Marine Air Conditioner Tripping the Breaker
There are two very different faults hiding behind the same symptom, and telling them apart takes one observation: does it trip the instant you start it, or after it has been running a while? The first is usually inrush, the second is usually load.
Tripping out: First Checks
Do not keep resetting it. A breaker that trips is doing its job.. Time it. Trips within a second or two of the compressor kicking in is a starting-current problem. Trips after ten minutes or an hour is a running-load or a heat problem.
Where this sits on the seawater loop
- Seacock
- Strainer
- Pump
- Condenser
- Evaporator
- Discharge
- Condensate
Electrical — though poor seawater flow can raise the current until it trips, so rule the loop out second.Marine air conditioning is water-cooled, and that is what makes it different from a house. The full cutaway is in the guide.
Tripping out: Diagnostic Steps
Work down it rather than picking the step that sounds most likely. The order is chosen so that the cheap, common causes are eliminated before the expensive, rare ones — which is also the order that stops you paying somebody to clean a strainer.
Note exactly when it trips.
This one observation splits the diagnosis in half, and it is the first thing any electrician will ask you.
If it trips on start-up, count what else is running.
A compressor draws several times its running current for a fraction of a second. On a 10 A pedestal with a kettle and a charger already going, the margin is gone. Start the unit first, then everything else.
Check whether it trips the boat's breaker or the marina pedestal.
The pedestal tripping is a supply-capacity problem and a soft start usually fixes it. The boat's own breaker tripping points at the circuit or the unit.
If it trips after running, feel the seawater discharge.
A unit struggling against poor seawater flow draws more current as head pressure rises, and eventually trips. This is the not-cooling fault wearing a different coat.
Try it on a different berth or a different pedestal if you can.
Marina pedestals do age, and a tired breaker trips below its rating. Ruling the supply in or out is worth doing before paying anyone.
When to Stop and Call a Marine Technician
Anything involving the fixed 240 V wiring on the boat is licensed work under AS/NZS 3004.2. You can observe and describe; an electrician has to open the panel.
Handling refrigerant in Australia requires an ARCtick licence under the Ozone Protection and Synthetic Greenhouse Gas Management Regulations, and fixed 240 V work on a vessel is licensed under AS/NZS 3004.2. Both exist for good reasons. Everything above the line is yours; everything below it is not.
Possible Causes of Tripping out
Start-up inrush on a loaded 10 A supply
A soft start module, typically $300–600 fitted, cuts inrush by roughly two thirds.
Everything else on the boat running at once
Sequence the loads. Free, and often the whole answer.
Rising current from poor seawater flow
Fix the flow first — see the no-flow page.
An undersized or shared circuit
A dedicated circuit is what the standard asks for. Licensed work.
A tired pedestal breaker
Report it to the marina. Not your equipment and not your cost.
Ranked by how often each one is the answer on Australian boats, not by how often it appears in a service manual. The seawater side dominates this list because our water is warm, our marinas are full of growth, and the strainer is the part nobody opens.
Reporting This Marine Air Conditioning Fault
Tell us the boat, the unit if you know it, and what you found at each step above. We will tell you what we would check next, and whether it is worth a technician's call-out or a new machine. We do not charge for that and we will say if the honest answer is that the unit has had its life.