Improving fridge efficiency

[Laundryman]

Prompted by the tread on keel coolers, that's a step too far for my needs. I'm always looking at things I have that are redundant with a view to another possible use. In this case I have a cool pad.ie the gizmo that your laptop sits on, that has integral fans to assist the cooling. My fridge compressor is fitted under the galley sink. Would it be worth mounting the compressor on top of the cool pad, or shall I just rip out the fans and fit them into the cupboard wall to extract the heat. I already have a 5v supply waiting. Thanks. Alan

 

[Skipper_Christoph]

You need to cool down the heat exchanger and not the compressor itself. Therefore i think it will be sufficient to install the fans into the cupboard wall in order to extract the hot air.
Christoph

 

[geem]

Getting the coldest possible air over your condenser coil is the requirement. In winter with relatively cool air in the boat this won't be a problem and your fridge should be running at maximum efficiency. In summer with high ambient temperatures it would be best to try and take cool air from the bilges as this air should be approaching sea temperature.

 

[lw395]

Getting the coldest possible air over your condenser coil is the requirement. In winter with relatively cool air in the boat this won't be a problem and your fridge should be running at maximum efficiency. In summer with high ambient temperatures it would be best to try and take cool air from the bilges as this air should be approaching sea temperature.

There are two sides to it.
One is the temperature of the air, the other is how fast it's flowing over the condenser.
Getting air from the slightly cooler bilge might use more fan power than getting the same cooling from more airflow.
The bilge may just draw in hot air from the engine.

It's a balance.

 

[J Neeves]

Our compressor has a 'computer' cooling fan, the whole lot sits under the saloon seating and there is a vent at just above sole level. We fitted another computer fan at the vent and installed ducting - so that the compressor fan and our installed fan worked at either end of the ducting.

We also installed ducting from the anchor locker into the space where the compressor was fitted, so taking basically the coolest air we can find direct to the compressor.

It is impossible to tell if it makes any difference - but we did, what we thought was, our best.

The computer fan we installed draws 0.1 amp and is wired to cut in when the compressor is 'on'. As long as we are at anchor the anchor locker 'points' into the wind, flow can be increased by opening the locker lid.

Jonathan

 

[vyv_cox]

Trying not to repeat what others have said, perhaps a summary? The heat exchanger works most efficiently when bathed in the coolest air available. This is almost always obtained from the hull in contact with the sea, maybe the bilge but maybe somewhere else on the hull. Air should rise from this point but needs somewhere for the warm air to exit after passing the heat exchanger. This may mean either recirculation if there is a clear path without interference from gear in lockers, or out of the boat if this can be arranged. Many people have found that simple ducting can help to maximise the airflow and, as mentioned by several posters, computer fans can help even more.

 

[KellysEye]

We never had a problem with the fridge temperature in the Caribbean where the air and water temperature were both 28C. It struck me that the key to the temperature is the insulation around the fridge.

 

[J Neeves]

Kelly - I think you are more than correct. Most of us can only invest in common production yachts with minimalist attention to galley efficiency. Consequently and sadly some of us are owners of inadequate fridges and are unable to discard our current unit for one with adequate insulation nor are we easily able to add further insulation. If a computer fan, often to be recycled, and that uses 0.1 of an amp, (and some ducting) makes a difference - its much cheaper than pulling the galley apart to enjoy your level of insulation and very much cheaper than a new yacht!

Another key to fridge efficiency is keeping the door closed - but that's not very practical (specially when the temperature is 28 degrees and the ice for the Bundy is in the fridge)

But even the most efficient fridge will still enjoy the benefit of extra and cool airflow.

Jonathan

 

[John_d_Smith]

Last summer in the Med my fridge could use 20ah during the night, i recon the compressor was running almost non stop. I fitted a computer fan behind the fridge and the just removing the air from the locker and the consumption dropped by more than half. This year i'm fitting one pushing air up from the bilge into the locker.

 

[Gwylan]

With all of the above.

We installed a computer, fan on a separate switch, this sucks cooler air from the bilges and blows it over the heat exchanger and drives the air out over the top of the fridge. With the separate switch we only have to use it when the ambient temp is high [ not often in the UK] and avoid the noise of another fan at night.

Keeping the fridge filled with stuff is good too. "Cold beer in cans is good for this dear".
Limiter on the circuit to prevent the fridge running the battery flat, dedicated battery with solar panel for the fridge helps. A bag of supermarket ice at the start of a trip and using a cool bag to transport cold stuff on supply runs from the supermarket also helps.

Loads cheaper and easier than taking the galley apart to try and put more insulation in.

 

[Norman_E]

The biggest issue with air cooled fridges is the ability get a good airflow over the heat exchanger using the coolest available air, and it is a fact that due to lack of space the compressor and heat exchanger are often crammed into small spaces with poor airflow. On my boat I have a large fridge with two cooling systems. One is the original Jeanneau standard air cooled system which has its own fan driving air through the heat exchanger, and the other is a water cooled system driving a large stainless steel cooling box full of gel which freezes. When on the hard only the air cooled unit can be used. I have found that very simple measures improve its efficiency a great deal. Firstly, cleaning all of the dust out of the heat exchanger, thus allowing the fan to blow a lot more air through it. Secondly, making bigger air holes in the cupboard that houses the unit, so that the fan can draw air in from the bilges and exhaust it into the cabin rather than just having to recycle the same heated air.

