water or air

[douglas_family]

we have a water cooled fridge, it seems to work ok but the water pump is very noisy! We could change over to an air cooled version.

opinions on which system is better appreciated obviuosly power consumption is a major consideration. i assume these will be similar.

Air cooled would vent hot air, how much will it make the boat to hot in summer?

thanks

 

[michael_w]

Keel cooled is a good solution. Simple, easy to fit, reasonable on the power consumed.

I'm planning on replacing my air cooled one next year.

 

[scarlett]

I am not recommending air cooled but you won't notice the hot air from the fridge as it will be too hot anyway!

 

[jennymckay]

Our water cooled fridge is very quiet, with no noise at all from the pump. It has a holding plate which makes it more efficient than our air cooled fridge. Both pull around 6 amps on 12 volt when running but, because of the holding plate, the water cooled runs for about a quarter of the time.
We also turn the thermostat to full freeze when running or battery charging, then back to normal so the water cooled compressor doesn't kick in again for a few hours.
Would definitely recommend water cooled, just get a quiet running pump.
(Reason for 2 fridges is because we do day charter in summer so we need room for all that beer!)

 

[douglas_family]

sounds like changing the pump maybe a good solution! recommendations for a quiet running pump?

 

[ccscott49]

Noisy pump? Need a new pump, should be all but silent.

 

[vyv_cox]

Yes, I agree. Our domestic water pump had been noisy for years and we thought it was just the way they were. Finally the noise seemed to be increasing so we replaced the pump, with the result that it is now almost completely silent.

Our refrigerator uses a normal domestic pump to pass seawater through the refrigerator condenser. It is very quiet. The fridge is a normal Waeco 80 litre one but with a water-cooled Danfoss unit instead of the standard air cooled one. It has transformed our battery management in the Med, running for about 25% of the time in ambient temperatures of 40 C plus.

 

[Jonny_H]

Sounds like a new pump is in order.

If you decide to change the fridge, here are some thoughts that we went through (new unit fitted last weekend!):

3 options were on the cards

1) Frigoboat water cooled - this uses an evaporator plate and a bronze underwater cooling plate. Good idea, but average power consumption was slightly higher than other options, and it involved more holes in the hull (which we are trying to avoid). Also, if the plate gets growth it becomes very inefficient.

2) Isotherm evaporator plate with an SP unit. This is a seacock replacement for the galley waste that uses water passing through the seacock to cool. Evaporator plate meant slightly higher power usage again. We had heard of issues with growth in the seacock causing problems.

3) Isotherm air cooled with ASU. The ASU unit freezes down with the engine running and is designed to work harder to match solar / wind generator output. The overall power consumption is therefore less, and the compressor doesn't run as much.

They do an ASU with the water cooler but its much more expensive. When it came to a choice between options 2 and 3 Isotherm recommended option 3. We've put the compressor in the cupboard under the sink (fairly spacious - and has bilge access for cool air).

Jonny

 

[vyv_cox]

<<< 3) Isotherm air cooled with ASU. The ASU unit freezes down with the engine running and is designed to work harder to match solar / wind generator output. The overall power consumption is therefore less, and the compressor doesn't run as much. >>>

This all sounds good in UK, but once a liveaboard in warmer climes the theory starts to break down.

1. We aim to run our engine as little as possible and preferably not at all. We sometimes remain in the same place, either anchored or stern-to, for up to 4 or 5 days. Running the engine at anchor is noisy, annoying and not good for the engine.

2. Air inside the boat remains at 35 - 40 degrees for days and nights on end. We have seen this throughout Corsica, Sardinia, Italy and Greece in July and August, and even in September and October occasionally. A very large duct is needed to pass air over the cooling coil, taking in air somewhere near sea level and discharging it higher, which is quite difficult to arrange on a yacht. I know of owners whose air-cooled fridge runs virtually full time under summer conditions.

