Imagine that you are just walking into the grocery store when your significant other calls and asks that you also pick up an avocado, but is insistent that it must have a small stone and maximum flesh. Normally the biggest challenge with avocados is finding the almost-ripe ones and then getting them home before they whisk through the ripe stage in transit and swiftly progress to the over-ripe stage just as you unpack them. But this stone-size issue poses a different challenge.

Now you're in the produce section and you find a choice of two offerings of avocado; regular and organic. Knowing the variety or origin is no help, (no Siri on your flip-phone and your Mum told you never to talk to strangers) and both are of the same size, color, and weight, with the organic version being higher priced. So, how would one determine which pile of avocados would have the highest probability of having the smallest stone?

If it were me I would take one from each pile, and then once back home secretly use a pin to pierce the skin to see which had the smallest stone. If the stone in that one is declared by your S.O. to be too large and you're accused of being an incompetent shopper, present the other and wager that the stone in that one would be even larger. That should be good for $10! (Warning! Trying the pin trick at the store will probably result in the manager demanding you purchase the entire display of avocados, as there's no way of knowing which ones you'd pricked with your germ-infested pin and then put back.) And because you had the savvy to buy two avocados, you now have more than enough flesh than was requested and the rest can go on the salad.

Choosing a marine air conditioning unit poses a similar conundrum.

You and your boat are ready to join the solar revolution. Even a small solar panel can trickle charge your battery to keep it topped up. It is known that a battery kept fully charged has a longer life than a battery left semi-charged for an extended period.

You can’t seem to be able to get away from it these days; politicians throwing out what may or may not be real facts in response to questions. This typically involves bombarding the interviewer with staccato statements that may or may not be correct and that require research before being able to call into question.

What happened to the good old rhetorical question? You know, interviewer asks a question and gets a question back in return. That’s always been a standard stalling technique, but now seems relegated for use when factual fire isn’t working.

I had a sorta close/mildly similar instance last week, but my experience involved phone company employees, not politicians.

I was in the UK when I picked up the bug.

I’ve just read a report suggesting that internet sales are really hurting the traditional chain stores. The number and frequency of retail stores that are closing in shopping malls is really quite alarming as more and more customers prefer to shop online from the comfort of their home.

In England recently I had to battle for space in a narrow country lane with a home delivery van from a supermarket. Nowadays you can order online and your weekly necessities are delivered right to your door, even to a remote shepherd’s hut in the middle of the moor.

If there are any remaining butchers, bakers, or candlestick makers left in English villages, they seem somewhat doomed. It’s enough to send you down to the pub for a pie and a pint, except they, too, are also closing in droves.

It seems social media is taking the place of traditional face-to-face social interaction.

Online shopping has become so easy, even returning stuff is a breeze. If something you bought doesn’t make you look as glam as you thought it would, or doesn’t do what you thought it would do, or if you simply don’t like it, then you can return it; no fuss, no muss. The web retailers now have really slick and well organized return systems that make this aspect of the transaction painless while not making it seem like you’re being punished for being such a dufus for ordering the wrong thing in the first place.

So, what’s not to like, and how does this relate to stuff we need for our boats?

After several discussions recently with customers contemplating adding solar to their electrically powered vessels, there is still a lot of confusion about exactly how much power can be realistically expected from solar panels. I have an inkling that these customers are so honed in to watts and kilowatts from their dealings with propulsion that they assume that all watts are equal.

But solar watts are a different animal.

The watt is a measure of power and is normally derived electrically from multiplying volts times amps (W = V x A), or amps squared times resistance (W = I² x R).

So, using simple math, if we have a 5,000 watt (5 kilowatt, or 5kW) DC electric propulsion motor running on 100 volts, we would expect it to be drawing 50 amps at full load. If the same sized motor was designed to run at 50 volts then the current draw would be double that at 100 amps.

For reasons of wire sizing and cost of ancillary equipment we’d want to keep the amps as low as possible, so the higher the voltage the better (except for having highly lethal voltages in damp environments). As you can see, the numbers are all very simply calculated and it’s all cut and dried, and it had better stay very dry indeed!

