Cool box to fridge conversion. Insulation.

[Porthandbuoy]

I've finally got round to converting my top-loading 60 ltr cool box into a fridge using an Isotherm GE80 kit. Fitting the evaporator plate was a bit fiddly; it just fitted across the hatch diagonally before being rotated and mounted high up on one side of the coolbox. Bluetack is your friend if you don't want to waste hours dropping and picking up the spacers and screws.

Working nicely my fridge was cycling ON/OFF every three and a half minutes.
Although the coolbox has about 20mm of cork insulation there is no access to the front, where there is a 25mm air gap to the veneer panelling, or sides where there is a good 20mm air gap on each side to bulkheads. There is also a substantial void underneath the coolbox, 50mm or more at the front, tapering to zero at the back.
How to fill these voids with insulation?

I drilled a few discrete holes, so discrete they cannot be seen, and used aerosol cans of expanding foam to inject foam into the voids. The nozzle that comes with these cans is too short so I used a length of aquarium hose to reach well into the voids. Slide the hose in, start injecting foam and slowly withdraw the hose injecting all the time. You can hear the difference when the foam is flowing into a void or into foam.

The result?
My fridge is sitting between 3 and 5 degC with the mechanical thermostat set between 3 and 4. It is cycling ON for just over 3 minutes and OFF for nearly 6 minutes.

 

[bedouin]

I have often wondered about this - I have a cool box that is barely insulated and would benefit from similar treatment

What foam did you use? My concern is that standard builders' foam is likely to be open cell and so absorb water over time

 

[MontyMariner]

My concern is that standard builders' foam is likely to be open cell and so absorb water over time

You could encapsulate the foam in bin / plastic bags or cling film

 

[fredrussell]

Definitely need to insulate my fridge but it is buried deeply within the galley. Might try the foam technique. It’s one of those jobs I’ve been putting off for a long time.

 

[Neeves]

Surely it is possible to source close cell foam.

Good post - its good to read of how to do it and that it is successful.

Inject until it starts to squeeze out of appropriately spaced holes. From front to back and or side to side.

Depends on the location but in Sydney we need sole insulation between hull (which is thin foam core) and bottom of the box. Sea temps are 25 degrees in summer.

Jonathan

 

[fredrussell]

Surely it is possible to source close cell foam…

Very difficult for some weird reason. In the UK, you need a license to apply the closed cell stuff. Dunno why though. Might be because it has a half life of 12 million years or summat.

 

[rogerthebodger]

I built a fridge on my previous boat with 50 mm foam all round but when I built my current boat in increased the insulation to 75 mm all round but left some at the back uninsulated in error. I hen used spray in foam to fill the fill the back on the duty cycle got netter and in high summer was less than 50 -50

So the more the insulation you can fit the less energy the fridge will consume and keep cooler longer over night

My fridge is also water cooled which also reduces the energy consumption

 

[john_morris_uk]

If anyone is seriously worried about the foam not being closed sell, you could do what we did.I stripped out the old cool box/fridge and insulated the void with Celotex (which is a closed cell foam insulation) and then measured the cuboidish shaped space and had a stainless steel liner fabricated. Worked really well although I was never brave enough to tell Mrs M how much the stainless steel liner had cost!. Dunno what the cycling time is for the fridge but in the days when we had the old mechanical thermostat, the whole thing turned into a freezer if you knocked it and turned it up it accidentally. The mechanical thermostat has now been replaced with a digital electronic thermostat that also tells us the temperature inside the fridge at all times. The fridge workings are water cooled.

 

[MontyMariner]

When I built mine I used wall insulation strapped around a storage box

ps just noticed 2007! and it's still working well

 

[bedouin]

There simply isn't the access on my boat to fit solid insulation without taking the whole boat apart - or cutting the existing cold box out through the (rather small) lid. I have considered adding insulation inside the existing structure but there is the problem of how to get a good hygenic, sealed surface if I do it that way

 

[bedouin]

Surely it is possible to source close cell foam.

Good post - its good to read of how to do it and that it is successful.

Inject until it starts to squeeze out of appropriately spaced holes. From front to back and or side to side.

Depends on the location but in Sydney we need sole insulation between hull (which is thin foam core) and bottom of the box. Sea temps are 25 degrees in summer.

Jonathan

If you read around the issue it is not particularly easy. Sourcing the foam is hard (but not impossible) but if it is not well applied it won't be closed cell. Put too much in and it can bulge and distort

 

[GunfleetSand]

I’ve used celotex for diy coolboxes. Old fishing tackle box 50mm top bottom and sides, mastic joints with danboline coating. Kept ice for five days high summer. Outside dims of box about 70L x 50H x 50D

Made a trunk style one for a big camping trip this year, 75mm insulation this time, trunk about 60 x 90 x 120cm. On Sunday we were enjoying chilled little french cold beers just from the gel ice packs added Wednesday morning.

The insulation is a real space hog but so effective. Clamped seals do help that bit more. Not got round to using thermal camera but that would be interesting, for me!

 

[fredrussell]

In the UK, you need a license to apply the closed cell stuff. Dunno why though. Might be because it has a half life of 12 million years or summat.

Correction: After posting this last night I was chatting to a boaty friend re closed cell foam and he put me on to this stuff:

PU (polyurethane) Foam Liquid

The stuff I referred to in post #6 is the industrial closed cell insulation foam applied by gun. Sorry for the confusion.