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Old 10-08-2018, 11:14   #76
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Re: Wo provides the best 12 volt refrigeration systems?

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Originally Posted by nmccubbin View Post
We are about to buy a small compressor/condenser using with an evaporator plate to add to out mechanical system. Reason is backup and to let our solar panel and windmill do some of the work
Thanks

I suspect that dissipating heat to the water rather than air, will make your system much more efficient/use less power.
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Old 10-08-2018, 11:18   #77
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Re: Wo provides the best 12 volt refrigeration systems?

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Originally Posted by skenn_ie View Post
I suspect that dissipating heat to the water rather than air, will make your system much more efficient/use less power.
not near as much as you would think in most cruising regions due to water temperatures
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Old 10-08-2018, 11:28   #78
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Re: Wo provides the best 12 volt refrigeration systems?

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not near as much as you would think in most cruising regions due to water temperatures

Air temperatures are likely to be even higher, and water is a much better heatsink. Just look at modern CPU coolers.
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Old 10-08-2018, 11:33   #79
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Re: Wo provides the best 12 volt refrigeration systems?

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Originally Posted by skenn_ie View Post
I suspect that dissipating heat to the water rather than air, will make your system much more efficient/use less power.


At first glance you would think so due to waters greater capacity to absorb heat.
However itís loads easier to move a bunch or air than it is to move a smaller amount of water, water requires of course pipes, pumps and if you use seawater then you have corrosion issues, stray current and growth.
A fan, is just a fan.

We would air Cool our air conditioners too like a house does, except the large air ducting to do so isnít nearly as convenient as a small hose pumping water, just a refrigerator doesnít move enough heat to justify water cooling, or the small amount of heat it moves isnít hard to get rid of with air, depending on how you look at it.
Remember the average fridge only produces about half as much heat as a human body does, when the fridge compressor is running.

Water cooling works of course, just isnít all that much more efficient and brings maintenance issues with it, that many donít find worthwhile.

Now using a vessels own fresh water tank as a place to move the heat is probably a very good idea, I think, if you desire water cooling.
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Old 10-08-2018, 12:00   #80
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Re: Wo provides the best 12 volt refrigeration systems?

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Originally Posted by Mike Banks View Post
If it draws an average of 1.5 amps in over a period of one hour--that rate will not change no matter for how long it runs, unless something changes..

Consumption is measured in watts--which is amps per hour times number of hours times the supply DC volts--which will give you the answer that actually means something.
Actually consumption is measured in Ah (ampere-hours) for DC. Watts is a measure of Power (W=V x A) If you want to know how much energy you used, you need to describe "watt hours"

what you described is the formula for Ah amp-hours. But you're missing the marketing trickery If someone says their fridge only uses 1.5amps. the important followup question is. Is that continuous or what duty cycle? If the fridge uses 1.5amps but runs non-stop. its uses 36ah and consumes the same energy as a 6amp fridge that has a 25% duty cycle.
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Old 10-08-2018, 12:25   #81
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Re: Wo provides the best 12 volt refrigeration systems?

Quote:
Originally Posted by nmccubbin View Post
We are about to buy a small compressor/condenser using with an evaporator plate to add to out mechanical system. Reason is backup and to let our solar panel and windmill do some of the work

I have lots of data on ColdEh, Dometic/Coldmachine and CoolBlue, and have read a lot on this forum.

Much of the information here is from the vendors. While very useful on the technical side, it does not provide independent opinions.

I would appreciate comments on reliability, tech support and spares service from users who live on board at least several month/year.
Unfortunately info on units more than about 5 years old is of little value, since manufacturing quality and service seems to have changed over the past few years.

