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Old 05-04-2012, 19:45   #1
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Fridge Reduce Amps Consuption

Trying to find a solution for the high amps usage of my fridge and freezer i found the following FrigoBoat water cooled condensers on the net, they claim a reduction of minimal 20% of the electricity usage. Does any one have experience with one off these?

Sounds great and easy to install.

Link: FrigoBooat Water Cooled Condensers

Regards, ceesH
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Old 05-04-2012, 21:09   #2
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Re: Fridge reduce amps consuption

After looking at Frigoboat, I installed a Vitrifrigio.
Basically the same unit but a heck of a lot cheaper (at least from the respective dealers in Seattle)
One happy camper.
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Old 05-04-2012, 21:16   #3
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Re: Fridge reduce amps consuption

In theory, all else being equal, it would depend on whether the water is cooler than the air. It often is.

I would suspect that you must take some care to keep the unit clean of any growth or slime that would act as an unwanted insulator .... same for dust on the air cooled condensers.

It has some drag while sailing. Air cooling requires power for a fan. Air cooling often adds unwanted heat to the cabin.

I think it's a good idea.
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Old 05-04-2012, 22:16   #4
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Re: Fridge reduce amps consuption

we have a 6 cubic foot fridge, but found we only needed half that much. filled the bottom with removable insulation boards. cut the amperage draw way down....
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Old 05-04-2012, 22:58   #5
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Re: Fridge reduce amps consuption

Quote:
Originally Posted by daddle View Post
In theory, all else being equal, it would depend on whether the water is cooler than the air. It often is.
Water is a MUCH better conductor of heat - water cooled units have better heat transfer adn are therefore much more efficient AND the heat is removed to the exterior of the boat.
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Old 06-04-2012, 01:55   #6
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Another hole in the boat? Is it that much more efficient?
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Old 06-04-2012, 06:39   #7
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Re: Fridge reduce amps consuption

I have a Frigoboat system. It is very efficient, particularly with its SSC (Smart Speed Control) which matches the compressor speed to the cooling load.

The only issue in installing is to use big wire, preferably 10 gauge but at least 12 gauge to wire the compressor to the DC panel. The system doesn't like voltage drops.

David
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Old 06-04-2012, 07:29   #8
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Re: Fridge reduce amps consuption

Hi - we have a small air cooled Frigoboat unit too and have used it for several years - so lots of experience. And same problems....

What we did to reduce amperage use was:

1. Remove the ice cube trays and put a plastic bag filled with water into the condenser unit. This froze and basically turned into a 10-lb block of ice - which really kept our small icebox very cold all the time - and reduced the running time/amperage use.

2. Removed the small fan assemble and wired in a 6" Hella fan to blow cooling air over the entire assembly. The Hella fan draws the same amperage as the tiny factory fan assembly but moves a much larger amount of air.

We have since replaced the first unit with a slightly different Frigoboat unit (one that is laid out in a horizontal design vs. our original "stacked" design) and opened up the area for even better airflow.

Instead of using a plastic bag filled with water, we now have filled the icecube tray area with the smaller size "blue ice" bricks.

The first unit we used for the 6-years, including 2 while we were in the Carribbean. It was always left on. We eventually bought a Wind Bugger to help keep the batteries charged and found that with the modifcations mentioned above and with the Wind Bugger producing power were able to go 60 to 90-days at a time without having to run the engine.

We really thought about the water cooled option when we replaced the old unit - water temperature is always going to be colder than air temperature in the tropics. Supposedly you do not need a pump to circulate the coolant (the motion the the vessel is enough) but I think that you will still have quite a bit of heat coming from the compressor - and may still need a fan to help with cooling.
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Old 06-04-2012, 07:47   #9
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Richard kahlmann argued quite strongly against water cooled danfoss units.

Dave
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Old 06-04-2012, 08:24   #10
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Re: Fridge reduce amps consuption

Quote:
Originally Posted by goboatingnow View Post
Richard kahlmann Kollmann argued quite strongly against water cooled danfoss units.
Dave
Post #5 ➥ Air-Cooled Compressor vs Air/Water-Cooled Compressor
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Old 06-04-2012, 08:26   #11
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Re: Fridge reduce amps consuption

Quote:
Originally Posted by goboatingnow View Post
Richard kahlmann argued quite strongly against water cooled danfoss units.

