Convert fridge/freezer setup to a spillover system

[phantomracer]

Installed a Frigoboat refrigeration system in our icebox last year. Overall it is works great..

Ran into a couple issues, however...
1) the icebox is woefully underinsulated
and
2) the freezer (vertical bin style) reeeeeealy isnt a freezer!

What I mean is, when the icebox gets up to temp, loaded with food, the compressor may be off for a while, as the cold food keeps everything cold....This makes stuff inside the freezer melt, as the compressor isnt running!

I have an idea I would like to run by those who have more experience, and open for other engineering solutions as well

I plan on adding more insulation inside the box using cryogel, maybe 1 1/4 inch or so. This should help the insulation problem.. still won't fix #2.

Would this work? insulate the freezer bin with cryogel, including the bottom, to keep the cold in.. but then the refrigerator wont get cold too fast..so I assume I will need a spillover of sorts..with a fan... or possibly just wrap, say the bottom half of the bin with cryogel, and leave the top half unwrapped to cool the rest of the fridge? This should (in theory.. in my head, anyway) leave the bottom of the freezer bin, frozen (ice, etc) without thawing..

Thoughts? suggestions?

here is a pic of the box ( before I secured the evaporator to the divider)

[a64pilot]

This is going to sound nuts, but #1 can't be all that bad, or #2 wouldn't exist.
Meaning if the insulation were all that bad, the compressor would never shut off.
I think if you better insulate your box, compressor will of course run less and your freezer will even be less of a freezer

I think your best answer may be to separate the box and do a spill over, having a freezer compt, and regulate the temp in the fridge section by airflow, whether just a hole and convection or a fan your choice.

But will your thermostat work as a freezer thermostat?

[phantomracer]

The insulation is borderline acceptable. It is from 1968. The walls and cover is a couple inches thick. It works, barely. The outside surfaces are very cold and there is a lot of condensation on the outside. So cold is getting out through the insulation..

When the icebox gets cold, and the compressor shuts off, there is nothing keeping the supercold air in the freezer bin (say around 0 F).. it starts to equalize with the rest of the box (39 F)

That is my idea by wrapping the bin in insulation, that would be its own freezer compartment. But I need to get some of the cold out of the freezer to the fridge section. I cant just drill a big hole in the evaporator Which is why I was thinking of just wrapping the bottom half, or the whole thing and using a fan on top to circulate the air. Bottom half of the bin= freezer, top cool the box.

Other option would be to remove the evaporator bin and install a flat plate evaporator and bend it, and insulate the dividers..then i would have way too big of a freezer...and that would be a huge job to R+R the evaporator and lines

[Anna Sail]

Some things to bear in mind:
1. Your evaporator plate works on convection current, i.e. air circulating around both sides of the plate. If you insulate it, you will eliminate surface area and in essence make your plate smaller.
2. The Frigoboat system also works on convection current around the interior of you ice boxes. If you have no way for the cold air to move from one area to another, then you do not have a spillover system, you have cubicles. Remember, cold air drops, warm air rises.
3. Your dividers need to be insulated. One inch is fine.
4. If your box is not well insulated, it will not function correctly. Period. 1968 was a good year, I remember it fondly, but really 47 years is more than one life time for insulation.

[phantomracer]

Originally Posted by Anna Sail

Some things to bear in mind:
1. Your evaporator plate works on convection current, i.e. air circulating around both sides of the plate. If you insulate it, you will eliminate surface area and in essence make your plate smaller.
2. The Frigoboat system also works on convection current around the interior of you ice boxes. If you have no way for the cold air to move from one area to another, then you do not have a spillover system, you have cubicles. Remember, cold air drops, warm air rises.
3. Your dividers need to be insulated. One inch is fine.
4. If your box is not well insulated, it will not function correctly. Period. 1968 was a good year, I remember it fondly, but really 47 years is more than one life time for insulation.

Thanks.. it is not a plate, it is a bin, as you can see from the pic.

