PLC Control Backplates for LV and HV Switchboards in a Commercial Building Services Project
Sector:
Buildings Management
Type:
New Build - Control System, Software
Platform:
Siemens
Certification:
CE / UKCA
Summary
DelaControl designed, built, and programmed a pair of PLC control backplates to manage circuit protection devices across Low Voltage and High Voltage switchboards in a commercial building services installation. The scope covered the full delivery: hardware, software, electrical design, thermal analysis, testing, and FAT.
Challenge
A building services contractor required control backplates to be integrated into existing LV and HV switchboards, providing automated control of circuit protection devices across multiple switchboard assemblies.
The backplates needed to gather data from breakers with data capture capability and pass this upstream to a higher-level control system via Modbus TCP or Ethernet TCP/IP. No power distribution or motor power control was required — only actuation via control signals at 230 V ac or 24 V dc.
Solution
DelaControl designed and built two control backplates based on the Siemens S7-1200 platform, with the CPU supplemented by digital I/O expansion modules to cover the required signal count. A Siemens SITOP power supply with UPS battery backup was included to maintain control availability during supply interruptions. Weidmueller-compatible terminal blocks and Phoenix Contact distribution blocks were used for I/O connection, with Rittal metalwork finished in RAL 7035.
Network connectivity was provided via Siemens unmanaged Ethernet switches, enabling the PLC to present breaker data to the site's higher-level control system. A Red Lion data acquisition unit was also included to support data capture requirements. The PLC software was developed in-house against operational truth tables provided in the customer's Low Voltage Single Diagrams, following DelaControl's own Software Design Specification in the absence of a formal customer-supplied control philosophy.
The full documentation package included electrical schematics (produced in AutoCAD Electrical or Eplan), general arrangement drawings in AutoCAD Inventor, thermal calculations using Rittal Therm software, an Inspection and Test Schedule, and a Declaration of Conformity against LVD, EMC, BS EN 60204, BS EN 61439-1, and BS EN 61439-2. Pre-delivery testing using I/O simulation was completed at DelaControl's Bristol facility, followed by a Factory Acceptance Test to which the customer was invited before delivery.
Key Facts
• 2 × control backplates built and delivered
• Siemens S7-1200 CPU 1214C with onboard 14 DI / 10 DO / 2 AI
• 4 × digital I/O expansion modules (SM 1221 / digital output type)
• Siemens SITOP 24 V / 20 A PSU with 24 V / 7 Ah UPS battery module and 24 V / 10 A UPS with Profinet
• 3 × Siemens unmanaged Ethernet switches (1 × 5-port, 2 × 8-port)
• Red Lion 5-channel USB data acquisition unit included
• 34 × Finder 24 V dc coupling relays for control signal outputs
• ABB 3-pole switch-disconnector isolator fitted
• Rittal AX sheet steel enclosure (800 × 1000 mm), RAL 7035
• Data output via Modbus TCP or Ethernet TCP/IP to higher-level control system
• Full documentation pack: schematics, GAs, thermal calculations, FAT schedule and certificate, Declaration of Conformity