Dave
Why??? Link please...

You are more fast then I, :-) Thanks CordMay

CeesH
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Old 06-04-2012, 08:28   #12
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Re: Fridge reduce amps consuption

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Originally Posted by foolishsailor View Post
Another hole in the boat? Is it that much more efficient?
not necessarily. A powerboat friend ran the fridge cooling system through his 500 gal fuel tank.
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Old 06-04-2012, 08:40   #13
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Re: Fridge reduce amps consuption

Quote:
Originally Posted by goboatingnow View Post
Richard kahlmann argued quite strongly against water cooled danfoss units.

Dave
A lot off bla bla bla, and not supported with figures.

1#. this system doesn't work with a seawater circulation pump.
2#. I think of connecting the keelcooler in serie with the existing aircooler.
3#. eliminating 2 heaters from the interior in a tropical climate is not that bad.

CeesH
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Old 06-04-2012, 09:19   #14
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Re: Fridge reduce amps consuption

Richard K is quite frankly one of very few experts in marine refridgeration and has written several very good boods and conducted numerous tests of different system components and has been at it for something like 30 years. If you are not seeing the specific data you are interested in I suggest contacting him directly as he is a wealth of knowledge and is willing to share it.

I am going with a frigoboat unit on my new fridge and intend to start with aircooled only and possible add a keel cooler down the road. This is very easy to do with frigoboat with one consideration. The compressor must be within 5' of the keel cooler as you can not add extensions to this freon circuit. The circuit that runs from the compressor to the evaporator in your box can be extended so compressor location is key.

Also regardless of whose 12VDC compressor you use the degree of effeciency is most impacted by box construction and insulation. If the insualtion is inadequate, contaminated with moisture, or if the box lid has air leaks you will not get significantly better energy consumption with any unit air or water cooled. All the units out there pretty much use the same Danfoss BD compressors. There are variations on the controls, evaporators, and consening units. I have chosen to rebuild my box and upped the insualtion to 4" min with 6" on the bottom and hull sides.

As I mentioned I am going with an air cooled frigoboat unit but I have ducting that will allow for the heat to be directed out of the boat. This is a big consideration for air cooled units.
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Old 06-04-2012, 10:10   #15
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Re: Fridge reduce amps consuption


For any boat’s refrigeration system to be energy efficient condenser’s sub cooling must not lower system high liquid pressure below its efficient high pressure range. Btu capacity and design of a refrigeration system will dictate which condenser cooling medium air or water is going to produce optimum performance. The main difference between a stationary refrigeration system and a smaller mobile boat refrigeration unit is how to control condenser’ sub-cooling, so as to keep high pressure in an efficient range. Refrigeration systems using Danfoss BD35 or BD50 compressors with a condensing unit’s Btu capacity of less than 1,000 Btu are more SCOP reliable when condensing gas temperatures produce high pressure saturated liquid pressures from 105 to 125 psi. With in this ideal operating pressure range pressures will vary as condenser cooling and evaporator temperatures change. Larger water cooled boat refrigeration systems to be efficient use either a hot gas bypass valve to control high pressure by raising high liquid pressure or a seawater bypass around water cooled condenser.

Superheat is the other side of equation that determines how much heat is absorbed and where in low pressure side of system this transfer occurs. Danfoss specs indicate optimum Compressor COP is reached with a condenser gas temperature of 130 F, (54 C). The third variable affecting sub-cooling and superheat is volume of refrigerant. Change condenser cooling mediums design temperature range and a performance unbalance occurs between Sub-cooling, Superheat and refrigerant charge.

When someone asks me about water cooling instead of air cooling one of these systems with a Danfoss BD compressor I recommend against it because in many cases it produces an unreliable and maybe less efficient system than a well designed air cooled system.

(COP) Coefficient Of Performance
(SCOP) System Coefficient Of Performance
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