That was my thinking..which is why I was thinking of making a sort of spillover system by just insulating the bottom half of the bin..so the top half will still cool the rest of the box..yes making it smaller to cool the rest of the box. if it doesn't work, i can just remove the insulation.. or put a fan in to help.. I intentionally got the larger bin, of the 2 they offer to be on the safe side (knowing the insulation was less than optimal..was worse than I thought!)

The main issue is the freezer is really not a freezer..when it shuts off.. it starts to equalize with the rest of the box .. and the inside of the bin is no longer near 0 degrees..and everything starts to melt..when it comes back on.. everything re-freezes.

I was going to leave the dividers as is, as they seem to transfer cold just fine

Just trying to get the freezer..well..to freeze and stay frozen!

[Anna Sail]

If you want freezing conditions inside the evaporator bin, do not put insulation on the evaporator plate itself (thereby making the plate smaller). In your situation you need as much plate exposed as possible to combat the poor insulation of your ice box). Put insulation on the structure of your ice box to keep the warm air out and the cold air in.

Sounds like your components are doing the best they can in the challenging conditions. You should also have your compressor running at the higher rpms, again, to meet the challenge of your box's less then ideal conditions.

Here's a thought: Where is your temperature sensor located? Is it a mechanical thermostat attached to the evaporator plate or a digital thermostat measuring the temperature of the box? If it's digital, is it located nearer the evaporator plate and with a set point measuring closer to freezer temperatures? Bear in mind, the thermostat is simply an on-off switch for the compressor. I would think if you want the compressor to come on more often to keep your freezer items frozen, then you need to tell it that.

[phantomracer]

Originally Posted by Anna Sail

If you want freezing conditions inside the evaporator bin, do not put insulation on the evaporator plate itself (thereby making the plate smaller). In your situation you need as much plate exposed as possible to combat the poor insulation of your ice box). Put insulation on the structure of your ice box to keep the warm air out and the cold air in.

Sounds like your components are doing the best they can in the challenging conditions. You should also have your compressor running at the higher rpms, again, to meet the challenge of your box's less then ideal conditions.

Here's a thought: Where is your temperature sensor located? Is it a mechanical thermostat attached to the evaporator plate or a digital thermostat measuring the temperature of the box? If it's digital, is it located nearer the evaporator plate and with a set point measuring closer to freezer temperatures? Bear in mind, the thermostat is simply an on-off switch for the compressor. I would think if you want the compressor to come on more often to keep your freezer items frozen, then you need to tell it that.

Thanks. I understand

However, there is nothing keeping the freezing temp IN the freezer bin. If I insulate the icebox perfectly, the compressor wont ever come on once it reaches its set temp (39)..then the temp between the freezer bin and the rest of the icebox will equalize over time

if the compressor ran more...to keep the frozen food frozen,, then the rest of the ice box will get much colder than 39.

Ideally, the refrigerated section should stay 39-40 and the freezer near 0

[Jolly Roger]

I recently converted my ice box into a full freezer. There is an article on my website which shows how I insulated the ice box. It may be helpful to the OP
JR.

[jamhass]

Phantom:

Ignoring general insulation issues, Yes, your basic problem stems from 2 items:

1) the bin is not separated from the fridge. As you have noted, this allows the air to circulate freely, causing the freezer to warm up.

2) the thermostat is measuring the fridge, thus not holding freezing temps. You could try moving the tstat to see if this helps, hopefully without overcooling the fridge.

In all probability, your best short-term solution IS to convert the box to a spill-over. You might get away with "simply" adding some insulation to the outside of the bin, closing off the bottom of the bin with a baffle and install a small fan in that baffle. Then, you put the main tstat in the freezer and use a second tstat in the fridge to control the fan and move air from the freezer when the fridge needs cooling.

A couple of addition "cold-saving" ideas to consider:

1. Is the seal on the hatch in good shape?
2. We use a yoga mat on the counter over our refer. Helps cut down on air leakage and adds a small amount of insulation. Also adds a non-skid surface. We know it works because the underside of the mat is always colder that the top.
3. If in a sunny place, drape a bit of fabric (beach towel, old sail bag, bit of canvas ...) on the outside of the hull to shade the refer. Can make a surprisingly considerable difference in how much the compressor runs.

