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Old 19-12-2012, 05:20   #1
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I Don't Need a Freezer!

Hi


I am trying to reduce AH used by our refrigerator, it is an AB cold machine 1993 vintage.

The system works very well, BUUUUT we are veggies and do not have any need of a freezer on board.

The unit consists of a small freezer box mounted high up in the fridge compartment, which as well as being a freezer, cools the cabinet too.

Anyone know if it is possible to remove the freezer box and replace with a simple cold plate? Or could i just fill the freezer box with blue cool bag ice blocks to essentially romove the ice box air volume.

I am also trying to reduce the volume of the cabinet, but I am having a mental block deciding how! Either pile insulation bords into the bottom to fill up the space below the main shelf or partition aff an area. The boards sounds easier!!

Charlie.
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Old 19-12-2012, 05:58   #2
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If you want to reduce AH and volume of the fridge, I would add insulation around all of the inside of the cabinet. That will make a big difference on an older system, assuming it only has a couple of inches of insulation right now.

For the freezer box, I would remove the door and end if possible and add a small fan to aid circulation.
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Old 19-12-2012, 05:58   #3
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Re: I don't need a freezer !

I have a new stand alone freezer after four years of fridge only. Yippee! Ice cream!

Theres a few things you can do with your freezer bay, yes the blue bag ice things are fine.
The extra space i removed by having some foam boxes of different sizes, one is an old 6 pack beer cooler with the lid taped airtight.

Also my unit is on a 12 volt timer so the fridge can be off at night when the batteries are low. As a vegitarian you may not need a cold refrigerator. Test the temps in the supermarket veg section, i think they are warmer than dairy section.

With those considerations the blue ice bags would never freeze so are useless, and if you pack the cold plate with foam it may just cool the thermostat and cycle it off begore the bottom is cool.
So you might just leave the freezer section open and foam the bottom of the fridge...

All experiments.
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Old 19-12-2012, 06:02   #4
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Re: I don't need a freezer !

Several questions so let me see if I can address most or all.

1. Yes you can replace the box, which is the evaporator or cooling part of the system, with a different type or shape. However in a unit that old it may be more expensive than it's worth, plus you do need to make sure that the new evaporator is properly matched with the compressor unit in size/capacity, type of freon, connectors, etc. I would stick with what is there if is is working and address the issue another way.

2. Depending on where you cruise a freezer could be occasionally handy. Frozen vegetables are better tasting and have much better nutritional content than canned and some areas (like the out islands of the Bahamas) fresh veggie supply is very limited and expensive when you find it. You can also freeze lots of other things that may be hard to get in remote areas like tofu, whole wheat bread, etc. Also, you can buy frozen veggie dinners that can be real handy when the weather is really rough and cooking a chore.

3. You can certainly add insulation to the inside of the box. Will help improve the efficiency of the system by reducing the interior volume so a smaller area to cool and increase the insulation of the box. I don't know about putting insulation in the bottom. Most boat fridges seem to pick up water inside and any insulation in the bottom of the box will quickly get wet, dirty and probably smelly. Maybe place some brackets or something on the very bottom for the insulation to sit on and create a "bilge" for the water underneath. If you want a permanent solution then fill the bottom of the fridge with insulation (like Dow blue foam board) and glass over the whole thing. If you do this you should use epoxy resin for the glass work since many other resin types will melt the foam.

4. Another option if you don't want to use the freezer section is to take the door off and let the cool from the inside circulate in the rest of the reefer box.
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Old 19-12-2012, 07:31   #5
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Re: I don't need a freezer !

Quote:
Originally Posted by Sulaire View Post
Hi


I am trying to reduce AH used by our refrigerator, it is an AB cold machine 1993 vintage.

The unit consists of a small freezer box mounted high up in the fridge compartment, which as well as being a freezer, cools the cabinet too.

Anyone know if it is possible to remove the freezer box and replace with a simple cold plate? Or could i just fill the freezer box with blue cool bag ice blocks to essentially romove the ice box air volume.

