By Alvin Wong, CEO of Innovative Green Power Sdn. Bhd.
Just over a month after installing an EV wallbox charger, a homeowner’s TNB meter box caught fire. The investigation found that a 100A fuse had been used — well above the design limits of a typical single-phase residential setup. This delayed protection during an overload and allowed dangerous heat buildup that led to the fire.
Why It Happened
1. Oversized Fuse
The original system likely supported only 60A, but a 100A fuse was installed. This prevented the fuse from tripping during faults, exposing wires and terminals to overheating and fire risk.
2. EV Charging Is a Continuous Load
Wallboxes typically draw 30–32A continuously for hours. On aging or undersized wiring, this creates thermal stress and degradation, especially when protection is improperly rated.
3. Lack of Proper Assessment
The fuse upgrade had been done by a previous electrician. The EV installer checked visually and deemed it “okay,” but no load calculation, thermal scan, or compliance check was done.
Why a Bigger Fuse Is Not a Solution
- It allows more current than the system was built to handle
- It delays fault detection and trip response
- It gives a false sense of security while removing real protection
What Should Have Been Done
- Keep fuse size at 60A unless the wiring, cable, and supply have been upgraded
- Limit the charger to appropriate load if staying on single-phase
- Always perform load assessment and thermal inspection before installation
Lessons Learned
- Do not upsize your fuse without proper system study
- Never rely on visual inspection or verbal assurances
- EV charging introduces new power demands that must be carefully managed
Summary
This incident could have been much worse. Thankfully, no one was harmed — but the risks were real. The main danger wasn’t the EV or the charger itself, but poor installation and improper system upgrades. Don’t compromise on installation quality.
Let our obsession with quality protect your safety.
Because when it comes to EV charging and electrical systems, there’s no room for compromise.
