Of Interest to Captains (November/December 2017)



by Brian Brown


You probably think this article is about air conditioning…but it’s really about cooling off your drinks and keeping your perishable items from spoiling. So here’s where this begins.

This article addresses making ice and keeping your food/drinks cool…and how to do it on a budget…about $500 all in. Note, buying a DC powered fridge and ice maker will cost you a couple of thousand dollars.

First, having a generator on board always helps but most of the people I know don’t have a provision for that on their sailboats under 40’. Well, they might have that little Honda generator that’s about a foot wide by 2 feet wide that purrs …and can run for 7 hours on a little more than half a gallon of gas. But they are expensive, around $1000 for 2000 watts. So let’s look at other ways to cool off that cost around $500.

In order to make this $500 equation work, we first need to look at the total wattage required for both an ice maker and refrigerator: 400 watts for an ice maker and 320 watts for a small fridge. Oops, did I mention that’s AC and not DC voltage? Most sailboats are DC. So let’s look at the power sources to provide 720 continuous AC watts (the combination of the ice maker and the small fridge).

There’s the motor, solar and wind power to produce DC power—but remember that DC power needs to be converted to AC. Solar and wind power rarely produce enough power to run a fridge and ice maker so it’s pretty much left up to the motor or generator to do the job. And with the motor running you’ve got to have an inverter—a unit that converts DC to AC– but inverters draw a tremendous amount of power. If your engine is off, an inverter can fully drain a battery in 15-30 minutes when fully loaded (running several AC powered devices). Even if your engine is on charging your battery an inverter can drain your battery. Beware…turn OFF the inverter and charge up the battery before shutting off the engine otherwise you might not be able to start your engines again! (Its best to have a back up battery not connected to any source on the boat—spending $99 for that battery is, well, priceless.

Step one—getting an inverter. A decent inverter—will cost around $300 and output about 3,000 watts. You don’t want the devices you attach to it to come close to the 3,000 watt total capacity. Its better if you run on a 2/3’s of the converters capacity…or about 2,000 watts. If you run it on a battery only while consuming 2,000 watts without running the engine it will drain the battery in about 15 minutes…so keeping the engine on when the inverter is on is critical…remember even with the engine on the inverter can drain your battery so learn what is the correct balance.

Step two—an ice maker and a small fridge will cost about $100 each. Wow eh? Yes, they will be small but a small ice maker will make 20lbs of ice in a 24 hour period or about a tray every 10 minutes. The fridge will be similar to the one like you had in your dorm room in college; probably a little bigger. Cooling off yet? You bet. Both will fit inside a small sailboat…the ice maker will most likely be countertop styled and promote easy access for those guests that are thirsty.

Step three—don’t expect miracles. The fridge and the ice maker will do their best job when you are docked on shore power…so let that party begin! But, once you leave the dock and are motoring make sure that you have your inverter going to keep that party going as long as you can because once you anchor and shut down the motor, you’d better turn off the fridge and ice maker…and have enough back up ice made that you can enjoy your day. With only the fridge running (320 watts) on a 3000 watt inverter you might be able to get a couple of hours on the battery without starting the engine.

So, let the party begin…but at the dock first OK?