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

New machinery usually trips a commercial property for one of five reasons: high starting current from motors, circuit breakers with the wrong trip curve, earth leakage from variable speed drives tripping RCDs, uneven loading across phases, or a supply and switchboard that no longer have enough capacity. Each has a different fix, so the first step is diagnosis, not a bigger breaker.

Here is how to tell which one you are dealing with.

Table of Contents

• Is motor starting current the cause?
• Is the circuit breaker the wrong type?
• Are RCDs tripping from earth leakage?
• Is the load unbalanced across phases?
• Is the supply or switchboard too small?
• What should you check before buying more machinery?
• How High Demand Electrical solves commercial tripping
• FAQs

Is motor starting current the cause?

Direct-on-line motors can draw a multiple of full-load current for a second or more on start. Compressors, pumps, conveyors and dust extractors are common culprits. Fixes include soft starters, variable speed drives, star-delta starting, or breakers with an appropriate trip curve selected by an electrician to suit the load and cable.

Is the circuit breaker the wrong type?

Breakers have different magnetic trip curves. A curve suited to lighting and general power may trip instantly on a motor's inrush. An electrician can change the curve only where the cable, fault levels and discrimination with upstream protection still meet AS/NZS 3000.

Are RCDs tripping from earth leakage?

Modern drives and electronics leak small currents to earth in normal operation. Spread across many machines on one RCD, the total can exceed its trip threshold. Solutions include splitting circuits across more RCDs, using RCD types suited to drive loads, and checking for a genuine insulation fault. Never bypass an RCD. See why safety switches keep tripping.

Is the load unbalanced across phases?

When large single-phase loads are added to one phase, that phase can overload while the others have spare capacity. Rebalancing circuits across phases is often a low-cost fix. The Service and Installation Rules of NSW also have load-balancing requirements, explained in our balancing of load article.

Is the supply or switchboard too small?

If the main switch trips when the whole site is busy, the total demand may be exceeding the supply, main switch or consumer mains rating. Power logging shows peak demand per phase. If headroom has run out, see whether you need a larger three-phase supply.

What should you check before buying more machinery?

• Nameplate full-load current, starting method and phase requirement.
• Recommended circuit and protection from the manufacturer.
• Current maximum demand from logging.
• Switchboard space, cable route and isolation requirements.

An electrician can then design the machinery connection properly the first time.

How High Demand Electrical solves commercial tripping

Our electricians diagnose the cause with fault finding and logging, then fix it at the right level: starter, protection, circuit layout or a commercial power supply upgrade. As a Level 2 ASP contractor (Licence 397193C) we can also handle any network-side works.

FAQs

Related reading

• Does a commercial property need a larger three-phase supply?
• Circuit breaker keeps tripping: causes and safe fixes
• Power Keeps Tripping? When to Call a Level 2 Electrician
• Why power logging should happen before adding EV chargers, solar or batteries