Safety Switch Trips Only When the Aircon Runs (Brisbane Electrical Causes & What To Do)
A Brisbane-focused guide explaining why your safety switch (RCD) trips only when the air conditioner turns on, the most common electrical causes behind it, and the warning signs homeowners should never ignore.
If your safety switch trips only when the aircon runs, it’s not random.
It’s usually a sign of an electrical fault or earth leakage and Brisbane humidity + summer load makes it happen more often.
Why this matters:
A safety switch trips when it detects electricity going somewhere it shouldn’t.
That means the system is protecting you from:
electric shock risk
overheating wiring
potential fire hazards
expensive aircon damage if ignored
Below are the most common Brisbane-based causes.
1. Earth Leakage Fault in the Aircon (Most Common)
This happens when insulation inside the aircon starts breaking down.
Common triggers:
age and wear in compressor wiring
heat expansion inside the outdoor unit
moisture exposure after storms
dirt buildup causing overheating
Typical signs:
trips instantly when cooling starts
trips after 1–5 minutes of running
gets worse on hot humid days
2. Moisture Inside the Outdoor Unit (Storm Season Trigger)
Outdoor units are exposed to Brisbane weather year-round.
Moisture can enter:
terminal blocks
electrical joints
capacitor housing
control boards
Signs this is the cause:
only trips on wet or humid days
trips after rain, then works later
trips most often on first start of the day
3. Damaged Wiring Between Indoor & Outdoor Unit
Aircon cabling can run through:
roof spaces
wall cavities
outdoor conduit
behind units or brackets
Damage can happen due to:
rodents chewing insulation
brittle cable from roof heat
cable strain from poor installation
weather cracking exposed wiring
renovation accidents
This is serious because faults worsen quickly and can become unsafe.
4. Compressor Fault (High Leakage Under Load)
The compressor is the highest-load part of the system.
If it starts failing, it may:
leak current to earth
trip when compressor starts working harder
trip during hot afternoons more than mornings
Common signs:
runs briefly then trips
system struggles to cool before tripping
outdoor unit louder than normal
trips mostly during peak heat
5. Capacitor or Fan Motor Fault
Failing components can cause abnormal current draw or earth leakage.
Common culprits:
capacitor
outdoor fan motor
contactor/relay
compressor start components
Signs:
outdoor unit hums then trips
fan isn’t spinning properly
starts then shuts off fast
trips only during startup
6. The Safety Switch (RCD) Itself Is Faulty or Too Sensitive
Not the most common cause, but possible.
More likely when:
multiple circuits share one RCD
switchboard is older
you’ve noticed random trips even without aircon use
A licensed electrician can test the RCD and confirm if it needs replacement.
7. Voltage Fluctuations (Brisbane Heatwave Days)
During extreme summer demand, Brisbane homes can experience voltage dips.
This can cause:
aircon struggling to start
higher stress on components
faults triggering safety trips
Signs:
works at night but trips during the day
trips during peak afternoon load
trips more when other appliances run
What You Should NOT Do
Do not keep resetting the safety switch repeatedly.
Repeated trips can:
damage aircon components
overheat wiring
cause progressive failure
turn a small fault into a costly repair
If it trips more than once, stop using the system until it’s checked.
When It’s a Safety Emergency
Turn the system off and call a licensed electrician immediately if you notice:
burning smell near the outdoor unit
buzzing or crackling noises
sparks
melted insulation or wiring covers
switchboard feels hot
safety switch won’t reset
it trips instantly every time
Final Word: It’s a Warning, Not an Annoyance
If the safety switch trips only when the aircon runs, it’s almost always a fault that will worsen.
In Brisbane, this is common during:
high humidity weeks
storm season
summer heatwaves
The sooner it’s diagnosed, the cheaper and safer it usually is.
👉 Need an aircon electrical inspection in Brisbane?
Contact Exclusive Electrical & Air to test the aircon circuit, check for earth leakage, and identify the exact cause before it becomes unsafe.