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Old 31-08-2016, 09:57   #46
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Re: Freezer Insulation of R-40 per inch or better

You're both right, it's that you're using different reference points for your percentages.

Waterrat is looking at the percentage in energy savings from R2 value all the way through R40, or absolute values.

Sv Third Day is looking at successive energy savings, or relative values.

For example: R2 box using 100 A/day
R4 box using 50 A/day

Both can agree this is a 50% reduction in energy usage.

R8 box using 25 A/day

WR would call this a 25% reduction in energy usage, based on the original 100 A/day baseline
SV TD would call this a further 50% reduction, based on the 50 A/day used by an R4 box

R16 box using 12.5 A/day
WR would call this a 12.5% reduction compared to the 100 A/day baseline
SV TD would call it a further 50% reduction from the 25 A/day used by the R8 box

R32 box using 6.3 A/day
WR would call it a 6.3% reduction compared to the 100 A/day baseline
SV TD would call it a further 50% reduction from the 12.5 A/day used by the R16 box

Both ways of looking at it are technically and mathematically correct. However, I prefer to look at it from WR's perspective, because it more dramatically illustrates how much savings in energy one would gain from additional layers of insulation. At some point, it's not economically or physically feasible to go any thicker on the insulation due to the cost, diminishing returns, and resultant tiny fridge/freezer space.
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Old 31-08-2016, 10:10   #47
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Re: Freezer Insulation of R-40 per inch or better

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Old 31-08-2016, 10:11   #48
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Re: Freezer Insulation of R-40 per inch or better

Quote:
Originally Posted by socaldmax View Post
Both ways of looking at it are technically and mathematically correct. However, I prefer to look at it from WR's perspective, because it more dramatically illustrates how much savings in energy one would gain from additional layers of insulation. At some point, it's not economically or physically feasible to go any thicker on the insulation due to the cost, diminishing returns, and resultant tiny fridge/freezer space.
I get exactly where he is coming from and I was making the point to him (and others) that it's the wrong way to look at it and is VERY misleading. As he said in his first post, looking at it this way lead him astray. And will others as well.
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Originally Posted by Waterrat10 View Post
Seems to me a lot of work for little gain. A good seal R 10-12 seems most prudent.
He is stuck on the marginal % increase of adding more R-value to the box and this wrong approach lead him to conclude that stopping at a R10 box was a good idea. Why...because he is misapplying marginal utility without true understanding.

Now come on socaldmax…you know a R10 box sucks and will suck the life out of your battery banks while out cruising. A cruiser should shoot for at least a R20, with R30 being preferred. But by looking at it from the starting point of **** (R-Value of 2) and then fooling yourself that the % of differential change between going from "****" to a R10 vs R20 isn't worth it, he would be setting himself up for a disaster.

That vantage point of ranking where you want to go by where you are starting from on a % basis is bogus and shows a lack of real world experience, knowledge, and understanding. We know it's bogus because it told him logically that a R-10 was the good place to stop. We see these type of real world mistakes all the time and I'm trying to keep him and others from making bonehead mistakes. 95% better than **** insulation can still be **** insulation.

Facts are facts:
Each time you double the R-value of your Box you generally cut the power usage in half...that concept doesn't change.
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Old 31-08-2016, 10:16   #49
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Re: Freezer Insulation of R-40 per inch or better



Based on this graph and the exponential decay of returns for R-value. The wonderful 50% you are referring to is from a smaller and smaller piece of the puzzle. A jump from R-2 to R-10 will cut my power consumption by 80.95%. Going from R-10 to R-20 will only save me 50% of the remaining energy or an additional 9.5%f of my total. Going from R-20 - R-40 will only save an additional 4.75% of total energy needed to maintain my fridge. Based on the number from this graph.

If at R-2 I use 100 amp hours and I go to R-10 I will save 80.95 amp hours of my 100 amp hours needed. If I go to R-20 I will save and additional 9.5 amp hours. If I then add an additional R-20 for total of R-40 I will save 4.76% of the total. Therefore if my total energy needed to run my fridge at a given R vale would look like this.

R-2 = 100 amp hours
R-10 = 19.05 amp hours
R-20 = 9.55 amp hours
R-40 = 4.79 amp hours

This is under ideal condition and not opening or closing the ice box. The reality is that air leaks, what the specific heat of stored contents and the corresponding air space etc will have much more to do with amp hours used then adding R-20 to a box that is already well insulated and sealed at R-20. So you can cheer your 50% all day long but 50% of 5 means a lot less to me then 50% of 100.

