Refrigerator Performance

[Richard Kollmann]

Understanding your boat’s refrigerator.

Comparing a boat’s ice box conversion unit’s performance to a home refrigerator of even older boat refrigeration systems is a mistake. A home refrigerator is designed around the cabinet size with each component selected to collect and dispose of a given amount of heat energy. Home refrigerators are also assembled, serviced and tested in a controlled environment your boat’s ice box conversion unit is not treated with the same reliability control, this is why performance varies from one boat to another.

Small 12/24 volt ice box conversion units in the past were advertised so the consumer would believed one unit could be efficient in various size boxes. In the last five years when buying a 12/24 volt conversion refrigeration unit there are over one hundred options to choose from, compressor size and speed selection, evaporator size and type, to various heat removal mediums. A small conversion refrigeration unit will be efficient and perform properly only when the right unit is selected, installed correctly and the insulation is sufficient to deliver the desired box temperature in a planned geographic cruising area. The causes of poor refrigeration performance can usually be corrected by first identifying the deficiency and correcting it. If a refrigeration system satisfies the desired temperature in the box its performance is good but if the daily power consumption is higher than expected, then conditions that effect short run times or long run time high pressures, need to be investigated.

The most common causes of poor performance on small 12/24 volt refrigerator are:
• Poor airflow through condenser.
• Condenser fan is not shrouded.
• Heated air that passes through condenser is allowed to pass through it again. Air cooled condensing units are designed to be efficient when ambient air temperature is between 70 to 90 degrees F.
• On units cooled by water, poor water to refrigerant heat transfer will lower overall performance.
• Compressor cycles off and on too often.
• Too much refrigerant, this is even possible on a new unit.
• Small amount of refrigerant was lost on installation of line connectors or the system has a small leak.
• Thermostat incorrectly installed.
• Compressor speed too fast or too slow.
• Air or incorrect gas mixture in refrigerant.
• Very old box insulation or when insulation is wet.

Common misunderstandings about small 12/24 volt boat ice box conversion refrigeration units:
• That most refrigeration mechanics know how to correctly service them, they don’t.
• The shorter the compressor run time the more efficient the system is, not true, on variable speed models they will run longer and are more energy efficient when running at a slower speed.
• Poor refrigeration performance is generally related to lack of insulation, no but high energy consumption might be linked to lack of insulation.
• A holding plate with less surface area than the recommended size evaporator is not as efficient as the thin plate evaporator and may also result in poor performance and high daily power consumption.
• Water cooling a small 12/24 volt unit will provide better performance than air cooling, only true in rare cases and never more reliable than air cooling.

[KenKrawford]

Richard,

Thanks for your input on the refrigeration issue.
For those reading this, Richard has a web site devoted to marine refrigeration - http://www.kollmann-marine.com/. He has also written a book titled "Do-It-Yourself Boat Refrigeration".

Disclaimer - no affiliation, just very interested in the C350 refrigeration problems.

[Triumph]

As the Cat 350 Owners rep to the factory, I have approached Gerry Douglas at Catalina, and requested his help in determining the best fixes to make our units more efficient.

Our first step appears to be a better evaluation of the system. I will perfom this on my unit, are there others of you that could also do this for us? I have the evaluation fomat, you do not need to be an expert.

Bill

[Tim April IV]

Bill - what happened to the survey data that was collected earlier this year? I'd be interested in see some of the results - how many owners participated, etc.

[R.B.]

Bill,

I would be willing to give you a hand. Although I am not sure how much help I would be since I am in the North on Lake Huron. Our boat just went in for the 1st time last week. I used a thermometer to check the freezer and it was at -14 degrees celsius and the fridge was at 8 degrees celsius. Both dials were about half way. Cabin temp was around 22 degrees celsius, outside temp was 10 degrees celsius.

Note: I only go to the boat on weekends.

If you think I can help, let me know.

-Ralph

[Richard Kollmann]

Bad Advice vacuum system

I am surprised that a manufacturer’s technical rep would advise a boat owner to evacuate one of these small systems, as a fix for poor performance, unless you gave him more information than posted here. This advice is a cheap shot at troubleshooting to get off the hook and builds in real performance problems that then become the owner’s problem.