Thanks
For reliability I would buy the simplest, air cooled, evaporator plate, Danfoss based unit you can find, preferably from a reputable dealer near you. Chances are it will last for years, (ours, from West Marine, has) and any refrigeration man can check it and recharge it if needed. The electronics are simple to replace. In my opinion, all of the efficiency upgrades such as eutectic plates and water cooling are not worth the cost and fuss.
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Old 10-08-2018, 12:36   #82
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Re: Wo provides the best 12 volt refrigeration systems?

No refrigeration system is better than the insulation of the box.
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Old 10-08-2018, 12:47   #83
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Re: Wo provides the best 12 volt refrigeration systems?

We have a basic Danfoss unit. It may be 30 years old. Bit rusty. Water cooled condenser. It works well. Spent 6 months in Tonga. No worries. We also have engine driven compressor so can really pull the temperature down if needed. Only repairs we have done was when we bought the boat 5 years ago it was needing a tidy up, regassed, etc.
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Old 10-08-2018, 12:59   #84
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Re: Wo provides the best 12 volt refrigeration systems?

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Yes, itís standard, but as Richard pointed out as with everything, not all connectors are created equal.
Also a thin plate evaporator is often a critical orifice, which means that getting the correct amount of refrigerant level is very important, and pretty darn difficult to get just right, and it has to be just right, and I mean to less than an ounce.
TXV systems often have a decent sized drier installed, and the drier can act as an accumulator of sorts and hold some excess refrigerant, so charge isnít nearly as critical or as hard to achieve as a critical orifice system, a little extra doesnít hurt and gives a buffer if you do happen to have a tiny leak.
I probably shouldnít post this, have some others confirm or deny please, but the Cool Blue in particular can be bled down to just a little refrigerant pressure is left, a vapor charge if you will, then a complete can of refrigerant added and itís right at the correct amount of refrigerant, no gauges, no sensitive scales weighing charge, watching frost lines adding in 2 sec shots of refrigerant etc. All you need to carry with you is a can of refrigerant and a service hose, which you can buy at any Walmart etc anyway so depending on where you travel, you donít even need to carry that.

I should bring up though if you buy an extra can, read the label carefully to ensure its nothing but R-134a, cause for some reason itís getting tough to find just refrigerant without dyes, leak sealers, and other gases blended in. Maybe go to an HVAC supply store to get a can.
a64pilot, I sure can not find fault with your beliefs on small refrigeration design. I will point out refrigerant expansion valves do not store excess refrigerant in accumulators. Refrigerant is stored in a receiver although the Cool Blue system does have a filter dryer also inside liquid receiver. On these small 12 volt systems the accumulator traps that protects liquid refrigerant and oil slugs from reaching and damaging compressors are located inside a correctly designed evaporator or eutectic plate. On thin plate evaporators these accumulators are visible as circles near end of refrigerant flow.
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Old 10-08-2018, 13:06   #85
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Re: Wo provides the best 12 volt refrigeration systems?

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It's OK Newhaul, sometimes we have to settle for second best! (Don't tell Rich I said that!)
Not really and all that aside, you have made an excellent choice.

Cheers OzePete
Pete Now I am designing a new one for the defender .
I am needing a system for spill over freezer and fridge
Freezer is 1.5 cf and fridge would be 3.5 cf .
Both are going to be adjustable via a movable divider .
I'm insulating with 60 mm of Cryogel at r8 per 10mm so r48 sounds like overkill but I have the material and space to do it so why not.
The freezer surface for the plate is 14 inches by 23 inches I would like to do it with a 1 inch thick plate if possible and no water cooling. ( no more holes in this boat. ) entirely off grid (400 watts solar and same with wind)
do you have a system that will do the job and if so price delivered to USA postal code 98443.
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Old 10-08-2018, 14:09   #86
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Re: Wo provides the best 12 volt refrigeration systems?

I can definitely recommend a Ozefridge system. I installed one in 2007 & it has been running 24/7 since. The eutectic tank system is ideal for using when away from shore power, less cycling once the tank is frozen. As we spend a lot of time in the tropics l was advised to get the water cooled model. A large gain in efficiency & uses a small pump to circulate the on board tank water. No problems with barnacles and corrosion. The electronics are also smart enough to automatically start the unit when it sees excess power & give the tank a pull down. This works well with my solar system that have usually fully recharged the batteries by midday. The system is self contained in a single stainless box & is easy to install.
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Old 10-08-2018, 14:23   #87
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Re: Wo provides the best 12 volt refrigeration systems?

Richard I wasnít aware that critical orifice thin plate evaporators had receivers. What then drives the requirement of the charge weight being so precise?
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Old 10-08-2018, 17:34   #88
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Re: Wo provides the best 12 volt refrigeration systems?

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Originally Posted by a64pilot View Post
Richard I wasnít aware that critical orifice thin plate evaporators had receivers. What then drives the requirement of the charge weight being so precise?
I think you may have misunderstood the poster. Only TX valve systems (must) have a receiver. A receiver acts like a storage area to accommodate the variation of refrigerant as the TX valve modulates. Capillary systems are much simpler not needing a receiver, sight glass or TX valve but both system types need a suction accumulator.
The suction accumulator should cause any un-evaporated refrigerant (Liquid) to evaporate before returning to the compressor.

Cheers OzePete Ozefridge | 12 Volt Refrigeration Systems
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Old 10-08-2018, 17:40   #89
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Re: Wo provides the best 12 volt refrigeration systems?

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Richard I wasnít aware that critical orifice thin plate evaporators had receivers. What then drives the requirement of the charge weight being so precise?
Only refrigerator refrigerant control devices like expansion valves and low pressure regulator flow regulator valves require a refrigerant storage receiver tank. All types of refrigerator evaporators including eutectic plates can discharge damaging liquid towards compressor. Capillary tube flow control orifice systems are easer to protect against
liquid feed back to compressor as there is very little actual liquid refrigerant in a cap tube type system. Expansion valve systems may have twenty times more liquid refrigerant than a Cap tube system. My designs as well as others require at least a ten foot length of suction line to insure liquid is condensed to a vapor before reaching compressor. With only four feet of this tube covered with insulation.

The concern over excessive liquid refrigerant remaining in evaporator results from the natural movement in all systems of refrigerant seeking a cool area to migrate to when compressor is not running. On compressor start up refrigerant flow is always the greatest exposure to compressor liquid overloads. This is why suction line accumulators are designed into every well designed refrigerator system.
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Old 10-08-2018, 18:08   #90
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Re: Wo provides the best 12 volt refrigeration systems?

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Originally Posted by newhaul View Post
Pete Now I am designing a new one for the defender .
I am needing a system for spill over freezer and fridge
Freezer is 1.5 cf and fridge would be 3.5 cf .
Both are going to be adjustable via a movable divider .
I'm insulating with 60 mm of Cryogel at r8 per 10mm so r48 sounds like overkill but I have the material and space to do it so why not.
The freezer surface for the plate is 14 inches by 23 inches I would like to do it with a 1 inch thick plate if possible and no water cooling. ( no more holes in this boat. ) entirely off grid (400 watts solar and same with wind)
do you have a system that will do the job and if so price delivered to USA postal code 98443.
Hi Newhaul,
Your proposed fridge / freezer cabinet dimensions and insulation factor suits the use of an Ozefridge A480 12VDC refrigeration condensing unit coupled to a model 53-35-4 Stainless steel eutectic plate. This eutectic plate is 530mm X 350 x 40 thickness overall. The 40mm thickness is 25mm (1") tank thickness with 15mm rear offset from the wall to also allow cooling from behind. Full details of this package at our web site.


Thanks to a favourable dollar exchange rate, this complete package would cost US$1492.00 including UPS delivery to 98443. (Not including any local tax)
Delivery to your US address is usually 10 days from order.

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Cheers OzePete Ozefridge | 12 Volt Refrigeration Systems
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