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Old 13-11-2019, 22:09   #1
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Boat refrigeration insulation gotcha for Australians (and maybe some others)

Hi all,

From time to time I am reminded that this is an international forum. Despite the absolutely brilliant sailing destinations in Australia, people chose to sail in other locations for some odd reason.

Anyway, this can lead to confusion, particularly when it comes to units.

Having received basically consistent advice on the insulation requirements for my boat fridge/freezer, I went looking for insulation suppliers here in Australia.

But all of the materials I could find had stated R-Values that would have required up to 920 mm of insulation or more to reach the various recommendations of R30 - R40 given here and by my supplier.

Well, it turns out, all of the Australian products were being quoted in SI units not the Inch Pounds used on this forum. (And, oddly enough, by my Australian refrigeration system supplier as well.)

So, if you are an Aussie, or live somewhere else where standard metric units are being used, note that there is a scaling factor of approximately 5.68 between the two systems, so an R40 recommendation on this site translates to about R7 when using SI rated materials.

https://en.wikipedia.org/wiki/R-valu...nch-pound_(I-P)

I will NOT need 920 mm of insulation after all... 200 mm will be ample.

Matt
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Old 13-11-2019, 23:50   #2
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Re: Boat refrigeration insulation gotcha for Australians (and maybe some others)

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Originally Posted by GILow View Post
..........

https://en.wikipedia.org/wiki/R-valu...nch-pound_(I-P)

I will NOT need 920 mm of insulation after all... 200 mm will be ample.

Matt
Good news for you Matt but really - taking advice from our northern up/over cousins, what were you thinking .

Glad you sorted it out and given all of the us the skinny.
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Old 14-11-2019, 01:16   #3
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Re: Boat refrigeration insulation gotcha for Australians (and maybe some others)

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Good news for you Matt but really - taking advice from our northern up/over cousins, what were you thinking .
Well, you know, some of them are not totally silly.

But when an Aussie refrigeration guy insists on using the same outdated units, I can't help feeling a bit peeved. I gently took him to task on the issue, and he responded with something along the lines of... "Oh, I can't keep up with all these changes...!".

I didn't have the heart to tell him that Australia went metric in 1966. Thankfully his refrigeration gear is a bit more up to date.
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Old 14-11-2019, 04:04   #4
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Re: Boat refrigeration insulation gotcha for Australians (and maybe some others)

Quote:
Originally Posted by GILow View Post
Well, you know, some of them are not totally silly.

But when an Aussie refrigeration guy insists on using the same outdated units, I can't help feeling a bit peeved. I gently took him to task on the issue, and he responded with something along the lines of... "Oh, I can't keep up with all these changes...!".

I didn't have the heart to tell him that Australia went metric in 1966. Thankfully his refrigeration gear is a bit more up to date.

Ever try and buy a faucet with supply and outlet fittings in Metric. No such thing as they are all Imperial and you have to have an adapter which usually comes with the package. (Usually the braided hose). The aerator threads are imperial as well.



Same as gas fittings which are all Imperial (US) and will never change at least until the US goes metric.



Canada is supposed to be a metric country as well. But I guarantee you that you will never find a shop that sells insulation rated in SI units. Whatever they are. lol
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Old 14-11-2019, 07:33   #5
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Re: Boat refrigeration insulation gotcha for Australians (and maybe some others)

Until the US goes metric...

Well, blue moons do occur.

So far, the populace do not seem interested, and until/if it is introduced all over the States, in all of the schools.....Well, I wouldn't hold my breath. The basic problem, I think, is that metrification is viewed as "foreign", rather than "better" or "more practical."

Ann
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Old 14-11-2019, 07:53   #6
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Re: Boat refrigeration insulation gotcha for Australians (and maybe some others)

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Originally Posted by GILow View Post

I will NOT need 920 mm of insulation after all... 200 mm will be ample.

Matt
Glad you didn't over insulate that box by almost 5x as needed. You would not have had too much heat influx w/920mm though!

It must have been confusing to get US R values of 30-40 for a freezer insulation, then try to purchase insulation there.
It does make sense at 200mm, you would get nearly an 8" equivalent or a R40 (US) if you are using a R5 US rated blue board.

Your experience is a good reminder that you sometimes need to "translate" information to ensure it makes sense before jumping in and building.


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Old 14-11-2019, 08:13   #7
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Re: Boat refrigeration insulation gotcha for Australians (and maybe some others)

Quote:
Originally Posted by GILow View Post
Well, you know, some of them are not totally silly.

But when an Aussie refrigeration guy insists on using the same outdated units, I can't help feeling a bit peeved. I gently took him to task on the issue, and he responded with something along the lines of... "Oh, I can't keep up with all these changes...!".

