Danfoss BD35/Frigoboat problem

[hoaga]

Hey Matt!
We're you the fellow we were in contact with when the end fitting on one of our hydraulic steering rams broke while we were on passage from Vanuatu to Indonesia?

Thanks for the idea about Oze Fridge. They look like great units. But do they only sell holding plate versions?

I prefer an evaporator plate in our dedicated refrigerator.

[Richard Kollmann]

In live aboard boat applications water cooled Danfoss BD compressor systems seem to operate well for 5 years before major troubles occur. Poor compressor cooling and the need to discharge stray low voltage are the main reasons for replacing the complete water cooled systems. The main reason for customer dissatisfaction with water cooled Danfoss compressor systems is the cost to analyze trouble and the out of service time involved is extensive. Water cooled units are the most unfriendly and most expensive units to maintain.

When a Fan cooled condensing unit is used to replace a Keel cooler unit system there may be an additional 3 amp-hrs per day required to equal energy performance of keel cooler units.. Fan cooled units when correctly installed do not seem to have a life limit if they do it might be twenty five years. The fan itself in a live aboard boat is known to fail in 6 to 9 years. Aluminum evaporators have a service life on any of these small units of around 12 years.

Using creative advertising and Rube Goldberg add on gadgets may sell more units but only until serious boaters catch on.

[Celestialsailor]

Originally Posted by senormechanico

I agree with Jedi.

Way too many boaters have no idea how little it takes to damage underwater metals.
It works great when you know what you're doing, but is a giant hole in the wallet when you don't.

This is true and hence why there are failures in these units. Also, because of the water pump and the fact that in the tropics, the cooling water is much warmer I think there is little gain, if any, over an air cooled model.

[s/v Jedi]

Originally Posted by Celestialsailor

This is true and hence why there are failures in these units. Also, because of the water pump and the fact that in the tropics, the cooling water is much warmer I think there is little gain, if any, over an air cooled model.

That may sound logical but I can assure you that it isn't. The air is probably the exact same temperature as the water in the tropics. If it's not, then the air is warmer than the water. So, temperature wise, water will be better. Next is the thermal conductivity of both, where water is 20 times as conductive as air (List of thermal conductivities - Wikipedia, the free encyclopedia) and you'll get the idea why water will outperform air. And then we didn't address the power requirement for the fan yet, which further decreases the efficiency. Last but not least is the heat load inside the boat when in the tropics. It simply makes it unbearable.

[Boatguy30]

A fan uses what 1/20th the energy of a water pump? It been week proven that the BD 35 and BD 50 work best air cooled. Pop a hatch if it gets out the BTU input into a large cabin is quite small.

Interestingly Richard Knollman just posted a very similar post to this on his forum. He reckons anything beyond a simple fan cooled unit is just marketing hype and added profit. To each his own I suppose. I'm installing an air cooled unit in a third boat of mine this month. nothing but success so far in tropical conditio

[colemj]

I think some of you are confusing water cooled systems with keel cooler systems. They are not the same type nor operate the same way.

Mark

[s/v Jedi]

Originally Posted by Boatguy30

A fan uses what 1/20th the energy of a water pump? It been week proven that the BD 35 and BD 50 work best air cooled. Pop a hatch if it gets out the BTU input into a large cabin is quite small.

Interestingly Richard Knollman just posted a very similar post to this on his forum. He reckons anything beyond a simple fan cooled unit is just marketing hype and added profit. To each his own I suppose. I'm installing an air cooled unit in a third boat of mine this month. nothing but success so far in tropical conditio

A keel cooler does not use a pump. Richard Kollman does not live aboard in the tropics

[senormechanico]

"Just pop a hatch" isn't always a good idea.
Jejenes, a.k.a. Flying Teeth is but one reason.

[Richard Kollmann]

Interesting debate and yes water is a much better conductor of heat. When a refrigeration process like this small unit depends on a controlled warm temperature range to control refrigerant flow it is easier to control air as a cooling medium inside a boat than water on a 1/20 hp unit. These capillary tube refrigeration units depend on narrow pressure ranges on both the high and low pressure sides of the refrigerant flow process. If one of these units is to operate efficiently high pressure liquid must be warm enough to maintain 105 to 115 psi pressure on the high side and this depends on condenser size and cooling medium’s efficiency. On capillary tube systems near perfect liquid pressure can be maintained by adjusting refrigerant volume up to raise pressure or reducing volume to lower liquid pressure, although it is better to have control over cooling mediums temperature. This is why Frigoboat’s refrigerant instructions differ from all others by not providing refrigerant quantity by weight.


