diy holding plates? What design considerations?

[mlydon]

i was considering the idea of constructing my own holding plate, and was wondering about design limitations.

Background: i own a '75 Allied Seawind, which came with a seafrost engine-driven holding plate system. it works just dandy, but the ice box it's installed in lacks sufficient insulation to keep things cold - without ice, the plate is thawed 3 hours after you charge it. i recently purchased a second plate here on CF, but it turns out i don't have enough wall space in the box to mount it.

Proposition,

weld up a stainless box that fits my ice box with lots of volume to it, fit it with copper coil, and fill it with brine.

sounds simple enough, right? so why is it every commercial holding plate out there is around 3 inches thick?

I was contemplating making the plate thick, more like a block than a sheet. say a triangular section that sits in the bottom of the box, dimensioned 8-10" thick,
or curved back, conforming to the outer wall of my icebox, leaving a straight, deep cavity for food. Stood off the walls/floors for airflow, of course.

what say you all? Is there a good reason the prefab ones are 3" thick?

any other consideration?

anyone done it?

Matt

[Richard Kollmann]

I manufactured more than 200 holding plates before I retired over 60 of them were custom plates with many pictured in my DIY Boat refrigeration book. The only company that was and still is successful building plates with Brine eutectic solution is a truck plate builder in Tennessee. In comparing brine against a safe non corrosive solution brine plate can be 15% smaller than a lifetime safe eutectic plate.
I built plates as large as 24 gallons and as small as one gallon. All my plates were frozen by a compressor the same size as you now have. The boat with the 24 gallon plate also had a 17 gallon plate each having its own expansion valve to take full advantage of your compressor’s output.