 

[vyv_cox]

Loads cheaper and easier than taking the galley apart to try and put more insulation in.

Exactly. Our boat is equipped with a top loading 'cool' box that has a very limited amount of insulation surrounding it. Increasing the thickness of insulation would be an almost impossible job, the box being so deeply embedded in the construction of the boat. Apart from that we find a top loader to be far less convenient than a conventional front opening refrigerator. We are perfectly happy to accept the slight increase in electrical consumption that a poorly insulated Waeco 65 litre fridge offers in return for the convenience of opening the door to take a beer out.

Having said that, the benefit of a water cooled heat exchanger instead of air cooled has been massive.

 

[William_H]

You need to cool down the heat exchanger and not the compressor itself. Therefore i think it will be sufficient to install the fans into the cupboard wall in order to extract the hot air.
Christoph

I would tend to disagree here. The compressor itself will get hot because that is where the gas is compressed and is first in the line of hot gas. I think the compressor is just as important as the condensor (heat exchanger) in the cooling of the gas process. Of course often they are both together anyway but don't neglect cooling the compressor. olewill

 

[geem]

I would tend to disagree here. The compressor itself will get hot because that is where the gas is compressed and is first in the line of hot gas. I think the compressor is just as important as the condensor (heat exchanger) in the cooling of the gas process. Of course often they are both together anyway but don't neglect cooling the compressor. olewill

Cooling the compressor will have negligible impact on fridge efficiency. Achieving good airflow at the coldes possible temperature over the condenser, during summer will effect efficiency. Forgetting fridge tub insulation, refrigeration efficiency is directly related to condensing temperature.

 

[J Neeves]

Many condensers and compressors are 'in line' cool one you and you cool the other. In fact given they are all bolted together in line I find it difficult to see how you can cool one and not cool the other.

Jonathan

 

[geem]

Many condensers and compressors are 'in line' cool one you and you cool the other. In fact given they are all bolted together in line I find it difficult to see how you can cool one and not cool the other.

Jonathan

Jonathan, I don't disagree. I was just making the point that it's the condenser that is the target not the compressor. My air cooled condenser has a fan bolted across the face of the coil. The whole installation is mounted in a chimney that takes air from the bilges. The compressor gets some cool air but it doesn't need a fan on it when there is one directly on the condenser. If the compressor/condenser unit is mounted in a cupboard with poor passive ventilation then mechanically cooling the space for condenser/compressor will off course improve efficiency.

 

[theoldsalt]

I just love all thse discussions regarding refrigerators on a boat in the UK. I have never used one and very rarely felt the need for one. The sea temperature around the UK is low enough to adequately cool drinks (in a water filled bucket, on a lanyard over the side or in the bilge). I always overnight in harbour so shop daily for fresh food. Am I alone?

Getting out on the boat is to get away from most home comforts including the TV; but that's another topic.

 

[Colvic Watson]

I just love all thse discussions regarding refrigerators on a boat in the UK. I have never used one and very rarely felt the need for one. The sea temperature around the UK is low enough to adequately cool drinks (in a water filled bucket, on a lanyard over the side or in the bilge). I always overnight in harbour so shop daily for fresh food. Am I alone?

Getting out on the boat is to get away from most home comforts including the TV; but that's another topic.

For day and weekend sailing you are right, a standard coolbox is fine. But we dislike overnighting in harbour on a cruise and anchor/moor whenever possible. A trudge ashore to hunt down a shop that sells fresh meat and stuff is a pain. Things like fridges extend our cruising. But the real joy of a fridge is icy cold drinks on a hot day, not tepid ones from a bucket - and I never knew how good ice was until we had a fridge that could make it on the boat,

 

[vyv_cox]

I just love all thse discussions regarding refrigerators on a boat in the UK. I have never used one and very rarely felt the need for one. The sea temperature around the UK is low enough to adequately cool drinks (in a water filled bucket, on a lanyard over the side or in the bilge). I always overnight in harbour so shop daily for fresh food. Am I alone?

Not all of us keep our boats in UK. For us a fridge is just about essential if fresh food, milk, etc is not to be bought every day. It is quite common for the temperature inside the boat to be in the mid to upper 30s and the sea temperature in the high 20s. We are able to anchor in quiet bays for a week or more without the need to shop.

 

[J Neeves]

geem, I was not being critical - we seemed to be over-analysing!

Oddly - since living in Oz I have learnt to dislike ice cold tasteless beer and recall fondly drinking, relatively, warm Old Peculiar at Masham. I'm almost definitely at variance with a majority - but I also dislike iced Guinness and its criminal to drink single malts with ice.

But if you want to 'get away' from retail outlets, for even a few days (let alone weeks) and enjoy fresh meat and store freshly caught fish (and lobster) then sadly the burden of the fridge is essential and anything that makes the unit more effective needs to be aired and discussed. But a white wine chilled in the sea off Tasmania (16 degrees) is perfectly acceptable (and its stupid keeping it in valuable fridge space). Once you have ducted the coolest air you can find in and the warm air out, added an extra or a couple of extra fans - fridge efficiency is all about planning (and maximising your green energy input.)

Jonathan

PS Another sad fact, the more green energy you 'make' the more energy you seem to use - Parkinson has a lot to answer for.