3. Our sea-water cooled system was effectively home built, although my son has specialist knowledge in the subject. The Danfoss water cooled unit is a straight replacement for the air cooled one. The supply water is T-ed into the engine supply, so no extra skin fitting. The discharge goes through a small fitting above sea level. Total cost was little more than the standard refrigerator plus a secondhand pump. It is very efficient and only runs about 25% of the time.

 

[jeremyshaw]

As previous posts have suggested, a lot depends on the environment in which you are operating.

If your ambient water temperature is low, then water cooled is much more efficient.

If it is high, the difference is a lot less. For example in the Caribbean where water temp and air temp are closer together.

Water has the disadvantage of using more power (pump) than air (fan), but if the temperature gradient is high this is cancelled out.

Water also has the disadvantage of requiring more maintenance - filter issues and occasional descaling.

One good solution is to use the ship's fresh water storage tank as the heat sink. That way you get the efficiency of water without the problems of sea water transfer. And many of us would be quite happy to have our fresh water a degree or two higher. Keel coolers also achieve a similar result.

In the Caribbean we have switched from water to air cooled, but in the Med, on a year round basis, water cooled is probably more efficient.

Pump noise is of course also influenced by location, mounting, vibration etc.

 

[mocruising]

We had exactly the same problem as you and solved it last season. Our water cooling pump that cools both the fridge and freezer was very noisy. It was a 24 V Par Max 4. Kept me awake at night. We changed it for a 12 Frigoboat and the problen was solved. Never hear it now with both fridge and freezer on full blast in the height of the summer.

 

[douglas_family]

Thanks for all the useful information. I think we will try changing the pump to see if that improves the situation. The noise is annoying but as we sleep in the other hull doesn't bother us in the night so i dont want to undertake any major work like using the fresh water tank for cooling although it sounds like a great solution. We are in the med at the momment and intend to spend most of our time on anchor, and we dont want to be running the engines!

Thanks

 

[wanderlust]

With all due respect. You advise is now out of date. This made sense for the technolgy that was around about 7 years ago. The new breed of water cooled units use a keel cooler with no pump. This system is far superior to the alternative water cooled systems about. You can expect a 100 litre fridge with 4 inches of polyeuranthane insulation to use less than 2 amps of power. In the uk waters this drops to more like 1 amp. We used this set up in the Caribbean where the water temperature was up to 28 degrees. No other system can compare with this for low energy consumption. There is no maintenance on this kind of water cooled system other than the occational scrub of the bronze keel cooler.
Even with one third of the fridge space converted to freezer (set at minus 12 deg C) the unit was run on its lowest comressor speed. The low speed uses 2.5 amps when running. The compressor didnt run all the time so still very efficient!

 

[jeremyshaw]

"With all due respect. You advise is now out of date. This made sense for the technolgy that was around about 7 years ago. The new breed of water cooled units use a keel cooler with no pump. This system is far superior to the alternative water cooled systems about."

That's interesting. I had been told that keel coolers were not as efficient as pumped systems in warm waters as you don't get the same throughput. But you obviously had great efficiency with your system. I'm planning to replace my holding plate system so I'll check it out some more.

 

[jennymckay]

Our water cooled fridge is an Isotherm with ASU, but this is neither use nor ornament - we run it on manual all the time as both our 240v AC battery charger and our TWC-controlled alternator put out more than 13.5 volts (typically 14.4 volts for periods), and the ASU just starts blinking and the fridge is not being cooled.
As with everything else, keep it simple.

 

[Jonny_H]

Sounds like your ASU is faulty, per the instructions the holding plate should ramp up at anything over 13.2 volts and should have no maximum. When I emailed Marathon Leisure (Isotherm dealers) they said:

The Isotherm ASU senses voltage, 13.2V kick in and 12.8v drop out. Above 13.2 it runs the compressor hard to freeze the plate, and it stops when a) plate is frozen, b) voltage drops below 12.8v. When the plate is frozen it doesn't run - other than to keep the plate topped up if voltage is over 13.2v.

If your ASU doesn't function at 14.4 volts I would suggest it isn't functioning properly as this is what it is designed to do.

Jonny