Surprising results with a spill-over fridge.

[GILow]

Originally Posted by OzeLouie

Suggest the two air transfer holes be high up in the dividing wall and far apart as in this sketch below. An optional stainless steel 'tray' can be used as a heat exchanger but best to be removable as they can sometimes block with ice. This is mostly an advantage if operating in a high humidity area. Also the fridge side air being contained to within the exchanger greatly reduces the build up of frost / ice on the freezers cold plates.

Important to have 100% lid or *door sealing when using a fan inside a fridge cabinet as the extra air movement will increase the introduction of unwanted warm and moisture laden air that will decrease efficiency and decrease periods between defrosts.
*Use a light inside cabinet on a dark night to locate any seal leaks.

TOP VIEW Click on to expand...

Attachment 241023

I like it!

But how about aluminium instead of stainless? Much better thermal conductivity AND a weight saving too.

[OzeLouie]

Originally Posted by GILow

I like it!

But how about aluminium instead of stainless? Much better thermal conductivity AND a weight saving too.

Aluminium should be fine. Suggest measure up and check on-line for a suitable sized caterers tray say about 20mm deep and with edge for seal..

[GILow]

Originally Posted by OzeLouie

Aluminium should be fine. Suggest measure up and check on-line for a suitable sized caterers tray say about 20mm deep and with edge for seal..

Great idea!

[skipgundlach]

Originally Posted by OzeLouie

(clip...)

An optional stainless steel 'tray' can be used as a heat exchanger but best to be removable as they can sometimes block with ice. This is mostly an advantage if operating in a high humidity area. Also the fridge side air being contained to within the exchanger greatly reduces the build up of frost / ice on the freezers cold plates.

(clip)

This is an interesting idea, one that I'd never seen before.

If I understand you properly, your spillover isn't, really, but rather a ducted fan which is sealed against any moisture which might accrue in the freezer section via the refrigerator air being introduced.

You'd still have the humidity entry when you opened your freezer, but it would be tiny compared to the much-warmer air entering via the typical spillover.

The question would be, "How much heat can this duct remove?"

If it reasonably would keep up with the demands of your frig section, AND, as implied, is removeable, defrosting would be a great deal simpler, as all the ice-becomes-water could be dealt with outside the freezer compartment.

How come this isn't standard practice, and reefer makers offering such ducted air exchange? I'm currently facing a VERY frosted freezer, and to defrost it takes hours (the ice behind the evaporator plates has to melt, too), and every bit of resultant melt water has to be removed, one way or the other. And my insulation is so effective that the walls of the freezer will remain cold for days, slowing the melt process.

I use a fan blowing into the box for loosening the ice (warming the evaporator plates - three of them, from Seafrost, replacing the single huge wraparound Frigoboat - until the ice will slide off),rather than heating up the plates, but there's still a substantial amount of water to remove from the bottom, and the walls are still sweating after the plates are warm, so I have to keep drying/mopping until I restart it (don't want free water freezing on the bottom!).

[hzcruiser]

Originally Posted by OzeLouie

Suggest the two air transfer holes be high up in the dividing wall and far apart as in this sketch below. An optional stainless steel 'tray' can be used as a heat exchanger but best to be removable as they can sometimes block with ice. [...]

Some very good points there, thanks a lot, Louie!

[evm1024]

Interesting - My fridge side is consistently below freezing. The freezer and fridge are insulated to R30 on all sides and the divider between them is R10 (2" XPS) with a 75mm hole and a fan that (if it ever got warm enough in the fridge) that would draw air from the freezer to the fridge.

The divider is not very well sealed and from what I am reading in this thread is likely too "thin".

I do like the idea of making an aluminum "heat exchanger" that fridge air is drawn through as needed. That could be a simple as adding a 3rd layer of XPS along the edges of the divider and them placing an aluminum plate on that. Add in another hole and poof.

Food for thought.

[skipgundlach]

Originally Posted by evm1024

Interesting - My fridge side is consistently below freezing.
(clip.)

In cases where I put my freezer far enough down, I too have that issue with the reefer.

The cure is to limit the amount of air exchange possible; in our case, the spillover is a 1" gap (total square inches same as the fan opening); we stuff it with a leftover tee chunk (we use old tee shirts for polishing rags) to slow down the air transfer...

So, if the reefer being too low is a problem, just restrict the air exchange somewhat...

[waterman46]

Getting ready to replace my defunct and non-repairable separate freezer and reefer with a spill-over.

My big question is not whether the fridge gets too cold (that's easily remedied) but whether all parts of the freezer remain at well below freezing at all times.

I suspect the area of the freezer near any holes in the divider wall, will get much warmer.

What is your experience in this regard? And where is your freezer evaporator positioned with respect to the divider wall? Can evaporator position be optimized?

[skipgundlach]

Originally Posted by waterman46

Getting ready to replace my defunct and non-repairable separate freezer and reefer with a spill-over.

My big question is not whether the fridge gets too cold (that's easily remedied) but whether all parts of the freezer remain at well below freezing at all times.

I suspect the area of the freezer near any holes in the divider wall, will get much warmer.

What is your experience in this regard? And where is your freezer evaporator positioned with respect to the divider wall? Can evaporator position be optimized?

In our case, there are 3 (replacing the properly bent/shaped 3-wall flat evaporator plate) evaporator plates, looking like thin cold plates, of SSteel, assuring that one will not damage the housing when defrosting. The cold comes from the woven 1/4" copper tubing inside their protective shell, with entry and exit on opposite sides of the tops. They're connected with ell fittings.

So, all but the divider has cold making on them. I'm in the defrost cycle as I write; it was mostly snow, which I scraped off before starting the ambient-air fan blowing into it. That has resulted in a fast defrost...

