A Good Whacking

 man at sailboat helm

Why you shouldn’t run your Frigoboat Keel Cooled system out of the water

“You’ve been a very naughty boy, Tompkins, and you must take your punishment. Disobedience has consequences.” So says the headmaster in a typical schoolboy romp in the boys’ magazines of my youth. A few whacks from a cane and life goes on, although these days I suspect it might be a virtual whacking incorporating a VR headset.

Unfortunately, some misdeeds require considerably more than just a simple fix, especially some of the mistreatment we see Frigoboat systems subjected to. Sometimes it’s accidental, sometimes it’s over-enthusiasm, but sometimes people also simply ignore the manufacturers’ instructions.

The Frigoboat Keel Cooler refrigeration system is a case in point. The actual Keel Cooler component is a condenser/heat exchanger that is the external component of a thru-hull fitting and is mounted on the exterior of the boat, under water, and is designed and engineered to be in operation only when the vessel is in the water.

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RIP Holding Plates

Holding Plates Museum

And so it came to pass that the days of the holding plates in marine refrigeration systems has come to an end. Amen to that!

Holding plates piled500x479Our “collection” of these expensive, heavy, and cumbersome hunks of stainless steel is now destined for the scrap pile. This long overdue but necessary move will free up valuable warehouse space for more of the aluminum flat-plate evaporators that have all but replaced the holding plate.

But for those of you unfamiliar with these items we should look at what exactly a holding plate is/was.

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Refrigeration products offered by Coastal Climate Control

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Variable Speed Refrigeration and Air Conditioning Compressors

Green plugI recently had an air conditioning system replaced at my house. Out went the old energy hog with a noisy, fixed speed compressor, and in came a high efficiency unit with a quiet compressor and fan, both of which run at variable speeds. So, today’s question is: Why does varying the compressor speed increase efficiency, and how is that achieved?

Golden Rule: The longer and slower a compressor can run, the more efficient it will be
Danfoss BD CompressorEfficiency in refrigeration and air conditioning systems is measured as a ratio of power out to power in, and can be in several forms. The Energy Efficiency Ratio (EER) is the ratio of output cooling energy in Btu’s to input electrical energy in watts under certain fixed conditions. So a system with an EER rating of 10 will produce 10 Btu’s of cooling for every watt of power consumed under the specified conditions. The Seasonal Energy Efficiency Ratio (SEER) that is used in commercial and residential equipment is similar to the EER, but is assessed over time and under varying conditions.

When a fixed speed compressor is operating under light-load conditions, i.e. nighttime, cool weather, etc., a fixed-speed compressor will be running for short spurts and do a lot of cooling in a hurry, which is inherently very inefficient. If we were to be able to slow the compressor down during periods of light load, the system would run longer and be more efficient overall, but would still have the required capacity available for high heat-load conditions.

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Vacuum Pump Alone Won't Cure Blockages in Refrigerator Systems

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.

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Cleaning a Frigoboat Keel Cooler

Cleaning a Frigoboat Keel Cooler

Frigoboat's Keel Cooler, installed on over 40,000 vessels worldwide, offers water-cooled heat exchange for your refrigeration system without the use of a pump. This means no strainers to clean, no noise, and little maintenance.

The Keel Cooler is embedded in sintered bronze, which is primarily copper, making it naturally anti-fouling. Add to this the fact it is warm to the touch when in operation means there should be little sea growth on it.

However, in some areas the water is rich with algae and other sea life and a build-up can occur. Not a problem. Simply use a stiff, nylon brush or green scrubber pad to wipe the accumulation off the keel cooler. Pesky barnacles may require a plastic scraper, but please resist the temptation to use a metal scraper or wire brush. Both of these devices could harm the sintered bronze coating and potentially the embedded cuper nickel tubing containing the refrigerant.

There is quite a collection of Eco-friendly "Barnacle Buster" products that can be used to help dislodge crustations, but please read the instructions carefully.

If you have continued issues with excessive growth on your keel cooler, a single coat of anti-fouling paint can be applied with little to no noticeable loss of performance. Bear in mind, though, that you can then no longer use your keel cooler as a grounding plate for an SSB or other radio device.

