Fridge / Freezer Ideas..

[OzePete]

Fridge / Freezer ideas.

Here is the first of a series of refrigeration ideas and discussions that should help members achieve a better outcome from their existing or new, fridge / freezer.
There will be others, especially those with industry experience who I hope will add to this thread, but please stay on the topic, other issues can be covered later in another thread.

Number One topic:
1: Fridge and freezer cabinets. (New)

The most important component of a fridge or freezer is the cabinet.
Refrigerating a cabinet involves removing heat from its interior thus causing it and stored product to become and stay cold. A refrigeration ‘heat pump’ is normally used to remove that heat, however, as efficient as the refrigeration unit may be, it is all to no avail if the heat entering the cabinet exceeds the ability to remove it. Cabinet insulation is used to resist that heat penetration allowing the refrigeration unit to do it job.
While it is near impossible to totally prevent heat penetration, there are a few key factors imperative to restricting heat entering.

A: Cabinet design. Because proportionately the greatest area of heat penetration is the base, (heat rises) a taller rather than shallow cabinet will be more efficient.

B: Given the available space, often the most ideal insulation thickness may not be practical and some compromise may be necessary. One offset can be to reduce the top of the cabinet’s insulation thickness 50% and add that to the bass. (Unless in direct sunlight) This will considerably improve the cabinets overall resistance to heat penetration without compromising storage capacity, besides those bottom items won’t be quite so hard to reach!! See sketch below..

C: Vapour sealing. This is extremely important especially for freezers. Cabinet insulation that is not totally sealed (enveloped) will accumulate moisture and become useless. Many times I have heard people say ‘my fridge was great for years but lately it runs a lot more’. Sad! When asked I often say ‘imagine if your finished cabinet was submerged, would you be sure that no water got into the insulation? Even screws into the cabinet should be fitted, then removed and the hole filled with Sikaflex then refitted, it is that important!

D: Cabinet and lid /door lining materials. Avoid using metal especially for a freezer! Use only non conductive materials like f/glass, ABS plastic etc. Be sure that all lining joins are sealed 100%.

E: Lid / door seals. These are best using a very soft closed cell sponge. Something that compresses easily and forms a total air movement barrier is best. Normal domestic fridge seals are quite rigid and usually don’t work very well for theses small cabinets.

F: Insulation. The quality and quantity of insulation is most important especially as it directly relates to the refrigeration system and therefore power efficiency. Recommended insulation R factors should be adhered to for best results unlike thin walled domestic or dorm fridges where they are connected to the mains and refrigeration ability / power consumption is not that important.

G: Heat load. Once the cabinet dimensions and factors such as insulation type and thickness are known, any competent refrigeration equipment supplier can calculate a heat load, relate this to a suggested system and estimate the daily power consumption. This estimate should relate to at least a 40C environment.

2: Fridge and freezer cabinets. (Existing)

A: If the power consumption is excessive or the refrigeration struggles, fit a sheet of say 50 – 100 mm thick urethane tightly across the cabinet bottom interior. (May be in two or more pieces) Seal to the old wall and base with butyl mastic. Cut a new base liner from say ABS plastic or similar and fit down over the new insulation with a good seal..

B: Check the cabinet’s inner and outer linings and seal off any gaps, cracks or crevices. To check your lid / door seal, put a strong light inside the cabinet at night and observe any escaping light areas as they will need attention.

C: If your fridge / freezer has a temperature sensor that is floating free in the cabinet reading air temperature, water proof it with a coating of silicon then locate it in a tall glass of water. Place this glass centre / side of the cabinet away from the cold plate. This will greatly reduce rapid cycling and as a consequence greatly reduce power consumption.

D: Check for insulation saturation. If there is sweating or cold patches on the outside of the cabinet, then the insulation will need replacing.

E: If an old cabinet smells, switch off wash it thoroughly, and allow to dry with lid open, then leave a dish full of vanilla essence inside for a day or so.

I hope others will add to this thread and we can move to other refrigeration tips as separate threads later.


Click on picture to expand.

Cheers OzePete Ozefridge | 12 Volt Refrigeration Systems

[OzePete]

Should have also mentioned that using a small (say 60mm) fan inside the cabinet that runs whenever the fridge unit is running, will also help to prevent stratification in the cabinet, speed up temperature pull down of added warm product and improve the refrigeration units efficiency. These tiny fans only use <1 watt and can usually be connected in parallel with the refrig units condenser fan.

Cheers OzePete

[Warby12]

Thanks Pete, appreciated. We are contemplating building a small freezer at the moment.

[Pete7]

Pete,

What are your views on the Waeco type portable units for use as a freezer. We have a fridge but it's not big enough to covert, so thinking about a separate freezer.

