Adding or Changing Refrigeration: Things to Think About

By Carolyn Shearlock © 2011 • all rights reserved

Photo of DaveIf you’re installing refrigeration for the first time, or doing a major upgrade on your existing system, you may be overwhelmed by the decisions you’re having to make simultaneously.  Perhaps a few thoughts here will provide a framework.

I need to begin by giving credit to my husband, Dave — that’s him at right, on our first charter, several years before we bought Que Tal.  As we cruised, and again as I outlined this article, we talked repeatedly about the topics here.  And while I may actually write the article, his input is invaluable.

Like many things in cruising, from your choice of boat to the route you take, there are no universal answers in choosing a refrigeration system.  But understanding how one decision will impact others can narrow down the range of appropriate choices for your situation.

Refrigeration isn’t one item; it’s a system

Adding or upgrading refrigeration on a boat isn’t like going out to an appliance store, buying the one you like and having it delivered.  On a boat, you need to consider:

  • Power and how you’ll supply it
  • Where you’ll install the compressor
  • The box – size, location and construction all must be considered
  • What brand?

They all have to work together to make having refrigeration pleasant, as opposed to a frustration.

(UPDATE:  Since I originally wrote this article, several readers have written me about Engel refrigerator-freezers as being a great option — see the full article on them here.)

Power

For most cruisers, the first questions with regards to refrigeration are “how much power will it use?” and “how can I provide the power?”

Your other choices will determine how much power the refrigerator uses, as will even your choice of how you power it.  If your refrigerator is next to the engine compartment, as is typical on many boats (a serious design flaw), running the engine to provide power – whether via alternator to the batteries or directly for an engine-driven system – actually will heat up the box and cause you to need even more power to cool it down.  The same is true if the refrigerator is next to a generator compartment.

Relatively few boats opt for engine-driven refrigeration any more.  With an engine-driven system, you run the engine a couple of times a day, generally for 30 to 60 minutes at a time, to cool down large chill plates that then keep the box cool until the next run time.  There are several disadvantages to this system:

  • You’re tied to a schedule for running the engine – even if you’re at the dock, anchored or sailing along with plenty of wind.
  • The temperature in the box fluctuates over the course of the day, particularly in warm climates.
  • It’s almost impossible to have a freezer with an engine-driven system.
  • If you have a problem with your engine, you’ve just lost your refrigerator as well.
  • Fuel cost and engine maintenance add up, not to mention the extra engine hours you’ll rack up.

While some large boats opt for 110-volt systems using generators and inverters, and I’ve known a couple of trawlers that used RV propane systems, by far the majority of family cruisers opt for 12-volt systems.  A 12-volt system operates off the main battery bank, and power for it can be generated any way you’d otherwise charge the batteries:  solar, wind, towing generator, alternator, shore power or generator.  Most boats use a combination, and virtually all have to increase their power generation capabilities when they install refrigeration if they haven’t had it before.

Two things to consider with a 12-volt system:

  • If you are heading from a relatively cool climate to a hot one (say, going from San Francisco to the Sea of Cortez or Maine to the Caribbean), expect to use a lot more power for your refrigeration than you’re accustomed to.  Lots of boats coming to the Sea of Cortez found themselves scurrying to add solar panels or buy a generator as the weather warmed up.
  • Make sure your battery bank is sized for the load you’ll be putting on it.  Every system is different as to how efficient it is (more on this later), but it’s likely you’ll need 100 amp-hours or more a day if you’re in a hot climate.

Compressor

It’s worth taking a bit of time to think about where you can – and where you should – place the compressor.  Yes, you have to find a spot where there is room and that may seriously limit the choices.  But don’t just opt for the first place you find.

In simple terms, most compressors work by transporting heat from the refrigerant to the air around it.   It will operate much more efficiently if there is good air flow around it – and if it is kept as cool as possible and if the air that reaches it is as cool as possible.

Therefore, putting the compressor in the engine compartment is not good.  Nor is putting it in any enclosed location with only small louvers for air circulation.  NOTE:  A few systems use a keel cooler that transfers heat to the water instead of air cooling — with these there is little choice in placement.

You also have to consider distance from refrigerator box, as the refrigerant has to make a full loop from the compressor to the evaporator in the box and back.  Bends in the tubing and also a long distance make for more resistance to circulation of the refrigerant and hence a less efficient system.  Be sure to check the specs before buying a compressor to be sure that it will work in your planned location.