A refrigerator is vacuumed to remove air, contaminated gas and to dehydrate moisture from a system. Since these units are generally shipped pre-charged when sold they can only be contaminated by someone trying to connect a servicing gauge set to them. Moisture causes evaporator plate to remain above 33 degrees F. Contaminants in refrigerant like air or other gases will show up as high daily power consumption and lack of frost on areas of evaporator.

The first step in troubleshooting is to avoid destructive testing and eliminate all non destructive tests first.

[Triumph]

R.B. - thanks, but I'll look for someone in a hotter climate, and with an older hull. I believe that Catalina improved the insulation somewhere in the 300's. I'll find out that fact if I can for us.

Tim on April IV - Ken Krawford conducted the survey, and he has shared the recults with me. I then shared some of the information with Gerry at Catalina. The results were that most owners that responded are not satisfied with their systems performance. And that the units run more than they should.

Ken Krawford will also be testing his unit for us. I'd love just one more. Ken and I have hooked up an engine hour meter to our Adler Barbor units to help us record the run times. We also have digital thermometers.

[R.B.]

Well you must be right about the improvements on the newer Cats. We have had 30 degrees plus Celsius (>90 Farenheit) for the past 3 days. I went up to the boat this weekend, pulled the thermometer out of the fridge and it read just below freezing. All of our juice and pop was solid.

I guess I have to play with the settings a bit. I had set both to the middle, I now turned both up a little. I'll see what happens this week.

-Ralph

[william vanwagoner]

I was wondering if there was any update on this issue? Now that summer is here, the refrigeration is not enough to keep food cold, and I am spending a small fortune on ice. I understand that survey done earlier this year indicated that many were having this issue, and that something may have been done on hulls beginning in the 300s. Does anyone know the status???

[Triumph]

I recently got a reply back from Gerry Douglas at Catalina. He said that in later models, they added 1" of insulation, which made the box a little smaller. They also removed the wall betweent he fridge and freezer, eliminating the fan as well.

I have asked him if this is his recommendation, and I'm awaiting his reply. We are also trying to do some testing for our industry expert to give us feed back on. He is actually waiting on me to send him results, and when I get my battery charger back from Charles Marine, I'll finally be able to conduct his tests.

I'm working on it, but it's taking forever to get more info - sorry .

If anybody has removed the wall between the fridge and freezer, and can give me feedback, please do so.

[Dave Granata]

I for one am pretty desperate for a solution. We were out for 4 days during July 4th weekend and both boxes were between 47 and 50 degrees. Some food went bad. It works with shore power and the air conditioner running, I can get 30 in the freezer section.

Before we left we froze all of our small water bottles (about 30) and two large 1.5 gallon jugs of water to try and assist the thing. All food and drink was cold prior to placement in the fridge so the unit did not have to actually chill stuff, it just had to maintain. It didn't. We also never opened the front door on the thing and we were quick on the rare occasion when we opened the top doors. My cooler with ice appears to have better heat loss properties and we were in and out of that thing all day.

I would be fine with giving up on space inside for better performance. I'm just not sure how Catalina would be able to do it or even if they will do it for the early models. I wonder what removing the divider would do? I think it may be better to remove the front door and seal it up. Line the thing with those vacuum panels that are like R-28 per inch of thickness. Just thinking out loud.

I hope Gerry Douglass can judiciously come up with a game plan for some relief and solution to this problem.
Dave G
#226

[Armin]

Dave,

How long does it take for your unit to build up 1/4 inch of ice on the evaporator? The Alder/Barbour manual suggests that you need to make sure that the unit is air tight if you have more than 1/4 inch buildup within 3 - 4 weeks. Before using expandable foam to seal the area between the top of the refrigerator/freezer and the countertop, my unit would ice up within one week. After applying foam to that area and to the cut out between the door and the box, my refrig/freezer only needs to be defrosted once every 6 to 8 weeks. To assure better performance, I added the Adler/Barbour vent kit with fan to the unit. With these modifications my unit holds a temperature of zero to minus five degrees F in the evaporator coil, five to ten F in the bottom of the freezer and 35 to 45 degrees F in the refrigerator dependent upon the setting of the temperature sensor which controls the "spill over fan."

