Make freezer Smaller, How?

[Sid at SailAway]

I'm with Rich on this one. We have a Lagoon 410 and the freezer is just too deep to reach into and we don't need all the space. The foam boards work great to raise up the bottom and taking up air space as well. When it comes time to defrost and clean we just pull them out and put them back in when done.
Rich can probably verify this but you really shouldn't use food or liquid items to take up the extra space. Some folks put gallon jugs of water in the freezer thinking that they will take up space and make the freezer more efficient. You have to keep in mind that it takes energy to keep the water frozen, thus there goes trying to make the freezer more efficient. Oh, and Rich can you save me a cold beer this time in Annapolis??

[MarkJ]

I have a few small foam coolers with the tops taped securely on. Stuffed in the fridge they use excess room but also can be removed when needed.

[Cheechako]

So I've always heard it's more energy to cool air space in a fridge/freezer than filled space. true or not?

[SV THIRD DAY]

We have two different topics I think being mixed up in one here.

There is a difference between filling in the feezer volume with foam blocks or water jugs and then adding insulation to the side walls. Filling the internal volume of the box helps reduce the air exchange when the door is opened and acts in a way as a "food holding plate" but it doesn't do a lot to help reduce the amount of heat that needs to be pulled out of the box. To stop heat coming into the box, that is another issue and is where the insualation needs to be added to the box walls. Less heat that comes in....less heat that needs to be removed by the compressor.

[Mycroft]

Originally Posted by SV THIRD DAY

Filling the internal volume of the box helps reduce the air exchange when the door is opened and acts in a way as a "food holding plate" but it doesn't do a lot to help reduce the amount of heat that needs to be pulled out of the box.

Rich, you make it sound like there isn't much benefit in filling the space in a top-load freezer. True?

[Cheechako]

so... lets say we have a one cubic foot freezer. We block the drain and fill it with water. We then freeze it solid. Would the power usage to maintain that for a week be more than if it was totally empty with only air in it?

[Dsanduril]

Getting air cold and keeping air cold takes very little energy. The problem comes in trying to keep your cold air in the box and not exchange it with warm air from the outside. If you can keep the cold air in one place then all you have is heat leakage through the walls, and heat leakage through the walls is solely dependent on the internal temperature and the external temperature. Doesn't care what is inside at that temperature.

The block of ice will be a holdover device, so your compressor will run less frequently, but longer each cycle. Of course, in the real world keeping air exchange at zero is not a trivial problem, so overall you probably end up with more energy usage with a box full of air. That's not a result of the box full of air so much as it is leakage of that air (and also the additional start/stops on your compressor - each start/stop wastes a little energy, and with only air you won't have much cold mass to lengthen the cycles).

[SV THIRD DAY]

Originally Posted by Cheechako

so... lets say we have a one cubic foot freezer. We block the drain and fill it with water. We then freeze it solid. Would the power usage to maintain that for a week be more than if it was totally empty with only air in it?

The energy would be the same, with the caveot that the box lid stays shut. It's a common myth that a full box will use less power than an empty box. But all the full box is doing is two things:

1. getting rid of the air that spills out and is replaced with warm air each time the door is open. (so that does help a bit)

2. The full box food acts as a "holding plate affect" to help stabilize the box temperature.

The bottom line when talking energy usage is the INSULATION. In your example the unit would use about the same amount of energy because what matters from an energy usage standpoint is removing heat from the box that migrates in through the insulation. Empty box, full box, frozen block of Ice Box....in order to maintain their temperatures you still have to pull out the exact same amount of heat, which is what is coming into the box through the insulation. The contents of the box (air, food, Beer, Ice) really don't matter because they are not creating or using energy to remain at the same temperature.

What folks know with front opening boxes is that every time they open the box the cold air spills out and is replaced with warm mosit air, making front opening boxes the hardest to refrigerate, so in this case having the box full would help. But in the absense of the air exchange it's all about INSULATION not about what is in the box. Adding bottles of water to keep frozen doesn't add to the insulation value of the box to keep out heat, is just acts like a "holding plate" to help stablize the box temp, which ok...maybe that is a good thing, but that doesn't really result in less/more power usage at the end of the day.

[Cheechako]

But once you spend the energy to freeze the ice up front... doesn't the holdover save run time?

[Cheechako]

Here's a thought for those with deep boxes; two of my boats had top and front doors, with a shelf/rack betwen. I loved that arrangement as I could quickly reach in the bottom and grab a cold drink etc with little open time. Adding a front door would allow you to fill some of the space with things you could use!

[SV THIRD DAY]

Originally Posted by Cheechako

But once you spend the energy to freeze the ice up front... doesn't the holdover save run time?

No.
Having what we will call "paracitic holding plate" in the way of ice jugs of food may help the system stay off longer because the paracitic holding plate material can absorb some of the incoming heat before reaching the compressor kick on point, but then think about what happens when the compressor turns on. It has to remove all of that heat both from the Box and from the paracitic holding plate (aka food or water jugs). So now the compressor needs to run longer. So it's a wash.

Here is a perfect example of this:
We use two sizes of holding plates a full and then a 1/2.
The full plate has more BTU absorbtion ability because it has more frozen solution in it than the 1/2. But the power usage for the two plates is pretty much the same. The full plate will stay off for 4hrs and run for 1hr to remove the heat is absorbed. The 1/2 size plate will stay off for 2hrs and run for 30 minutes to pull out the heat it absorbed. At the end of the day the total energy usage of the two different size holding plates is withing the margin of error of our test measuring equipment.

We got the same results with a empty box vs a full box. The energy usage is the same, with the only real difference coming from air exchange when the box was opened, which isn't as much of an issue on a top opening box.


About front doors on the boxes....energy disasters. It's not just the cold air being replace with warm air...but more importantly it's the humidity that is in that warm air. Front opening boxes have much bigger issues with frost build up on the evaporator or holding plate. Once you get more than 1/4" of frost built up on your evaporator, it starts acting like an igloo and inhibiting the efficient heat movement from the box to the evaporator. