Selecting the best refrigeration package is essential. Please consider:
It is futile to apply an efficient refrigeration system to an inefficient cabinet. While the refrigeration unit is responsible for removing heat from inside the cabinet, the cabinets insulation and construction materials are responsible for restricting heat from re-entering. It is like a ‘tug of war! Therefore the first consideration is the cabinet. Its size, insulation type and thickness, the lid/ door opening and the interior lining materials will all have a bearing on the selection of the most suitable package.
We have provided the tables below as a starting point based on properly insulated, top opening cabinets with non-conductive interiors and catering for normal galley / domestic use and using condenser water cooling.
Estimates are for top opening cabinets operating in extreme conditions. (>45C maximum day and 30C minimum night temperatures)
Those with ‘twin’ or * indicate twin (thin) plates are suggested. Water cooling of the condenser is essential to obtain these results with the twin plate models.
Please note that long shallow freezer cabinets will require much more refrigeration than a traditional cubed or tall cabinet so refer to the next size or two larger on the chart as a guide or contact Ozefridge for a calculation.
Ozefridge only manufacture refrigeration systems to suit existing cabinets or cabinets built by others. We don’t build cabinets, but here are some cabinet construction and system installation suggestions.
Cabinet Insulation etc.
Adequate cabinet insulation quality and quantity is essential when operating a refrigerator or freezer from limited power supplies. The lining materials used, cabinet shape, door / lid location and seal are all important to consider if best performance and power efficiency is to be achieved.
Insulation thicknesses used in the manufacture of domestic type fridge freezers that operate from mains power, are simply inadequate when powering from a limited power source.
While the refrigeration system removes heat thus lowering the fridge / freezer cabinet (and products within) to the desired temperature, the insulated fridge / freezer cabinet’s job is to restrict more heat from entering.
Unfortunately no cabinet is 100% successful at resisting heat penetration and so the cabinet will eventually warm up requiring the system to run again. The more the cabinet can resist heat penetration and thus temperature rise, the longer the system remains off.
As an example a good cabinet may be unable to prevent say 20 watts of heat per hour penetrating, therefore if the system applied can remove say 100 watts per hour of running it will have to run 20% of the time. The same system applied to a cabinet letting 80 watts enter will run 80% of the time, while a very poor cabinet letting more than 100 watts enter would see the cabinet temperature rise and the system run continually.
For refrigerators we suggest a minimum of 75mm thickness of refrigeration grade urethane for walls and 100mm for the base. For freezers we suggest 100 mm for walls and 150mm for the base. (Heat rises as it attempts to penetrate the insulation therefore the base is most important and the top least important assuming it is not in direct sunlight.)
The insulation must be vapor sealed (enveloped) and preferably lined with non heat conductive materials such as plastic or fiber-glass. If metal linings can’t be avoided, the metal must not run from the exterior to the interior without a broad thermal break. The same applies to lids / doors which should also have soft broad seals. Even the slightest seal gap will impair performance.
Fig 1 & 2: Long, low cabinets and tall cabinets will produce stratification.
(Variation of temperature) Some users prefer this as it allows items requiring
different temperatures to be better catered for. For example, drinks are placed
nearer the eutectic plate while the butter, veg etc is afar. A cabinet circulation
fan can be used to agitate the cabinet air, even out the temperature and speed
up product cool down.
Fig 3: This sketch indicates that by installing the eutectic plate in the bottom of a
tall cabinet, the stratification is increased to the point that the lower portion can
be used to hold frozen items while the upper area can be used for normal fridge
items. The grey divider indicated needs to be removable. (Often simply a towel
or similar). This method is a compromise that while not a proper fridge / freezer
combination cabinet, it will suit when frozen items are occasionally stored.
Fig 4: While top opening cabinets are more efficient, many prefer the
convenience of front openers. This sketch indicates how the door can be part
of the front providing ease of use without losing all of the cabinet’s air when
opened. Use of storage containers inside the cabinet also helps to prevent loss
of cold air.
Generally the eutectic plate or plates are mounted as high as possible in the cabinet.