I am also trying to reduce the volume of the cabinet, but I am having a mental block deciding how! Either pile insulation bords into the bottom to fill up the space below the main shelf or partition aff an area. The boards sounds easier!!

Charlie.
If you are wanting to change the AH the only thing you can change is the physical properties of the box as a system. AHs in are just going to equal the the BTUs of the heat transfer into the the system. So adding some insulation by installing more insulation blocks inside works.

The next thing is how you use the system what you put in it, the temp you try to maintain, how often you open it.

If it was me I would add the blocks inside to add insulation and reduce volume (the volume isn't as important as the added insulation). I would put some of those blue freeze blocks in the freezer, not to change any AH really but to provide thermal mass. The blue blocks will still result in the same total AHs for use but will reduce the system cycles allowing you operate the system different if you want.

On my last boat that had your type of system I just didn't need all the volume of the box. Some I installed a bunch of the insulation panels and just didn't put anything in the little freezer at all.
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Old 19-12-2012, 07:31   #6
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Re: I don't need a freezer !

Charlie, Changing evaporator to a smaller one may increase daily amp-hrs by compressor over powering evaporator. Adding insulation might show some improvement. Your problem is a 1993 AB fixed speed compressor with too much capacity that can only by reduced by the thermostat. Your AB thermostat is designed to control evaporator temperature at +12 degrees when set to number 3 or 4 on dial. Box temperature is controlled by evaporator’s ability to absorb box heat.

If you are only looking for lower amp- hours which means higher box temperatures set refrigerator to lowest number. If AB refrigerator thermostat can not be set low enough replace it with a Cooler Zone temperature thermostat that is not connected to evaporator.
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Old 19-12-2012, 07:59   #7
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Re: I don't need a freezer !

we also had a fridge that was too big - 6 cf. other problem was that it was too deep, making it difficult to get things out of the bottom. so i just stuffed the bottom of the box with insulation boards i bought at lowes. now it's 3.5 cf and just fine. the a-b doesn't run as much anymore either....
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Old 19-12-2012, 10:00   #8
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Re: I don't need a freezer !

Here are some other thoughts:

In the interest of reducing heat transfer (energy) from the outside of your fridge to the inside -

Reduce internal surface area of your insulated space to the smallest possible. The shape with the best volume to surface area ratio is a sphere (not a practical shape to build a boat fridge). The best practical shape is a cube. A pizza box shape would be bad - it has a lot of surface area per unit volume.

Any insulation you add to the interior of your fridge needs to be sealed around its edges so that cold air may not circulate behind or under.

Adding objects to the inside of the fridge to reduce volume will not decrease heat transfer through the fridge walls unless the objects themselves become a crude form of insulation (and therefore become warmer than the rest of the stuff in the fridge).

Adding mass to the inside of the fridge is analogous to a flywheel. It will take more energy to make the mass cold (spin up) and it will take more time (when compressor is off) for the heat to return (spin down) The net energy gain is zero. Refer to Newtons laws of conservation of energy.

Steve
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Old 19-12-2012, 10:30   #9
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Thanks for all the valuable input/ ideas.

Reading your posts, hows about buying a hard plastic cool box, not putting anything in it, but taping it shut. Then put 1or2 of these in the bottom of the fridge.

Because these cool boxes are insulated, would it be the case that the fridge would not be trying to cool the air inside them, but would just asume that the volume of the fridge had reduced, and therefore not cycle on/off as much.

The boat is a hans christian 41 to give you an idea of the fridge size, it has a large slatted shelf with about 12" below it and above it, the space ontop is adequate for us.

Cool boxes would be easy to fit which to me is a huge bonus!!! Question is...... Would it work?!

Charlie.
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Old 19-12-2012, 10:57   #10
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Re: I don't need a freezer !

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Originally Posted by Sulaire View Post
Thanks for all the valuable input/ ideas.

Reading your posts, hows about buying a hard plastic cool box, not putting anything in it, but taping it shut. Then put 1or2 of these in the bottom of the fridge.

