building a drop in freezer/refrigerator box

[coopec43]

Originally Posted by GordMay

Coopec may be thinking of a [infra-red] “Radiant Barrier” air gap, to prevent thermal conduction.
This would be an inappropriate misapplication of this technology.

Thank you for telling me what I am thinking

People who sale in cooler water where sea temperature 50° F would not have a real problem with warmth coming through the hull to the freezer box.

But where sea temperatures are 86° F insulation is a real problem.(Particularly if it is a steel hull)

If air can circulate around a freezer box (because of convection currents) the currents will take heat away from the box. The manufacturer of my unit said not to install the freezer in an any enclosure less than 100cu ft. (My condenser is not water cooled) I assume that is because they want convection currents to take hot air from the condenser to other parts of the yacht.

I know from fiberglassing experience how temperatures can build up in confined spaces where there is no circulation of air to take heat away (I always have a bucket of water ready in case of fire)

I think I'll take advice of a refrigeration mechanic who has worked on marine freezer units in the tropics!

[Scubaseas]

Originally Posted by coopec43

Would you rather put your hand on a hot-plate of your stove or keep it one inch from it?

It's not rocket science!

I could see using an air gap to avoid condensation in the insulation but if you want to claim air is a better insulator than foam then I can't argue with that.

Air has an R value. An air gap lined with foil has even more R value. Foam insulation has an even higher R value than either air alone or air with foil.

Would I rather touch the stove with my bare hand or with a thick oven glove on might be a better analogy. Air is a better thermal conductor than foam which is why foam has a higher R value than air? If air was such a good insulator what do you need insulation for?

[Coolerking]

We build refrigeration packages for boats of all shapes and sizes.
My only advice is to make the box as insulated as possible, with a 100%vapor proof barrier both inside and out.
Make sure the linset pass through is also sealed 100%
Once the foam is wet it's game over.

[jhulmer]

This is how I did mine and it works well.
https://www.cruisersforum.com/forums...ay-204423.html

[coopec43]

I most certainly don't claim to be expert on the science of building freezer boxes but here is a very simple article on The Science of Insulation

https://www.knaufinsulation.com.au/h...tion-explained

And here is article on Thermal Conductivity of Some Selected Materials and Gases

https://www.engineeringtoolbox.com/t...ity-d_429.html

Air, atmosphere (gas) 0.0262
Aluminum Oxide 30
Asbestos, loosely packed 1) 0.15
Brickwork, common (Building Brick) 0.6 -1.0
Cork, re-granulated 0.044
Cotton Wool insulation 0.029
Fiber insulating board 0.048
Glass 1.05
Insulation materials 0.035 - 0.16

Those figures support my Fridge Mechanic's advice to leave an air gap between the hot hull and the insulation.

But then you would have to consider convection.....

Convection occurs in gases and liquids. If a hot surface is in contact with cooler air, heat is conducted to the air. This air then becomes warmer and therefore less dense than the adjacent cooler air. The warmer, lighter air rises upwards and is replaced by cooler air, causing a continuous flow of air by natural convection – gradually removing heat from the hot surface to the air.

[Scubaseas]

Originally Posted by coopec43

I most certainly don't claim to be expert on the science of building freezer boxes but here is a very simple article on The Science of Insulation

https://www.knaufinsulation.com.au/h...tion-explained

And here is article on Thermal Conductivity of Some Selected Materials and Gases

https://www.engineeringtoolbox.com/t...ity-d_429.html

Air, atmosphere (gas) 0.0262
Aluminum Oxide 30
Asbestos, loosely packed 1) 0.15
Brickwork, common (Building Brick) 0.6 -1.0
Cork, re-granulated 0.044
Cotton Wool insulation 0.029
Fiber insulating board 0.048
Glass 1.05
Insulation materials 0.035 - 0.16

Those figures support my Fridge Mechanic's advice to leave an air gap between the hot hull and the insulation.

But then you would have to consider convection.....

Convection occurs in gases and liquids. If a hot surface is in contact with cooler air, heat is conducted to the air. This air then becomes warmer and therefore less dense than the adjacent cooler air. The warmer, lighter air rises upwards and is replaced by cooler air, causing a continuous flow of air by natural convection – gradually removing heat from the hot surface to the air.

Your link has air at .0262 and Urethane foam at .021 for conductivity

R value of air is about 1.01 for 1" to 3"
R value of urethane closed cell foam 6.2 to 6.7 per inch. This is poured in foam. Board urethane is about 7.25 per inch.