Rest assured, your keel cooler should last the life of your Frigoboat system.

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Bending Instructions for Frigoboat's F-type evaporators

Bending Instructions for Frigoboat's F-type evaporators

(as found in Section 6 of the Frigoboat manual)

The F-type flat evaporators may be carefully bent on a minimum 1.5" radius to follow the shape of the icebox. This is best done by holding a section of suitably padded PVC pipe (with an outside diameter of 3.0" or greater) firmly down on the plate, and then carefully bending the section upwards with the palm of your hand.

The stainless steel plates need more force to bend and may require the assistance of a second person. This must be done slowly and with great care to avoid excessive kinking of the channels in the evaporator.

Never attempt to bend a plate downwards over a pipe, as damage may result.

In order to prevent the paint from cracking, the area to be bent should be warmed with a hair dryer or heat gun to approximately 200 degrees F before bending.

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R134a Recharge Guidelines

R124a cannisterThere is much talk and discussion in certain forums about how to determine the correct refrigerant charge level for a capillary tube refrigeration system, but there is only one, simple method that will result in the perfect charge in a Frigoboat system; the frost-line method. Pressures and current draw can be monitored to confirm that these are within expected limits, but there is no better way to guage the refrigerant level than with the frost-line method.

Frigoboat R134a charge guidelines

The following is intended to be a guide for a boat operator with average mechanical skills. It will describe what symptoms to look for in a correctly charged Frigoboat system so that an evaluation can be made as to whether service is required. No refrigerant gauges are necessary for this evaluation, and their use is required only for major repairs and for evacuating the system.

Never use, or allow a technician to use, anything other than pure refrigerant R134a in a Frigoboat system. Cans of refrigerant R134a with additives must never be used, nor must stand-alone additives be introduced into the system. These additives include but are not limited to: leak detecting fluid, leak stopper, dye, extra oil, conditioner, etc. Serious damage can result from the use of such products, which are designed for use only in auto air conditioning systems.

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Electrical testing on Frigoboat 12/24v systems

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,

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Changing O-rings on Frigoboat systems

Oring-448x227-cmprsdThe couplings used on Frigoboat component refrigeration systems are proprietary to Frigoboat and are designed for long and trouble-free service. Some time ago it was noticed that there was an increase in reports of leaking o-rings, and many were found to be caused by the coupling becoming excessively hot, damaging the rubber in the primary O-ring. Causes of excessive heat can be:

- badly fouled Keel Coolers;
- using a Keel Cooled system when out of the water and without temporary water cooling;
- inadequate ventilation of an air cooled unit;
- poor or restricted water flow in a pumped-water system.

The type of rubber in the O-rings was subsequently changed to better handle excessive heat, but damage may still result if any of the above situations are allowed to prevail.

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Capilliary Tube (Cap Tube) Issues

Capilliary Tube (Cap Tube) Issues

All compression refrigeration systems depend on some device to separate the high and low pressure sides of the system. In a capillary (cap) tube system, this is the capilliary tube itself, which, as the name implies, has an extremely small micro-bore at its center that is less than the diameter of a needle.

There are two main issues that can occur with cap tubes: a particle blockage at the high pressure end near the compressor (picture on the left), and a moisture, wax, or oil problem at the other next to the evaporator (picture on the right). The Guide below describes the symptoms and recommended remedies for cap tube problems.

Capillary Tube Troubleshooting Guide

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Refrigeration 101


I’ll try not to get too technical on this subject, but there are some basic principles that you need to know before we get going. Firstly, we won’t be talking about hot and cold too often. It will be all heat, just at different temperatures above absolute zero (-460 deg F).

Next, we will be working in a unit of heat measurement known as a British Thermal Unit or Btu, and this is defined as the amount of heat required to raise or lower 1 pound of water 1 degree Fahrenheit.

Also it is important to remember that heat travels in one direction only; from a warm, high temperature area to a lower temperature area, and that we don’t “make cold”, we simply remove heat from one area and transfer it to somewhere else.

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It's that darn flasher again!

flasherInner 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?

