Air conditioning aboard is usually seawater-cooled; heating comes either from the same unit running in reverse or from a fuel-fired air heater. When either fails, it is a safety matter as well as comfort: leaking seawater and exhaust gas.
Seawater-cooled air conditioning
- Seawater circuit
- Seacock, strainer, pump and condenser. A blocked strainer or tired pump is the first reason a unit keeps tripping.
- Condenser
- Corrodes in seawater; a leak means both lost refrigerant and water in the bilge.
- Condensate
- If the drain blocks, water spreads behind linings and under the sole.
- Ducting
- Uninsulated ducts sweat and grow mould; distribution goes out of balance.
Fuel-fired air heater
- The exhaust must exit the hull sealed, with heat-resistant lagging along its run.
- Combustion air and exhaust must be kept apart from sleeping areas.
- A working carbon monoxide detector should be in the sleeping areas.
- Ask for service records; a heater left unused for long soots up its combustion chamber.
Renew or repair?
A new condenser and pump often extend a unit's life by years. If it runs on an old refrigerant and parts are unobtainable, renewal is considered; capacity is then recalculated cabin by cabin and the load the generator and shore supply can carry is checked.
Power demand
Air conditioning is among the heaviest power users aboard. On shore power in a marina that is no problem; at anchor it usually needs the generator. When choosing or renewing a system, check that generator and shore connection can carry the load. On compressors with a high starting current, a soft starter can reduce the momentary load on the generator.
The raw-water circuit
On seawater-cooled units, efficiency depends heavily on the raw-water circuit. A blocked strainer, a line narrowed by growth or a weak pump reduces cooling and causes frequent faults. Cleaning the strainer regularly in season and flushing the circuit yearly by the maker's method keep efficiency up. Seeing steady water from the discharge is the simplest check.
Condensate
When the unit runs, moisture in the air condenses and collects in a tray. If the tray drain blocks, water overflows, spreads into the interior and behind linings, and in time causes rot and mould. Checking the drain line regularly prevents this hidden damage.
Heating safety
A fuel-fired heater's exhaust must be completely separate from the boat's interior, with its outlet where gas cannot come back in. A CO detector in the sleeping areas is a basic precaution on boats with heaters. The heater is serviced yearly to the maker's instructions.
On survey
Each unit is run, outlet air temperature measured, raw-water discharge and pump checked; on a fuel heater, the exhaust run and outlet are inspected. Findings go into the report with photos and, where relevant, thermal images.
Renew or service?
An old unit can usually be swapped for a new one, but before the swap the ducting, raw-water circuit and electrical feed are checked for suitability. If the refrigerant type has changed, whether the old lines can take the new gas is asked. Sometimes renewing just the pump and strainer improves performance more than expected.
Running the system briefly at the start of the season and checking the discharge and outlet temperature shows a mid-summer fault early, while there is still time to fix it calmly.