I understand having an air break for moisture. And why good vapor barriers are critical to a good installation. I can see why an airspace can be necessary for some building construction but it's for condensation, not convection.

If your air space is say 2" you have an R value of 1.01 and if you filled that same 2" space with foam you would have an R value of 12.4 to 13.4.

Is the sea temperature that much higher than ambient air? And with a delta k of .005 does it matter that much between air versus foam and the hull?

If you want an air space put an airspace in.

[Scubaseas]

Originally Posted by the bookie

Hello everyone, I just literally threw my norcold DE 0061 over the rail and onto the hard at the yard. The nevercold is gone and I'm left with this predicament of what now? I have looked at the same model and it has horrible reviews and I promised myself I wouldn't go that route again. I'm almost sure I'm going to go with the cool blue as it looks easy enough to assemble and such. I'm currently looking at building my box. I ordered the 2 part pour foam and such but my question is the wood itself. Do I have to seal the wood with clear epoxy or can I just throw 3-4 coats of 2 part epoxy paint on there and call it good. Is that a common practice to use epoxy paint inside a refrigeration box? I also wonder if anyone in the tropics use a non water cooled system like cool blue and has it held up well? I'm currently sailing the mid atlantic waters around NY but will be bringing her south this winter and bringing her back in the spring. She's a 45ft steel ketch and well insulated. I welcome all opinions! Regards

I have a AB Cold machine with a holding plate. If the ambient air temp is below about 90*F it cools as well with or without water circulation. The coolblue looks like it's got a much bigger condenser than my old AB unit. It should work fine I think as long as it's not mounted someplace hot like the engine room. Mine cools a lot better if I run an exhaust fan when the engine is running as the compressor shares some airspace with the engine room. A well insulated box will do more than a water cooled condenser. When my circulator pump died it did fine on just air cooling in tropical weather, just took a bit more energy. System still works fine and it's been over 20 years. I should upgrade the control module for the compressor but it's pretty far down my list.

Wood? What wood? I built my box with 2" foam panels, vacuum panels and glassed the inside with pigmented epoxy. I also poured urethane foam around the back and bottom of the original humongous ice box (a bit over 8cu ft). The lid has a house fridge magnetic seal on it. No drain, no wood anywhere.

[coopec43]

Originally Posted by Scubaseas

Your link has air at .0262 and Urethane foam at .021 for conductivity

R value of air is about 1.01 for 1" to 3"
R value of urethane closed cell foam 6.2 to 6.7 per inch. This is poured in foam. Board urethane is about 7.25 per inch.

I understand having an air break for moisture. And why good vapor barriers are critical to a good installation. I can see why an airspace can be necessary for some building construction but it's for condensation, not convection.

If your air space is say 2" you have an R value of 1.01 and if you filled that same 2" space with foam you would have an R value of 12.4 to 13.4.

Is the sea temperature that much higher than ambient air? And with a delta k of .005 does it matter that much between air versus foam and the hull?

If you want an air space put an airspace in.

Don't you believe you should be removing heat by convection?

[akopac]

Hey guys.
I just finished reading this whole thread and various branches. I just got finished epoxy/glassing the bulkheads in my box. I had started another thread on sizing, but got that settled. I have a pile of blue sheet foam and flexible FRP to line it and for other stuff.
So to the point. I have foil, left over Heat Shied from the original build, and can get reflectix. I’m going to the tropics. 100F air/86F water.
Do I need an IR barrier on all sides or just between the hull and insulation?
Do I need an air gap between the hull/bulkheads and the reflectix/foil or between the insulation and reflectix/foil?
Should I us reflectix, heat shield, or foil?
My first thought was running drydeck down the hull, venting top and bottom put IR barrier, then flexible FRP on top epoxy glass water tight sealed to bulkheads and counter, then lay build foam and box on top as in drawing included.
Thoughts?

[Scubaseas]

Looks like a great place for a palmetto bug to hang out or mold to grow. I'd put reflectix/foil in against the hull and go for max insulation. Your reflectix would be your vapor barrier. Or put in some Tyvek if you want. I wouldn't bother with drideck or the FRP sheet. Now if you seal it off an hold vacuum on the space you'd have the best of both worlds. The whole point of insulation is not to have the heat transfer to the surface, no matter if that surface is an air gap or hull. You're worried about convecting off a negligible amount of heat. Your Relectix is a pretty good decoupler as is. Just my $.02.