Hope this helps,

Armin
MakeWay hull#207

[Hans Grasman]

Armin
Thanks for the info.
Does the fridge/freezer unit run all the time? That seems to be my problem that the unit constantly draws power.
I cover the entire top of the unit with a beach towel which helps a lot to keep the cool air from escaping.
I am also going to put an insulated pad inside on top of the fridge/freezer content to keep things cooler.
Hope we will eventually find a cure.
My real problem comes when I stay on the hook for a couple of days.
Hans
Belcourt #165
PS I only use the boat in Florida from late Oct. thru middle of May

[Armin]

Hans,

I have not tried to measure the duty cycle by means of an hour meter. I would judge the duty cyle to be near 50 to 60 percent. Since you will not be back to your boat until October, I will try to install a hour meter within the next month to record the run time. I should mention that I keep the A/C on my boat at 76 degrees F when I am not out on the hook, since I pay a flat fee for shore power and since it reduces the possibility of unpleasent oders in the boat. When on the hook I try to run the engine for one to one and one half hours per day to charge the batteries.

Hans, have you contacted Catalina about the improved insulation kit for the lids. Warren will send them to you if you ask. Also take a look at the joint between the refrig/freezer box and the counter top with an inspection mirror. If the joint is not fully sealed, inject the expandable foam.

Good Luck,

Armin

[Dave Granata]

Hi Armin,
I have sealed the top ( between the counter top and walls of the fridge) with duct seal roping and insulation weatherstrip tape over that.
After several days on the hook, there was a little frost on the evaporator but my guess is that we put block ice in the fridge and freezer sections and when that starts to melt it creates the moist environment that promotes frost (maybe??? I'm reaching for any explanation here).

I also have the duct kit but have yet to install it because I'm not sure how to vent it out of the boat. If I tie into the exisiting engine compartment vents, that will the compressor be sucking in hot air?? Another though I had was to drill a hole near the cockpit shower and install the vent grill there. How did you do yours?

My problem is similar to Hans in that it's fine at dock with shore power on and the A/C running. It's a different story though out on the hook for more than 2 days.
Dave G

[Armin]

Dave,

As you know the power vent kit from Adler/Barbour includes a shroud, the 4 inch length of duct and the blower. I had the shroud mouted in front of the condenser so that the cooling air is pulled through the condenser and blown over the compressor. (Although the fan on the compressor unit can be reversed, the standard configuration draws the cooling air through the condener coils and blows over the compressor.) The duct which is attached to the shroud is channeled below the cabin sole toward the center of the boat so that the air is drawn from the relatively cool air near the bilge. To exhaused the hot air, install a"Y" into the engine vent duct on the starboard side and lead a duct toward the pressure side of the fan.

Hope this helps,

Armin

[Richard Kollmann]

Dave, I read your post on refrigerator problems the weekend of the forth. After reading my mail and this forum it seems that one common solution is not going to solve the refrigeration problems on the Catalina 350 series boats. I have no information about the box sizes, compressor model and most important the type and size of the evaporator, but from what I have seen there is nothing that would say insulation is the problem. One person indicates too many amps-hrs per day another has moisture in refrigerant and you indicate the evaporator does not contain frost and boxes does not get cold enough.

Frost

When a boat refrigeration unit is operating properly frost will form on the evaporator and this has nothing to do with insulation. If a well balanced icebox conversion refrigeration unit is placed in a large room with no air movement and an ambient air temp of 80 degrees or cooler, the evaporator will develop frost over its entire surface. The exception to the above would be in the desert and where there are no moist items in the area.

Spillover Divider

The objective of a wall separating in a refrigerator is to create two separate temperature zones cooler/refrigerator or refrigerator/freezer. The degree of insulation in the divider will determine the boxes temperature difference (delta T). A one half inch divider might provide a difference of ten degrees and a few more degrees if there were no holes in it.

Ability to Cool

If a compressor runs continuously with an efficient condensing unit and evaporator, and also has frost present on 100% of evaporator the problem is either the box is too large, the insulation is in adequate, or new type compressor speed is too slow.

