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Old 25-02-2014, 05:10   #61
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Re: Danfoss BD35/Frigoboat problem

There was a cruiser in the San Blas building some units with a copper tube box instead of an aluminum box and using an expansion valve instead of cap tube.

He claimed the highest efficency of all, but clearly didn't have the marketing hype. He had a long multipage write up I sent to Richard about 8 years ago. Maybe Richard still has a copy.

I'm glad some are happy with the keel cooler. There seem to be many agreements against them good to have the additional info.
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Old 25-02-2014, 06:46   #62
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Re: Danfoss BD35/Frigoboat problem

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Originally Posted by Richard Kollmann View Post
After designing, manufacturing, and testing more than 200 holding plates it is my opinion standard evaporators provide better box temperature and better energy performance than holding plates.
Does that hold true for a 5cu ft. freezer?
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Old 25-02-2014, 09:07   #63
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Re: Danfoss BD35/Frigoboat problem

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You guys take a commercial approach while I have the engineering approach. You completely ignore everything I write about how energy consumption is measured, orobably because you don't understand it. But that doesn't stop you from denying it using arguments about how well a manufacturer tested it. Right.
Not at all....
In the post I was addressing, you simply stated "engineering facts" about how a holding plate works that were wrong. The engineering mistakes were pointed out to prevent yet another internet cruiser rumor, but were aparently ignored, no problem at all. People can read the thread and decide for themselves.

As a scientist myself with a handfull of patents that paved the way for an early retirement and family cruise, I know that data and sound engineering is what pays the bills at the end of the day over marketing hype. The only thing left when the sales fluff and marketing hype is risnsed away by the hard testing ground of cruising reality is results. Data and results trump hype and BS in the long run and with 45 yrs in making marine refrigeration units...Technautics has a little of both.


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Old 25-02-2014, 13:10   #64
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Re: Danfoss BD35/Frigoboat problem

Come on Jedi, energy consumption is easy! I see it as;
How many amp/hrs required to obtain a set temp in the freezer for a set period.
Please explain to me how that is wrong? I never claimed to know everything about this - or even much! - further education is allways appreciated! :-)
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Old 25-02-2014, 13:28   #65
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Re: Danfoss BD35/Frigoboat problem

Does that hold true for a 5cu ft. freezer?


Jcapo, Actually Freezer holding plates are even less efficient than refrigerator plates because of Btu losses do to a very low temperature liquid phase change to a solid. Example given in earlier mentioned freezer plate with its eutectic point set to -22 Degree C ( -7.5 F) complete liquid phase change would take many hours of this small compressor's running time at 50% Btu capacity. Freezer holding Plates require large compressors to complete plate freezing in a short time at temperatures near 20 F degrees below eutectic freeze point, or alternative energy from shore power, wind, solar or water generators to supplement battery charge losses.
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Old 25-02-2014, 16:06   #66
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Re: Danfoss BD35/Frigoboat problem

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Originally Posted by senormechanico View Post
In the tropics, you can feel body heat of another person from a couple feet away.
Depending on who the body heat is...it's not always a bad thing...
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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?
Unfortunately, we are all part of the human condition. I don't care who they are. No mater how meticulous some cruisers are, they forget, they get sick. "Did I or did I not replace that zinc". "The diver said it was ok". On and on and on. As we all know the term KISS, really applies.

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Originally Posted by Neptune's Gear View Post
Actually, there are PLENTY of stories about air cooled units failing, or being inadequate in the tropics.


Many installs also end up running almost full time, and get turned off, due to the large power requirements.

The OZE fridge units have the advantages of both, as they can be both Air AND water cooled. BUT they use FRESH WATER- they don't consume it, just borrow it and return it slightly warmer. No anodes, no marine growth, no thru hull to suck in rubbish etc. Really simple, and really efficient. We have Ice cream on the equator - our freezer temp varies from -15c to -22c as that is the cycle I have set. Have a look on my web site below, and click on refrigeration if you are interested.

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Let me dispel those stories for you, since I'm out cruising, All but one failure I have seen were keel coolers. I'm not talking a lot. Maybe 3 in the last 6 month. There was one air cooled whose connector seals failed. It was the old "R12?" (pre 1995) coolant type. So I'm sure we are talking about a 20 year old unit.
My unit runs 17 minutes out of an hour because the box was properly insulated. So, less that 2 amps. per hour. It would not matter if it was a water cooled or air cooled unit if the box had 1" of cheesy Styrofoam insulation. I have 1" of Aerogel, 2" of Styro, then back-filled with 1"-2" pour foam depending on the hull to box. Close to R-30. After that there is little efficiency to gain. It was well in the 90's last week. I think that qualifies as hot. Much warmer in the boat of course.
As far as using a vessels fresh water to cool the refrigerant, I would imagine this heats it to an extent that might be distasteful as cool drinking water. Unless I'm misunderstanding something here.
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Originally Posted by Boatguy30 View Post
Whew 175 times a day! My Nova Kool freezer used to run 20 minutes every hour (roughly) air cooled in the tropics. Was running on the slowest RPM setting.
See post above. I'm having the same results
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Old 25-02-2014, 18:07   #67
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Re: Danfoss BD35/Frigoboat problem

Quote:
Originally Posted by Richard Kollmann View Post
Does that hold true for a 5cu ft. freezer?


