Boat electrical systems in winter

Most Southern California boaters, with the exception of a few alpine lake stored boats, don’t have to worry about snow accumulation or the water freezing around the boat. We have our own set of challenges brought upon by lower temperatures, rain and infrequent visits. We addressed shore power cords in our last article, here we address other issues.
As the temperature drops, heaters come out of the lockers. We find portable electric heaters on virtually every boat we inspect. Some heaters are better suited for use aboard a vessel. Some heaters will cut their power if they tip over, some have a wide base and are less likely to tip over, but few are designed to be left unattended aboard a boat. Above is a melted circuit breaker for a built in cabin heater.
Bring aboard only the most suitable type of heater, remember the boat may be used by somebody less familiar with boats than you are. Gas heaters, wood stoves and other improvised heating devices have also been known to cause problems.
The use of heaters and decorative lights increases the amperage in the AC electrical system and this increase can cause problems to develop or become apparent.
During a recent pre-purchase survey of a 50 meter power vessel, one of the crew was surprised to learn that several of the air conditioners also functioned as heaters. The older vessel had a combination of heat pump style units and household type units which only functioned in the cool mode. They were surprised to learn that the heat pump units functioned in both the heat and cool modes. This type of heater is much safer than a portable heater.
Boat fact: reverse cycle / heat pump type air conditioning units’ function is most effectively tested in the heat mode in Southern California. Heat is distinct versus blown air which can feel cool.
Winter is our rainy season, in addition to checking deck drains, hatch drains and the associated hoses and valves, this is a good time to check bilge pumps. If you don’t know how to check the automatic function of your bilge pump, learn. You-tube has everything. Know that your automatic bilge pump will only work as long as its battery is charged.
De-humidifiers are usually much safer than space heaters. Many boat air conditioners have a de-humidifier function as well. While de-humidifiers can prevent mould and mildew, we suggest inspecting the boat after the first rain for any leaks. Your boat will eventually leak, the quicker the leak is found and fixed the better chance you have to reduce resulting damage. Leaks onto electrical components can lead to problems. A common finding is water accumulated in dome lights. It is not uncommon to find water leaking on to or near electrical distribution panels, as they are often outboard near the hull to deck joint and below deck hardware.
Finally, if you are going to keep frozen food aboard, especially seafood or bait, be aware of potential problems from a loss of shore power. Standard galley refrigerators can leak and significant damage has occurred when frozen fish thaw. Consider a deep freezer for your fish or bait, their design will capture this disgusting soup and limit the damage.