I didn't have the heart to tell him that Australia went metric in 1966. Thankfully his refrigeration gear is a bit more up to date.
So in 1966, Australia essentially learned to gauge dimensions in fractions of 2.54 centimeters. 1/8th of 2.54 cms conveniently being 0.3175 cm, which is all so easy to remember and then to calculate from such base of units.

Indeed one needs to be cautious when citing units of measure, for example, as you have learned that R-value and RSI-value are not the same units of measure. Take for example, my foot fits inside s a size 10.5 or an eleven device, USA units and our shoes are typically sold in the bargain style, that is if you buy one, you get one free. I generally purchase a right sided shoe and then get a matching southpaw shoe to complete the pairing for my two feet.

Y'all downunders do still speak upover English, [well a form of anyway].

Back to the subject of refrigeration. Have you given consideration to selectively utilizing vacuum insulated panels for constructing your chilly box? Well I might as well now add another thermal measurement, the k-value just to insert more confusion.

From Wikipedia: https://en.wikipedia.org/wiki/Vacuum_insulated_panel

"Heat transfer occurs by three modes: convection, conduction and radiation. Creating a vacuum practically eliminates convection, since this relies on the presence of gas molecules able to transfer heat energy by bulk movement. A small decrease in pressure has no effect on the thermal conductivity of a gas, because the reduction in energy-carrying molecules is offset by a reduction in collisions between molecules. However, at sufficiently low pressure, the distance between collisions exceeds the size of the vessel, and then the conductivity does reduce with pressure.

Since the core material of a Vacuum Insulated Panel / VIP is similar in thermal characteristics to materials used in conventional insulation, VIPs therefore achieve a much lower thermal conductivity (k-value) than conventional insulation, or in other words a higher thermal resistance per unit of thickness. Typically, commercially available VIPs achieve a thermal conductivity of 0.004 W/(mK) across the centre of the panel, or an overall value of 0.006-0.008 W/(mK) after allowing for thermal bridging (heat conduction across the panel edges) and the inevitable gradual loss of vacuum over time.

Comparison to conventional insulation
The thermal resistance of VIPs per unit thickness compares very favourably to conventional insulation. For instance, standard mineral wool has a thermal conductivity of 0.044 W/(mK), and rigid polyurethane foam panels about 0.024 W/(mK). This means that VIPs have about one-fifth the thermal conductivity of conventional insulation, and therefore about five times the thermal resistance (R-value) per unit thickness. Based on a typical k-value of 0.007 W/(mK), the R-value of a typical 25-millimetre-thick (1 in) VIP would be 3.5 m2K/W (20 hft2F/BTU). To provide the same R-value, 154 millimetres (6 in) of rockwool or 84 millimetres (3 in) of rigid polyurethane foam panel would be required.

However, thermal resistance per unit price is much less than conventional materials. VIPs are more difficult to manufacture than polyurethane foams or mineral wools, and strict quality control of manufacture of the membranes and sealing joins is important if a panel is to maintain its vacuum over a long period of time. Air will gradually enter the panel, and as the pressure of the panel normalizes with its surrounding air its R-value deteriorates. Conventional insulation does not depend on the evacuation of air for its thermal performance, and is therefore not susceptible to this form of deterioration. However, materials like polyurethane foam are susceptible to water absorption and performance degradation as well.

In addition, VIP products cannot be cut to fit as with conventional insulation, as this would destroy the vacuum, and VIPs in non-standard sizes must be made to order, which also increases the cost. So far this high cost has generally kept VIPs out of traditional housing situations, However, their very low thermal conductivity makes them useful in situations where either strict insulation requirements or space constraints make traditional insulation impractical. VIP performance is also temperature dependentwith increasing temperature, conductive and radiative transfer increase. Furthermore, typical panels cannot operate much above 100 C (212 F) due to the adhesive used to seal the thin envelope."
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Old 14-11-2019, 14:31   #8
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Re: Boat refrigeration insulation gotcha for Australians (and maybe some others)

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Until the US goes metric...

Well, blue moons do occur.

So far, the populace do not seem interested, and until/if it is introduced all over the States, in all of the schools.....Well, I wouldn't hold my breath. The basic problem, I think, is that metrification is viewed as "foreign", rather than "better" or "more practical."

Ann
Using a base ten makes a hell of a lot more sense, however the SAE system is ingrained and understood. Talk of change is old and unlikely. Lets go Whitworth. Sp?
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Old 14-11-2019, 15:44   #9
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Re: Boat refrigeration insulation gotcha for Australians (and maybe some others)

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Until the US goes metric...

Well, blue moons do occur.

So far, the populace do not seem interested, and until/if it is introduced all over the States, in all of the schools.....Well, I wouldn't hold my breath. The basic problem, I think, is that metrification is viewed as "foreign", rather than "better" or "more practical."