Solar watts are different, and I’m referring here to the wattage rating of the panel(s).

In the wake of the recent celebrations of science and scientists, I could not let the occasion go without a mention of the late Richard Feynman. For those of you not familiar with the name, Feynman, as well as being a brilliant scientist, was also a fascinating human being and a bit of a maverick who delighted in upending normal thinking and throwing the occasional curve-ball.

In his second book “What Do You Care What Other People Think: Further Adventures of a Curious Character?”, Feynman describes how he was once intrigued at how the brain tracks time, and was curious to see how accurately he could gauge one minute by counting.

Are you, or is anyone you know, a Temperature Control Freak? You know the type; constantly fiddling with air conditioning and refrigerator controls and reporting on them to anyone within earshot. Well, I have such a friend.

TCF, as we will call him, has a digital temperature controller/thermostat and tells me that 39.2°F is the perfect temperature for his fridge. How he comes to this conclusion is beyond me, and quite honestly I don’t want to ask. Suffice to say that he’s happy with that after several months of laborious experimentation. And then there is the freezer ...

Now a fridge can only be between a narrow band of temperatures; too cold and it’s a freezer, too warm and it’s not a fridge. But a freezer can be kept at any temperature below freezing; from marginally frosty to cryogenic. It’s all down to how you intend to use it.

Foodstuffs will be preserved as long as they are frozen, but the appearance and edibility when thawed will differ with different temperatures and time. In Europe there is a star rating system for freezers as follows:

I once read in a sailing magazine something like the following: “It’s boat show time, so let’s take a look at some of the products they are trying to foist on us poor unsuspecting boaters”. As a marine vendor I was incensed to read that, and vowed never to advertise in that publication. I never did, and eventually it folded. Go figure ....

There has long been a feeling that stuff sold for boats was generally overpriced simply because it has a “marine” tag. This seemed to be more prevalent in the 80’s and 90’s, so maybe back then there were indeed a plethora of cheap and tacky items labeled as marine that would have been better suited for the kiddies backyard camping or a day at the beach.

Or maybe it’s because nowadays the internet is playing devil’s advocate and unscrupulous manufacturers just can’t get away with things like they once could. Today’s efficient means of communication ensure that when even minor issues are reported, they require a good customer service oriented response.

Now that replacement parts can be easily sent to remote locations seemingly beyond the edge of beyond, a worthwhile warranty is also increasingly important. Imagine a business getting a call from a customer on a satellite phone in mid-ocean, fretting that his fridge is running longer than it used to. “We’ve got ourselves another fridge-fretting sat-phoner” is the common cry. Oh yeah, it happens.

At Coastal we see and hear many tales of woe

There seems to be many misconceptions regarding solar panels, particularly concerning marine installations on vessels. I’m thinking that maybe it’s because we all see solar panels on houses and assume that what applies to roof-top installations also applies to boats. Wrong!

Here’s some solar facts. Typical solar panels with silicon cells will:

• Produce electrical power whenever they are exposed to light, and this is proportional. Small amount of light - small power output.
• Produce full voltage even in very low light, often even indoors, but only if they are disconnected and not being asked to produce any power. Potential voltage output depends mainly on the number of cells. Each cell typically produces around 0.6 to 0.7 volts.
• Produce full current output only if there is a big enough load, the sunlight is good enough, and shading is non-existent. Potential current output depends on the size and type of cells.

In general; the quantity of cells determines voltage; the quality of cells determines amperage.

Now, what we are after in a boat solar application is to grab whatever power we can whenever there is available sunlight, and that means from dawn right through to dusk, not just at noontime. I often hear customers say that there is absolutely no shading at the back of their sailboat, but then when it is suggested that maybe in early to mid morning or mid to late afternoon, the presence of a humongous mast and associated rigging might shade a stern-mounted panel, they will humbly agree. From that sort of response one could deduce that many boaters are under the assumption that solar panels will really only work for a couple of hours each side of noon. Not so Horatio.