Jcapo, Actually Freezer holding plates are even less efficient than refrigerator plates because of Btu losses do to a very low temperature liquid phase change to a solid. Example given in earlier mentioned freezer plate with its eutectic point set to -22 Degree C ( -7.5 F) complete liquid phase change would take many hours of this small compressor's running time at 50% Btu capacity. Freezer holding Plates require large compressors to complete plate freezing in a short time at temperatures near 20 F degrees below eutectic freeze point, or alternative energy from shore power, wind, solar or water generators to supplement battery charge losses.
I understand that. I have a 14 year old DIY 1/2hp DC Blissfield CE split system with Grunert plates that will need to be replaced maybe sooner than later. The decision will be to build a evaporator system or another holding plate system.
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Old 25-02-2014, 18:48   #68
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Re: Danfoss BD35/Frigoboat problem

Celestialsailor, while I'm not out cruising right now, you are not the only one with experience.
Air cooled units fail as well, same as every other mechanical and electrical system. Also units that are switched off due to excessive power consumption is, in my view, a failure of the system - it is not doing what it should be. I've seen this quite a bit.

Out of the 105 Boats doing Sail Indonesia in 2010, only about 10 had refrigeration capable of keeping icecream on the equator without a genset. We did.

I am certainly not saying Air cooled units don't work. They can.

The whole idea of refrigeration is to remove heat from a box. Water is more efficient as a heat sink than air. It can be done with either, but efficiency and therefore economy of electrical consumption is important to most cruisers. Of course people are fee to choose, as you have.
Oh yeah, by the way, in my install, the freshwater used does not noticeably warm up, but I use a pretty decent size tank (about 250ltrs when full), and that tank is built in, so it guess it loses it's heat thru the hull. It does not taint the taste of the water in any way. In the tropics, water is too warm to be nice to drink out of the tap anyway - thats what the fridge is for!
Happy sailing! :-)
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Old 25-02-2014, 20:10   #69
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Re: Danfoss BD35/Frigoboat problem

s/v third day - a question. not trying to start a fight or a rant here. just a question.

i looked at your cool blue webpage. the system appears to be the typical danfoss unit with compressor, control module, fan, etc. there is a holding plate. there is tubing to connect the two. so what makes it cost $2950?

a similar adler barbour unit with evaporator costs less than half that, iirc.

remember, i'm not getting into the hot discussion presently going on; would just like to know what makes the cool blue so expensive....
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Old 25-02-2014, 21:07   #70
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Re: Danfoss BD35/Frigoboat problem

Quote:
Originally Posted by Neptune's Gear View Post
Celestialsailor, while I'm not out cruising right now, you are not the only one with experience.
Air cooled units fail as well, same as every other mechanical and electrical system. Also units that are switched off due to excessive power consumption is, in my view, a failure of the system - it is not doing what it should be. I've seen this quite a bit.

Out of the 105 Boats doing Sail Indonesia in 2010, only about 10 had refrigeration capable of keeping icecream on the equator without a genset. We did.

I am certainly not saying Air cooled units don't work. They can.

The whole idea of refrigeration is to remove heat from a box. Water is more efficient as a heat sink than air. It can be done with either, but efficiency and therefore economy of electrical consumption is important to most cruisers. Of course people are fee to choose, as you have.
Oh yeah, by the way, in my install, the freshwater used does not noticeably warm up, but I use a pretty decent size tank (about 250ltrs when full), and that tank is built in, so it guess it loses it's heat thru the hull. It does not taint the taste of the water in any way. In the tropics, water is too warm to be nice to drink out of the tap anyway - thats what the fridge is for!
Happy sailing! :-)
Matt
I'm just stating what I've seen. But to say that "Actually, there are PLENTY of stories about air cooled units failing, or being inadequate in the tropics.
Many installs also end up running almost full time, and get turned off, due to the large power requirements".
Is not a fair statement to the unit but rather the insulation of the box.
I do appreciate your input on the water cooling in the tank against the hull. That would work for me also as I have a F/G water tank integral to the hull. But...many boats do not have that. More likely 2@ 100 liter tanks. Ironically I suppose you could cool drinking water in the fridge, causing further inefficiency.
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Old 25-02-2014, 21:39   #71
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Re: Danfoss BD35/Frigoboat problem

yep, I have a lot of water. The fridge system uses the smaller water tank. We have 800ltrs in total - no watermaker. Yes, the fridge system must be considered as a whole system, cabinet design, insulation etc.. much energy can be wasted, even (especially?) in production designs, due to holes in, and poor insulation - thickness and quality.
to say putting water in the fridge so you can have a cold drink is inefficient - what,therefore anything we add to the fridge is inefficient? The whole point is so we can cool things down!
Anyway, I've said enough about this. I'll respond to specific questions, thats all.
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Old 25-02-2014, 23:35   #72
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Re: Danfoss BD35/Frigoboat problem

