Fridge Fan - like the big boys do...

[GT250]

Another get rich idea: And if it takes off, you heard it here first from me!
I was thinking of fitting a 240v fan into the inside of the fridge - tucked away (at an angle), in some corner...

Over the last year or two, i have noticed that milk (same brand etc), will go off quicker if placed close to the inside of the door, as against the outside of the door.
I understand most fridges have 'air flow' paths (and the manufactorers make a big thing about it as well in the advertising), that might run all the time (I don't know).

However, when shopping in the big boys stores (WW, C, IGA) and so on, you can feel the cold air flowing in all their vegie, pies, icecream cubicles etc - but no flowng air in all the fridges we have owned etc..

Looking at a 240v 80mm BB fan $30 - 100,000hrs life.
Of course i don't need the thing running at 3000rpm - and don't want it to consume 12watts - as it will be running all the time.

Was wondering what the option was to have a VR to wind down the speed to what suits (lower noise as well) - BUT - would this lower the Watts?

Also, what do you think about a 240v BB fan in a 3-5 °C 'moist' environment, running at 200rpm?

[Skepticist]

I'd be trying a triac phase-shift type speed controller (aka light dimmer) on such a fan experimentally at first. Such a potentially moist environment could pose some special problems for insulating a mains powered device though as you don't want the fridge periodically shutting down the house, assuming you have an RCD for protection.

[Uncle Fester]

Was wondering what the option was to have a VR to wind down the speed to what suits (lower noise as well) - BUT - would this lower the Watts?

Also, what do you think about a 240v BB fan in a 3-5 °C 'moist' environment, running at 200rpm?

I don't think that is a good idea.

You really only need a very light airflow for this.
I would use a 12V DC fan either out of a Computer PSU or better new for 2$ like here:


I would run it off a 9V DC regulated power pack, wihich you place outside the fridge compartment of course. Will use about 2Watts, very quiet. Find a power pack with efficiency level of IV or V. If it does not have an efficiency level rating, don't buy it.

[Uncle Fester]

Put your hand underneath the fridge door. If it feels a little bit cooler then you have a seal leak, which might be the actual reason why your milk is going sour just inside the door.
I always kick(lightly) the bottom of the door when I close it. The seals look fine but the door maybe slightly warped. Might be a way to adjust it but I sometimes feel the need to kick something lately. Sort of satisfying.

[moeee]

My milk went off the very same way what you said , by having it in the rack built into the door.
I now place my milk inside the fridge like where it is colder.
Problem solved.
COST - NIL!!

[gordon_s1942]

From what I understand a so called 'Frost Free' refrigerator uses an air flow throughout the compartment but I dont think it runs continually.
One had a small switch in the Freezer compartment that stopped the fan when the door opened.

What happened to your milk is a reason I dont like vertical freezers because every time you open the door, the cold air pours out and it naturally takes time for that area to resume the correct temperature.

I think we would all be surprised to see just how many times in a day a 'Fridge door is opened and for how long and just what Temperature the door shelves are at.
Maybe put a couple of thermometers into the 'Fridge, one at the door and one internal and see what variances occur.

[GT250]

Thanks for all the replies.

I guess it's like cooler/cold rooms - large fans running all the time. I think it's a matter of continuous cold air that would stop 'resting' air getitng warm, if that makes any sense!

@ nomeat, nah, seals are fine, no leaks. Got plenty of computer like that one, but was trying to do away with adaptors etc, and get a straight 240v one. Just concerned about moisture etc, also a Ball Bearing one instead of a sleeve type.
How do you work out the 2watts consumption?

A 80mm 240v consumes 12watts which would equate to $8 per qtr extra on the electric bill.

Can't put the milk anywhere else, besides a different part of the sliding rack the other containers are on - just that the milk - most used - goes where it is easly plucked out and returned. I've tried to move it, but 'someone else', keeps putting it back

So the idea was to fit a fan - running all the time, but as low power as possible / moving enough air - running from the internal light power source, so no holes drilled

[crazy]

If the door switch was double pole, you could wire the fan so that when the door is opened and light comes on, fan goes off.
That would help stop air movement with the door open which would i guess lead to move temperature loss.

[Mgoldbe1]

I don't think that is a good idea.

You really only need a very light airflow for this.
I would use a 12V DC fan either out of a Computer PSU or better new for 2$ like here:


I would run it off a 9V DC regulated power pack, wihich you place outside the fridge compartment of course. Will use about 2Watts, very quiet. Find a power pack with efficiency level of IV or V. If it does not have an efficiency level rating, don't buy it.

My Sheep Rooter (F&P) has this same 12V fan (although rubber suspended) running all the time as standard fitment. It's mounted behind the rear internal panel. Also, I don't recommend using 240v in there.