Ann
Some of us started with Imperial (proper Pommy ones of course) changed to CGS at age 14, MKS at age 16, then SI at 18. Some years later I was transitioned you the American units for my refrigeration works.. not certain any of it makes sense other than SI though!
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Old 14-11-2019, 15:58   #10
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Re: Boat refrigeration insulation gotcha for Australians (and maybe some others)

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So in 1966, Australia essentially learned to gauge dimensions in fractions of 2.54 centimeters. 1/8th of 2.54 cms conveniently being 0.3175 cm, which is all so easy to remember and then to calculate from such base of units.

There's always someone who completely fails to grasp the fundamental principle of number bases.


2.54 centimeters is NOT a base unit. Apart from conversion to/from archaic imperial units, that figure is irrelevant.



Why divide by 8 in a decimal based system?


Why use a system which has different number bases for different uses?
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Old 14-11-2019, 16:02   #11
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Re: Boat refrigeration insulation gotcha for Australians (and maybe some others)

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Originally Posted by GILow View Post
Well, you know, some of them are not totally silly.

But when an Aussie refrigeration guy insists on using the same outdated units, I can't help feeling a bit peeved. I gently took him to task on the issue, and he responded with something along the lines of... "Oh, I can't keep up with all these changes...!".

I didn't have the heart to tell him that Australia went metric in 1966. Thankfully his refrigeration gear is a bit more up to date.
Could your refrigeration guy by any chance hail from victoria?
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Old 14-11-2019, 16:14   #12
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Re: Boat refrigeration insulation gotcha for Australians (and maybe some others)

I loved Terry Pratchett's explanation:

NOTE FOR YOUNG PEOPLE AND AMERICANS: One shilling = Five Pee. It helps to understand the antique finances of the Witchfinder Army [this from Good Omens book] if you know the original British monetary system:

Two farthings = One Ha'penny.
Two ha'pennies = One Penny.
Three pennies = A Thrupenny Bit.
Two Thrupences = A Sixpence.
Two Sixpences = One Shilling, or Bob.
Two Bob = A Florin.
One Florin and one Sixpence = Half a Crown.
Four Half Crowns = Ten Bob Note.
Two Ten Bob Notes = One Pound (or 240 pennies).
One Pound and One Shilling = One Guinea.

The British resisted decimalized currency for a long time because they thought it was too complicated
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Old 14-11-2019, 18:03   #13
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Re: Boat refrigeration insulation gotcha for Australians (and maybe some others)

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Originally Posted by JPA Cate View Post
Until the US goes metric...

Well, blue moons do occur.

So far, the populace do not seem interested, and until/if it is introduced all over the States, in all of the schools.....Well, I wouldn't hold my breath. The basic problem, I think, is that metrification is viewed as "foreign", rather than "better" or "more practical."

Ann

Blue moons do occur but in this case I think we will have to wait until hell freezes over and I don't see that happening anytime soon.


However, in the US a lot of science and engineering is already in metric because it's just better and easier. In fact in one class the prof decided to require an answer in US units on an exam just to make sure the students could do it. I asked several friends after the exam about that question. All of us worked the problem in metric since it was so much easier, then converted the final answer to US.
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Old 14-11-2019, 18:20   #14
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Re: Boat refrigeration insulation gotcha for Australians (and maybe some others)

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>>>>>>>>>>>>>>>>>>>>>>>>>


>>>>>>>>>>>>>>>>>>>>>>>


I will NOT need 920 mm of insulation after all... 200 mm will be ample.

Gee, Matt, isn't that still a lot? I moved to BC from California, so I'm still getting used to litres and meters. How come they don't spell meters metres??? But 200mm is 2000 kilometers and that's a long way to go, isn't it?


I usually failed math class 'cuz I misused decimals places to the chagrin of every one of my instructors and professors.


And aren't there 3.785 ounces to the yard?


I have, you should know, gotten over the pint and gallon thing, though. I always order "a coupla pints, please."
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Old 14-11-2019, 18:22   #15
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Re: Boat refrigeration insulation gotcha for Australians (and maybe some others)

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Originally Posted by mcarthur View Post
>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>

Two farthings = One Ha'penny.
Two ha'pennies = One Penny.
Three pennies = A Thrupenny Bit.
Two Thrupences = A Sixpence.
Two Sixpences = One Shilling, or Bob.
Two Bob = A Florin.
One Florin and one Sixpence = Half a Crown.
Four Half Crowns = Ten Bob Note.
Two Ten Bob Notes = One Pound (or 240 pennies).
One Pound and One Shilling = One Guinea.>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>

I thought one of the house rules here was no poetry.
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