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Should you keep your ice box full to save energy?

stuffed-dreamstime m 38862411Here's a fact: Heat travels in one direction only; from warm to cold. So if a temperature difference exists between two items, the warmer item will lose heat to the cooler item; so the warmer item gets colder, the colder item gets warmer.

Simply put, when we put warm beers into a cooler of ice, we don't actually cool down the beer as much as warm up the ice! When heat leaves the beer for the ice, the beer gets colder as a result, and soon the contents are all at a wonderfully refreshing 32F temperature. And thanks to the laws of science and beerology, everything will stay that way until all the ice has melted and the beer has been consumed.

And now here's a conundrum: Should you endeavor to keep your fridge and freezer as full as possible in an effort to save power usage?

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Rules of Engagement

gauges-handheld-dreamstime m 76282015-640x427     It's happened again, and I'm getting really tired of it. Yet another call from a boat owner who called in what he thought was a trained and experienced marine refrigeration technician to fix a poorly performing system, and now it's working worse than it was before! Why? Because the technician had added refrigerant, or "put in a shot of Freon" to what previously was a perfectly charged system.

     Our office here spends way too much time on the phone and in e-mails helping customers correct mistakes made by mostly well intentioned but misinformed and inexperienced technicians. Too often it seems that adding refrigerant has been a Hail Mary move, made after diagnosis was unsuccessful, and done in an effort to show the customer that at least something had been done. And that's where all the problems start ....

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There ain't no app for that!

man-gauges-dreamstime m 33496565Recently, a customer contacted us for some troubleshooting advice. He said that his refrigeration system was not working and the compressor not running. Apparently he had a technician look at the system who reported that he checked the refrigerant level and said it was OK.

Now that may sound like encouraging words from someone the owner perceived would know a heck of a lot more about refrigeration than himself, but it demands some investigation.

Just like the laws of physics there are laws of thermodynamics, but these are almost incomprehensible to the layman, and appear to most of us as gibberish and gobbledygook. Nothing so simple as "what goes up must come down" and "for every action ..." yada yada.

You'd think that with only four laws of thermodynamics things would be easy, but even the numbering of them seems deliberately designed to confuse. The last of the four laws is the Third Law. There no half-laws, the First Law is the second, and the Second Law the third. The wayward law is designated the Zeroth Law and comes before the first law. (This feels a bit like trying to explain the rules of cricket).

Hidden in those laws somewhere is the revelation that (in very simple terms): if a substance exists in an enclosed environment in both liquid and gaseous forms, the temperature and pressure are directly related. Let's call this the Law of Fridgernomics for ease of association.

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Danfoss-Secop Compressor Fault Codes Explained

question-mark-light-string-dreamstimemedium 63743826Anyone with a refrigeration system on their boat or RV that is powered by a Danfoss (now Secop) BD35 or BD 50 compressor should be aware of the diagnostic diode function, which, with a simple flashing LED, tells you the fault reason that caused your compressor to stop.   Much of the following also applies to the BD80 compressor controller.

By connecting a simple 10mA 12v LED across the "D" terminal and a "+" terminal on the electronic controller attached to the compressor, you will have added a powerful fault-finding tool that may save you a lot of time and trouble later on.

Why the manufacturer elected not to incorporate a diode in the controller housing is anyone's guess, but Coastal Climate Control comes to the rescue here with three options:

1. A Coastal Diagnostic LED kit with an LED that you can either install permanently or keep in the spares kit.

2. A Merlin II compressor speed controller that also incorporates a diagnostic LED.

3. A Guardian digital thermostat/compressor speed controller that features a diagnostic LED

OK, so now you have some form of diagnostic LED installed, what is it going to tell you? If your fridge or freezer system unexpectedly stops working, i.e. other than the thermostat stopping the compressor, and you go take a look at the diagnostic LED, what exactly are you looking for?

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Defrosting Your Boat's Refrigerator, Again?!

ice box over frostingRemember back when you had to defrost your home refrigerator every couple of weeks? It was a fact of life. And then those frost-free refrigerators came about. No more defrosting!!

