CoolBlue - is it worth the extra $$$

[multihullnz]

Yes, fridge is small and well insulated. Too small. We carry an Engel as well for passages and as a beer fridge when cruising. When on passage the Engel gets used for the everyday items, milk, butter, yoghurt, cheese etc. This means we are in and out of the other fridge much less. Hence it performs better than if frequently opened. A false reading on it's economy to be fair.

[CSY Man]

Originally Posted by Paul L

I'd be leary of all these options to try and make use of the holding plate in this fundamentally small 12v system if you are using it in a spillover system. It is hard enough to get a good setting for your thermostat that keeps the freezer parts cold enough, the refrigerator portion warm enough and the total system efficiently low enough daily amps use.

It worked great on my boat: Holding plate and spill-over system:
I drilled four 1" holes between the two boxes and lined them with glued in PVC.
2 holes on the bottom, 2 on the top. Each hole had "doors" to open or close for adjusting temperatures in the fridge. I could have done with less holes, initially It would get freezing cold in the fridge, ended up stuffing paper towels in 2 of the holes.
All in all the system far exceeded my expectations.

[Paul L]

Originally Posted by multihullnz

Yes, fridge is small and well insulated. Too small. We carry an Engel as well for passages and as a beer fridge when cruising. When on passage the Engel gets used for the everyday items, milk, butter, yoghurt, cheese etc. This means we are in and out of the other fridge much less. Hence it performs better than if frequently opened. A false reading on it's economy to be fair.

Maybe a fairer number would be to add up the daily amp-hr usage for both fridges since your cool blue setup is sufficient for your normal needs. I suspect on your setup it is still pretty good.

[Paul L]

Originally Posted by CSY Man

It worked great on my boat: Holding plate and spill-over system:
I drilled four 1" holes between the two boxes and lined them with glued in PVC.
2 holes on the bottom, 2 on the top. Each hole had "doors" to open or close for adjusting temperatures in the fridge. I could have done with less holes, initially It would get freezing cold in the fridge, ended up stuffing paper towels in 2 of the holes.
All in all the system far exceeded my expectations.

The point was not that the spillover can't be made to work. It was that using a holding plate to efficiently take advantage of the times of day when you have excess energy is an over complication when you are dialing in a spillover system.

[CGirvan]

Originally Posted by CSY Man

It worked great on my boat: Holding plate and spill-over system:
I drilled four 1" holes between the two boxes and lined them with glued in PVC.
2 holes on the bottom, 2 on the top. Each hole had "doors" to open or close for adjusting temperatures in the fridge. I could have done with less holes, initially It would get freezing cold in the fridge, ended up stuffing paper towels in 2 of the holes.
All in all the system far exceeded my expectations.

So 2 1 inch holes worked well as a spillover system. How much insulation between the 2 boxes?

[SV THIRD DAY]

Originally Posted by CGirvan

So 2 1 inch holes worked well as a spillover system. How much insulation between the 2 boxes?

Thermal dividers between the refrigerator and freezer boxes are usually 3/4" to 1" thick. If it's too thin without enough R-value the entire divider absorbs heat from the refrigerator.

Typically we put a 2" single hole in the center bottom of the divider 1" up from the bottom of the box with a flapper piece of plastic that can be adjusted to pinch off or allow for more cold air flow. Then for the top of the divider, you can either leave an air gap of about 1" between the divider wall and box lid, or put in two 1" holes. You don't really need a way to block the top holes because the air flow can be controlled well with the bottom hole.

Once you get the standard spill over system set up and going, they typically work well with only natural air convection. But to enhance the temp stability evenness (is that a word?) you can add a small 10CFM fan in the refrigerator box controlled by a thermostat to circulate the air and help stabilize and stratify the box temps.

[a64pilot]

I put two 2" holes in the bottom of mine, but have found that I leave them plugged with a paper towel or Gorilla tape or the fridge gets too cold. I was going to do the plastic cover, just never got around to it.
I keep the freezer around 5 F, if it weren't so cold I'm sure I would need to open the holes.


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[model 10]

Originally Posted by SV THIRD DAY

But to enhance the temp stability evenness (is that a word?) you can add a small 10CFM fan in the refrigerator box controlled by a thermostat to circulate the air and help stabilize and stratify the box temps.

The refer guy down on the Rio is using a metal plate in the freezer box wall and the fan blows on that.

[Boatguy30]

Novakool has made me some really nice systems with several flat roll bond plates in series so you have a separate freezer box and refer box running on one compressor.

They have in the past charged very little for this custom work and my last complete system with plates was under $1000. Also nice on a small multihulls or other small box as the plates take up very little space.

