Electrical Distribution Board Design & Electrical Design BS7671 Sign-Off
- Chris Downing
- Apr 10
- 2 min read
What is Electrical Design for Distribution Boards?
Electrical design is the process of turning load requirements into a fully compliant installation plan in accordance with BS 7671.
For distribution boards, this includes:
Load assessment
Circuit design and allocation
Cable sizing
Protection device selection
Fault protection verification
Voltage drop calculations
Why Electrical Design is Required Under BS 7671
Electrical Design BS7671 requires all electrical installations to be:
“Designed, constructed, and verified”
A compliant design ensures:
Correct cable sizing
Proper circuit protection
Safe disconnection under fault conditions
Without this:
Installations may fail inspection
Delays occur on site
Safety risks increase
What’s Included in an Electrical Design BS7671 Package?
Load Assessment
Calculation of total demand and system loading
Cable Sizing Calculations
Based on:
Current carrying capacity
Installation method
Voltage drop
Fault protection
Protection Device Selection
Correct selection of:
MCB / RCBO types (Type B, C, etc.)
Ratings and breaking capacities
Distribution Board Schedule
Clear layout of all circuits and loads
Single Line Diagram (SLD)
Visual representation of the system
Design Assumptions & Limitations
Defines scope and protects all parties
Information Required for Electrical Design
Incoming Supply Details
Supply type
Prospective fault current (Ipf)
Earth fault current (Ief)
External earth loop impedance (Ze)
Upstream protective device
Final Circuit Information
Load details
Cable lengths
Installation methods
Cable types
Environmental conditions
Common Issues Contractors Face
Waiting on cable sizes before starting install
Uncertainty around breaker selection
Failed inspections due to missing design
Delays caused by incomplete documentation
Single Phase vs Three Phase Distribution
Smaller systems may be suitable for single-phase supplies, but higher load applications often require three-phase distribution.
Benefits of three-phase:
Balanced loads
Reduced current per phase
Improved system performance
Electrical Design for Automated Systems
Systems such as AutoStore often include:
Multiple distributed loads
Long cable runs
Mixed load types
These require:
Careful load distribution
Accurate cable sizing
Detailed documentation
Why Use a Specialist Electrical Design Service?
Outsourcing electrical design:
Reduces risk
Saves time
Ensures compliance
We provide:
Full BS 7671 compliant design packages
Fast turnaround
Contractor-ready documentation
Get a Quote for Your Electrical Design
If you have a project that requires electrical design or distribution board sign-off, we can help.
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