Our last post prompted a question about refrigeration from a reader in France, so here’s a few comments on that subject.
When we were in the Med meeting fellow cruisers (the vast majority of whom were aboard sailing yachts) one of the most common discussion threads was the difficulty of keeping house battery banks charged. In virtually all these cases the cruisers with these issues had battery powered refrigeration. Modern technology has certainly reduced refrigeration’s power requirements, but there’s no doubt it’s still likely to be your biggest current draw.
Boat refrigeration is powered in one of the following ways:
1. An engine driven compressor – this is very efficient, but only operates when your engine is running. Usually the same compressor powers both a refrigerator and freezer. There can be issues with controlling temperature as in some installations items in the refrigerator section will freeze if the system is run too long.
2. DC power from battery bank - is efficient but results in heavy current draws,
3. AC power from generator and/or inverter. Very efficient but note that quite a large inverter is needed due to refrigeration’s high start up current draw.
4. A combination of above - is ideal.
I haven’t included LPG powered refrigeration as with a pilot light it’s regarded as unsafe for marine applications.
Whatever system is used stainless steel lined appliances seem to work better than plastic lined ones and those with built-in brine plates make them even more effective. A big advantage of systems 2 and 3 is they invariably allow for continuous operation on shore power using a battery charger in the case of DC or an inverter generally passing current directly through to the appliance in the case of AC.
On our last boat we used AC power from our genset or shore power and found that worked extremely well. Depending on the ambient temperature and the number of people aboard (more people = more “drain” on refrigeration) we ran the genset for about 60-90 mins morning and evening. During that time we’d also charge the batteries and often do some washing, heat the hot water tank and use the water maker.
Rapport has an Engel refrigerator (with a small freezer section) in the galley powered both by AC and 24V DC plus a combination refrigerator / freezer powered by an engine driven compressor. The latter works fine if you are cruising every day, but if anchored or staying in a marina for several days we had no freezer without running an engine for a couple of hours a day, so we decided to install an AC powered freezer on the flybridge. On boats we prefer chest to front opening freezers. The latter are more convenient to use but in our view not as effective. Where possible and mainly due to price we believe it’s best to use standard household appliances so we chose a 220V powered Haier HCF101 chest freezer with 101 litres capacity costing only $439 (about 242 Euros). We installed a double AC power point in the flybridge and the freezer is protected from weather by the flybridge's vinyl screens. When on shore power our inverter passes incoming AC current directly through to connected AC appliances. Underway with the engines charging the batteries we use the 4.1Kw inverter to provide AC power and at anchor we also use the inverter while using the genset to periodically boost the batteries. We find the refrigerator and freezer combined draw less than 5 amps. Since our cooking is electric we need to run the genset during the evening in any case and can then also heat our hot water and sometimes use our water maker.
This is the compressor driven chest freezer located in the cockpit
A few tips we've found useful:
1. Pack your refrigerator and freezer as full as possible to make them operate more efficiently. Use different sized bottles of water to use up any spare space.
2. Turn them OFF or down during the night to conserve battery power. When not being opened they lose little temperature overnight.
3. Use your thermostat - when you have charging power available turn the thermostat down (ie colder) so the appliance runs more or less continuously and when you have no power turn it up so it runs less.
4. Use your freezer to freeze bottles of water. Each day or two put some in your refrigerator to help keep its temperature down. As the water bottles thaw use them for cold drinking water and replace.
5. If you have more food and drink to keep cool than your refrigeration capacity allows use your freezer to freeze a few bottles of water and freezer pads, then store additional supplies in an Esky, changing the bottles over every couple of days. This is particularly good for bulky vegetables and salads as well as wine and soft drinks (beer needs to be colder!)
6. Cans of drinks store more easily, are easier to dispose of and seem to get colder than glass or plastic bottles.