[ka4wja]

Paul,
1) First off, there are a couple real professionals here on Cruiser's Forum, that will be able to help you out more than you will ever imagine!!

Richard Kollmann
Cruisers & Sailing Forums - View Profile: Richard Kollmann

Rich Boren
Cruisers & Sailing Forums - View Profile: SV THIRD DAY




2) Secondly, I'm just an amateur compared to Richard and Rich...but, I've not only been sailing with 12vdc refrigeration (and dealt with many of its problems) since I was a kid in the 1960's....and improved my own current 12vdc system (BD50 based, AB Cold Machine) with lots of extra insulation, etc...and have read all of Richard's books (cover-to-cover)!!

But, they way I see your problem, it is actually quite simple...
a) You do not have a freezer, and you desire a freezer..
b) The guys that sold you the new Frigoboat system either didn't tell you everything upfront, or you didn't explain your box / system and desires properly...
c) You have VERY old, and VERY poor insulation....

{please note that the "bin" is an evaporator....not a freezer....although I know that some sell/market it as such, it really isn't a "freezer"....}


3) Albeit there are contradictions in what you write, but using your words...

Originally Posted by phantomracer

Installed a Frigoboat refrigeration system in our icebox last year. Overall it is works great..

Ran into a couple issues, however...
1) the icebox is woefully underinsulated
and
2) the freezer (vertical bin style) reeeeeealy isnt a freezer!

These underlined sentences are not only contradictory, but they actually tell you what the problem is...
That is you do not have a freezer, and you desire one..
And, that the insulation of the box is very poor!!

There are numerous "experts" that will tell you anything you want to hear on-line...
I'm not one of them...and neither are Richard, Rich, and most of the rest of the guys who have tried to answer you here...

Bottom line is:
--- You need to insulate the boxes much better...
--- You need to design (and/or purchase) the proper frig/freezer unit(s) for your new design and desires....

Insulating the "bin" is not going to work for what you want...



I'd like to point out a harrowing fact for you...

If you are still in Massachusetts, with water temps in the high 50's / low 60's??? and cool nighttime air temps, even in the summer....and your frig system isn't working for you now...
You will NEVER get anywhere near as good performance once you cruise south!
You'll be surprised how many folks coming from New England and Chesapeake area, find the 85-95 degree water and 90+ degree air temps to make what they thought was a "working frig", simply turn into a "generally cool spot", once they get to Florida, Bahamas, Caribbean, etc.!!
(and add to the fact that few "marine refrigeration guys" actually know how to make the darn things work better, many end up buying lots of new stuff, and never find satisfaction!)

Ever wonder why the hottest topic around cruisers picnics is "refrigeration"??




4) I did some pretty involved tests/experiments myself years ago....and seriously improved my system, a LOT!!!
Have a look..
Frig/Freezer



I really do hope that I helped!!

fair winds..

John

[phantomracer]

Originally Posted by ka4wja

Paul,
1) First off, there are a couple real professionals here on Cruiser's Forum, that will be able to help you out more than you will ever imagine!!

Richard Kollmann
Cruisers & Sailing Forums - View Profile: Richard Kollmann

Rich Boren
Cruisers & Sailing Forums - View Profile: SV THIRD DAY




2) Secondly, I'm just an amateur compared to Richard and Rich...but, I've not only been sailing with 12vdc refrigeration (and dealt with many of its problems) since I was a kid in the 1960's....and improved my own current 12vdc system (BD50 based, AB Cold Machine) with lots of extra insulation, etc...and have read all of Richard's books (cover-to-cover)!!

But, they way I see your problem, it is actually quite simple...
a) You do not have a freezer, and you desire a freezer..
b) The guys that sold you the new Frigoboat system either didn't tell you everything upfront, or you didn't explain your box / system and desires properly...
c) You have VERY old, and VERY poor insulation....

