Power

Draft — Michael to rewrite in his own words.

The old shore-power inlet had a burnt earth terminal. That is not a small thing. The earth wire is a safety conductor and in normal operation it carries no current at all, so for it to have got hot enough to scorch means that at some point real current went through it — most likely an earlier battery charger failing live-to-chassis, years ago, on a dock with no protection to catch it.

It has taken three weekends of thirty-minute bursts, because it has been 104 degrees and that is genuinely all you can do. But as of this evening there is a new SmartPlug inlet, the internal feed is run in heavier cable with proper service loops at both ends, and every bit of it passes through a galvanic isolator before it reaches the panel — which is what stops the neighbours' boats slowly dissolving our anode through the shore earth.

The charger came up. Ten amps into the batteries. It works.

I spent an evening constructing increasingly elaborate theories about this. A failing compressor. A tired thirty-three-year-old breaker. The new, heavier cable finally letting the compressor draw the full starting surge it had never been able to draw through the undersized extension cord it used to run on.

The actual answer arrived the following morning, unbidden, in the way these things do. I had closed every seacock when the boat was laid up. Marine air conditioning is water cooled. I had asked the compressor to run with no cooling water at all, on a boat that had been baking in the sun all day, and it had done exactly what a compressor does in that situation: stalled against its own head pressure.

Opened the seacock. Bled the air out of the pump. No tripping at all.

There is a lesson in there about diagnosis, and it is not the flattering one. I had four plausible theories, each of them well-argued, and the answer was a valve I had closed myself and forgotten about.