Why Is My Switchboard Buzzing or Humming?

Byron Knight, Licensed Electrical Contractor

QLD Lic. 1511406 · 20+ years’ experience · Gold Coast & SEQ · Updated September 2026

Most guides answer this with “it’s never normal, call immediately”. That isn’t quite right, and the imprecision doesn’t help — because some switchboard noise genuinely is normal, and telling people otherwise makes it harder to recognise the noise that isn’t.

Here’s how to tell them apart.

What the sound itself is telling you

The dividing line is roughly this: a steady low hum is electricity doing its job. Anything irregular — buzzing, crackling, hissing — is electricity going somewhere it shouldn’t.

Why a faint hum can be normal

Australia’s grid runs at 50 Hz, and alternating current produces low-frequency vibration in ferrous components. Older magnetic-type breakers, and any transformers in the installation, can produce a barely perceptible drone as a result.

Which is the useful part of the finding. Operational hum isn’t the problem — but investigating a hum frequently uncovers loose hardware, which is. A noise worth checking isn’t the same as a noise that’s dangerous in itself.

The single most useful question: has it changed?

More diagnostic than the sound itself. A board that has hummed faintly for a decade is behaving as it always has. A board that was silent last month and hums now has changed state, and change is what matters.

1. When did it start? Sudden onset points to a specific event — a new appliance, a storm, recent work.
2. Is it constant or intermittent? Noise that appears under load points to a stressed circuit rather than a failed component.
3. Is it getting louder? Progression means the fault is developing, not stable.
4. Can you localise it? A specific breaker versus the whole board narrows it considerably.

What’s actually making the noise

• A loose connection arcing. The most common serious cause. Terminals loosen over years of thermal cycling, current begins jumping the gap instead of flowing across it, and that arc produces both the buzz and concentrated heat. It’s the same mechanism behind lights flickering across multiple rooms — one fault presenting as sound, the other as light
• An overloaded circuit. A breaker carrying near or above its rating for extended periods gets stressed, and stress produces both heat and noise. Often accompanied by tripping
• A failing circuit breaker. Internal components wear. A breaker that buzzes may be approaching the point where it won’t trip reliably — which matters more than the noise does
• A worn or failing safety switch. Covered separately below, because the consequence is different
• Moisture ingress. Common here, particularly through storm season. Water and salt air both create leakage paths, and hissing or sizzling often points this way
• Aged boards carrying modern loads. A board designed for a 1980s household now running today’s appliances, air conditioning and EV charging is operating outside its design assumptions
• Pests. Ants and small insects genuinely do nest inside switchboards in South East Queensland. The nesting material and the bodies both create paths for current where there shouldn’t be one

A humming safety switch is its own problem

Worth separating out, because the risk isn’t fire — it’s the absence of protection.

An RCD that hums may be worn, damaged or failing internally. The concern is that a compromised safety switch may not trip when it needs to, which means the protection you believe you have isn’t there. You’d have no way of knowing until the moment it was needed.

If you can localise a hum to a safety switch specifically, that’s worth acting on promptly even without any other symptom. Our guide on RCDs versus RCBOs covers what should be protecting each circuit and how the arrangement changes your exposure when one device fails — on a shared RCD, one failing device removes protection from up to three circuits at once. A safety switch that keeps tripping is a different symptom pointing at the same family of causes.

If there’s a burning smell, what to do about a burning smell covers the immediate sequence. For the broader triage, see what counts as an electrical emergency.

What not to do

• Don’t open the board. Removing the cover exposes live components. This is licensed work regardless of how confident you feel — see what you can legally do yourself in QLD
• Don’t tighten anything. Even if you suspect a loose connection, tightening terminals on a live board is exactly how people get hurt
• Don’t ignore it because the power still works. Arcing faults progress. The board working today says nothing about next week
• Don’t keep resetting a breaker that’s buzzing after it trips

What we check on site

1. Isolate and safely open the board to inspect terminations for discolouration, heat damage or visible arcing marks.
2. Thermal imaging across the board under load. A degrading connection runs hot before it fails, which is exactly what a thermal scan finds — and why it’s the tool that turns a noise into a located fault.
3. Torque-check terminations to specification, since loose connections are the most common serious cause and the one the manufacturers’ own findings point at.
4. Test the RCDs — confirming they trip within the required threshold, not merely that they exist.
5. Assess circuit loading, to establish whether a circuit is running beyond what it was designed for.
6. Check for moisture ingress and pest activity, both common in Gold Coast boards.

If the board turns out to be aged beyond economic repair, what drives a switchboard upgrade covers what replacement involves.

Why Gold Coast boards are harder on themselves

• Heat. Sustained high ambient temperatures increase resistance at connections, which increases heat, which accelerates degradation. Boards in direct sun or poorly ventilated positions fare worst
• Salt air. Coastal properties see accelerated corrosion at terminations, particularly within a few kilometres of the beach — the mechanism is set out in why Gold Coast switchboards corrode faster
• Storm season. Wind-driven rain finds its way into external boards and meter enclosures that seemed weatherproof, and surges add their own stress
• Pests. Subtropical conditions mean ant activity in enclosures is a recurring cause rather than a curiosity

In practice the boards we open with the worst termination corrosion are in beachfront Palm Beach, Currumbin and Mermaid Beach properties, and the ones with the worst heat exposure are west-facing boards through Robina and Nerang with no shade on them.