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Old 26-05-2018, 15:29   #1
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Act like you are the design engineer for a boats refrigeration

I would like to hear from a number of experienced Boaters what they believe the real difference is between any two totally different Icebox Conversion Refrigeration units. The box to be used is 5.6 cubic feet 24 in wide 20 in long and 20 in deep. with three inches of insulation and a 16 by 20 in top lid opening. The ambient temperature where box is located will average 80 Degrees F. 24 hours a day.
Special requirements for this coastal cruising boat with two people on board are:
• Low daily power consumption
• Low reasonable cost of refrigeration unit
• Condensing unit design to adapt to most locations in a boat.
• Simple installation.
DIY maintenance
• Because mobile refrigeration must be repaired locally any refrigeration trained technician should be able to repair this refrigeration system.
• Replacement parts and components are available within a day or two and hopefully there are no proprietary parts that can not be replaced by a similar part. As experienced in the past boat refrigeration companies go out of business and their after market support goes with them. How long are the replacement parts going to be available?
• It is difficult to achieve normal refrigerator zone temperatures in small refrigerated boxes; Drink cooler, Refrigerator section and Freezing section.
• Small icebox conversions for cruising boats should at least have a dual temperature box.
• Standard mechanical thermostat that can be set to control temperature in freezing section without freezing items in refrigerator section.

I have selected a well known Nova Kool basic icebox conversion refrigeration LT201 system and its twin plate RT 6 box evaporator. Nova Kool still uses the popular Danfoss engineered compressor Yes, I know this compressor is now made in China but so are the other five off brands of look alike 12/24 volt compressors.

What ice box conversion refrigeration and its components will you recommend from your boating experiences and what added improvements would you add to improve the above requirements for this size box.
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Old 27-05-2018, 08:28   #2
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Act like you are the design engineer for a boats refrigeration

Since no one has replied I’ll toss my 2c in to get the ball rolling, although I’m not sure I fit the experience part.

What you ask is sort of a unicorn, to say it another way, you want good, easy and cheap. Usually it’s a pick one or two, you don’t get them all.

However if I had to do it again, I think I would seriously consider Nolex’s solution, that is a commercial off the shelf 12V cooler / freezer. That gives you the closest I believe to easy, good and cheap, and beyond warranty, heck with fixing it, they are cheap enough you can just go to a box store and buy another, the good ones are surprisingly rugged and long lasting.
However it likely means surgery on the boats cabinetry, so there goes easy.

But for an icebox conversion system, I have a Cool Blue, which I think it good quality, reasonably efficient, and easy to repair. No proprietary components. However it ain’t cheap.

Assuming Oze Pete comes through with what he is promising price wise when he brings his systems into the US, well I can see how maybe he will make a huge dent in the market, sort of like Henry Ford did with his Model T, cause his prices are surprisingly low for what at first glance seems to be a quality product.
I assume he is counting on high production numbers to make money at those prices, Economy of scale?
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Old 27-05-2018, 11:27   #3
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Re: Act like you are the design engineer for a boats refrigeration

Would like to slap the clown that designed Adler Barbour systems. Have nothing but grief. One expert has a zillion troubleshooting steps I can't begin to understand. Another says rip half of it out and rewire without a whole component. Tried several (!) thermostats with no improvement. Does what it wants,when it wants regardless of setting....
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Old 27-05-2018, 12:19   #4
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Re: Act like you are the design engineer for a boats refrigeration

"• It is difficult to achieve normal refrigerator zone temperatures in small refrigerated boxes; Drink cooler, Refrigerator section and Freezing section."
Does your client really need a separate third zone for "drinks cooler" ? Most of us just keep the cans someplace cold, and ignore the label instructions on the Heineken bottle about suggested serving temperature.

Presumably if you want only one base system but at least two different box temperatures, you're going to need a second thermostat and a fan to steal cold air from the freezer and use that for refrigeration. (Which is what home refrigerators are doing these days as well.) Those could be no-name parts, easy enough to make almost anything function.

If I were designing from scratch, and the fridge was going to be more than a convenience, I think I might actually prefer one fridge box, and one freezer box, with separate systems. Maybe more money and more energy, but the redundancy versus trying to find a competent repairman surely has some value?

But when you say repair anywhere...I'd have to guess Danfoss is the closest to a "universal" compressor that's out there?
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Old 27-05-2018, 13:45   #5
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Act like you are the design engineer for a boats refrigeration

When you say Danfoss, to be fair, I think you really need to say Danfoss type, cause there are clones that function wise are pretty much the same.