{please note that the "bin" is an evaporator....not a freezer....although I know that some sell/market it as such, it really isn't a "freezer"....}


3) Albeit there are contradictions in what you write, but using your words...
[/U]These underlined sentences are not only contradictory, but they actually tell you what the problem is...
That is you do not have a freezer, and you desire one..
And, that the insulation of the box is very poor!!

There are numerous "experts" that will tell you anything you want to hear on-line...
I'm not one of them...and neither are Richard, Rich, and most of the rest of the guys who have tried to answer you here...

Bottom line is:
--- You need to insulate the boxes much better...
--- You need to design (and/or purchase) the proper frig/freezer unit(s) for your new design and desires....

Insulating the "bin" is not going to work for what you want...



I'd like to point out a harrowing fact for you...

If you are still in Massachusetts, with water temps in the high 50's / low 60's??? and cool nighttime air temps, even in the summer....and your frig system isn't working for you now...
You will NEVER get anywhere near as good performance once you cruise south!
You'll be surprised how many folks coming from New England and Chesapeake area, find the 85-95 degree water and 90+ degree air temps to make what they thought was a "working frig", simply turn into a "generally cool spot", once they get to Florida, Bahamas, Caribbean, etc.!!
(and add to the fact that few "marine refrigeration guys" actually know how to make the darn things work better, many end up buying lots of new stuff, and never find satisfaction!)

Ever wonder why the hottest topic around cruisers picnics is "refrigeration"??




4) I did some pretty involved tests/experiments myself years ago....and seriously improved my system, a LOT!!!
Have a look..
Frig/Freezer



I really do hope that I helped!!

fair winds..

John

When I said overall it works great.. I meant mechanically. The system is working. my icebox insulation isn't, as I and you mention. I am already planning the insulation upgrade (tons of cryogel)

Yes the rep for frigoboat did say 'what is inside the bin is a freezer. I had no experience with 12v refrigerators... now I understand.

I liked the bin as it was pre-bent and fit in my icebox quite nicely, and having the benefit of a freezer was appealing.

I am trying to make the best of what I have installed. I would prefer not to remove the evaporator bin and replace it with a bin/unbent unit (a lot of work, and not inexpensive)

I am aware the system won't work well if I go south. I have no plans to do so in the near future.

This was the reason for my post.. Although it sounds logical in my head, I was unsure if it was practical in the real world.

So, at worst, I have a refrigerator and a slightly colder refrigerator section (inside the bin)

I do like not having to carry cubic tons of ice to the boat for every outing!

There are other issues (which I have discussed in other threads) power/batteries and charging issues, etc..

Learning as I am going! So insulation the bottom and partial sides of the bin won't create a mock spillover system. in my head it works, but probably wouldnt

[jamhass]

Originally Posted by phantomracer

So insulation the bottom and partial sides of the bin won't create a mock spillover system. in my head it works, but probably wouldnt

Don't see why not. Only issue really is can the compressor keep up with heat loss. So far, it sounds like you are fairly happy with the refer temp, and are only concerned with getting/keeping the freezer cold.

Having the freezer "embedded" in the fridge compensates significantly for less-than-ideal insulation.

Assume for a moment that you isolate the freezer by closing off the bottom and insulating the sides as much as possible. Most of the heat gained by the freezer comes from the refer surrounding it. Assuming the refer is cool that can be a fairly small amount of heat so the freezer can get quite cold.

If you "control" the amount of spill-over "cold" to the refer with a small fan and separate tstat as I suggested earlier, it will almost certainly work and require far less effort that rebuilding the box and/or changing to a new evaporator. Costs almost nothing to try: little foam board, small 12 v fan, simple tstat, bit of wire...

We switched to electric refer (a single Frigoboat Capri 50 compressor) a couple of years ago on our 27-year old boat with a very large 15-cubic foot box having original refer insulation. I added about 3 inches of rigid foam to the hull-side of the box, but left the rest of the box original. Half the box (hull side) is freezer with the evaporator, rest is refer with a small fan controlling flow between the two.

We cruise 8 months/year in Mexico and have no trouble maintaining the refer and fridge using primarily solar -- which also runs computers, nav aids, radios, autopilot, TV, stereo and watermaker.