CT24 MCU
User Manual
29
9M02-7608-A001-EN
Version 2.0
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Wires must be bundled to keep mechanical rigidity and maintain good wiring practice.
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16 AWG (1.5 mm) is the minimum gauge that can be used if the load is unknown, up to the relay rating of
5A, and in a normal industrial environment of 40ºC.
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Lower gauges may be used for known low current loads.
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Care must be taken with any common supply wires as these will be carrying the load of many outputs.
5.8
Examples of Wire Sizing
5.8.1 Low Duty Application (Typical Crane)
A typical crane contactor (sealed) would have a rating less than 40W; however, contactors vary widely and the
rating should be checked.
For a five speed function (intermittent use):
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The common wire may be carrying 200 W (=5X40) at 48 VAC, for a current of 4 A (=200/48). Therefore,
18 AWG might be used.
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The actual drive out to a single hoist contactor could be 0.83 A (=40/48), so 24 AWG would be adequate.
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If the voltage were 110 VAC, the current would be 1.8 A, so 22 AWG might be used.
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The actual drive out to a single hoist contactor could be 0.36 A, so 24AWG would be adequate.
5.8.2 High Duty Application (Crane with Multi Select or Machine)
For a multi select set of five outputs (continuous):
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The common wire may be carrying 200 W (=5X40) at 48 VAC, for a current of 4 A. Therefore, 16 AWG
might be used.
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Each select output might be 0.83 A (=40/48), so 24 AWG would be fine.
5.8.3 High Duty Maximum Current Application
For multiple outputs running 5 A loads (continuous):
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Common carrying up to two relay loads is possible using 14 AWG; otherwise, use 16 AWG.
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Each relay output conductor requires 16 AWG.
5.9
Connection of Wires to Interface Connectors
While it is possible in some cases to use wires without ferrules, sometimes the use of ferrules will inevitably make
the connection to the RIA and Phoenix interface connectors easier and neater. The use of ferrules may also be
required when looping a common feed to multiple relays, particularly if it is determined that larger wire gauges are
necessary. The following section will simplify the selection of ferrules according to the pre-determined wire
gauges.
5.9.1 Interface Connectors
These may have either a spring clamp or a screw connector.
5.9.2 Overview
All of the machine interface connections used on the MCU have pluggable terminal blocks for easy maintenance
and board replacement.
Both spring clamps and screw terminals are available.