I keep my freezer around 10F and my fridge close to mid to upper 30’s as a spill over with out any trouble.
We were gone for a week and came back and it was 37 and 14.
Maybe I just got lucky, but a spill over seems to be a dead simple thing.
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Old 27-05-2018, 14:41   #6
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Re: Act like you are the design engineer for a boats refrigeration

Quote:
Originally Posted by a64pilot View Post
Since no one has replied I’ll toss my 2c in to get the ball rolling, although I’m not sure I fit the experience part.

What you ask is sort of a unicorn, to say it another way, you want good, easy and cheap. Usually it’s a pick one or two, you don’t get them all.

However if I had to do it again, I think I would seriously consider Nolex’s solution, that is a commercial off the shelf 12V cooler / freezer. That gives you the closest I believe to easy, good and cheap, and beyond warranty, heck with fixing it, they are cheap enough you can just go to a box store and buy another, the good ones are surprisingly rugged and long lasting.
However it likely means surgery on the boats cabinetry, so there goes easy.

But for an icebox conversion system, I have a Cool Blue, which I think it good quality, reasonably efficient, and easy to repair. No proprietary components. However it ain’t cheap.

Assuming Oze Pete comes through with what he is promising price wise when he brings his systems into the US, well I can see how maybe he will make a huge dent in the market, sort of like Henry Ford did with his Model T, cause his prices are surprisingly low for what at first glance seems to be a quality product.
I assume he is counting on high production numbers to make money at those prices, Economy of scale?
a64 pilot, What I was looking for was several boater’s recommendations on converting a boat icebox to refrigeration by providing them with a general intended concept for a standard coastal cruising boat refrigerator. There is nothing mythical, easy, or cheap in my typical unit. Inexpensive without unproductive gadgets is what I mean by Low reliable costs. The unit I selected does meet my basic concept for the application I defined. Of the over 100 different icebox conversions sold today there are more than a few that can be used to fill the required needs for a cruising boat of less than 35 ft. I expect responses that will differ as refrigeration means different things to different boaters. On this size box refrigeration there will be no appreciable difference in energy efficiency as long a the kit manufactures instructions are followed. The recent wasted band-with over different type evaporators on this forum was over the difference of 1/3 of an amp per hour.

I have designed a large number of spillover systems in order to have a single or duel plate evaporator chill two different temperature zones. In my 5.6 cu ft example the size and shape of box makes a spillover system difficult.
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Old 10-06-2018, 07:41   #7
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Re: Act like you are the design engineer for a boats refrigeration

Richard,
Have tried repeatedly to register at your forum and get nowhere. Never hear back, president name is over a year out of date, etc.
I have some issues I'd like to ask there.
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Old 10-06-2018, 08:17   #8
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Re: Act like you are the design engineer for a boats refrigeration

Quote:
Originally Posted by a64pilot View Post

However if I had to do it again, I think I would seriously consider Nolex’s solution, that is a commercial off the shelf 12V cooler / freezer. That gives you the closest I believe to easy, good and cheap, and beyond warranty, heck with fixing it, they are cheap enough you can just go to a box store and buy another, the good ones are surprisingly rugged and long lasting.
However it likely means surgery on the boats cabinetry, so there goes easy.

After doing an icebox conversion ourselves just recently, that would be my advice as well. Putting in a complete off the shelf cooler is so much easier and in the end much cheaper as well, because all the insulation stuff, glue, paint, and so on really sums up.



Sadly, on our boat there is no space where we could fit a cooler with a decent capacity (40L or more).
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Old 10-06-2018, 08:45   #9
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Re: Act like you are the design engineer for a boats refrigeration

It is highly unlikely that the proposed cabinet refrigeration project would be applicable to all but a few. So instead of this rather restrictive exercise, perhaps the boat owner may wish to determine his / her cabinet size, type of usage etc. themselves, then search for suitable equipment manufacturer / supplier options specific to their own project.

So for anyone planning a new refrigeration system, here are some suggested ideas that should make a successful refrigeration project more do-able and end with the desired performance:
(Hopefully other industry suppliers may wish to add to this list)

1: Gather as much relevant information about your project as possible like:
1a Interior cabinet dimensions and is it a top or front opening cabinet.
1b Cabinet wall thickness if possible and insulation type if known.
1c Cabinet interior lining material. (Is it conductive like metal, or non conductive like FG or plastics?)

2: Decide if cabinet is to be used as:
2a All fridge,
2b All freezer,
2c A combination of both and at what proportions,
2d Able to operate as either all fridge or all freezer.

3: Determine in what environments the vessel will operate in and use the most extreme for computations.

4: Decide where the refrigeration condensing unit is to be located, the locations ventilation situation and the distance from the evaporator(s).

