Insitu fridge requires insulation - what material to use

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superboots

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My standard built in fridge in a Bavaria Ocean lacks adequate insulation especially towards the hull. the compressor is unable to reduce the temperature inside the box by more than a 7 degree difference to the external temp. I want to fill the space around the box wth insulation but access is very limited.Sprayed foam would be the obvious choice but I am worried it could degrade with water contact - the hull deck joint above is not water tight.Or that it would not spread to fill the total space behind the box. Perhaps a high performing cavity wall insulant would work. So what would be the best material to use?
 
The best material, assuming that you can fit it into the space is something like Celotex or equivalent. Comes in various thicknesses from 25mm to 100 in 25 mm steps, some merchants do intermediate sizes such as 60mm. This has a very high insulation value and is far better than polystyrene.

I have just built a fridge from scratch in a locker and have used 50mm of Celotex which I am advised is adequate for a fridge in Northern Europe. For a freezer or hotter climate you need more insulation.
 
Spray foam is a nightmare unless you can provide plenty of vent holes. I've just used it on the boat to fill a 2m x 200mm x 100mm void beside the aft bunk. I had to drill 35mm holes every 250mm to let it expand and allow it to cure. It is moisture curing and needs to "breath" to cure. It helps to break off the excess as it builds up. It will not cure if you spray it into a big void through one hole, it will seal around the outside and stay liquid in the middle, don't ask me how I know! One point though, the DIY aerosols are all open cell foam and will soak up water despite the tins saying they are "water resistant". You can get closed cell but it is two pack and expensive to buy in small quantities.
 
nigelmercier said:
I also want to insulate my fridge, but can't see how without removing the unit. Excessive PU foam could help me do this! :)
Click to expand...

If you can get the vent holes in it it will work. I was so dubious about my job that I mocked up the void an experimented with hole configurations until I could get it to fill and cure. As I said earlier I had to have 35mm holes at 250mm spacings along the length of a 2m x 200mm x 100mm horizontal void. Cost me a fortune in foam to experiment but at least I now know it's limitations.
 
That's why I am thinking of somthing like granuals that could be blown into a bag. I only have access to one bottom side of the fridge furniture. To use boards would mean dismantling worktop and the lockers above which would not be easy.
 
I need to do something very similar - but haven't found a good solution yet.

I reckon this is quite like cavity wall insulation - so try googling for DIY solutions for that. It seems that poly beads may be a good solution - but not sure how you would actually apply them.
 
The fact that your compressor can only cool to 7 degrees below ambient doesn't sound right to me. However poor the standard insulation might be I would expect it to be possible to pull the fridge down by at least 20 degrees - albeit that it may have to work very hard to do so and take too many AHr's out of the batteries...
 
If the space between the fridge and the hull is getting wet from a hull/deck leak the existing insulation may have got saturated. If so its insulating qualities will have been severely degraded. This might account for at least some of the poor performance.

Can you get access to that area to check?
 
Bilge Rat said:
The fact that your compressor can only cool to 7 degrees below ambient doesn't sound right to me. However poor the standard insulation might be I would expect it to be possible to pull the fridge down by at least 20 degrees - albeit that it may have to work very hard to do so and take too many AHr's out of the batteries...
Click to expand...

I was about to write the same. It sounds like the unit is short of gas. 7 degC is not an insulation problem it's an refrigeration issue.
 
I don't think the compressor is faulty, its all been checked. The fridge box is quite large - about 80 cu ltrs and the fridge is much colder at the end with the element than the other end next to the hull. I have been running it on shore power so not a battery roblem either. Interesting to know from other Bav owners how their fridge works
 
nigelmercier said:
Good idea: http://www.myonlinediary.com/wall-insulation/
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I've figured out a way to do this from below the fridge.
Collect cardboard tubes from loo-roll or kitchen roll.
Cut a suitable hole in the panel under the fridge, in the corner of the locker.
Cut tube into lengths that can be fed vertically into the hole.
Make joining rings with offcuts, and PVA to one end of tube sections.
Cut first tube at 45 degrees, and angle it so the cut points away from the corner.
Feed up into hole adding PVA to joints as you go.
Stop when tube touches worktop. Allow to dry.
Use the bead blower system as above, when no more will go in, plug the tube and go sailing.
Try again a few days later, repeat until the void is full.
 
Last edited:
nigelmercier said:
I've figured out a way to do this from below the fridge.
Collect cardboard tubes from loo-roll or kitchen roll.
Cut a suitable hole in the panel under the fridge, in the corner of the locker.
Cut tube into lengths that can be fed vertically into the hole.
Make joining rings with offcuts, and PVA to one end of tube sections.
Cut first tube at 45 degrees, and angle it so the cut points away from the corner.
Feed up into hole adding PVA to joints as you go.
Stop when tube touches worktop. Allow to dry.
Use the bead blower system as above, when no more will go in, plug the tube and go sailing.
Try again a few days later, repeat until the void is full.
Click to expand...

Sounds like a plan. Don't forget to apply for your Blue Peter badge though! :)
 
superboots said:
I don't think the compressor is faulty, its all been checked. The fridge box is quite large - about 80 cu ltrs and the fridge is much colder at the end with the element than the other end next to the hull. I have been running it on shore power so not a battery roblem either. Interesting to know from other Bav owners how their fridge works
Click to expand...

A proper check of the fridge system will involve connecting pressure gauges to check pressure of gas at inlet and outlet of the compressor. This will confirm enough gas and the compressor working correctly. Next thing to check is the adequacy of cooling air of the compressor and condensor. A fan to shift air around this area could help a lot.
Obviously really bad insulation will cause poor performance but I still would suspect the refrgeration system first. good luck olewill
 
The polysyrene beads seems the solution but I think it would be necessary to used closed cell polystyrene as the risk is the insulation will degrade from moisture absorbion - coming from boat leaks or condensation. I wonder if it is obtainable? - I might even use some for an uninsulated cavity wall........
My thoughts on filling are. 1) make an opening in the base of the locker placed by the worktop and with a blower, blow the beads in. Use a small concrete vibrator at the base of the fridge to settle the beads and then top up. seal this hole with foam. Close the locker base with a screwed lid for later inspections. Blowing the beads from the bottom of the fridge box seems tricky.
 
I would think that any insulation designed for cavity walls would do for the boat as well - cavity walls are not necessarily dry.

I am now seriously considering this as it may be a cheap and easy way of solving my problem - all other solutions seem to require major engineering - my concern is that I don't know how well sealed the area in with the cool box is installed is - I may find beads popping up all over the boat :)
 
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