So why have we seemingly gone backwards in evolution and are having to defrost our boat's refrigerator/freezer boxes so often? Why can't our boat's fridge be frost-free too, you ask as you drape your frozen food in towels to keep it safe as you patiently wait for the ice to melt from your evaporator plates.

Natural defrosting is the only safe method, although a small amount of addition heat is OK, say from a portable inspection light in the box. Those who are impatient might consider using a hair dryer or heat gun, hot water, or, (shudder), an ice pick, but these are not recommended, as high heat and physical force are very likely to cause nasty and highly undesirable side-effects.

And who gets the finger pointed at them as the culprit for this lack of frost-free living? Why, the refrigeration manufacturer of course, although after reading the following, you may shift the blame elsewhere.

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So What Makes You Think Your Compressor is Bad?

danfoss-secop bd compressorMost marine refrigeration, and all Frigoboat systems, use the Danfoss BD 35 and BD 50 compressors which are incredibly reliable machines and very robust. It takes a lot of abuse to "kill" one (they don't simply die from natural causes), so if you suspect that your compressor is faulty, it's important to know how these compressors work, how they can be damaged, and what symptoms to look for.

The Danfoss BD 35 and BD 50 compressors are identical except that the BD 50 has a little more cubic capacity and therefore a slightly higher Btu rating. The compressor and motor are hermetically sealed inside a steel canister and supported on vibration-absorbing springs. There is no shaft seal that could leak refrigerant.

COMPRESSOR – The compressor is a single-cylinder device with a crankshaft that when rotated pushes a piston in and out of a cylinder, compressing the gas. A simple valve plate allows gas to be drawn in on the down-stroke, and the gas to be compressed and then released on the up-stroke. The compressor assembly is mounted above the motor, and the vertical crankshaft is a continuation of the motor shaft.

MOTOR - The compressor crankshaft is rotated by means of a poly-phase inductively coupled motor that has no brushes to fail or wear out. There are three sets of windings arranged around the stator, and the ends of these windings terminate on a three-pin connector that provides for the electrical connection through the compressor shell. The rotor is built around the shaft that connects directly to the compressor crankshaft.

– Also known as a "module", this is a vital part of the compressor, and the motor cannot run without it. The controller is mounted on the compressor on a special bracket, and secured with a screw. It is electrically connected to the motor via a three-wire plug that is pushed on to the three-pin connector on the compressor shell. The compressor controller basically takes the 12v or 24v DC input and energizes each of the three windings in turn, causing the motor shaft to rotate. Varying the speed at which the windings are energized varies the speed of rotation of the shaft.

So what could possibly go wrong?

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Air Cooled or Water Cooled?

Air Cooled or Water Cooled?

Which marine refrigeration system is better when cruising in warm waters: air cooled, pumped-water cooled, or Keel Cooled?

A well designed and fabricated air cooled refrigeration system, like the Frigoboat Capri 50, should be able to maintain refrigerator and freezer temperatures in the tropics if the application, installation, and operation are all within the manufacturers' guidelines.

But in tropical/Caribbean conditions, air cooling will be 25% to 35% less efficient than water cooling. As a result, the overall power consumption of an air cooled system will be considerably higher than for a pumped-water cooled system, and very much higher than for a Keel Cooled system.

Many serious cruisers these days install hybrid Air-plus-Keel Cooled systems, where the air cooling is only used when the boat is hauled for any reason. For a new installation, this could be a Frigoboat Capri 50 installed together with a Keel Cooler, with a switch installed in the fan circuit of the Capri 50. Existing Frigoboat Keel Cooled systems can be easily converted to an Air-plus-Keel Cooled system by installing an Air Add-On condenser. This is accomplished with the use of just basic tools, and without any adjustment to the refrigerant charge.

If your boat is aluminum, then due to corrosion considerations that prohibit the installation of a Keel Cooler, you would be best served by installing a pump-water cooled system like the Frigoboat W50. That, together with the Air Add-On air-only condenser for use when hauled out, will provide the same efficiency as a Keel Cooled system, although the added current draw from the water pump will negate some of the power savings normally experienced over an air cooled system.

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