And another important consideration is access for maintenance, recharging the system and other repairs.  Okay, so access is never good on a boat.  But at least don’t put it where you have to stand on your head or dismount the compressor to check a trouble light or recharge the system.

The Box

Contrary to home refrigerators, the “box” for most boat refrigerators is custom made.  Consequently, if you’re building a new box, you’ve got virtually unlimited options.

Top-loading or front-loading? If you’re used to a “shore” refrigerator, front loading just seems so much more natural.  And yes, it’s usually easier to see what’s there.  But front loaders have a nasty tendency to have food fall out if the boat moves while the door is open.  And you need to install clear plastic strips to keep as much cold air in the refrigerator as possible when the door is open.  And the opening needs to be either fore or aft facing in a sailboat – otherwise everything will fall out on one tack or the other.

After taking a bit of time to get used to it, I actually preferred my top loader.  With a bunch of bins to keep things organized, I could find things quickly.  And they stayed in place, no matter what tack we were on or how rough the seas.  I was even able to open the refrigerator and make sandwiches while we were riding out a hurricane at anchor and rolling gunwale to gunwale.

Size.  To some extent, a smaller refrigerator is more efficient as there is less space to cool.  And yes, having a refrigerator full of cold items as opposed to air is more efficient.  But you also need some air space in the refrigerator for that “cool” to circulate.  And if things are so tightly packed that you have to remove half of what’s in the refrigerator to get the item you need out, that’s not efficient, either.

A very deep refrigerator can pose problems.  One of the top gripes for many women is “standing on my head to get things out of the frig bottom.”  (From Mary, on Facebook.)

And let’s face it, you want a refrigerator that’s large enough to hold what you want it to.  And that’s a personal “feeling” — you may want enough meat, drinks and veggies for a month at a time, or just food for a weekend.  Read my related article on Reducing What You Store in the Refrigerator, though, before making a decision on how much space you need.

Location. If you’re just re-doing the refrigerator, you’re probably more or less locked in to a location.  But if you’re re-doing the galley, the top priority should be to keep the refrigerator away from the engine compartment (generator compartment if that’s an issue, too).  Second priority would be to keep the refrigerator away from the hull and the sun heating it up.  The more it’s away from anywhere that sun will beat down on it (such as next to the companionway), the better.

Insulation. In general, the thicker and higher the R-value, the better.  Materials are constantly evolving, so I won’t make specific recommendations.  Of course, if you have a limited space, the thickness of insulation is a tradeoff with space inside the refrigerator.

General design. A lid that latches down (instead of just being held by gravity or a magnetic strip) with a thick gasket is best – far less cold air will seep out.  The lid won’t fly across the boat in a knockdown, either!

An outside surface (surround) that reflects heat will also do wonders to help your refrigerator run more efficiently.  Que Tal had a teak surround that frequently got warm to the touch in summer – you know that’s not good.

If you decide to put a drain in the bottom for when you defrost, it needs to have a trap in it – and the trap needs to be within the insulated area.  An alternative is to be able to securely close the drain.  Otherwise, hot air from the bilge (well, maybe not hot, but hotter than what’s in the refrigerator) will rise into the refrigerator and you’ll constantly be having to cool it.

Freezer. There are all sorts of design possibilities for having either a separate freezer or a freezer compartment within the refrigerator.  The size of the freezer determines how much meat you can carry, as well as how many meals you can prepare ahead for a passage.  But it takes a lot of energy to freeze foods in the first place, although not a lot to keep a full freezer frozen.

My freezer was about ½ cubic foot, and I found it adequate (I boned all meat before freezing so as not to waste space on non-edible items), but I would have loved a larger one.  If you want to have ice, remember to allow room for trays (be sure to get the vertical ones) in addition to food.  Note that very few boat freezers are cold enough to keep ice cream.

The Brand

The longer we cruised, the more adamant we became about buying brands – and models within brands – that lots of other cruisers were using or that were composed of generic parts.  Regardless of whether it was refrigeration or another system, we found over and over again that having something that other people – both helpful cruisers and local repairmen – knew of and could get parts for was worth not necessarily having the “latest and greatest.”

Good repair manuals that you can actually get, off the shelf parts, and universal fittings are crucial once you’re away from the original installer.  I also like companies that will respond to technical support questions by e-mail (you don’t want to deal with support issues by sat phone).  The time to think about these issues is before you plunk your money down.