Because these cool boxes are insulated, would it be the case that the fridge would not be trying to cool the air inside them, but would just asume that the volume of the fridge had reduced, and therefore not cycle on/off as much.

The boat is a hans christian 41 to give you an idea of the fridge size, it has a large slatted shelf with about 12" below it and above it, the space ontop is adequate for us.

Cool boxes would be easy to fit which to me is a huge bonus!!! Question is...... Would it work?!

Charlie.
Re-read my post that is just ahead of yours.

Steve
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Old 19-12-2012, 11:51   #11
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Re: I don't need a freezer !

Placing objects inside your fridge does not reduce the surface area (which is what really counts) of your insulated space. Adding your boxes could reduce the transfer of heat (energy) to the inside of your fridge if you use the boxes as insulation and properly seal off the edges so as to prevent cold air from circulating behind them. I think a better way to prevent the transfer of heat to the inside of your fridge is to use insulation as your added insulation.

Many people have experienced a decrease in refrigeration power consumption when they fill their fridges completely with items (food and drink). Many have come to the conclusion that the reason for this is because there is less air volume to cool. This idea does not follow known laws of conservation of energy and physics.

I believe the real reason people experience a power savings (when they fill their fridge with items), is a result of those items becoming a crude form of insulation. This is fine as long as one is willing to accept that the items near the edges of the space will not be as cold as the items near the evaporator.

Steve
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Old 19-12-2012, 12:07   #12
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Re: I don't need a freezer !

Cant you just turn it down? You dont want veggies too cold anyway. You could put an insulative board between the evaporator and the veggies.... so the veggies dont sit against it and get ruined and the unit will run less as it is sensing the "cold" in the evaporator. or the blue ice bags might be great... if when they are frozen they dont make the box too cold.
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Old 20-12-2012, 02:08   #13
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Re: I don't need a freezer !

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Originally Posted by Sulaire View Post

Cool boxes would be easy to fit which to me is a huge bonus!!! Question is...... Would it work?!

Charlie.
Yes it works for me. The other advantage is if you buy lots of food you pull out the box so theres more fridge room. Then as you nibble your way through it you can reduce your fridge space with the box again till you find another supermarket.

Any good closed cell packaging from electronics boxes i kepp and cut to appropriate sizes for different shelves.
I am doing the same for my new freezer the ice cream likes -5 or colder, but theres lots of air that doesnt ned to be frozen!
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Old 20-12-2012, 06:28   #14
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Re: I don't need a freezer !

Someone asked about my new freezer
Its the Dometic cf-25 25 litres
$409 plus shipping in the USA from
Dometic CoolFreeze Portable Refrigerator Freezer CF-25 CF-025DC -..

Its not using many amps at all but i havent had it long enou riunning the way i want to tell.

But I love it!
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Old 20-12-2012, 08:03   #15
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Re: I don't need a freezer !

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Originally Posted by Panope View Post
Placing objects inside your fridge does not reduce the surface area (which is what really counts) of your insulated space. Adding your boxes could reduce the transfer of heat (energy) to the inside of your fridge if you use the boxes as insulation and properly seal off the edges so as to prevent cold air from circulating behind them. I think a better way to prevent the transfer of heat to the inside of your fridge is to use insulation as your added insulation.

Many people have experienced a decrease in refrigeration power consumption when they fill their fridges completely with items (food and drink). Many have come to the conclusion that the reason for this is because there is less air volume to cool. This idea does not follow known laws of conservation of energy and physics.

I believe the real reason people experience a power savings (when they fill their fridge with items), is a result of those items becoming a crude form of insulation. This is fine as long as one is willing to accept that the items near the edges of the space will not be as cold as the items near the evaporator.

Steve
Adding to the above post:

Another reason having a full fridge (no air) may reduce power consumption is that it reduces the amount of cold air that spills out of the space when the door is opened. This is probably a big factor when dealing with a front loading fridge design, and a small factor when dealing with a top loading design as the cold air tends to stay inside via gravity (cold air heavy).

Steve
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