My math is correct and my reasoning is sound. Your 50% rule while true is very misleading on actual gains.
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Old 31-08-2016, 10:22   #50
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Re: Freezer Insulation of R-40 per inch or better

[QUOTE=

Both ways of looking at it are technically and mathematically correct. However, I prefer to look at it from WR's perspective, because it more dramatically illustrates how much savings in energy one would gain from additional layers of insulation. At some point, it's not economically or physically feasible to go any thicker on the insulation due to the cost, diminishing returns, and resultant tiny fridge/freezer space.[/QUOTE]

This is well said. It is more dramatic but it give the impression that you are saving a boat load of energy for every doubling of insulation when you are saving significantly less compare to your previous doubling. It is misleading salesmen politician math. If I go to arogel I should just buy and engal fridge because the arogel is so darn expensive I could get a better and more efficient fridge for the same cost.
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Old 31-08-2016, 10:28   #51
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Re: Freezer Insulation of R-40 per inch or better

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Originally Posted by Waterrat10 View Post
My math is correct and my reasoning is sound.
In the land of the blind, a one-eyed man is King.

How many Marine Refrigeration projects have you done, Technautics has done thousands, but what do I know anyway. Best forget everything I've told you before it gives you a headache...swallow the Blue Pill.

But best of luck to you, you're gonna need it.
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Old 31-08-2016, 10:51   #52
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Re: Freezer Insulation of R-40 per inch or better

If I was full time cruiser and I had space I would got to R-20 and maybe R-30 but not paying for vacuum panels and aerogel. That is crazy. The cost to go from R -20 to R-40 is huge for a very small gain. Keep my fridge or freezer full and well sealed would save me significantly more amp hours. Then going from R-20 to R-40. If I took and Engel drop in fridge using 3 amp at 12 volts and left the box open and empty and it ran 24 hours I would us 72 amp hours. Reality with it full and opened occasionally it would probably be less then 25 amp hours and that is a 1000 bucks. Now it is probably already R-30 so to cut that in half and get to R-60 It would cost me 2-4 grand for a savings of 12.5 amp hours. I can find a better way to make up that difference. I could go to a 24 volt system, maybe go LIFePO4 batteries, MPPT controller vs PWM, more and or better solar panels. Lots of better way to get a better return on investment. When the above graph starts to flatten out you gain very little.
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Old 31-08-2016, 10:55   #53
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Re: Freezer Insulation of R-40 per inch or better

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Old 31-08-2016, 10:57   #54
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Re: Freezer Insulation of R-40 per inch or better

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Old 31-08-2016, 11:01   #55
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Re: Freezer Insulation of R-40 per inch or better

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Originally Posted by SV THIRD DAY View Post
In the land of the blind, a one-eyed man is King.

How many Marine Refrigeration projects have you done, Technautics has done thousands, but what do I know anyway. Best forget everything I've told you before it gives you a headache...swallow the Blue Pill.

But best of luck to you, you're gonna need it.

If you have done thousands of Marine Refrigeration then give me some real numbers. What is the average energy use of your installs. Half full not opened in 24 hours. What is the average R value of said units. If you say I need to spend a couple extra grand to save 5-10 amp hours well bull crap. I can insulate a box to R-20 with EPS and freeze some jugs of water in a drop in freezer and pack it around my food and have a fridge that will go days to a week before I need to refreeze my water again for very little cost. I hear crazy numbers like saving 40 amp hours going from R-20 to R-40. That seems really high. Real world gains with opening during use and half full the difference between a R10 to R20 to R40 are not going to be 50% not even close.
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Old 31-08-2016, 11:05   #56
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Re: Freezer Insulation of R-40 per inch or better

I wish someone would bring some facts to the table and make points with some science then rely on credentials and insults.
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Old 31-08-2016, 11:31   #57
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Re: Freezer Insulation of R-40 per inch or better

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Originally Posted by SV THIRD DAY View Post
I get exactly where he is coming from and I was making the point to him (and others) that it's the wrong way to look at it and is VERY misleading. As he said in his first post, looking at it this way lead him astray. And will others as well.


