for bi-directional transmission of analogue and digital data over a
simple 2-wire connection.

Snubbers

The relay and triac modules have an internal 15nF/100

Ω ‘snubber’ connected across their

output, which is used to prolong contact life and to suppress interference when switching
inductive loads, such as mechanical contactors and solenoid valves.

WARNING

When the relay contact is open or the triac is off, the snubber circuit passes 0.6mA at
110Vac and 1.2mA at 240Vac. You must ensure that this current, passing through the
snubber, will not hold on low power electrical loads. It is your responsibility as the
installer to ensure that this does not happen. If the snubber circuit is not required, it can
be removed from the relay module (but not the triac) by breaking the PCB track that
runs crosswise adjacent to the edge connectors of the module. Insert the blade of a
screwdriver into one of the two slots that bound it, and twist.

The table below shows the module connections and which functions each module can
perform. The heating output is normally connected to module 1, the cooling output to
module 2 and the alarm output to module 3, although the actual function of each module will
depend upon how your controller has been configured.

Note:

Module 1 is connected to terminals 1A and 1B

Module 2 is connected to terminals 2A and 2B

Module 3 is connected to terminals 3A and 3B.

This manual is related to the following products: