Engine-Driven Refrigeration?

By Carolyn Shearlock © 2012 • all rights reserved

The Pros and Cons

Periodically, I get an email from someone asking me whether I like engine-driven refrigeration, or how it compares to 12 volt, or something similar.  So here goes . . .

Okay, the “advantage” of engine-driven refrigeration is that it doesn’t take power from your house batteries.  It uses a pulley mounted on your engine to run the compressor.  But think about whether this is really an advantage.

If you use a 12-volt system, you can supply the power from any charging source you have — shore power, solar, wind, water, generator or yes, the engine and alternator.  Even if one source goes down, you can still have refrigeration as long as you’ve got an alternate source to charge the batteries.

Even if you’re charging the batteries for a 12-volt system by running the engine, it’s unlikely that you’ll have to run it as long as you would with an engine driven system (this depends somewhat on your alternator, but a new high-output alternator is cheap compared to the cost of running the engine longer).

Now for the disadvantages to an engine-driven system.  I’m assuming a pure engine-driven system, not one that lets you switch to 12 volt or shore power (those are relatively rare):

  • You have to run the engine every day — generally twice a day, about 12 hours apart — if you have food in the refrigerator.
  • If the engine goes down, or you’re short on fuel, too bad.  No refrigeration.
  • If you’re at a marina and have shore power, too bad — you’re still going to have to run your engine two hours a day.
  • If you’re on the hard, you won’t have refrigeration since you won’t be able to run your engine.
  • Leaving the boat — even for just 24 hours — means that you have to find someone to come aboard and run the engine (and flip the refrig on while they do so) or you have to clean out the refrig before you leave.
  • All those extra hours on the diesel — without much of a load — are hard on it.  You’ll need a rebuild just that much sooner.
  • And you’ll be changing the oil about every 3 weeks, even if you don’t use the engine for propulsion.  Think of the time, cost (oil and filters) and hassle.

Additionally, it’s rare to have an engine driven system that has a freezer compartment.  I’m not saying it can’t be done, just that it’s not the norm whereas most 12 volt systems do incorporate at least a small freezer.

Okay, so by now you’ve gotten the idea that I don’t really like engine-driven systems.  Fifteen years ago they were fairly popular on boats, but it’s rare to see a new one installed now unless it’s a dual source system.

Que Tal, our boat, actually had two totally separate refrigeration systems in the same box — one 12 volt and one engine driven. At some point way in the past, an owner had installed the engine-driven system.  Just before we bought her, however, the previous owner installed an Adler-Barbour 12 volt system but left the engine driven system in place.

If you really want redundant systems, this is the way to do it — two chill plates, two compressors, everything.  Nothing in common except the insulated box.  And so, when we motored, we would flip on the engine-driven system for an hour.  For one thing, the engine-driven chill plate was on the wall of the refrigerator next to the engine, so this blocked the engine heat (yes, this was a bad design but the way the boat came to us and we decided against totally rebuilding the galley . . .) and it’s also a good idea to periodically run any mechanical device to keep it lubricated and moving.

So the engine-driven system did take a bit of load off the batteries.  But had the boat not come with it, would we have spent the money on it?  No way!  Had the boat come with only an engine-driven system, would we have installed the 12 volt system?  Yep.

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Comments

  1. We don’t liveaboard but our Catalina 42 came with an engine driven system and that thing has been a workhorse for us! I agree with your negatives although we do have a freezer and man, it works great! After Superstorm Sandy, we lost power and hubby went to the boat (which was fine) and got the fridge/freezer started. I happened to find ice the second day at the marina and brought it to the boat. It was pretty wet. loose ice but that was OK – it was ice. By the time hubby brought it home a few hours later, it was a block – frozen solid. 🙂

    But we just coastal cruise part time. We’re land based, and when we do cruise, we tend to not go to marinas because we can’t afford it. So we’re usually running anyway, not having any issues running the system. When we are at a dock it is a pain but otherwise, it works pretty well for us. I don’t see us replacing the system because it would be costly and honestly, with us just cruising a few weeks a year, it works. If we were to go new right now, we’d get a dual system, I’d guess.

  2. If you’re going with 12v here’s another thing to consider; Keel Cooling. Not sure if anyone else does it but Frigoboat have systems that can be built into most fridges retrofit or otherwise. Instead of using fins or a fan over fins to dissipate the heat from the coolant they run it through a network of pipes in a stud on the outside of your hull – beneath the waterline obviously. Essentially it uses the sea as a heat-sink. They reckon on average 30% more efficient. In UK waters I reckon Amelie Rose’s is closer to 60% – poss even more in Winter and Spring when the sea is cold. The upshot is with a domestic 12v bank of 315 aH our fridge goes on when we join the boat and off when we leave and our domestics survive just fine. Storming stuff, and essential as we’re a charter boat feeding up to 8 for trips of up to a week…

  3. Engine- or hydraulic- systems make a lot of sense in commercial boats where the engines pretty much run non-stop. They make less sense in power-cruisers and have no business on a sail boat.

  4. We purchased our Gulfstar 37 (l975) last spring and it has an engine cooled fridgeration system and we are looking to change it. We are currently living on board for the winter in Toronto and we have been buying bags of ice and using it now as an icebox which is working well until we switch it out. Thanks for the great information

  5. 12v def the way to go. Air cooled and simple has worked best for us living aboard full time in tropics. Keel ccoler is just another hole in the boat and in the tropics air temps equal water temps so nothing really gained there. Plus keel coolers don’t work when on the hard. We supplement our box with a dometic plug in cooler that serves as a freezer. Runs on 12v and consumes about 25ah/day.

    • I build my own keel cooler out of a coil of copper tubing inside my fresh water tank, witch is part of the hull and below the water line, the heat thus dissipate through the hull into the sea.In 15 years of full time cruising, I have never ran out of drinking water, never noticed a temp increase in the drinking water, eliminated the water pump needed by the fridge, and best of all it works just as well when hauled out.

      JB

  6. Our boat is a ’97 and was a Sunsail charter boat and this is what it came with when we bought it in 2002. It’s actually been fantastic for us although we don’t live aboard. We sail in northeastern waters (Long Island Sound to Buzzards Bay and Vineyard sound) and hardly ever go on a dock while we’re cruising. If we are traveling between one point and another, it’s easy to charge up the fridge (and freezer – we have a GREAT freezer on board) and when we’re in port, 30 minutes twice a day is all we need. We call this time “Clean the Boat Time” when everyone pitches in to clean the boat. The load on the engine is decent to drive the system so it’s not a burden on the diesel engine. It’s actually worked out really well for us. We could put a 12v system on it too but we really haven’t seen the need for it over the last 13 years.

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