Short Cycling

When compressor cycles to often if indicates the compressor is overpowering the evaporators ability to transfer the energy produced by compressor, or there is a problem with thermostat temperature sensing. Repeated compressor cycling will result in excessive daily amp-hrs.

Thermostat

The thermostat on these small capillary tube systems control evaporator temperature and not box temperature. Where the thermostat dial is positioned on one boat’s refrigerator has no relation to the dial position on another boat.

Insulation

How much insulation is enough depends on boat’s cruising area and the refrigeration units Btu capacity. In the tropics it is desirable to have insulation rated at R30. At Latitudes north of 30 with seawater temperatures of less than 76 degrees insulation with an R 15 rating is generally expectable. Most production boats are delivered with two to three inches of urethane insulation on five sides and little or none at the top.
When a icebox conversion unit is selected for a box it must be sized for a reasonable amount on food and drink throughput per day. When dealing with a small box and two people on board a standard box’s daily Btu heat load can be doubled in warm weather do to product throughput. In this case compressor and systems output may be more important than the total insulation R value.

Getting the Best Performance From Your Refrigeration Unit.

Refrigeration is a system that absorb heat not wanted or needed and reject it elsewhere, to do this each component of a system must be capable of transferring matching heat energy. The heat load of an insulated box will determine compressor, condenser and evaporator size.
It is almost impossible to purchase an ice box conversion refrigeration unit to match every application or cruising temperature environment, so field modifications may be necessary to improve performance.
• Air cooled condensers are only efficient if the air that passes through them is not allowed to pass through again. This means that ambient air is drawn from one area and must be exhausted to another area.
• Condenser intake air temperature of 70 to 90 degrees F is preferred. The best condenser installations are when the condensing unit is sealed against a vent in a wall or cabinet door. If a condensing unit can not draw in ambient air them an extension tube and fan can be added drawing cabin or bilge air in. Pressurized air will then find some place to escape and not re-enter condenser.
• Volume of air across condenser is as important as its ambient temperature. Most condenser fans used with BD compressors have a capacity of less than 50 cfm airflow and may lack the capacity needed in warm climates. The same size fans are available in 80, 90, 100, and 130, cfm. The answer to correction ineffective condenser cooling sometimes is a larger fan.
• Capacity on the BD35 and BD50 compressors can sometimes be increased by increasing their speed if the evaporator has the ability to capture additional heat energy.
• Heat energy transfer of evaporators in these ice box conversion units depends on conduction in still air. If evaporator is not efficient enough to handle compressor’s a small fan moving air across it could make it more efficient.

Expected Energy Consumption

One of the most common questions asked is how many amp-hrs a day will my refrigerator use? The answer is as much as needed to produce the cooling effect needed.
A six cubic ft. production box operating at 35 to 40 degrees and no freezing section, in tropical conditions will consume as much as 60 amp-hrs per day. If the cabin or water temperature is 25 degrees cooler the daily amp-hours might be 30. The daily use of box, efficiency of system along with temperatures will determine power consumption.
For a boater to be satisfied with his refrigeration it will depend on the upgrades to his onboard electrical grid. Standard alternators and voltage regulators are not good enough for a 12 volt cycling refrigeration.

[knotmeter]

I have noticed from reading the boards that many 350 owners are having problems with their refrigerator. I have had many of the same problems and have made some modifications to my system that have improved its performance. I have created a web page that shows these modifications. Hope this will be of help to some of you.

https://home.comcast.net/~teriwhine/frig.htm

Michael Bourassa
Inamorata Hull 148
Grapevine, Texas

[Richard Kollmann]

Knotmeter, I have a couple questions:
What are the measurments (size) of your evaporator?

What speed is your compressor running at? From the picture the speed resistor number is on top of thermostat.

Can you describe the areas where frost is present on evaporator and tubing?

Are you indicating the freezer will get no colder than 28 degrees?

[KenKrawford]

Michael,

I just finished looking at your pictures and modifications. It appears that you have put in a lot of time and effort to help address a problem that most of us struggle with on our boats.
My bottom line conclusion is that it seems rediculous that we have to resort to these methods on a boat that costs upwards of $150,000 to have a refrigeration system that is usable.