Why New Machinery Causes a Commercial Property to Trip (and How to Fix It Properly)

Why does new machinery cause a commercial property to trip? In most Inner West businesses it comes down to one of four causes: motor start-up inrush tripping a circuit breaker, earth leakage from drives and electronic equipment tripping a safety switch, an overloaded circuit or phase, or a supply that's too small for the new total load. Each has a different fix, and the one fix that's never right is simply fitting a bigger breaker.

⚡ Quick Answers: Machinery Tripping the Power

• Trips only at start-up? Usually inrush current or the wrong breaker trip curve.
• Safety switch trips, breaker doesn't? Earth leakage, either cumulative leakage from drives and filters or a genuine insulation fault.
• Trips after running a while? Usually an overloaded circuit or phase.
• Main switch trips? Total demand may be exceeding your supply capacity.
• Can I fit a bigger breaker? No. The breaker protects the cable; oversizing it is a fire risk.
• How is it diagnosed? Testing plus power logging while the machinery runs.

1. Inrush and starting current

Electric motors, compressors, coolroom refrigeration, large transformers and some LED drivers can draw several times their normal running current for a split second when they start. If the circuit breaker has a trip curve designed for light loads, or the circuit is already carrying other equipment, that surge can trip the magnetic element of the breaker the moment the machine starts. It's common with new coffee roasters, dough mixers, air compressors and CNC equipment in Marrickville and St Peters workshops. The fix is usually a dedicated, correctly sized circuit with a breaker curve suited to motor loads, or a soft starter or variable speed drive to reduce the starting surge.

2. Earth leakage tripping the safety switch

Safety switches (RCDs) trip when current leaks to earth rather than returning through the circuit. Variable speed drives, EMI filters, commercial induction cooktops and IT equipment all leak a small amount of current by design. One device is usually fine, but several on the same RCD can add up to a trip, especially at start-up. Some drives also produce leakage that a standard RCD type doesn't handle well, so the RCD type needs to suit the equipment. Just as importantly, RCD tripping can mean a genuine insulation fault or water ingress, so it has to be tested, not bypassed. Removing or bypassing a safety switch is dangerous and illegal. Our safety switch guide explains how RCDs work.

3. Overloaded circuits and unbalanced phases

If tripping happens after the machine has been running for a while, the thermal part of the breaker is usually responding to sustained overload. New equipment is often plugged into an existing general power circuit that already carries other loads. On three-phase sites, new single-phase equipment is sometimes all connected to the same phase, overloading it while the other phases sit lightly loaded. Moving the equipment to a dedicated circuit and rebalancing loads across phases often solves the problem without any supply upgrade. Cable ratings matter here, and our guide to cable amp ratings shows why.

4. When the supply itself is too small

If the main switch or service fuses trip, or lights across the whole site dim when the machine starts, the total demand may be exceeding what the supply can deliver. That's especially common in older Inner West shopfronts and warehouses now used for kitchens, breweries and fabrication. A supply upgrade may be needed, but only after logging confirms it. Our guide to whether a commercial property needs a larger three-phase supply covers how that decision is made.

5. Why a bigger breaker is never the answer

A circuit breaker is sized to protect the cable it feeds. Swapping a 20 amp breaker for a 32 amp one on a cable rated for 20 amps means the cable can overheat before the breaker ever trips. It might stop the nuisance tripping, but it creates a fire risk, breaches AS/NZS 3000 and can void insurance. If a machine needs more current, it needs a circuit designed for it.

6. How we diagnose it

1. Check which device trips (circuit breaker, RCD or main switch) and when.
2. Test insulation resistance and earth leakage on the affected circuits and equipment.
3. Check circuit loading, breaker ratings and trip curves, and RCD types.
4. Power log the switchboard while the machinery runs to capture current, voltage and events.
5. Recommend the fix: dedicated circuit, correct protection, load balancing, soft start or a supply upgrade.

Our guide to power logging explains what the data reveals.

How High Demand Electrical helps

We're a Level 2 ASP team (Licence 397193C) that works with Inner West cafes, restaurants, breweries, workshops and offices. We find the real cause of tripping, fix it properly, and if your supply genuinely is too small, we handle the upgrade with Ausgrid too. If it's tripping right now and you can't trade, our emergency electricians can help.

Commercial Tripping FAQs (Inner West)

Why does my breaker trip only when the machine starts?

That usually points to inrush or starting current. Motors, compressors and transformers can draw several times their running current for a moment at start-up, which can trip a breaker with the wrong trip curve or a circuit that's already heavily loaded.

Why does the safety switch trip but not the circuit breaker?

A safety switch (RCD) trips on earth leakage, not overload. Variable speed drives, EMI filters and some electronic equipment leak small currents to earth, and several of them on one RCD can add up to a trip. It can also mean a genuine insulation fault, so it should be tested.

Can I just install a bigger circuit breaker?

No. The breaker protects the cable. Fitting a larger breaker without upgrading the cable can let the cable overheat and is a fire risk and non-compliant.

How do you find the cause of tripping?

By testing insulation and earth leakage, checking circuit loading and breaker types, and power logging the switchboard to capture current, voltage and trip events while the machinery runs.

Does tripping mean I need a bigger power supply?

Not necessarily. Many cases are fixed with a dedicated circuit, the correct breaker or RCD type, load balancing or a soft starter. A supply upgrade is only needed if measured demand exceeds the supply capacity.

Stop the Tripping for Good

New equipment tripping your power? Book a commercial electrical diagnosis, explore power supply upgrades, or call 0402 559 777. We'll find the cause before recommending any spend.