Re-insulating My Refrig. Box the Hard Way.

[jhulmer]

I did find this post on testing insulation on Richards website blog. The proposed test is logical, however, it didn't work as expected.

Hopefully Richard will comment farther.

Insulation Ice Test

[skipgundlach]

Originally Posted by jhulmer

Skip
I agree if ain't broke don't fix it! That's why I hope others will reply with additional suggestions on how to test the insulation of an existing box.

OzePete's test is a smart simple test that anyone can do. I would like to hear more similar simple tests that a anyone can perform on their own.

In the course of proving to the naysayers who blamed my box that my SeaFrost unit was too hungry, one of the easy tests was to measure every available side of the box (in our case, top, front and back, including in the ER for the back) against a nearby surface directly opposite.

The delta was in the low tenths of a degree which the pros decided meant my box was fine...

[RaymondR]

Originally Posted by jhulmer

Raymond,
thanks for pointing this out. A friends steel boat I sail on a good bit, and help build, was insulated with spray in urethane foam and then painted to seal it from moisture. Your right it has held up very well.

I think that using the XPS board (blue, pink, board) is arguably the best choice for insulation of a fridge but it is difficult in my case to form to an odd shape working from the inside out.

If I had a nice neat box that was of a uniform cubic, or Trapezoidal shape with flat sides rather than the curved side, I would have used more of the XPS and filled in with pour foam.

Jim

I am going through the process of attempting to reduce the compressor run time on a 20 year old boat I bought a couple of years ago. So far I have managed to re-gas the system and get itb frosting things as advised. It appears to have helped a little.

Next I intend to pack the freezer section with plastic juice bottles filled with a eutectic solution of table salt and water and see if I can get an idea of both the volumes required to provide at least overnight holdover capacity and whether or not the existing compressor/condenser unit will re-freeze the eutectic over a six hour period. Doing it this way I can add increments to arrive at a good estimate of actual BTU's required and also compare it with the compressors ratings.

Whilst I am mucking about with the above I will also have a go at an assessment of insulation efficiency using the techniques recommended by Richard, OzePete and others.

I have been through the working in a box with fibre glass and found it a thoroughly unpleasant experience. Consequently I am pondering on methods to increase the insulation rating of the box in this boat by accessing and perhaps replacing the foam without destroying the fibre glass work.

One of the techniques I have considered is introducing acetone to dissolve the extant foam, suck the residue out, and then introducing the two pack foam liquid into the resulting cavity a bit at a time. I'm sort of stuck on how do I do it without turning the entire boat into one of those fuel in air explosives.

Since the box is fairly big I am now considering using the blue sheets you mention in your post which I would pre-fit and then glass over before gluing them onto the inside of the existing box thereby avoiding having to work inside the box with glass and resin as much as possible.

[OzePete]

Originally Posted by jhulmer

Rgleason
Again I'm Know expert but I would be suspect of the insulation too at that age. Especially, after this project. I though mine was fine but John convinced me it was probably crap, and it was. Give Ozipete's test a try and see what you find.

Jim

Hi Jim, Obviously your insulation was well and truly faulty and you have done a great job of re-insulating it. As you know only too well it is a sod of a job and that is why I encourage users to avoid unless they really do have to go down that path!

Back to urethane insulation and its longevity etc. Since urethane took over insulating fridges in the 1950's there has been a wide range of products and brews available, some very good but some very bad. Add to this the installation methods used that also vary from good to horrible! Therefore it is wrong to generalise about insulation simply regards age etc., but there are some best practices that will ensure a better outcome..

Generally there are two methods used for fridge / freezer cabinet construction or re-insulating, and the merits of these will vary dependant on each specific application.
The most important issue as others have mentioned here, is to totally vapour seal the insulation. Next is the thickness and heat resistance property (R factor).. Specially important for marine application.

One method is to use two mix urethane but this is very tricky and can end in *tears if not done correctly. (We have a doc that points out some of the issues with using two mix along with a suggested procedure.. email if a copy is needed)
This method is preferred if the cavity to be insulated is an irregular shape. I would also suggest only procuring the two part urethane chemicals from a reputable manufacturer and ensure that it is refrigeration insulation grade and not just 'bog filler'!

(*My first attempt at re-insulating a two door fridge back in the 60's saw it end up looking like a pumpkin! And buying that client a new fridge hurt!)

The second and possibly most reliable and safer method is to use slab insulation sheets of say Dow Corning 'Blue board'.
We don't build cabinets but often try to assist those building or re-insulating.

We suggest using a single thickness for walls of say minimum 75mm, a thicker single piece for the base and another single thickness for the top. (The top being half the bass thickness) Form each panel and glue together (or in place) Vapour seal the entire insulation with a paint-on sealant or plastic wrap, position into the outer liner then finish interior with white 5mm ABS plastic liner panels trimmed to suit and glued into place.

Every situation is different and variations to the above will be needed to suit a specific project, but hope these ideas can help.

Cheers OzePete Ozefridge | 12 Volt Refrigeration Systems

[rgleason]

Jhulmer wrote:
Rgleason

Again I'm Know expert but I would be suspect of the insulation too at that age. Especially, after this project. I though mine was fine but John convinced me it was probably crap, and it was. Give Ozipete's test a try and see what you find.
Jim

Jim, thanks for this nudge. I will do the tests and report back. As you can tell, I've been avoiding this problem for awhile. We've managed by cutting 1/2" yoga mat from Walmart to line the refridge and make two pieces that slide under the top opening, which reduce the area.

I have been considering adding 1" polyurethane or dow styrofoam in the engine compartment and on the plywood bulkhead under the port cockpit seat, after drilling holes in that bulkhead and spraying more foam. However these are kind of stopgap.