He is stuck on the marginal % increase of adding more R-value to the box and this wrong approach lead him to conclude that stopping at a R10 box was a good idea. Why...because he is misapplying marginal utility without true understanding.

Now come on socaldmax…you know a R10 box sucks and will suck the life out of your battery banks while out cruising. A cruiser should shoot for at least a R20, with R30 being preferred. But by looking at it from the starting point of **** (R-Value of 2) and then fooling yourself that the % of differential change between going from "****" to a R10 vs R20 isn't worth it, he would be setting himself up for a disaster.

That vantage point of ranking where you want to go by where you are starting from on a % basis is bogus and shows a lack of real world experience, knowledge, and understanding. We know it's bogus because it told him logically that a R-10 was the good place to stop. We see these type of real world mistakes all the time and I'm trying to keep him and others from making bonehead mistakes. 95% better than **** insulation can still be **** insulation.

Facts are facts:
Each time you double the R-value of your Box you generally cut the power usage in half...that concept doesn't change.




And at some point, another $400 worth of insulation and a 2 cuft fridge isn't worth the measly 2 or 3 A/day of savings.

He never said R-10 was good enough, he was discussing going all the way to R-40. Actual energy usage and actual cost per R value needs to get plugged into the equation for each person to determine when they've hit that point of diminishing returns. It's going to be different for each situation, based on original box size, energy usage, desired box size, solar panel output, etc.

Yes, each doubling in thickness results in a 50% decrease in energy usage.

Any reasonable person would think twice about going from 8" to 16" of insulation just to save an additional 2 A/day, especially in light of how much fridge or freezer volume they will lose. Even though it is another 50% energy savings.
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Old 31-08-2016, 11:39   #58
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Re: Freezer Insulation of R-40 per inch or better

Quote:
Originally Posted by Waterrat10 View Post
I wish someone would bring some facts to the table and make points with some science then rely on credentials and insults.
You mean like this:
Quote:
Originally Posted by SV THIRD DAY View Post
So lets look at the data from the graph so others won't make the same mistake.

At R10 the graph shows 10MMBTU rate of heat transfer
At R20 the graph shows 5MMBTU rate of heat transfer
Then at R40 the graph shows 2.5MMBTU rate of heat transfer

Now, since heat transfer rate is directly proportional to system power usage and thereby Amp Hour consumption, it's pretty clear that it will take about twice the daily power to deal with a 10MMBTU heat transfer rate Box with R10 than it would with a Box with a 5MMBTU heat transfer rate with R20. Same in going from R20 to R40.
.
Or like this:
Quote:
Originally Posted by SV THIRD DAY View Post
Sticking with our 80AH R10 example that I gave in my first response to seeing your graph for simplicity:
R10 80AH
R20 40AH = Saves 40AH
R40 20AH = Saves 20AH

You save half as much daily power with each successive doubling of the R-value. That's why there is a diminishing return of the power savings...cutting in half of a smaller number each time you double the R-value keeps giving you a smaller number. It's why most people settle on a R20 or R30 Box but rarely do they go up above the R40 range, it just isn't worth it from a Cost/Energy savings standpoint.
The problem you have isn't that the experts in the field are not bringing some Science and Data to the discussion, your problem is that you simply are not willing to think about it and understand it.

Quote:
Originally Posted by Waterrat10 View Post
I hear crazy numbers like saving 40 amp hours going from R-20 to R-40. That seems really high. Real world gains with opening during use and half full the difference between a R10 to R20 to R40 are not going to be 50% not even close.
Sorry Amigo...because you don't know doesn't mean that it's no so. (hey that's like a Rev Jackson Rhyme)

The whole reason I'm so damn confident in what I'm saying is because unlike your guess numbers and concepts, mine are based on real life data from a test boxes of different R-Values (R10, R20, R30, R40) and different sizes (2CF, 5CF, 7CF, 9CF, and 12CF). Tests were ran at different ambient temps (70F, 80F, and 90F) in triplicate with each test being of 4 days in duration once the box reached thermal equilibrium for 24hrs. During those tests the boxes were opend and closed at a set frequency and duration to make the test data points comparable and the ambient humidity was held constant. Six different types of marine refrigeration systems (the basic names you know on the market) were put through the different test conditions…you know…real science. These type of detailed controled condition tests are more than most people can afford to do, but when you have a company full of scientists that's what they do…they like to blow tens of thousands of dollars buying data loggers and cool crap to take data and analyze it.