Pete

[OzePete]

Originally Posted by Pete7

Pete,

What are your views on the Waeco type portable units for use as a freezer. We have a fridge but it's not big enough to covert, so thinking about a separate freezer.

Pete

Hi Pete,
Have not had much experience with them, although they are minimal but then they are low cost also. I would suggest looking for one with the best insulation if you are going to operate as a freezer.
Sorry cant be of more help.

Cheers OzePete

[OzePete]

Originally Posted by OzePete

Fridge / Freezer ideas.

Here is the first of a series of refrigeration ideas and discussions that should help members achieve a better outcome from their existing or new, fridge / freezer.
There will be others, especially those with industry experience who I hope will add to this thread, but please stay on the topic, other issues can be covered later in another thread.

Number One topic:
1: Fridge and freezer cabinets. (New)

The most important component of a fridge or freezer is the cabinet.
Refrigerating a cabinet involves removing heat from its interior thus causing it and stored product to become and stay cold. A refrigeration ‘heat pump’ is normally used to remove that heat, however, as efficient as the refrigeration unit may be, it is all to no avail if the heat entering the cabinet exceeds the ability to remove it. Cabinet insulation is used to resist that heat penetration allowing the refrigeration unit to do it job.
While it is near impossible to totally prevent heat penetration, there are a few key factors imperative to restricting heat entering.

A: Cabinet design. Because proportionately the greatest area of heat penetration is the base, (heat rises) a taller rather than shallow cabinet will be more efficient.

B: Given the available space, often the most ideal insulation thickness may not be practical and some compromise may be necessary. One offset can be to reduce the top of the cabinet’s insulation thickness 50% and add that to the bass. (Unless in direct sunlight) This will considerably improve the cabinets overall resistance to heat penetration without compromising storage capacity, besides those bottom items won’t be quite so hard to reach!! See sketch below..

C: Vapour sealing. This is extremely important especially for freezers. Cabinet insulation that is not totally sealed (enveloped) will accumulate moisture and become useless. Many times I have heard people say ‘my fridge was great for years but lately it runs a lot more’. Sad! When asked I often say ‘imagine if your finished cabinet was submerged, would you be sure that no water got into the insulation? Even screws into the cabinet should be fitted, then removed and the hole filled with Sikaflex then refitted, it is that important!

D: Cabinet and lid /door lining materials. Avoid using metal especially for a freezer! Use only non conductive materials like f/glass, ABS plastic etc. Be sure that all lining joins are sealed 100%.

E: Lid / door seals. These are best using a very soft closed cell sponge. Something that compresses easily and forms a total air movement barrier is best. Normal domestic fridge seals are quite rigid and usually don’t work very well for theses small cabinets.

F: Insulation. The quality and quantity of insulation is most important especially as it directly relates to the refrigeration system and therefore power efficiency. Recommended insulation R factors should be adhered to for best results unlike thin walled domestic or dorm fridges where they are connected to the mains and refrigeration ability / power consumption is not that important.

G: Heat load. Once the cabinet dimensions and factors such as insulation type and thickness are known, any competent refrigeration equipment supplier can calculate a heat load, relate this to a suggested system and estimate the daily power consumption. This estimate should relate to at least a 40C environment.

2: Fridge and freezer cabinets. (Existing)

A: If the power consumption is excessive or the refrigeration struggles, fit a sheet of say 50 – 100 mm thick urethane tightly across the cabinet bottom interior. (May be in two or more pieces) Seal to the old wall and base with butyl mastic. Cut a new base liner from say ABS plastic or similar and fit down over the new insulation with a good seal..

B: Check the cabinet’s inner and outer linings and seal off any gaps, cracks or crevices. To check your lid / door seal, put a strong light inside the cabinet at night and observe any escaping light areas as they will need attention.

C: If your fridge / freezer has a temperature sensor that is floating free in the cabinet reading air temperature, water proof it with a coating of silicon then locate it in a tall glass of water. Place this glass centre / side of the cabinet away from the cold plate. This will greatly reduce rapid cycling and as a consequence greatly reduce power consumption.

D: Check for insulation saturation. If there is sweating or cold patches on the outside of the cabinet, then the insulation will need replacing.

E: If an old cabinet smells, switch off wash it thoroughly, and allow to dry with lid open, then leave a dish full of vanilla essence inside for a day or so.

I hope others will add to this thread and we can move to other refrigeration tips as separate threads later.


Attachment 170238 Click on picture to expand.

Cheers OzePete Ozefridge | 12 Volt Refrigeration Systems

I had hoped that others with more marine cabinet construction experience (we only build systems these days!) would have added to this thread with some more tips.
I recall an earlier thread that touched on cabinet construction, (I think it was John) that had some good build ideas that perhaps could be added / linked here.

Cheers OzePete