Cool blue at one time claimed efficiently roughly twice the engineered capacity of the danfoss compressor but I guess not many folks look at that much real data.

[SV THIRD DAY]

Originally Posted by Guy

The refer guy down on the Rio is using a metal plate in the freezer box wall and the fan blows on that.

The problem in having a metal divider between the refrigerator and freezer box sections is that it can make it difficult to control the refrigerator temp. If the surface area of the divider is too large then your refrigerator will be too cold and if too small then your refrigerator will be too warm. Typically you will be fighting the "too cold" refrigerator without an insulated box divider.

[Pelagic]

Originally Posted by SV THIRD DAY

Thermal dividers between the refrigerator and freezer boxes are usually 3/4" to 1" thick. If it's too thin without enough R-value the entire divider absorbs heat from the refrigerator.

.

That's interesting Rich....
I made a THIN removable solid divider between my dedicated Fridge and Freezer boxes.

Each with their own compressor/thermostat/ holding plate system (Ozefridge)

My thinking was that the individual thermostats and different phase change mix will hold the required different temps.

The purpose of making divider remove able... was emergency only, that if I lost one compressor system at sea, I could remove the divider and share the remaining system, to salvage the foodstuffs.

Any thoughts?

[SV THIRD DAY]

Originally Posted by Pelagic

That's interesting Rich....
I made a THIN removable solid divider between my dedicated Fridge and Freezer boxes.

Each with their own compressor/thermostat/ holding plate system (Ozefridge)

My thinking was that the individual thermostats and different phase change mix will hold the required different temps.

The purpose of making divider remove able... was emergency only, that if I lost one compressor system at sea, I could remove the divider and share the remaining system, to salvage the foodstuffs.

Any thoughts?

OzeFridge makes a good solid unit and I helped a good friend I cruised Mexico with install one in his Ovni 36. I like them.

Ideally the removable thermal divider would not allow for heat transfer and the two systems would be independent unless, as you say, one of the system was to fail and then you could remove the divider and not completely lose everything in one box.

We could be debating over small system efficiencies, but that's what techy guys do in online chat forums...ha ha ha.

Two reason I would like there to be minimal heat transfer in the divider even with two independent systems are:

1. This may not be an issue based on the box and divider heat transfer specifics, but you could run into the problem of your refrigerator getting too cold if too much heat is taken up through the divider and into the freezer.

2. It takes more BTUs to maintain the larger freezer to ambient temp Delta T than it does for a refrigerator and the compressor works harder, or should I more properly say runs longer. So by letting some of your refrigerator heat into the freezer through the divider you could be causing your freezer system to work harder than it otherwise would. Sure the total BTU's removed from the combined boxes will be the same at the end of the day, but the freezer compressor is typically having longer run times and pulling down the freezer plate eutectic solution to a lower temperature than the refrigerator system during each "on cycle". So my guess is that the end of the day, you could eek out some additional efficiency by not having your freezer system deal with the heat from the freezer box PLUS whatever heat comes in through the thin divider.

Like I said, we could be Tech Nerding this out a bit too much hey...you asked...ha ah

[ErikFinn]

Rich, I love to read your techy nerding posts every time. Please keep them coming. I wanted to say this because sometime we see a negative guy post something negative and its neither productive nor nice. You are a huge asset Rich, thank you.

[daletournier]

I just dont get this argument. The holding plate is easily more efficient based on the fact it stores excess energy. I have had both types of systems and my current Ozefridge holding plate works really well and im cruising in Asia. If you couldn't store excess energy then it may not be as efficient, BUT you can! I dont need graphs etc to show me this. Batteries are down less in the morning with the holding plate system.

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[CSY Man]

Originally Posted by Paul L

The point was not that the spillover can't be made to work. It was that using a holding plate to efficiently take advantage of the times of day when you have excess energy is an over complication when you are dialing in a spillover system.

Perhaps in your mind it is an over-complication but it worked good for me.
The compressor ran roughly 10 hours per 24, pulling 50 amp hours.
It did not matter whether it ran day or night, the house bank could absorb it and the solar panels replenished regardless. IF the batteries were full and the compressor did not run, I would simply adjust the thermostat to a lower temperature to force a start.
The spill-over system had nothing to do with it and I hardly ever adjusted or screwed with it: Peehaps if I inserted a case of warm beer, I would open a "door" for quick cooling, otherwise I would not touch the vent doors for weeks at a time. Pretty much automatic and easy to keep an eye on things with cordless temp sensors in both boxes transmitting to big display in the galley. Hour meter on the compressor and a Battery Monitor for the house bank would allow me to measure efficiency and load to a tenth of an amp or degree.