Once upon a time, a long time ago, there was only one brand of refrigerator that would work on 12v DC boat power. There must have been many thousands of them out there back in the day, predominately on powerboats, and a lot still exist to this day.

These refrigerators have one or two compressors typically mounted on the rear of the cabinet, and these compressors require 20v-30v AC for their operation. When 115v AC mains power is available, either from shore power or a generator, the power for the compressor(s) is supplied by using a simple transformer to lower the 115v AC down to the lower AC voltage required by the compressor(s).

But when the boat unplugs from the dock or the generator quits, the compressor is then powered from a built-in inverter that produces the required low voltage AC from the 12v DC supply. Due to losses inherent in inverters and the desire not to involve electronics unless absolutely necessary, these fridges would always be supplied with separate wiring for connection to both 115v AC and 12v DC, with the system automatically switching to 115v AC if it is available.

Fast forward to modern times, and we are now blessed to have marine fridges utilizing the super-efficient Secop (formally Danfoss) compressors that are powered by 12v or 24v DC. Under normal circumstances, when the vessel is at the dock and plugged in to shore power, the battery charger will be on and supplying the DC power for the fridge. The batteries are not involved in this process, as the DC from the charger does not go into and out of the batteries, but is supplied directly to the fridge from the charger.

In this situation there will always be 12v or 24v DC available, but if circumstances dictate that the charger will not be left on, or that at times there will be no 12v or 24v DC available,

There has long been a debate about air cooling versus water cooling for marine refrigeration systems. Water cooling has traditionally been generally accepted to be between 25% and 35% more efficient in warm/hot ambient conditions, but some of that efficiency gain has to be offset by the energy required to run a water pump.

The Frigoboat Keel Cooled system is water cooled and does a fantastic job without the need for a fan or a pump. That will be mentioned later, but the following compares air cooled systems to traditional water cooled systems using sea water with a pump.

Many boaters these days seem to be opting for air cooled refrigeration systems even though they’re heading south into hot climates, and despite the notion that air cooled is inherently less efficient than water cooled. Why is that?

When you want solar on your boat... You Want Solar On Your Boat! Now, where you put it depends on what real estate you have available that is relatively free of potential shading and yet still gives you room to move around.

Those of you with a sail boat need to be aware of the shadows cast by your mast, boom, and rigging. If you have a power boat, be aware of the shadows cast by your radar, arch, antennas, water toys, helicopter, etc.

So, let’s look at what others have done.

1. Dingy davits are popular locations for either glass panels or lighter weight semi-flexible panels. The davits themselves should be specifically designed and fabricated to carry the extra weight. Notice the clever person who put lightweight panels in-line with the davits to allow easy access to the dingy and swim ladder.

     Walking through the gaudy and gay Miami Bayside entertainment area during the Miami Strictly Sail show last week, whilst dodging obstacles such as parrot-wielding hawkers and perfume swatch pushers, I spotted a sign promoting a bar/restaurant called “Mangoes”.
     This, reinforced recently by the sight of them on a supermarket shelf, reminded me that if I ever go back to St. Lucia, I have been promised free mangoes there for life.

How that all came about makes for quite a tale.

     When this mailing goes out we will be exhibiting at the Miami Strictly Sail, which is part of the mega Miami International Boat Show. Now don’t go thinking that we do this just to buff up on the tan during a bleak Maryland winter, oh no. No, this is purgatory. This is some form of evil punishment hoisted on us, probably for being so slack and slovenly during the slow winter sales season.
     Our German suppliers refer to boat shows as “fairs”, which to me conjures up images of riding prettily painted uppy-downy horses on a glittering merry-go-round while eating cotton candy, but sadly that is mere fantasy.
     OK, so it is nice to get away from the office, pull on a pair of shorts and give the old pins an airing, but “doing” these shows is expensive, takes a lot of organizing and planning, and they are physically and mentally exhausting.

So why on earth do we bother?

A while ago I debunked some common misconceptions about solar panels in another blog here, but it seems I missed one that has come to light several times recently, i.e. the myth that to have proper, serious, useable solar power on a boat one must use residential panels, as marine solar panels are just itsy-bitsy wimpy battery top-up trickle-chargers.

