Bent copper busbar terminal modified to fit a consumer unit device, marked with a red arrow.

🔥 Modifying Consumer Units: Why “It Fits” Can Still Fail

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Consumer Units
18th Edition · Consumer Unit · FuseBox · Hager · Live Electrical
Posted by: electrical4less_mirek Avatarelectrical4less_mirek

⚠️ Mixing Brands in Consumer Units: A Risky Shortcut

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Modifying consumer units might seem harmless when you’re just trying to make things fit — but it’s a shortcut that can lead to serious risks. From mixing brands to bending busbars, these quick fixes often result in overheating, loose connections, or worse — a fire. And once you’ve changed it, the responsibility is all yours.

Mixing brands in consumer units can cause:

  • Loose busbar contact
  • Overheating terminals
  • Failed disconnection under fault
  • Or worse — a fire

Many unsafe installations start with modifying consumer units by mixing incompatible breakers and devices from different brands.

🔌 Consumer Unit Busbar Compatibility: Looks Can Be Deceiving

Even though most devices fit on the same DIN rail, not all devices are made the same.

Every brand has slight changes in:

  • Terminal size
  • Busbar slot width
  • Depth and clip tension

Just because it clicks doesn’t mean it’s safe.

🔧 What Happens When You Bend the Busbar?

Installers sometimes force things to work. A popular trick? Bending or cutting the busbar to reach terminals on an incompatible device.

But this creates:

  • Uneven contact
  • Hot spots
  • Arcing
  • Long-term failure

That’s why safe consumer unit installation always means: use matched parts, properly connected.

đź“Ź What the Regulations Say About Altering Consumer Units

BS 7671 Regulation 134.1.1 says:

“Good workmanship and proper materials shall be used.”

Modifying a busbar or mixing components voids compliance. The moment you change the setup, you take responsibility — not the manufacturer.

👨‍🔧 Can You Test a Modified Consumer Unit Yourself?

No.
Manufacturers test:

  • Heat rise
  • Contact pressure
  • Fault endurance
  • Mechanical wear

Can you test that on site? Definitely not.
If you modify the internal components of a consumer unit — like altering the busbar or installing mismatched devices — you become fully liable for the safety and compliance of that setup.

⚙️ Safe Consumer Unit Installation: Follow the Manufacturer

Best practices for installers:

  • âś… Avoid modifying consumer units — if a component doesn’t fit, it’s not meant to
  • âś… Use devices made for that board
  • âś… Follow spacing, layout, and busbar instructions
  • âś… Don’t alter the enclosure, terminals, or busbar
  • âś… Label any non-standard additions clearly

And for customers:

  • âś… Always hire a qualified, competent electrician — ask for registration with bodies like NICEIC or NAPIT to make sure the installation is done properly and signed off.

🧩 What About Timers, Contactors & DIN-Mounted Add-Ons?

Some devices don’t connect to the busbar (like timers or contactors). If they just sit on the rail and don’t interfere, they might be fine.

But always check:

  • Does the CU maker allow extra DIN gear?
  • Is it safe for airflow and spacing?
  • Are you following BS 7671?

If in doubt: don’t install it — or call the manufacturer.

🔥 Non-Compliant Consumer Unit Wiring: Real Risks, Real Fires

We’ve seen:

  • Melted busbars
  • Burnt terminals
  • Failed RCBOs
  • Dangerous EICRs from “adapted” boards

Even when the system seems to work, failure can come later — and it’s the installer’s name on the certificate.

đź›’ Shop Compliant Boards & Gear

We stock only fully compatible kits — so you won’t need to risk modifying consumer units on site. Looking for fully compliant kits? Browse our full range of Consumer Units — tested, trusted, and regulation-ready.

âť“ FAQs – Modifying Consumer Units

🔥 Can mixing brands cause fires?

Yes. Poor contact and added resistance cause heat. That heat leads to damage — or worse, fire.

👨‍🔧 Can I test a modified busbar install?

No. Only manufacturers do thermal and mechanical testing. On-site checks are not enough.

🧰 Can I add a DIN device that doesn’t touch the busbar?

Maybe. If the CU allows it and it doesn’t cause safety issues. Always check documentation and follow BS 7671.

đź“ś What regulation covers this?

BS 7671 Reg 134.1.1: You must use good materials and methods. If you change things, you’re fully responsible.

đź’¬ Join the Conversation – Modifying Consumer Units

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Have questions about brand compatibility? Ask below.
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