Family enjoying ice cream onboard boat

The debate rages on. Which is best: air cooling or water cooling for marine refrigeration systems?

A refrigeration system doesn’t “make cold”, it removes heat from one area and transfers it to another. There is actually no such thing as “cold”, just heat at different temperatures: cold heat, warm heat, hot heat, etc.

In our small marine refrigeration systems, this heat transfer is accomplished using a compressor and a refrigerant to collect heat from inside an insulated space and disperse it somewhere else via the magic of latent heat. The evaporator is the “heat collector” inside the insulated box while the condenser is the component that disperses that heat elsewhere. While the evaporator is specific for the size and configuration for the application, there are choices to be made regarding condensers and the medium they disperse the heat into.

But first, let's watch a demonstration of how a Frigoboat Keel Cooler System works in extreme tropical water conditions. Then we will discuss how this can be.

vacuum-pumpUnless other actions are also taken, using a vacuum pump to evacuate a R134a refrigeration system will almost certainly not result in a permanent resolution to particle or moisture blockages. This is true no matter how deep the vacuum or for how long the vacuum pump is run.

Moisture issues - Back in the day, when refrigeration systems used good old ozone-gulping refrigerant R12 and mineral oil in the compressor, moisture could be removed from the entire system, including the oil, simply by hooking up a vacuum pump and taking the system down into a pretty deep vacuum. Any moisture would evaporate out of the oil at this low pressure, and find its way out of the system as a vapor via the vacuum pump. Skip forward to the present day, and we now use more environmentally friendly refrigerants such as R134a which requires a synthetic oil for the compressor.

The Danfoss/Secop BD 35 and BD 50 compressors are supplied filled with a polyolester (POE) oil, which is extremely hygroscopic i.e. it will grab hold of any passing spec of moisture and won't let it go easily. In fact, the oil forms a molecular bond with the moisture, and no matter how deep a vacuum is applied, or for how long, those pesky moisture molecules will remain trapped in the oil unless another element is brought into play, and that element is heat.

voltage meterWe handle many calls for troubleshooting help, and the vast majority end up being electric problems, mostly with the boat’s power supply to the Frigoboat unit. While the voltmeter on the distribution panel might show more than adequate power, it is what comes out of the end of the two wires at the Frigoboat unit that counts, and there is a lot of potential in the wiring for gremlins to creep in and spoil the party.

Power supply testing on Danfoss DC powered refrigeration systems

To properly test the power supply to a Danfoss/Secop powered 12v or 24v system, the following testing procedure must be carried out. This will establish whether the power supply feeding the system is free of bad, loose and/or high-resistance connections. Reading the voltage on the panel or at the batteries is meaningless,

Dog Walking Business
Fast running refrigeration has its benefits, and it has a downside, too.

There’s quite a variety of passers-by to be seen from my front porch of an evening, and most seem to be walking a dog or two, or three.  The majority of walkers fit in a velocity band somewhere between comfortable stroll and brisk jog, but there are also those on the fringes of the extremes, and these are the most interesting to observe.

At the hyper-speed end is Speedy Meanie, and he’s a runner on a mission. He’s lean and long-legged, and usually shirtless (in Summer anyway). He and his hound bound along in perfect synchronicity and appear out of nowhere in a flash, so you need a keen eye to catch him. He’s well known in the neighborhood for having a bit of a mean temper, and woe betide anyone that dares to get in his way. If Speedy Meanie arrives just as one happens to be putting the bins out, one can get an earful of colorful curses if he has to maneuver around them.

At the opposite end of the scale is dear old Ambling Archie. Archie is a truly loveable little dog, and as well as being small, he is very, very slow. Unlike Speedy Meanie, it is Archie that controls the pace, which is excruciatingly slow and difficult to watch, while his companion digs around in his smart-phone for something interesting to help pass the time. Ambling Archie doesn’t go very far, just to the end of the block and back, but it’s all the exercise he needs, and it’s quality time for him and his master.

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