You do the math and make a matrix box for how many tests we have actually done and how long it would take...hint...YEARS of testing...not weeks or months.

Now I've tried giving you the benefit of my experience and knowladge gained from real world tests on the realities how R-Values relate to power usage, but if you continue to believe that increaseing the R-value form R10 to R20 doesn't cut the power by 50% or that going from R20 to R40 doesn't drecrease it by 50% again when I have data showing it…hey…I might as well stop casting my pearls before swine. Those that have eyes to see, let them see.

Now for some parting education, read what I wrote below that may help you understand your problem in alalyzing the data.
It's the best I can do at this point.

Quote:
Originally Posted by SV THIRD DAY View Post
I get exactly where he is coming from and I was making the point to him (and others) that it's the wrong way to look at it and is VERY misleading. As he said in his first post, looking at it this way lead him astray. And will others as well.


He is stuck on the marginal % increase of adding more R-value to the box and this wrong approach lead him to conclude that stopping at a R10 box was a good idea. Why...because he is misapplying marginal utility without true understanding.

Now come on socaldmax…you know a R10 box sucks and will suck the life out of your battery banks while out cruising. A cruiser should shoot for at least a R20, with R30 being preferred. But by looking at it from the starting point of **** (R-Value of 2) and then fooling yourself that the % of differential change between going from "****" to a R10 vs R20 isn't worth it, he would be setting himself up for a disaster.

That vantage point of ranking where you want to go by where you are starting from on a % basis is bogus and shows a lack of real world experience, knowledge, and understanding. We know it's bogus because it told him logically that a R-10 was the good place to stop. We see these type of real world mistakes all the time and I'm trying to keep him and others from making bonehead mistakes. 95% better than **** insulation can still be **** insulation.
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Old 31-08-2016, 11:45   #59
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Re: Freezer Insulation of R-40 per inch or better

Quote:
Originally Posted by socaldmax View Post
Any reasonable person would think twice about going from 8" to 16" of insulation just to save an additional 2 A/day, especially in light of how much fridge or freezer volume they will lose. Even though it is another 50% energy savings.
Red herring...no one has ever suggesting going to 16" of insulation to save 2AH/day.

However, OP did indeed say (and I quoted him) that the prudent thing to do would be to stop at R-10 based on a flawed application of Marginal Utility Analysis of R-value to Energy savings/cost/space. What he is failing to see and you are falling into the trap with him is that playing with the Marginal Utility numbers on the extreams of sub R10 and plus R30 and then applying that to the reasonable range in the middle is bogus and totally leads you to the wrong Marginal Utility Analysis outcome. Again...it is why he said that R10 would be prudent.

Hey I can do this all morning long as I'm waiting for the sun to warm my deck and I can lay some more epoxy and glass.
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Old 31-08-2016, 11:47   #60
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Re: Freezer Insulation of R-40 per inch or better

It always surprises me that folks like Rich entertain disgruntled commentators as much as they do. It's free (professional, in this case) advice. Take it or leave it, but stop bitching about it.

Quote:
Originally Posted by Waterrat10 View Post
If you have done thousands of Marine Refrigeration then give me some real numbers. What is the average energy use of your installs. Half full not opened in 24 hours. What is the average R value of said units.
He has 3,000 posts spread overs years on this forum where he has explained all this in detail.

Quote:
Originally Posted by Waterrat10 View Post
If you say I need to spend a couple extra grand to save 5-10 amp hours well bull crap. [...] I hear crazy numbers like saving 40 amp hours going from R-20 to R-40. That seems really high. Real world gains with opening during use and half full the difference between a R10 to R20 to R40 are not going to be 50% not even close.
He hasn't said you need to do anything.

He has simply stated that in his professional opinion honed from owning and running a marine refrigeration company and personally installing and repairing thousands of marine refrigerator systems, R20 is the minimum and R30 is the sweet spot. If you're under R20, you're likely to see either high battery drain or underperformance or both. Above R30 is likely costly and difficult. Every boat and boater is different so trying to arrive at a more precise rule is futile.

And like all opinions, it's a mix of gut feelings/art and home experimentation/science. If you're looking for a pure scientific answer, you're in the wrong damn hobby. There isn't even a remotely scientific answer to one of the most important aspects of a boats: anchoring!
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