[ol' boy]

Interesting project.... Takes me back to my Refrigeration Course days.

I went through a run of Milk going off prior to used by date last year (milk stored in door lowest shelf)

In my situation the problem was found to be the Milk our local IGA sold... Any Milk bought from another supermarket (Coles, Aldi) was fine right up to and often well past the used by date.

An interesting thing with Milk, is UV light will turn it sour, just as much as not having a stable cold temp will.

I have seen Milk deliveries sit 5 crates high in the morning sun until a shop owner has arrived.

[Mr 672A]

If it feels a little bit cooler then you have a seal leak,

I use a sheet of A4 paper to test the door seal all away around. Once the door is closed the removal of the A4 piece of paper should show resistance. If it comes out easy you have a seal problem

[Uncle Fester]

How do you work out the 2watts consumption?

• Voltage range, 6 to 13.8V.
• Current, 0.21Amps.

That would be about 2.5W @12V. the current will be less @9V perhaps 0.15A -> 1.35W (but not necessarily Ohm's law here). + perhaps 1W loss from an efficient power adaptor -> 2.35W.
You will be astonished how much air that still pushes.

Some years ago I employed 240V fans in vending machines. They failed every 1-2 years. The 12V fans in the computer supplies seem to last forever running 24/7.

So the idea was to fit a fan - running all the time, but as low power as possible / moving enough air - running from the internal light power source, so no holes drilled

The light goes out when you close the door. You need to get one pole from the door switch and one from the bulb. Considerable job to get at the door switch on my fridge. Easier to push a thin low voltage wire through the back. Tiny hole sealed with silicone. Perhaps follow the wiring of the light where it goes out to the back.

Unless you can find a fan with IP68 rating I would not like to accidently touch a 240V fan that is covered with condensation if the door is left open a bit longer.

[gordon_s1942]

An interesting thing with Milk, is UV light will turn it sour, just as much as not having a stable cold temp will.

I have seen Milk deliveries sit 5 crates high in the morning sun until a shop owner has arrived.

Is this why the free 'School Milk' used to 'Go Off' eh??
If your old enough to remember the 1/4 pint bottles of milk that were supplied to the Schools in NSW that were delivered before 9am and not distributed until around11am, no ice or refrigeration and left hopefully in the shade with the temps pushing above 30c in Summer, sometimes the milk tended to be a bit 'stodgy' when you got it.................
And I am damned sure the Milkman didnt have refrigeration on the horse drawn cart as he did his deliveries around the suburbs of Sydney in the 1950's and you had the choice of either getting a pint in a bottle or in the Billy Can straight out of the churn.
No 'Fridge' inside either, just a 'Coolgardy' safe or the Ice box to keep it in.

[GT250]

Ok. I get the msg about the 240v.
I'll go the 12v way.

@NoMeat: So a 12v fan and a 240v/12v adaptor or are you saying use a 9v adaptor to get the speed down and run the 12v at 9v?


@Gordon: I remember racing the milk float in England on my push bike! Milk was left on the doorsteps and some birds would pick the top off and get the cream...

@Oceanboy: Look at A2 milk. Dairy cattle in the 'past' had protein B. Nowadays it's Protein A.
A2 milk is protein B.
'Normal' milk contained Melonine (or something spelt like that - now they advertise it on the container as not being present!!!). This Melonine is a byproduct, green in colour. Some bright spark mentioned to put it into the milk, and no one will ever know....

The $2 2ltr milks "Specials" can have upto 16% Melonine - in 2ltrs that's close to a can of coke in size.

Melonine also makes the milk go off quicker, besides indigestion, loose bowels etc (which i had). Once i went to A2, it all stopped.
Due to falling $ sales, the major milk companies no longer put Melonine in the milk.

Must be amazing why they never mentioned it was in the milk in the first place!!!

[Uncle Fester]

@NoMeat: So a 12v fan and a 240v/12v adaptor or are you saying use a 9v adaptor to get the speed down and run the 12v at 9v?

The latter. It must be a stabilsed. A modern switched mode type.
The reason is longevity of the fan, lower noise and you should only need a very light airflow. Running it at 12V will however double the airflow.
In a PC they usually only run at max speed when the CPU is running hard so I have no idea how long they will last if they are always running at 12V.
I do a lot with brushless DC pumps lately(similar type of motor but the magnetic rotor is inside). If they need to run for many hours a day I use a bigger pump and run it at a lower voltage. I like it when things last long but that is a mentality not commonly found today.
If you have so many fans why not use two, run them on 9V and never be bothered with sour milk again(before use by date), even if one should fail