Refrigerator box Rebuild

[Strygaldwir]

Well, I pulled my old refrigerator out of my boat. It was recently submerged in water for a couple of days. From all I read, replacing the insulation is called for.

On inspection, I note that the prior insulation is only 2" arround the box. After reviewing Kollmans recommendations (http://www.kollmann-marine.com/insulation.html) I find that I need at least 4" of extruded polyurethane. Popped over to Bingham insulation in Ft Lauderdale. Sure enough, they have it, only in 2" 2 x 4' sheets though. So, I cut off the old fiberglass vapor sheild that was formed over the old insulation. I am now preparing to start gluing and reforming the box with insullation. Since the box fits into a rather large space, I have decided to put in fiberglass batting insulation and set the newly formed box in the space.

I am also thinking of puting in a vapor barrier and a layer of 1/2 reflective insulation (http://www.insulation4less.com/default.asp).

Questions:

Should I put a vapor barrier between the 2" layers?

Should I use a vapor barrier on the outside of the fiberglass, the inside of the fiberglass, or both?

Should the reflective side of the fiberglass face the hull, or the box?

Such a lot of questions for a small project.




Keith

[GordMay]

You should post these queries to Richard Kollmann - he's a real expert.
FWIW
Normally, VAPOUR BARRIER goes on the WARM SIDE of a wall.
I think you are installing a MOISTURE BARRIER, which should go on the WET SIDE of the wall. The moisture barrier is there to protect all the insulation against any moisture (or water) in the box.
I wouldn’t install a double moisture barrier (inside & out), as that would trap moisture (between layers) within the insulation.
The reflective side of the insulation (or a reflective “radiant” insulation) should be on the warm out-side. I wouldn’t bother with the “radiant” reflective shield.
Regards,
Gord

[rleslie]

"Should I put a vapor barrier between the 2" layers?"
No. Having a vapor barrier between will lead to "sweating" (moisture build-up) and reduce the insulation's effectiveness.

"Should I use a vapor barrier on the outside of the fiberglass, the inside of the fiberglass, or both?"
You always want insulation to breath. Put your vapor barrier on the inside only.

Roger

[Alan Wheeler]

And to add to the excellent replies. Don't use Fibre Batts. If they ever get wet, they are useless. They don't dry out well. That's if I understand the terms the same as we use them here in NZ.

[Strygaldwir]

Thanks all!

So I gues it will line up this way.

1. Inner box liner
2. 4" extruded polyurethane (r28)
3. 6 mil Moisture barier
4. fiberglass outer box liner
5. 4-6" Fiberglass batting - reflective layer next to fiberglass outer box. (r19)

[GordMay]

Some queries I'd pose to Kollmann, or other refer' experts:
1. Inner box liner
I'd expect that the inner liner would act as the moisture/vapour barrier, and you wiouldn't need the film (3)
2. 4" extruded polyurethane (r28)
3. 6 mil Moisture barier
Not required ???
4. fiberglass outer box liner
Should the outer liner be ventillated, or deleted ???
5. 4-6" Fiberglass batting - reflective layer next to fiberglass outer box. (r19)
Reflective layer to warm side - that is outside of box?

[Strygaldwir]

This is from Kollman's site (http://www.kollmann-marine.com/insulation.html :

Keep moisture OUT!

The worse thing that can happen to an insulated box is to have moisture penetrate into the layers of insulation which renders it useless as moisture is one of the best conductors of heat. A good insulation system for any refrigerator/freezer would be insulation that is encapsulated in plastic. If you cut open a new commercial refrigerator, you will find that all the insulation is covered with blankets of plastic that prevents any air from moving into the insulation. Air in the humid climates will deposit its moisture on any surface that is 10 degrees cooler than the ambient air. This means that a refrigerator operating over a long period of time with air leaks into the insulation will continue to accumulate moisture until the insulation reaches its saturation point. It is true that the new closed cell foams resist the moisture but there is still a loss in the "R" value over a long period of time. Therefore, if you are building a new box, make sure that the insulation is cocooned in a plastic of 4-6 mil. similar to that, which is primarily sold for paint drop cloths. This can be purchased at any hardware store. There should also be one reflective layer of aluminum foil somewhere in the insulation with the shiny side toward the sun. This can also be found in your home refrigerator. If you are building your own box, the standard Reynolds wrap Aluminum foil will work.

Currently, the inner box and door are attached to a 4 x 8 panel that is party of the galley's wood work. I am not going to replace that. This panel has a frame in the existing opening to allow me to mount the whole assembly as a unit.

I building an outer layer of fiberglass to protect the insulation from damage when this assembly is removed and reinstalled.

Reverse reflective layer. Put it next to hull!


No intentional ventilation in the outer layer. But, there are opening for temperature probes and coolant lines for plates.

I am putting the fiberglass batting in bacause the alternative is to put nothing there. The space next to the hull has stringers, conduits for plumbing, conduit for wiring bracing materials for cabinets, opening for propane line, curved surface for hull, etc. The refrigerator box is rather regular. Already I have to cut the foam somewhat to get around a hull stringer. The fiberglass is the maximum amount I can get into this space. It also allows me to maxmize the insulation where I have space and shrug when there is no space. Kollman says to try to get to R30. I can't get 6" of foam necessary for R30 all around the box. I can only do 4" for about 95% of the box. The combination is an attempt to get to R30.

Thanks for all the help!! Helps to have additional eyes!

Keith

[svcattales]

I have been doing some research on replacing our engine driven unit also. Rparts.com site has some refrigerators called Planet DC that are self contained with a Danfoss compressor built in. Anyone have any experience with this type? It sure would be a simple installation since the box is already made. Installation requires connection to DC power and that's all. Energy consumption for the 9.5 cu/ft model is only 30Ahrs/day. Sounds too good to be true.

[GordMay]

Sailnet Articles: Refrigeration ~ Part(s) I and II - by Tom Wood

Installing or upgrading a refrigeration system requires a great deal more thought than simply ordering the parts. In fact, it may be one of the most complex decisions you'll make when upgrading your boat since there are so many variables.

Refrigeration Part I: - by Tom Wood
http://www.sailnet.com/collections/g...ical%20Systems

Refrigeration Part II: - by Tom Wood
http://www.sailnet.com/collections/g...ical%20Systems

and:

Installing 12-Volt Refrigeration - by Sue & Larry:
http://www.sailnet.com/collections/g...ical%20Systems

FWIW,
Gord May