Yes...but the system is using the water to cool the refrigerant down and then spending energy to reverse it by cooling the water down. No need to respond, we're just discussing different philosophy's.
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Old 26-02-2014, 05:17   #73
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Re: Danfoss BD35/Frigoboat problem

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s/v third day - a question. not trying to start a fight or a rant here. just a question.

i looked at your cool blue webpage. the system appears to be the typical danfoss unit with compressor, control module, fan, etc. there is a holding plate. there is tubing to connect the two. so what makes it cost $2950?

a similar adler barbour unit with evaporator costs less than half that, iirc.

remember, i'm not getting into the hot discussion presently going on; would just like to know what makes the cool blue so expensive....
In 2003 I was putting in a system in my first cruising boat. I did all the calculation, btu leak, square footage surface area, cubic feet, etc, etc.

I was going to buy the cool blue from West Marine as my wife worked there. I rang up Technautics and he tried to convince me the unit he would sell me direct would be 20% more efficient than the apparently identical unit he was selling to West Marine.

Beyond this, his efficiency claims were far beyond what Danfoss published as the compressor being capable of.

So in business since 1968? Guess he's got income from some other sources to keep afloat.
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Old 26-02-2014, 07:09   #74
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Re: Danfoss BD35/Frigoboat problem

Quote:
Originally Posted by Neptune's Gear View Post
Celestialsailor, while I'm not out cruising right now, you are not the only one with experience.
Air cooled units fail as well, same as every other mechanical and electrical system. Also units that are switched off due to excessive power consumption is, in my view, a failure of the system - it is not doing what it should be. I've seen this quite a bit.

Out of the 105 Boats doing Sail Indonesia in 2010, only about 10 had refrigeration capable of keeping icecream on the equator without a genset. We did.

I am certainly not saying Air cooled units don't work. They can.

The whole idea of refrigeration is to remove heat from a box. Water is more efficient as a heat sink than air. It can be done with either, but efficiency and therefore economy of electrical consumption is important to most cruisers. Of course people are fee to choose, as you have.
Oh yeah, by the way, in my install, the freshwater used does not noticeably warm up, but I use a pretty decent size tank (about 250ltrs when full), and that tank is built in, so it guess it loses it's heat thru the hull. It does not taint the taste of the water in any way. In the tropics, water is too warm to be nice to drink out of the tap anyway - thats what the fridge is for!
Happy sailing! :-)
Matt
None of this makes any sense in terms of water-cooled vs. air-cooled.

If one had a perfectly insulated box, one could simply put their ice cream in it without any refrigeration system at all. With a slightly leaky box, one could add an ice cube to help. With a typical boat box, one needs to use a lot of energy to keep it cold - strangely enough, this "cooling" energy is proportional to the "heat energy" that is added to the leaky box. Neither air-cooled or water-cooled choices in compressors have anything to do with it (unless the installation is poor). That is just basic thermodynamics.

The efficiency of the heat sink in these small systems has almost no effect because the system does not produce enough heat to overwhelm either of the choices. This is not a case of "the more heat you can remove from the system, the better". These systems operate in a very specific heat differential range - and that range is relatively easy to maintain.

Unless the air-cooled compressor is kept in a small box in an engine room with no air circulation, it will always be sufficient to remove the exact amount of heat necessary to keep the temperature differential within the phase change range necessary.

In other words, if one does not have a well-insulated box and a properly installed compressor, one is just blowing hot air talking about air-cooled vs water-cooled.

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Old 26-02-2014, 08:13   #75
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Re: Danfoss BD35/Frigoboat problem

Mark, well put: "In other words, if one does not have a well-insulated box and a properly installed compressor, one is just blowing hot air talking about air-cooled vs water-cooled".

Using adequate air as the only cooling medium for a refrigeration system powered by a Danfoss BD compressor will not allow compressor to fail as long as refrigerant remains pure. Any use of water as a cooling medium will cause Danfoss BD compressors to fail. Can anyone debate this with quantified data per 1,000 hours? or information recommendation from Danfoss to use water cooling on this small series of their compressors?

Another good question to debate without opinions is the Coefficient Of Performance (COP) of a energy holdover eutectic plate and its affect on a total Systemís COP (SCOP)

I know every one can express opinions about how pleased they may be about a product or even creative advertising about what you believe someone should purchase. No one should brag on any refrigeration component that is proven to produce less than a 1.0 COP performance in a boat refrigeration operation, when Danfoss can demonstrate 1.74 COP on a BD50 at 2000 rpm and 1.66 at low speed on BD80 compressors. The higher the COP number the better the volume metric efficiency of a piston type compressor will be.

If you are confused about boat refrigeration and like what you have you may want to keep it, as it probably will still be working when you sell the boat. If cruising in salt or tropical waters keep Zincs fresh and compressor cool.
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