[jhulmer]

Originally Posted by akopac

Hey guys.
I just finished reading this whole thread and various branches. I just got finished epoxy/glassing the bulkheads in my box. I had started another thread on sizing, but got that settled. I have a pile of blue sheet foam and flexible FRP to line it and for other stuff.
So to the point. I have foil, left over Heat Shied from the original build, and can get reflectix. I’m going to the tropics. 100F air/86F water.
Do I need an IR barrier on all sides or just between the hull and insulation?
Do I need an air gap between the hull/bulkheads and the reflectix/foil or between the insulation and reflectix/foil?
Should I us reflectix, heat shield, or foil?
My first thought was running drydeck down the hull, venting top and bottom put IR barrier, then flexible FRP on top epoxy glass water tight sealed to bulkheads and counter, then lay build foam and box on top as in drawing included.
Thoughts?Attachment 235176

Personally I like this plan. But only if you can get at least 5-6" of insulation all around. Test your resin on the blue board, in my case the epoxy worked no problem but polyester dissolved it.

[akopac]

It’s all epoxy. The foam would be completely moister isolated from the outside world. I have 5” foam on the sides, 4” on top, and 6” on hull/bottom and wall opposite the hull. That dry deck is only 3/4 thick and gives a 1/2” air gap for IR heated air to convectively rise and draw heat away. Thought about painting hull facing side of FRP panel with titanium dioxide epoxy paint too. I have 2 part epoxy titanium dioxide paint. https://www.pcimag.com/articles/8722...-of-coatings-1

[Madehn]

i dont think you gain anything by the airgap except a place for water to condense- would fill it if possible- also a little concerned about lining with the FRP- i like the idea of using it from an ease of fabrication BUT what are you mounting your cold plates ( whatever form you are using) on? the FRP will not be sturdy enough to hold it and with 6 inch foam area before you get to any other substance then i think you will have issues- i would think about fiberglassing a 1/2 inch piece of foamboard with multiple layers of cloth on both sides then epoxying that piece by piece inside the box- use thickened epoxy as fillets in the corners and joins inside then gelcoat. I am in the process of doing that with my box right now. good luck!

[sorlie]

Originally Posted by Madehn

i dont think you gain anything by the airgap except a place for water to condense- would fill it if possible- also a little concerned about lining with the FRP- i like the idea of using it from an ease of fabrication BUT what are you mounting your cold plates ( whatever form you are using) on? the FRP will not be sturdy enough to hold it and with 6 inch foam area before you get to any other substance then i think you will have issues- i would think about fiberglassing a 1/2 inch piece of foamboard with multiple layers of cloth on both sides then epoxying that piece by piece inside the box- use thickened epoxy as fillets in the corners and joins inside then gelcoat. I am in the process of doing that with my box right now. good luck!

I'm building a refer from scratch too, so like the helpful info. Great idea to reinforce the attachment point & I'll do this. Thanks Madehn!

My scheme: build box up from hull - there's not room to drop even a custom box in. I will use liquid-applied vapor barrier over hull, cabinets, & bulkheads that form the cavity. Then many layers of Spaceloft aerogel. To support the FG panels forming the box interior, I will glue 5cm dia columns of cc foam spaced all over the interior. Those will have wooden dowel cores for strength. FG panels will be pieced in & sealed. The original top & hinged lid will get more insulation & go back on top. With adequate insulation I shouldn't get condensation, and I will have sealed moisture out. While I await warmer weather for the installation, I welcome constructive conversation - when we put our heads together, we get some pretty good ideas!

Reflectix needs >6mm air gap to reject heat transfer. I chose not to go that way.

[CarlF]

I would also not go the pour-in route. It's very hard to get full coverage without overstressing things. And those voids collect moisture that grows mold.The outside of a hull with sun shining on it gets very hot. You really don't want that touching foam. Better to have naturally circulating air carry the heat away.

I would use a combination of materials. 2" Foam, Aerogel, and vacuum panels. Where you have plenty of space just use foam. But in skinny areas put in the aerogel or vacuum panels.

Aerogel is very easy to work with. It comes in 1/4" thick layers. It's double the R value of foam. Cut it with scissors, stack it up, then wrap in plastic sheeting and tape. Buy it from Ebay. "Aspen Aerogel Spaceloft"

Vacuum panels are very expensive custom built but not expensive if you buy small ones in the standard sizes here. 1" is R50. You don't need a perfect fit. Just use foam or aerogel around the uncovered areas. https://www.rparts.com/index.php?cPath=84_32