5: Understand your power storage capacity and your power re-supply situation.

Now armed with those factors, you will be well equipped to contact prospective suppliers. Ask for a heat load, duty cycle and power consumption estimate. This information is the foundation towards making an informed refrigeration equipment selection and for planning power supply requirements.

I suggest giving preference to those who are manufacturers you can actually speak to as they will know what they are talking about, know about these issues, and are not just some brochure reading expert relaying puffery in order to clear whatever is on their shelves!

Below is a Heat Load, Duty Cycle and Power consumption estimator we created and use to confirm system suitability etc.
With this estimator we can quickly add anyone’s cabinet details for an instant report.

We offer this as a free, no obligation service to any member who wishes to email their relevant cabinet details as listed above, and/or as indicated in red on the sample estimator print out below. (Click on pic to expand)

Click image for larger version

Name:	Estimator 18.png
Views:	89
Size:	62.0 KB
ID:	171397

A few other considerations:
Digital thermostats are far superior in all ways to the old mechanical ones especially the water proof digitals. (Unless you’re the type that still drives a T model Ford because you prefer the crank handle starter and can’t break the habit, then go digital!)

Also back up support is a major factor especially for those cruising.
Some posters suggest you can dock in some obscure part of say the Pacific and bingo, the local sari sari store has a motor driver module for your BD35 or whatever, well that is simply fantasy stuff.
We have thousands of systems all over the world and have found that relying on the ‘local wire twitcher’ to fix your fridge is the last thing you need. Believe me, in many parts of the world there would be more chance of your system, which initially had a minor issue, ending up as scrap than having a correct procedure repair.

Our answer is firstly a user friendly DIY product with a detailed 24 page service manual, and seven days a week technical support available from our qualified refrigeration technicians. This backed up by an complete range of spares at all times. We have massive stocks of spares, and always dispatch AusPost express same day worldwide except Sunday.

So if anyone has a better service back up plan, or more stock ON HAND to support these products, lets hear about it.

Cheers OzePete Ozefridge | 12 Volt Refrigeration Systems
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Old 10-06-2018, 14:03   #10
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Re: Act like you are the design engineer for a boats refrigeration

I had hoped for something more when I posted this thread than a Superior creative market pitch. I asked for special requirements a boater might want for this coastal cruising boat with two people on board.

I expected some would want only a drink cooler. Others would want a area to keep a few items frozen. What about a tray of ice cubes every day. Many boaters want a duel purpose refrigerator even if the box to be converted is only 5 cubic feet.
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Old 10-06-2018, 14:31   #11
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Act like you are the design engineer for a boats refrigeration

We currently have a 14 cu ft box split half and half freezer / fridge.
Then we also have an Engel, we use it as a serious deep freeze with the intent of stocking up with it and depleting it as the cruise continues.
It’s a nice back up though just in case.
Our spill over due to its size and insulation won’t get to sub zero temps in Tropical weather.
I would have liked something bigger than a BD80, but understand that would likely be another system for a manufacturer to build, and there may not be much demand for so much cooling.

We make ice separately and store it in the spillover freezer. Ice trays are a PIA to us. We have the AB aluminum vertical ones stored somewhere, they were just too difficult to use.
I bought ones off of Amazon that had closable tops, but again a PIA.
In tropical weather, we go trough lots of ice.
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Old 10-06-2018, 15:18   #12
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Re: Act like you are the design engineer for a boats refrigeration

Richard, a fridge was one of the first things I fitted into the existing icebox a decade ago. Actually your measurements are about the size of the icebox we had to work with without serious cabinet work. It has worked perfectly and draws about 3Ah with outside air temps between 10c and 25c.

I fitted a Isotherm G80 kit from the local chandlers for two reasons. One price £300, it was affordable and secondly about the right size for the box. We don't have a freezer option and I question if it is really needed or is this what customers now demand, ice for drinks? The reason I question it is we coastal cruise but without making any effort to save water we run out after 5 days on a 31ft yacht so will head in to a harbour or marina then. This also gives us the opportunity to buy fresh food rather than need to freeze meat down.

Thinking about the way we have used it over the last decade we store meat, fish, milk and cheese and of course a bottle of wine or two. It is always full so little room for ice cubes or spill over system for a freezer.

I did spend quite a bit of time increasing the external insulation with several layers of foil backed sheets of 5.16" thick. Access and space was limited or I would have done more but all seams were then taped. The existing icebox drain was blocked with a bath plug to reduce losses. We use some beer mats in the bottom of the fridge which are changed every 2 days. This keeps down the condensation in the top loading fridge. Does reducing condensation help with efficiency?