LARGE FREEZERS or FRIDGE/ FREEZER COMBINATION CABINETS:
The Ozefridge twin eutectic plate systems suit freezers larger than 100 liter and
the ultimate fridge / freezer combination cabinet. (See Fig. 8)
The twin plate system refrigerates both sides of the freezer cabinet providing
more refrigeration where needed. The fridge side is refrigerated via the heat
Each twin plate system has one refrigeration unit coupled to your choice of
either twin P32-29, P40-33 or the P53-35 (Thin) eutectic plates.
(Plate sizes can be mixed)
To refrigerate the adjacent fridge area a thermostat controlled fan (orange)
pushes air through a hole in the dividing wall into a stainless steel duct located
on the freezer side of the dividing wall. Air travels along inside this duct and
back out into the refrigerator area providing cooling for the refrigerator side
without mixing refrigerator and freezer air and reducing ice build up on the eutectic plates. Combined cabinet size should not exceed 250 liters and must be well insulated.
Not only does the one Ozefridge twin plate system provide adequate refrigeration for the freezer, but also refrigerates the adjacent refrigerator cabinet. (See Fig 8)
Fig 5: This beautifully made fridge / freezer combination cabinet was owner constructed using Multipanel lining. The cabinet has Multipanel laminated over high density urethane sheet . It is essential that combination cabinets are properly insulated and sealed as this one is. Avoid metal for inner lining.
The freezer compartment (Fig 5) has an Ozefridge Package Five twin system being a AW480 refrigeration unit coupled to twin T53-35-4 eutectic plates mounted on opposite sides of the freezer area. The stainless steel heat exchanger plate can be seen on the freezer side of the dividing wall. This exchanger plate is only 15mm thickness and otherwise the height and width are custom made to suit each individual application. (Talk to Ozefridge about applications)
Fig 6: This picture is of the refrigerator compartment side of the same cabinet.
The Thermo-Fan unit is located over a 75 mm hole through the dividing wall.
When cooling of the fridge compartment is required, the remote digital thermostat powers the fan located in the dividing wall air hole forcing air through the 75 mm hole and into the heat exchanger duct. This air from the refrigerator is cooled as it travels through then out of the duct and back into the fridge compartment via the other 75mm hole in the dividing wall. (Left side)
Fig 8: Packages with twin eutectic plates. The package with twin plates use one AW480 refrigeration unit to refrigerate both of the eutectic plates. The eutectic plates can be a pair of any of our plate models. All twin plate systems should be the AW480 water cooled for best results.
Twin plate & twin compartment operating options:
Locate a twin in a properly insulated cabinet and use as a large freezer.
Locate in one section of a divided cabinet and operate as a freezer (Fig 5) and have a refrigerator in the second area controlled by a thermo/ fan unit. (Fig 6)
As above but operate both compartments as refrigerators.
As above but operates one compartment only as freezer or refrigerator.
Twin P53-35-4 plates are most commonly used for this application but other models may suit your cabinet dimensions better.
The Ozefridge Twin (refrigerates the freezer compartment) and, along with the optional Thermo-fan and heat exchanger kit, will also cool the adjacent refrigerator area. This is the most popular system for those starting out with a new refrigeration project,
See sketch below
This picture below shows a Digital thermo-fan kit with wiring harness
The Digital thermostat will sense when cooling is required in the
refrigerator side and start the fan. The thermostat can be digitally set to suit your requirement accurately while also providing fridge cabinet temperature read out.
The remote controller panel also has an on/off switch and an Auto/ Manual switch. This remote thermos fan controller panel matches the Ozefridge refrigeration unit’s controller panel. (See below)
Temperature of the freezer area is controlled by the refrigeration unit’s
The SS heat exchanger, prevents the warmer/ humid refrigerator air
mixing with the freezer air reducing the frost build up on the eutectic
As Ozefridge Industries Pty. Ltd. supplies refrigeration systems to be installed by others of whom we have no control over and into an existing or new cabinet that has insulation properties etc., that we have not supplied, we can not guarantee cabinet temperature outcomes or the system’s ability in this or any other quotation or statement.