The ida of dissolving the existing foam and spraying new seems like a good idea, but perhaps subject to some issues resulting in some hotspots..

[rgleason]

Peter,
I need to evacuate, find a slow leak, add a dryer as you suggested, replace schrader valves and caps. Before doing this I'm going to cut some plywood squares and check existing insulation condition and depth, photograph & report here on all insulation thickness throughout the box. I will do the temp measurements with ice in the box (at the -5degC operating temp). With outdoor temp too. What type of sensor is needed?
Then decide what to do.

Thinking ahead, I could remove the evaporator, and cut out the nice fiberglass box, remove the insulation and reinsulate with 3"-4" of Dow blue high density foam. How would I wrap it for vapor? Use 6mil polyethylene white plastic vapor barrier? Would I wrap each piece of insulation or with vapor barrier both sides, or simply lay the vapor barrier in first, add the Dow insulation, then another final layer of vapor barrier?

You mention covering the insulation with ABS plastic. Can this be bent to fit the hull curve?
Also is there a good way to seal the joints? I might be inclined to use new fiberglass (2 layers) and polyurethane paint on the inside.

I expect our top lid needs improvement with a double seal and at least 3" of insulation.

Also should I have an air gap and two layers of reflective insulation first? Maybe the bubble pack. Would it be better to have the insulated box decoupled from the hull and engine compartment plywood in some way?
Thanks

[rgleason]

ABS plastic sheet 96"x48"x1/8" on Amazon $113
Plastic corners are available
Oatey makes an ABS Plastic cement used for pipes.
Also there is a penetrating epoxy for improving the surface and strength of ABS 3D parts which could also be used to finish the inside. Since there is little UV this might be fine. I imagine that I could test West or MAS penetrating expoxy may work fine.

[john61ct]

Food-grade epoxy as the innermost layer?

[jhulmer]

Originally Posted by rgleason

Peter,
I need to evacuate, find a slow leak, add a dryer as you suggested, replace schrader valves and caps. Before doing this I'm going to cut some plywood squares and check existing insulation condition and depth, photograph & report here on all insulation thickness throughout the box. I will do the temp measurements with ice in the box (at the -5degC operating temp). With outdoor temp too. What type of sensor is needed?
Then decide what to do.

Thinking ahead, I could remove the evaporator, and cut out the nice fiberglass box, remove the insulation and reinsulate with 3"-4" of Dow blue high density foam. How would I wrap it for vapor? Use 6mil polyethylene white plastic vapor barrier? Would I wrap each piece of insulation or with vapor barrier both sides, or simply lay the vapor barrier in first, add the Dow insulation, then another final layer of vapor barrier?

You mention covering the insulation with ABS plastic. Can this be bent to fit the hull curve?
Also is there a good way to seal the joints? I might be inclined to use new fiberglass (2 layers) and polyurethane paint on the inside.

I expect our top lid needs improvement with a double seal and at least 3" of insulation.

Also should I have an air gap and two layers of reflective insulation first? Maybe the bubble pack. Would it be better to have the insulated box decoupled from the hull and engine compartment plywood in some way?
Thanks

As I understand it wood offers very little insulation probably due to its moisture content.

I would use XPS or Polyiso panels, if you insulate as you suggest. I have not tried it yet but I understand that you can heat XPS board with a heat gun and form it to a curve. You would have to use 1" thick or less and laminate them together with some gorilla glue or something while holding them against the hull.

I would use 6 mil poly sheet to line the outside of the foam area and seal it off with mylar vapor barrier tape. You can get both at the big box store. the goal is to prevent any moisture from finding its way into and around the foam and wicking away the cold (more correctly adding heat). (see some of my earlier pictures of this method)

Another option I considered was to use 2" XPS board cut and stacked in 2" layers like a deck of cards. Each block is fitted against the hull to fill the cavity. The box side can be kept straight and square. These layered blocks can be held in place and filled in by using foam in a can. This method will give you the ability to maximize the insulation. This will take some time to trial fit each block but the out come should result in maximum insulation.

[rgleason]

Jim wrote:
As I understand it wood offers very little insulation probably due to its moisture content.

Thanks for the advice. Yes, wood does not have high r-value. Perhaps .15.

[rgleason]

Was considering several reflective layers against the hull and engine side, made up of very thin reflective aluminum heavy foil and a 3/16" layer benjamin updike cedarsaver mesh, which will more effectively reflect topside and engine heat than closed cell foam.
Then add 3" + more foam depending on what fits

Jhulmer, thanks for the idea

[rgleason]

I think the new box must be watertight or insulation may get wet even if the insulation is encapsulated with vapor barrier.

[john61ct]

Originally Posted by rgleason

Was considering several reflective layers against the hull and engine side, made up of very thin reflective aluminum heavy foil and a 3/16" layer benjamin updike cedarsaver mesh, which will more effectively reflect topside and engine heat than closed cell foam

Reflectives only work facing out, in back of an air space at least an inch.

Space better filled with more foam.

[jhulmer]

Originally Posted by rgleason

I think the new box must be watertight or insulation may get wet even if the insulation is encapsulated with vapor barrier.

I think waterproofing is overkill and difficult to do. You are just trying to prevent moist air from coming in contact with cold areas, forming condensate water and soaking the foam.
Jim

[rgleason]

Dear Peter (Ozifridge) We have a BD80 compressor

Ozefridge - Danfoss BD80 Electric air and DCW cooled, C150/T45 for 4.55cu.ft. or 128 liter Model No 4530, Serial No 1605, June 2006


The manual for the BD80 shows 24vdc power as possible. Are the controls and h20 pump ok for that voltage? If so, how will performance change? Will more energy be used?


We've been discussing changing the electrical system to 24vdc in this thread