Recently on this forum I believe it was recommended to solve inadequate keel cooler problems and excessive compressor heat problems was to add Frigoboats fan cooled condenser in series with keel cooler.

Many comments are expressed about the heat added by a fan cooled BD compressor to a boats living quarters in 24 hours. The heat disposed of in cabin is equal to a burning candle
or one extra person onboard. When refrigerator is kept cold most small unit’s 300 milliamp condenser cooling fan will run less than 12 hours per day consuming 3.6 amp-hrs per day.

Fortunately most boater’s refrigeration units perform well enough to satisfy them. Component reliability problems are far fewer when a simple air cooled small refrigeration unit is selected.

[senormechanico]

In the tropics, you can feel body heat of another person from a couple feet away.

[darylat8750]

"just pop a hatch" to me indicates a poorly installed air cooled unit. My compressors are mounted so they expel the heated air through large, short ducts to the outside of the boat. No heat load to the interior and most of the noise seems to follow the vented air to the exterior also. 5 years (3 in the tropics) so far so good..........

[hoaga]

I'll be venting our hot air outside. Our boat has a very convenient way to do it.

Thanks for the info on the drawbacks of water cooling. I'll skip this...

3 amp hours per day (or even considerably more) is not an issue on our boat. As long as the fridge is cold enough, powering a fan won't be an issue.

so air cooled it is....

Now, to arrange the !@$#@$! haul out to remove the keel cooler.

Fortunately the weather is lovely, and the beer is cheap here .

[Neptune's Gear]

Hi Moonos, you need a min of about 20ltrs. 40 is better. No, you cannot put salt water through it - it does not have anodes etc. If the water runs out, the unit will automatically switch to Air cooling, until there is water available again. Normally, while using water, it also runs the air fan, just to keep the electronics cool. Happy to discuss via email (matt@neptunes-gear.com) if you want, rather than hi-jack this thread - or I could make another thread?

Cheers
Matt

[SV THIRD DAY]

Originally Posted by senormechanico

Way too many boaters have no idea how little it takes to damage underwater metals. It works great when you know what you're doing, but is a giant hole in the wallet when you don't.

EXACTLY....so the question then becomes:

Can you educate boat owners on the dangers how to test for it, find it, and solve it all while telling them that if they screw up they could lose their refrigeration system mid-cruise and have their wife kick their ass and want to go home?

Or with everything else a boat owner has to learn, deal with, fix and maintain wouldn't it seem to be an easier thing to just eliminate the headaches and risks posed by water cooled systems and scratch that potential problem from the list?

For every post about a failed keel cooler or water cooled condenser found on the Cruising Forum, how many reports have been made about air cooled condensers failing? Does that tell us something about the reliability of air cooled systems over water cooled or are all of the water cooled system failure just Cruiser or Install errors? Are water cooled systems really that harder to install than air cooled systems that the owner/installer needs to be more of an expert? What if anything can we take away from failure reports? If system A is said to be better than system B but system A has a higher failure rate (for whatever reason) can we really call system A better?

Look, we all tend to love, defend and tout the systems we were smart enough to research and pick over the other boob that picked the "wrong gear" for their boat. It's human nature and why it's also difficult to get anything more than brand loyalty feedback when people say "I love my XYZ" system without data. Add in the difficulty that every boat and refrigeration system use is different (box volume, insulation quality , Box temp set points, ambient temps, number of crew, number of openings per day) and it really takes folks like Richard that have taken the time to test systems side-by-side and have years of refrigeration experience to truly offer an authoritative comparison between systems.

[Neptune's Gear]

Originally Posted by hoaga

Hey Matt!
We're you the fellow we were in contact with when the end fitting on one of our hydraulic steering rams broke while we were on passage from Vanuatu to Indonesia?

Thanks for the idea about Oze Fridge. They look like great units. But do they only sell holding plate versions?

I prefer an evaporator plate in our dedicated refrigerator.

Yep, that's Me!!

Yes, holding plates only. Evaporator plates need to run more often...
Cheers
Matt