Nothing could be further from the truth!

Inner Secrets of the Danfoss/Secop BD35/50 Motor Controller (aka Module)

Well I can't actually give away any real secrets, because I don't think anyone really knows what goes on under that mysterious black plastic shell except for the manufacturer, but I do know a fair bit about what can and does go wrong with them.

But first let's take a step back and recap on what the little black box actually does.

The current generation of small, mobile refrigeration compressors from Secop (formally Danfoss) utilize a very simple motor with just three equal windings and no brushes or slip-rings. These three windings terminate in three pins that protrude from the compressor shell and connect to a push-on plug connected to the controller.

It's the controller's job to take the 12v or 24v DC input and spit it out in sequence to each of the windings in turn, causing sufficient torque to turn the rotor and so push the piston in and out compressing the refrigerant gas. So the motor actually gets a modified DC signal, a form of AC in fact, and by varying the rate of delivery of the signal to each winding and effectively altering the frequency, we can make the motor turn at different speeds.

That's it. All pretty simple in theory. As a means of altering compressor speed, the controller uses the switched input from the thermostat, and by adding resistance to this circuit it alters the speed at which the compressor will run.

So what could possibly go wrong?

You’ll never see anyone waving to you out of a super-yacht window. That’s not because the occupants are stuck-up unsociables, but simply due to the fact that the windows don’t open.

No wind scoops or Sears window units for these amazing machines, but rather a highly complex and sophisticated HVAC (Heating, Ventilating, and Air-Conditioning) system.

So let’s say you strike oil in your garden and are thinking of ordering a superyacht (defined as being a vessel over 80’). You want only the best and so you want Climma to provide the air conditioning, but how and where does it all start?

Want to know the quickest way to get everyone warmed up at a Christmas party? Take your clothes off!

No, seriously, instead of trapping all that body heat under clothing, why not spread the joy and warmth of the season to those around you? And you won't get cold, I promise you.

You won't really "get cold", because technically "cold" does not exist, just different degrees of heat, all the way down to absolute zero, -273°C. You may well feel cold, but what you'll really be doing by removing your clothing

Now that we have the option to install true non-sulfating Partial State of Charge (PSOC) AGM batteries like the Firefly and the Blue Plus range from Meridian/Northstar, we are faced with a new dilemma. These batteries could be at risk of failure due to voltage imbalances when connected as multiple units in a series configuration.

Read the specs of any lithium ion battery and you will see that the individual series-connected cells employ some sort of voltage balancing mechanism. Without this balancing act, some cells would end up working at different voltages and be charged at different rates, and if this situation gets too far out of whack with lithium ion batteries, well .... you know he rest.

Cells in AGM batteries work in a different way to lithium ion cells. Small imbalances between the individual 2v lead-acid cells (six of them in a 12 v battery) do not create any real inherent danger, but stringing together numbers of unbalanced 12v batteries in a series connection to raise the voltage does present the real possibility of premature battery death. The same potential exists also with 6 volt batteries connected in series, but the imbalances should in theory be much smaller, so for simplicity we'll consider only 12 volt batteries here.

I had the good fortune recently to be able to observe some younger colleagues who are also employed in the whacky world of marine refrigeration and air conditioning. On reflection, it could be said that these and other members of the millennial generation may have become so immersed in screens and keyboards that they've glossed over the important step of grasping a thorough understanding of the actual machines. Maybe they didn't get the memo. Maybe they don't feel they need to, as it's all there on the screen. Or is it?

Refrigeration and air conditioning machines are incredibly dynamic devices where the operating parameters and conditions are constantly changing. Much of this type of equipment now features digital displays and controls that give the operator a comprehensive view of how the machine is performing at that instant in time.

But does the modern-day operator have a good enough basic understanding of the subject to be able predict events and performance rather than simply being able to read numbers on a screen? I am mighty impressed at the way some younger fingers can flit at speed through menus, sub-menus, etc., especially as most touch-screens don't seem to be sympathetic to my hardened and calloused fingertips.

But what are these young eyes seeing?