Industrial Service
Sub-Mains Distribution
Sub-mains distribution installation and upgrades for industrial and commercial premises — from distribution board replacement through to LV cable design, MCCB specification, containment and full BS 7671 documentation.
What sub-mains distribution work actually has to deliver
01
Distribution boards that are full — no spare ways
A full distribution board with no spare capacity is a programme risk for any new load, fit-out or machine installation. We assess the existing board configuration and design an extension or replacement that provides the headroom required without oversizing the installation.
02
Cable routes that interfere with the existing plant
New sub-main cables in operating industrial environments have to be planned around existing plant, structural constraints and access restrictions. We survey cable routes before design and produce a routing plan that avoids interference with both active plant and future maintenance access.
03
Voltage drop that affects sensitive equipment
Undersized sub-main cables cause voltage drop that affects drive controllers, PLC systems and precision equipment. We calculate voltage drop across the full circuit length and specify cable sizes to maintain supply quality at the load.
04
No up-to-date single-line diagram
Many industrial sites have distribution infrastructure that has been extended over decades without updated documentation. We produce a verified single-line diagram and circuit schedule as part of every sub-mains project — giving the maintenance team a reliable baseline.
Technical detail
Standards & compliance
- BS 7671 18th Edition — distribution circuit design
- IEC 60947 — low-voltage switchgear and protection
- Voltage drop calculation to BS 7671 Appendix 4
- Short-circuit prospective fault current analysis
- BS EN 60529 enclosure IP rating requirements
Distribution boards
- Consumer unit and distribution board replacement
- MCCB and MCB protection specification
- RCD and RCBO protective device selection
- Metering and sub-metering provisions
- Arc flash boundary assessment on request
Sub-main cables
- SWA and XLPE cable design and installation
- Mineral insulated cable for fire-protected circuits
- Busbar trunking systems for large load centres
- Cable management sizing for capacity and future use
- Cable tagging, labelling and schedule production
Documentation
- As-installed single-line diagrams
- Circuit schedules and distribution board records
- BS 7671 test certificates and EICR
- Prospective fault current and voltage drop schedules
- O&M documentation for facilities management
The Numbers
18th
All sub-main designs comply with the current edition of the IET Wiring Regulations including Amendment 2.
0
Zero unplanned supply interruptions is the standard we hold every live-site distribution project to.
48hr
Single-line diagrams, circuit schedules and test certificates submitted within 48 hours of commissioning.
Why specify Con-Tec
Distribution Infrastructure Built to Last
Our Sub-Mains Distribution Approach
01
Capacity Assessment
Supply capacity review, prospective fault current analysis and existing circuit condition assessment before design begins.
02
Design & Cable Schedule
Distribution board design, cable sizing, voltage drop calculation and routing plan produced and submitted for approval.
03
Installation
Works delivered with careful isolation management, temporary supply planning and zero unplanned outages as the standard.
04
Commission, Test & Document
Full BS 7671 testing, single-line diagram production and circuit schedule submission within 48 hours of commissioning.
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What our clients say
“Con-Tec consistently meets the rigour our estates teams expect. Their compliance documentation, site discipline and turnaround on remedial works are exactly what large-scale healthcare contracts require.”
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