[GILow]

I just pack my freezer with due regard to the "warm" return air duct. Critical stuff, like chicken against the plates, frozen veggies closer to the divider. Everything remains frozen, but the stuff against the plates would surely remain coldest of all.

Originally Posted by waterman46

Getting ready to replace my defunct and non-repairable separate freezer and reefer with a spill-over.

My big question is not whether the fridge gets too cold (that's easily remedied) but whether all parts of the freezer remain at well below freezing at all times.

I suspect the area of the freezer near any holes in the divider wall, will get much warmer.

What is your experience in this regard? And where is your freezer evaporator positioned with respect to the divider wall? Can evaporator position be optimized?

[OzeLouie]

Originally Posted by skipgundlach

This is an interesting idea, one that I'd never seen before.

If I understand you properly, your spillover isn't, really, but rather a ducted fan which is sealed against any moisture which might accrue in the freezer section via the refrigerator air being introduced.

You'd still have the humidity entry when you opened your freezer, but it would be tiny compared to the much-warmer air entering via the typical spillover.

The question would be, "How much heat can this duct remove?"

If it reasonably would keep up with the demands of your frig section, AND, as implied, is removeable, defrosting would be a great deal simpler, as all the ice-becomes-water could be dealt with outside the freezer compartment.

How come this isn't standard practice, and reefer makers offering such ducted air exchange? I'm currently facing a VERY frosted freezer, and to defrost it takes hours (the ice behind the evaporator plates has to melt, too), and every bit of resultant melt water has to be removed, one way or the other. And my insulation is so effective that the walls of the freezer will remain cold for days, slowing the melt process.

I use a fan blowing into the box for loosening the ice (warming the evaporator plates - three of them, from Seafrost, replacing the single huge wraparound Frigoboat - until the ice will slide off),rather than heating up the plates, but there's still a substantial amount of water to remove from the bottom, and the walls are still sweating after the plates are warm, so I have to keep drying/mopping until I restart it (don't want free water freezing on the bottom!).

Hi Skip, Regards your question: "How much heat can this duct remove?"
This varies depending on several factors but generally if the freezer is a typical at say 33% of the combination fridge / freezer and operates at say -15C or lower then an exchanger with a surface area equal to 8cm square per litre of fridge side cabinet capacity would be more than adequate, but seeing as the exchanger will occupy most of the freezer side of the divider, it is preferable to make as large as possible. The exchanger should have a vertical baffle or two to ensure good heat exchange.

Many thermo-fan systems 'stealing' cold from the freezer either don't need an exchanger or if they do they rarely ice up if operating in a low humidity area and lid / door seals are 100%. Sublimation tends to keep the exchanger's interior ice free but not always. The important issue whenever a fan is used inside a fridge cabinet for whatever reason, is sealing to prevent outside moisture laden air entering. Best to test with a strong light inside the cabinet on a dark night. Note any light escaping and remedy it. Suggest using very soft sponge seals. (Not hard seals like a domestic cabinet) Temporarily block any seal leak with vaseline for a test.

Below: A typical Thermo fan kit using a digital temperature controller and 80mm fan. Fan can be located inside dividing wall for neatness. Must suck air from the fridge side. The larger fan running stronger but shorter time helps with sublimation. Other sketch is just some ideas...

[jamhass]

On our spillover system, the divider was 3/4 inch of rigid foam insulation sandwiched between 2 pieces of 1/4 inch plexi. A 1-inch through-hole at the top with a 1-inch 12v fan (like in a computer but small) run on its own thermostat, and another 1-inch hole at the bottom. Freezer worked great, even for ice and ice cream, and we never had freezing in the refer compartment. Beer stayed happy, as did I.

[skipgundlach]

Interesting responses, those two immediately above.

In my design I consulted with the engineers at the folks I bought the parts from in setting up my spillover. In my case, the 4.75" (less in fan cuz the frame...) fan in the very center of the spillover divider pulls air from the freezer, blowing it into the reefer. The top has a 1" full-width gap, the exact same square-inch size as the fan.

Both compartments have circulation fans in the coldest corner, blowing around the relatively-colder air to keep from having the bottom perhaps freeze in the reefer, and pushing the colder air up/mixing in the freezer. Both the circulating and spillover fans are mag-switch controlled so as to turn off when the door is opened. I have no practical means, at this point, of blowing air from the top of the freezer into the reefer. Even if I could, it seems to me that would stratify the warm air at the top and the cold air (both relative, of course) at the bottom...

The diagram above could be the same but with horizontal baffles; mine would have the suction fan at the bottom and the entry at the top, as noted above...

Our system has double gaskets; flats on the interior, gasket facing out, and on the periphery of the doors, facing in, of a 3/8" weatherstripping which looks like an "e", with the bottom of the usual position of an "e" being the contact point. As such, it easily covers any irregularity in the landing point (the door on the inside, and another set of flats on the outside). Click on this subgallery for more:
Pictures: Flying Pig 2013-2014 Shakedown

As both doors require some effort to fully close/latch, I expect that the weatherstripping is in solid contact. Indeed, when we decommission the system when we're leaving the boat (it is voracious for electrons, about double that of our preceding system by Frigoboat keel cooler), the weatherstripping returns to its original shape, and closing-to-latch is initially much more difficult on recommissioning...

[Scott Berg]

One more idea; we often fit a 24v fan on a 12v circuit; runs more slowly and moves plenty of cold air...

[john manning]

What an interesting morning it is on Cruisers Forum today. First post is Americans and some Europeans discussing which weapon is best for fighting off intruders. Next post a group of Australians discussing how best to keep the beer cold.

I am now going to go and build a spill-over fridge, its just such an interesting idea and one that is entirely new to me. Then if I ever have to deal with intruders I will throw cold beer cans at them.