In terms of a project it has been one of the really great changes we have made to this yacht to improve life on board and a decade on money well spent.
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Old 19-06-2018, 08:37   #13
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Re: Act like you are the design engineer for a boats refrigeration

Richard
As I have upgraded my refer and freezer box over the last year your material has been very helpful.
My question is about how/ if you can zone one compressor to support two boxes and switch on and off for example the reefer side while still driving the freeze?
a spillover system is not an option for me.
Our system is a 3 plate Seafrost which has given great service for many years. It has two "circuits" one an engine driven compressor and the other a 110 volt shore assist. Each compressor drives the plates independently of the other.
In the last year have completed taking out almost all of the 1978 poured in foam and replacing with the PPG "pink" foam board. Where possible 8" of foam board for an R 40 value which the bottom and hull side. The other sides vary from R 30 to R 20 depending on location. This week should finish the top and hatches with a combo of pink board and Cryogel Z for a minimum R35 target value.
The freezer has @ 3.25 cu feet of usable capacity after subtracting out .75 cu feet taken up by the two plates. The reefer side is @ 4.75 cu feet of usable capacity after subtracting out .38 cu feet of space taken up by the single plate.
So my two questions:
1) Is there a practical thermostatically controlled valve that would divert from the refer side when a pre set plate temp was achieved and then all refrigerant would drive the two freezer plates? As it is keeping the freezer plate at 0 degrees F is straight forward but the refer then is way too cold.
The admiral is not pleased with the frozen lettuce and frozen beer not such a crowd pleaser either. This is mostly a concern on the shore assist side when at dock side or hopefully on the hook powered by my solar panels.
2) My goal is to be able to maintain the system by solar while on the hook with occasional engine runs to catch up if necessary. While my Seafrost 110 volt Shore Assist unit can maintain the system run through an invertor it just sucks too much power; near 30 amps dc. My question is if the 110 volt unit could be reasonably replaced by a single Danfos 12 volt unit. I see a lot of two danfoss solutions ; one for the refer side and one for the freezer side. If possible with one it would be much simpler and less expensive.
Thanks for your advice
Tom
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Old 19-06-2018, 10:58   #14
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Re: Act like you are the design engineer for a boats refrigeration

SeaFrost hybrid system with three plates. First are the two freezer plates operated in series by one refrigerant flow control (black or gray) box? Is the refrigerator plate supplied by refrigerant from a third flow control box? Are these eutectic plates aluminum or stainless steel?
SeaFrost has used two 110 volt units, is your compressor 1/6 HP or the big ½ HP condensing unit? Does this 110 volt unit supply refrigerant to all three plates?
AIt s I understand it the present system performs well but there is no control over refrigerator box temperature things freeze in refrigerator box.

1. Just By improving the insulation the engine driven and 110 system could be OK except for refrigerator box gets too cold. One solution to raising refrigerator box temperature is to cover the lower portion of refrigerator plate with moisture resistant starboard ½ in plastic and provide a thermostat spillover fan between the two boxes. It is the amount of plate surface area exposed that conducts heat into a eutectic material. Reduce surface area of a 24 degree F plate box temperature can be maintained above freezing then if necessary a small spillover can control desirable temperature.

2. More information is needed on old system refrigerant flow control before addressing solar operation of refrigeration. There are several options available to refrigerate two boxes and three plates from one 12 volt Danfoss designed BD50 compressor system.

Richard
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Old 19-06-2018, 12:14   #15
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Re: Act like you are the design engineer for a boats refrigeration

Richard
The 110 volt system is a SA 2 which uses a 1/4 hp motor drawing 3 amps. It is air cooled with 134A refrigerant.
Originally it was installed with 2 freezer plates and a spill over fan with thermostat to control refer temp. This didn't work well and couldn't keep the freezer cold enough.
Cleave at Seafrost suggested that the insulation be up graded. I couldn't get my head around that 4" of insulation in a well built box wasn't good enough. I should of course have taken his advice!
At some point he got tired of my sniveling and made me a good price for an additional plate for the refer which I installed. Basically we just overpowered the box with refrigeration. It worked well but after 20 years or so I figured out that it was under performing and solar powered aspirations were not going to be attainable..
Last year replaced 75 % of the insulation with new and not surprisingly performance was markedly better. Just now replacing the top and hatches insulation and expect another bump up.
The engine drive compressor and the SA 2 are totally separate and can be run individually or at the same time. They each have their own black box flow control.
I believe but not certain that the flow goes from compressor to freezer plate # 1 then to freezer plate # 2 and then to refer plate before return.
The cold plates are aluminium 18" x 12" x 3"
Thanks
Tom
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