Conclusion

As you work through these questions, you’ll almost certainly have to make some compromises to end up with a system that works for you.  The trick is to realize the tradeoffs as you’re making them, and not after the fact when things aren’t working the way you envisioned.  For example, a tiny box with thick insulation won’t use much power – but will it give you the food and drinks you want?

A refrigerator is an expensive piece of galley equipment – even more so if you have to add extra batteries and upgrade your power generation.  As brands and models are always changing, and we only have experience with the Adler-Barbour system that a previous owner chose (and which worked well), I don’t want to recommend specific systems.  But as you talk to sales reps, realize that there are numerous components to the refrigeration system, and choices in each affect the others . . . and your ultimate satisfaction!

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Comments

  1. Downeaster32 says:

    Most compressors have a single fan, and this is typically mounted to blow from the cabin on to the compressor and into the locker. I believe a big chunk of efficiency can be gained by adding another fan. The fans do not take much power themselves (small computer case fans). One fan is the intake which draws air over the compressor & cooling coils inside whatever locker they’re mounted. The second fan is an exhaust, which pulls the now-warmed air back out of the locker and into the cabin again. In my setup, the fans are pointed 90 degrees from each other, on each side of a corner locker. I don’t have comparison power measurements, I just notice the fridge seems to run much less and the locker stays much much cooler (and fresher smelling too).

  2. The most perfect explanation about refrigeration for small boats I have seen yet. Renato, Rio de Janeiro city, Brazil. Thanks a lot !

  3. Hi,Thanks for your explanation. Given I am doing a full refit on my yacht your explanation helped in that I have a lot more to think about in what we need to do before I go ahead and make that final decision. Thanks a lot… David “Pelikan” Singapore

  4. Nicely done and THANKS!

    I’m in the planning stages of building (I hope) a 44 footer to live aboard/cruise full time. I came across your article in doing research and greatly appreciate the explanation given. I had looked at “normal” marine refrigerator/freezers that look similar to home units but run off 12v or 24v when not connected to shore power. Your article has me leaning much more towards a custom built top loading system now, especially since I can add much more insulation in a custom system and therefor use much less power.

  5. Billy Forde says:

    There is an insulation product called Spaceloft. Search for it on ebay. I wrapped my top loading box in this and could not believe the difference. Its a bit expensive but amazing insulation. It more than halved the time the compressor runs. My box is now more cold and requires less than half the power to keep it that way. The point about the 2 fans is a very good one. I’m going to try that. It makes perfect sense to me to expel the warm air the fan has extracted from the heat exchanger. Also cold air sinks, when you open a top loader very little cold air escapes as colder air naturally falls back into the sealed compartment. When you open a front opening fridge almost all the cold air flows out the bottom like water and warm air rushes in to the top of the fridge so forget about a front opener. Sail on and remember you can never know too much!!

  6. P. Childs says:

    The simplest system with the least power draw is an Engel. No more antiquated 1940 technology components and systems that won’t freeze ice cream. The ONLY system on our boat that is dependable, modestly priced and outperforms day in and day out is our Engel. Small amperage draw, and can be either cooler or freezer, instantly, on your command of the thermostat. it will automatically revert to 110 or 12v when changing from shore to ship power. We love the portable marine unit, but would like to take it a step further and throw the cold plate amp hog nightmare overboard and replace with a drop in Engel or another
    Engel portable. We could have three more Engels for the amount of wasted money poured into maintaining the antiquity of cold plates, lines, and pumps.

    • Could not agree more with regarding junking the hold plates. Mexicolder has been advocating this for years. Portable systems are good put truly lack insulation which is the cornerstone to success and thus the amp draw in super hot climes like the Sea of Cortez….day after day 100F PLUS. Mexicolder has a long proven track record in this respect. We use a double fan cooled condenser, they only way in serious heat as a static coil is not enough.

    • captain ron says:

      Yes i keep 2 of then . one 80 lt freezer witch i run the boat motor until it freezes to minus 10 and have ready made frozen meals already made up and sealed . then i only open it once every few days and take out what i need and put into a 2 nd fride at 3 deg and use at will . the freezer uses very little power when all is frozen . u carnt keep opening it all day long to get out food and drink or it won,t stay frozen .Every months or so i refill it with prepared meals and freeze it down solid again .

  7. Frank Collins says:

    I also found it helpful to purchase a small RV refrigerator fan. The fan circulates the cold air and runs a week or so on 2 “D” batteries. On EBAY the run about $20.. I put the small fan box as close to the freezer as possible

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