Ice Box Refit and Instalation of a Adler-Barbour CU200

[PeteW]

Dale,

Thanks but yikes. Not sure why anyone would want to destroy that insulated tub.  Based on what I can glean from your photos; here is why I think the Grumman/Allied engineers knew what they where doing when they designed that box.

Some say its too big, but out here in southern CA all the liveaboard sailors I know fish for tuna. So I say the Pearson designers intended for there to be a big freezer/refrigerator. Alright maybe a little too big for the 365 but we hear the same box went in the 424. Not sure what came from the factory. Was it optionally a big ice chest (explains the size too) or did it come with say that big AC/DC Grunert unit I've seen in some or an engine mounted compressor? So we are talking nothing  less than 1500 BTU/HR capacity.

Alot of chatter on this site about beefing up the insulation and what size compressor to install. Much of it seems based on solid theory but nonetheless purely empirical. From Dales photos here is what I calculated:

The stock box looks to have 2" of closed cell foam insulation. I will wing it by saying that gives you an R12. Recall that R= Square feet x Delta Tf X hr/BTU.  So the standard box 48 degrees delta /12 x 16 sq feet = 60 BTU/hr heat loss. ( top side not included)  Adding 1" of foam (r18) decreases that to 40 BTU/hr loss.  What that means is if you put 10 lbs of ice in a pan and place that pan in the box it will melt (1430 BTU) in 23 hrs. An extra inch of foam means it will take 35 hrs to melt. This seems to come very close to reality but think the box actually performs better meaning the real loss number may be less than 60 BTU/hr loss. ( because to delta T is actually much lower)  I'm going to conduct this experiment in a controlled environment, meaning I will put the ice on a scale and collect the cold water in a pan below it.

So doing more math, you get almost the same result by simply dividing the box in half with a thermal wall. But we are talking only  tens of BTU per hour less loss. If a BD50 pumps 600 BTU/hr this means it will have to run an extra 48 minutes per day to keep up with the beefed up insulation or 1/2 sized  box designs. That's about 6 amp hours of extra battery capacity /day at 80 degree outside ambient.

Between all the calculated data I have and the empirical evidence from this blog supports the idea that you will not build a freezer in that box with a single BD50 compressor (CU200). It will at best be a nice refrigerator with a few ice trays. That reduces the delta T and the thermal loss to around 46 BTU/hr in the standard box.

Note: to get the BD 50 up to 600 BTU/he you need a 470 ohm resistor in series with the thermostat to speed up the compressor. You will also need to mount a CPU fan on the controller to keep it from overheating. Current goes from 5 to 7 amps. Twin DB35's or the BD80 would be my minimum choice in DC compressors for an actual freezer unit in the standard Pearson box.

Pete W.   Pearson 365 hull#6

[Dale Tanski]

Pete,
That tear out was long ago but I remember that the side wall insulation was around 4" thick.  The foam is a pour in place polyurethane that has an R value of around 7 to 8 per inch.  Say R7 x 4" = R28. 
Dale

[PeteW]

Dale,

Thanks again.  So that means that  48 degrees F delta / r28  X 16 square feet surface area = 27 BTU/hr loss. Makes for a pretty decent ice box as-is. I ignore the top of the box for heat loss in my surface area number, assuming no cold air goes out the top but we know that's not completely true.  Should have my home brew BD50 system installed by end of this week.  Pete

[Sta-Sea-Dawn]

Wow.all this theory and numbers...questions I have......will the cu200 be enough

[egoodhue]

I am in the process of starting to mod the countertop and pulled off the fiddles. Basically I have a bare formica top like your picture. My question is: was the formica glued down when you removed the top to the side plywood. Mine does not appear to lift off easily so before I go and break something I might regret I figured I would ask.

[Dale Tanski]

Ted,
Yes that High Pressure Laminate was glued down with contact cement.  The only possible way you might get it up in one piece is to heat the HPL with a heat gun.  The heat will soften the glue and often you can separate it.  This method is typically used when old contact cement glue becomes to "dry" and lets go and the surface material is no longer sticking.  You heat it up, the glue often becomes soft and sticky again and you can make it stick to reattach the surface material.

Care must be taken not to get the HPL too hot as it will discolor and even bubble.  What ever you do, don't catch it on fire as this stuff burns unbelievably enthusiastically well.

You do have a way out of this dilemma however as Formica has a color that matched what was on my boat almost perfectly.  What I mean by that is if they touched, you could detect a slight color variation, but a few inches apart and you can not tell the difference.  To be fair, two separate sheet with different batch/date numbers will have the same problem.  So head to your local mom and pop distributor or the big box outlet and grab some samples to match it up.  Formica is less than a couple of bucks a square foot.  If you go this route, hail me back and I will give you some advice on how to work with the stuff if needed.

Dale

[egoodhue]

thanks for the info. Darn I wish I had asked BEFORE I took the fiddles off as I had to drill them out as the screws heads were glued and stripped. My next approach will be to take a cut out type tool and set the depth for 1/2 ' or so and try and match the opening width of the existing cutout.
If that does not work I guess we remove the formica completely and replace it with a wood vernier and upgrade the whole area which is bit more work than I wanted but what the heck boats are just money and labor pits anyway.

Ted
SV "Fantasia"

[Sta-Sea-Dawn]

Dale,

Thanks again.  So that means that  48 degrees F delta / r28  X 16 square feet surface area = 27 BTU/hr loss. Makes for a pretty decent ice box as-is. I ignore the top of the box for heat loss in my surface area number, assuming no cold air goes out the top but we know that's not completely true.  Should have my home brew BD50 system installed by end of this week.  Pete

Pete....How is the DB50 working out...I am looking att he DB50 Adler Barber with the v53 horizonal evaporator....thoughts?