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Brand: Allen-Bradley
Allen-Bradley 1747-L20C Fixed PLC
Description
An SLC 500 fixed controller with mixed input and relay I/O
The Allen-Bradley 1747-L20C is an SLC 500 fixed controller with twelve sinking 24 V DC inputs and eight AC/DC relay outputs. The input arrangement includes the high-speed-counter input identified in the manufacturer manual.
Its DC input designation should not be confused with the controller supply. The L20C configuration is AC line powered and provides a 24 V DC, 200 mA user supply. Other L20 suffixes use different input, output or supply arrangements, even when the overall point count is the same.
Technical specifications
| Parameter | Specification |
|---|---|
| Manufacturer / range | Allen-Bradley / SLC 500 fixed hardware |
| Catalog number | 1747-L20C |
| Inputs | 12 sinking 24 V DC inputs |
| Outputs | 8 AC/DC relay outputs |
| High-speed-counter input | Provided in the L20C input configuration |
| Controller power | AC line powered |
| User supply | 24 V DC, 200 mA |
Replacement planning and wiring
The relay-output execution is distinct from the triac-output L20D and the DC-transistor-output configurations. Match the output load and existing circuit wiring to the exact L20C diagram rather than selecting by twenty I/O points alone.
For an installed-system replacement, retain the controller program, record the full hardware label and check the power and field-wiring arrangements. The user supply rating is 200 mA; account for connected field devices rather than treating it as an unrestricted external power supply.
Documentation and quotation
The SLC 500 fixed-hardware installation manual contains the L20C configuration entry and dedicated wiring diagrams. Send the complete controller code, quantity, installed series identification, program requirements and terminal photographs with an enquiry.
Browse PLC & I/O Cards for related hardware.
Datasheets & Documents
- Manual SLC 500 Fixed Hardware Installation and Operation Manual Download
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About brand
Catalog numbers beginning 1756, 1734, 1746 or 5069 are read at a glance by anyone who maintains Allen-Bradley control panels. The brand, the control hardware name of Rockwell Automation, dates back to 1903 in Milwaukee, USA. Seven Star LLC sources and supplies Allen-Bradley PLC and I/O modules, communication adapters and PowerFlex drives for plants in Oman, matching catalog number, series letter and firmware against the manufacturer's documentation.
Allen-Bradley product families listed here
Current controller platforms on this page are ControlLogix, with the 1756-L85E ControlLogix 5580 controller and the 1756-PA72 chassis power supply, and CompactLogix 5380, with the 5069-L320ER and 5069-L340ERM. Distributed I/O is represented by POINT I/O: the 1734-AENTR dual-port EtherNet/IP adapter and the 1734-IB8 digital input module. Allen-Bradley drives listed are the PowerFlex 525 and PowerFlex 755. For installed systems there are SLC 500 parts: the 1746-A10 chassis, 1746-NI16I analog input module, 1747-ASB remote I/O adapter, 1747-KE interface and 1747-M13 memory module. A Trusted TMR digital input module (T8403) is also listed.
Where Allen-Bradley hardware is used
ControlLogix and CompactLogix controllers run packaged equipment and plant utilities: compressor and pump skids, water and wastewater plants, power distribution, material handling and packaging lines. PowerFlex drives control pumps, fans and conveyors. Across the GCC, a large base of SLC 500 racks is still running, and Allen-Bradley spare parts for these systems are a frequent request.
Ordering Allen-Bradley modules and drives: what we need
Send the full catalog number, the series letter and, for controllers and communication modules, the firmware revision printed on the side label. Compatibility with an existing project depends on these. For PowerFlex drives, give the complete catalog string, which encodes voltage, current rating, enclosure and options, plus the motor nameplate data. For SLC 500 parts, tell us the rack size and processor so that we can check slot and power supply loading in the manufacturer's manuals. A label photo avoids most mistakes.
Browse Allen-Bradley products by category: PLC & I/O Cards, AC Drives.
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Frequently Asked Questions
Does the controller run from a 24 V DC supply?
The L20C configuration is AC line powered. Its 24 V DC designation identifies the field inputs and user supply.
What output type is fitted?
It has eight AC/DC relay outputs.
Does it include a high-speed-counter input?
Yes. The manufacturer manual identifies the high-speed-counter input in the L20C configuration.
Can another L20 suffix be selected by point count alone?
No. The suffix changes the input, output or power arrangement. Match the complete catalog number and wiring.
What should be supplied for a replacement quotation?
Provide the full label, quantity, hardware series, existing program requirements and photographs of the power and I/O wiring.
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