Building Odyssey
Freezer Box Insulation
Friday, September 13, 2013
Sea Frost in New Hampshire has supplied the custom evaporator plates and compressors for our refrigeration system. Cleave advised me to use isocyanurate foam board insulation as it has a higher r-value than blue styrofoam. Poured in place foam was not really an option., and the problem with it is that it cannot be sealed well against moisture. I found a suitable material called iso board at, of all places, an industrial roofing contractor supply. It is used as an underlayment for hot tar roofs. The stuff I got was 1-1/2” thick and had an outside layer of fiberglass reinforced resin saturated paper. It was about 1/5 the cost of other iso insulation from an insulation company at about $15.00 per 4x8 sheet.
Keeping the heat out. Or the cold in?
The first step was to mount the plates and drill the holes for the the gas lines. I marked the mounting holes from the inside, drilled them and then inserted 10-24 machine screws from the outside. The heads were then tig welded to the stainless shell,creating studs onto which the plates could be hung. I also placed some studs midway down in the box for mounting a shelf. Then the plates were removed and stored.
The foam board was messy to cut and I found that a fine toothed handsaw worked okay. The surfaces of the first layer that would be in contact with the stainless steel box were very well sealed with West epoxy, including the edges. I didn’t want condensation between the insulation and shell to saturate the foam.
I suppose a foil faced foam would have eliminated this step. I used polyurethane construction adhesive to glue the foam sections to the shell. This stuff is great, sticks really well to everything and is somewhat flexible.
I used various methods to clamp the foam tightly in place including ratchet straps, bar clamps and, ultimately, left over lead ballast ingots as weights.
Any gaps along edges were filled with canned spray foam insulation, then trimmed after it hardened. The entire outside was again thoroughly sealed with West epoxy. In all there is mostly 4-1/2” of insulation, with 3” on the angled part at the rear. But there is also then 2” of the EPDM foam on the hull adjacent to this, so heat movement should be reasonable. I wish there was room for more, but there simply wasn’t space. As it was, it was a very tight squeeze.
Above right, the view inside the refr box showing the single evaporator plate. The freezer box, below, has twin plates. Sea Frost did a good job making the lines the right length to allow the plates to be fitted.
The picture below shows the galley installation on the left with the refrigerant lines running aft though the bulkhead to the pilothouse. The compressors will be located here, against the hull under the side deck in a cabinet. This is the nav. station, so there will be good access to the compressors. They are air and water cooled and there will be a water outlet though hull installed here as well.
