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Improve Fridge Efficiency


Doodlebug

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Hi all, long time no see :) been busy working :( 

We have just bought a 12v fridge - finally!! 

It is one of the tiny models that has the 'radiator' hidden behind the fridges outer shell. To me this seems somewhat inefficient at transferring the heat. I assume there are a whole load of pipes behind that move the heat into the outer shell. 

Has anyone taken off their outer shell in order to improve the efficiency of the fridge?

Another thought - there is the option of fitting a 12v fan that will cycle with the compressor. However will this improve the efficiency enough to warrant doing so. If the fan is drawing .5 of an amp the fridge would need to turn on for quite a bit less time to make it worth fitting it. 

Many thanks!

Doodlebug

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I suspect each person would get slightly different results as it will depend on the boat design, weather and amount of use.  Why not use a KillaWatt type plug to measure the daily energy use with and without the fan? ( I realise you will need a 12v version)

So, here's one to look at http://www.ebay.co.uk/itm/60V-100A-Watt-Meter-Digital-LCD-Battery-Voltage-Amp-Monitor-RC-DC-Power-Analyzer-/162468670184

Edited by mross
added 12v version
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11 hours ago, Doodlebug said:

there is the option of fitting a 12v fan that will cycle with the compressor. However will this improve the efficiency enough to warrant doing so.

Yes. 

Drill a 100mm hole in the floor and fit a pc fan drawing cool air from the bilge to blow over the fridge cooling fins and it will be far more efficient. 

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I found drilling 100mm holes through a solid oak floor difficult so drilled a few 50mm ones thennset 2 computer fans on a board, wired in series to slow them down and reduce noise. Board is at 45 degrees across the back of the fridge housing so as to direct air up the innards.

Edited by pearley
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On 08/08/2017 at 21:44, Doodlebug said:

Another thought - there is the option of fitting a 12v fan that will cycle with the compressor. However will this improve the efficiency enough to warrant doing so.

Depends on the temp of the condenser (as said, sometimes the shell itself) and heat buildup behind/around the fridge.

If the condenser doesn't get more than lukewarm and there's good natural ventilation around the fridge, then it's unlikely to make a biiig difference, but still maybe worth a try, most likely to help in high summer.

If the condenser is built into the shell, the heat will probably come from the sides and not the back, worth bearing in mind if the fridge is a tight fit in a cubby hole.

Edited by smileypete
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IMRE it's only the larger (height wise) units that have coils bonded to the case internally. So anything  that's under-counter will still have external coils at the rear. I've no idea whether an external fan achieves anything freely, but as a 12v computer fan is cheap as chips - why not.

A hidden bonus is that if you use said fan to exhaust air from the bilge, that of itself is a jolly good reason for fitting it /them anyway.

I did.

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And on the other side of the equation, a fan blowing extra cold air from the bilges into the boat will raise the number of air changes per hour in the cabin and consequently raise the amount of fuel used for heating the boat, marginally.

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1 hour ago, Mike the Boilerman said:

And on the other side of the equation, a fan blowing extra cold air from the bilges into the boat will raise the number of air changes per hour in the cabin and consequently raise the amount of fuel used for heating the boat, marginally.

There's always one Moaning Minnie ;)

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On 12/08/2017 at 19:53, OldGoat said:

IMRE it's only the larger (height wise) units that have coils bonded to the case internally. So anything  that's under-counter will still have external coils at the rear. I've no idea whether an external fan achieves anything freely, but as a 12v computer fan is cheap as chips - why not.

A hidden bonus is that if you use said fan to exhaust air from the bilge, that of itself is a jolly good reason for fitting it /them anyway.

I did.

Quite a few (all?) of the current chinese made undercounter units don't have external condenser grids.

If the fan only runs when the compressor runs and uses say 3% of the power that the compressor does, it only needs to reduce the runtime of the compressor by 3% to be worthwhile.

Generally I'd say that a large slow running fan will move air more quietly and efficiently than a smaller fan. Most PC fans seem to happily run from as little as 5 volts. Doesn't really need to blow air up from the bilge either, just increasing the airflow round the condenser will help.

 

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