On Refrigeration

When we were deciding on equipment for the 52, one of the things we considered was replacing the standard Sub-Zero 700TCI refrigerator/freezer with one that is more energy-efficient. Home appliances, with self-defrosting freezers and ice makers, generally are designed for applications where power is plentiful. We’d heard complaints from other Nordhavn owners that the Sub-Zero power draw was excessive. In our marine application, we’d often be off-grid on battery power, and would need to run the generator to charge the batteries. The greater the power draw, the more often we’d need to run the generator. In the Sub-Zero’s favor, other owners had raved about the quality of the unit, almost more than seems reasonable. After all, it is just a refrigerator.

Another concern we had with the Sub-Zero 700TCI was it’s unusual dimensions. We’ve tried hard to avoid having any non-standard equipment that limits our replacement choices should the unit fail. For example, we increased the galley cabinet depth by two inches to accommodate a standard 24″-depth GE Profile dishwasher instead of the 22″ Miele that is the standard choice. While the 15.3cu Sub-Zero fit made good use of the galley space, we couldn’t find another production unit that came close to matching its dimensions of H 80″ x W 27″ x D 24″. Side-by-side fridges, although also designed to be built into the cabintry, were 4-5″ deeper and 8-10″ wider. Some companies made a similar design of fridge on top and freezer drawer below, but these units were still 8-10″ wider and 4-5″ taller. Standalone fridges existed that were similar to the Sub-Zero in width, but they were 6-8″ deeper. We would have had to make major changes to the galley layout to accommodate a more standard unit.

The only other option was to have a custom unit built. This we could get with a more efficient, remote 24-volt compressor. We’d get better power efficiency with improved servicability. The refrigerator/freezer would just be a box with few points of failure, and the remote compressor would be relatively easy to service or replace. The main downside of these units would be food quality–the custom units generally are not frost-free and don’t control humidity as well as a standard fridge. In that regard, we expected the custom units to be similar to the 12-volt marine combo refrigerator/freezer we had on our previous boat. The boat appliance did not keep food nearly as well as the GE Profile side-by-side that we had in our house at the time, and we expected the Sub-Zero would be better than the GE.

In the end, we stuck with the Sub-Zero 700TCI for the galley. We did, however, change the grill design while we were at the yard. The standard install includes teak panels, with a teak grill below to hide the equipment. Several owners felt the grill restricted the airflow, increasing power consumption, and had removed or replaced theirs. And we’d been told that Sub-Zeros installed with the original stainless steel and no teak panels were more efficient. The teak should provide some extra insulation, so this didn’t make sense until we saw a stainless steel unit installed on a Nordhavn 55 in the yard: the space below was open with no grill. So we changed our design to match, with just a teak piece that extends from the bottom freezer drawer to partially cover the equipment, and no grill. In addition to improving airflow, this also makes cleaning dust buildup there much easier.

We did make one refrigeration change to install a 24-volt Dometic RPF-50 freezer in the lazarette. At the time, the separate freezer option for the 52 was a Sub-Zero UC-24C fridge/freezer combo installed in the stairwell to the staterooms. We didn’t like the idea of having the unit in the stairwell, partly because that’s conveniently accessible space to give up for something that we’d not have to access frequently. But, more importantly, a freezer failure could send smelly meat fluids down into the cabinetry and be near impossible to clean. And we wanted a full freezer, not a combo unit, so we opted for the Dometic instead.

Having had the boat for over two years now, we are very happy with the decision to keep the Sub-Zero in the galley. Those who extolled it’s virtues were correct: food keeps incredibly well. When we go on longer trips, we use the same tricks that we did with the previous boat to keep food fresh. In particular, we use Evert-Fresh or Debbie Meyer food-preserving bags. The bags allow gases to escape, and keep fruit and vegetables fresher longer. Since moisture can speed up spoilage, we put a paper towel in each bag and replace the towel when it is damp. We’ve had good luck with all kinds of produce, including green onions, lettuce, corn, lemons and artichokes. With the marine refrigerator we had back then, this doubled or tripled the shelf life, depending on the product. With the Sub-Zero, the shelf life is quadrupled or more. The picture taken below is a head of Romaine lettuce four weeks after purchase, and it still was fresh even after six weeks.

We’re also happy with our choice of the Dometic for the lazarette. We only use it for longer trips, but it allows us to stock up on bread, meats, etc and not need to stop for groceries for well over a month. The Dometic isn’t frost-free, however, and we have found that food such as ice cream doesn’t keep well long-term there compared to the Sub-Zero–more support for keeping the Sub-Zero. The marine fridge/freezer on the previous boat was not frost-free either, and we’d annually need to defrost it to remove thick ice build-up. So far we’d not had to do that with the Dometic–ice just doesn’t build up. This may be partly due to our not opening it frequently when in use, that we only power it on for a few months at a time, or it might be a higher quality unit.

While the Sub-Zero does consume more power than the other options, we’re very happy to have it. The boat is pretty power hungry, and while we’ve not measured it, we don’t feel the Sub-Zero is a major a contributor to the overall power draw. Having fresh produce last longer makes us more self-sufficient–diesel is much more readily available in certain parts of the world than is fresh produce. This also allows us to last longer between stops, even if fresh produce were readily available. We’ve designed the boat for self-sufficiency, and having to the run the generator to top off the batteries is comparatively not that big an issue.

 


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5 comments on “On Refrigeration
  1. Greg says:

    5.17.2017
    Hi!

    how secure has it been in remote foreign shores for: your selfs & your boat ! do you plan destinations ahead of time?

    • Regardless of where you are from or where you plan to cruise, there is crime and the best defense is to be aware of it, don’t go where it is truly dangerous, and lock up personal effects and don’t appear to be juicy target.

      The only place we have cruised where crime has been a concern is the Caribean. There are parts of the Caribean where there have been atttacks and even killings so, while in the area, we kept plugged in to where there were issues and were more thoughtful about where we went. This was really that limiting and didn’t play a huge part in the trip but it was part of our thought process. There were places in South Africa where it would be highly unwise to go at night and probably ill advised during the day.

      Perhaps the biggest impact on our cruising plans, far eclipsing those few issues above, is pirate activity. We would have loved to have gone through the Suez Canal and travel through the Med after our Indian Ocean crossing but, in our opinion, it’s not worth the risk. Our strategy with Piracy is avoidance. We don’t go where there is reported pirate activity.

      Overall in our trip around the world, security hasn’t felt like a huge problem and we haven’t yet had a security related issue.

  2. Practicality depends upon the boat Frank. Dirona really doesn’t have much in the way of top surface that isn’t walked on so it would be difficult to have enough panels to make a dent in consumption on this boat. For boats optimized to conserve power, solar can be a nice solution. But, for boats optimized for living, power consumption is higher and space isn’t available. Have a look at how much power your house is consuming and figure out how many solar panels will be needed at the panel efficiency levels of your latitude.

    On a boat, the panels are usually mounted on a horizontal surface not aimed at the sun which further reduces efficiency. And the panels are often shadowed by other equipment.

    See http://perspectives.mvdirona.com/2012/03/17/ILoveSolarPowerBut.aspx for more detail on the difficulty of solar when you are space constrained and operating at high power densities.

    Short answer: On Dirona, we don’t have much space where we put panels and horizontal panels in northern lattitudes don’t produce much so more panels are required. So, we’ve not gone down that path.

    –jrh

  3. Frank Ch. Eigler says:

    How practical would it have been to nail some solar panels on top of the boat to extend battery life?

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