What Happens During a Fuse Board Replacement? Step-by-Step Guide for Portsmouth Properties
Replacing an old fuse board (now known as a consumer unit) is one of the most important electrical upgrades you can make to your home. Modern consumer units offer much better protection, reduce fire risk, and ensure your property meets the latest wiring regulations.
If you’re unsure what actually happens during a fuse board replacement, this step-by-step guide explains the full process — tailored specifically for Portsmouth homes, including what to expect, how long it takes, and why a qualified electrician is essential.
1. Initial Safety Checks & Power Isolation
Before anything else, your electrician will:
- Carry out a full safety assessment of your existing installation
- Switch off the main power supply
- Confirm all circuits are completely isolated
- Assess the condition of existing wiring
This ensures the replacement is carried out safely and in accordance with BS 7671 regulations.
2. Removing the Old Fuse Board
Once the system is safe, the old fuse board or outdated consumer unit is removed.
Typical older units found in Portsmouth include:
- Rewireable fuses
- Old-style cartridge fuses
- Non-RCD protected boards
These units do not meet modern safety standards and offer limited protection compared to today’s RCBO/RCD consumer units.
3. Installing the New Consumer Unit
Your electrician will install a modern consumer unit that includes:
- RCD protection (reduces risk of electric shock)
- MCBs/RCBOs for each circuit
- Surge Protection Device (SPD) — now required in many installations
The new board is mounted securely, labelled correctly, and prepared for testing.
4. Full Electrical Testing of Every Circuit
This is the longest part of the process and the reason a consumer unit replacement must be done by a qualified electrician.
Each circuit is tested for:
- Earth continuity
- Insulation resistance
- RCD/RCBO performance
- Correct polarity
- Suitability for reconnection
This ensures your home’s wiring is safe and compatible with the new board.
5. Power Reconnection & Final Checks
Once testing is complete:
- Circuits are safely reconnected
- The whole consumer unit is energised
- Final checks are carried out on every circuit
- Labelling and documentation are completed
At this point, your home’s power supply is restored.
6. Certification & Building Control Notification
A compliant replacement always includes:
- Electrical Installation Certificate (EIC)
- Part P Building Regulations notification
- Documentation for your records & home insurance
Your electrician will submit details to building control, ensuring your Portsmouth property is fully compliant.
How Long Does a Fuse Board Replacement Take in Portsmouth?
A typical replacement takes:
- 4–6 hours for standard homes
- Longer if circuits are old or need corrective work
Older Portsmouth homes — particularly Victorian terraces and 1960s properties — may require additional upgrades before the new board can be fully signed off.
Why Upgrade Your Fuse Board?
A new consumer unit gives you:
- Better protection from electric shock
- Reduced fire risk
- Compliance with the latest UK electrical standards
- Increased home safety
- Peace of mind during home sales or insurance reviews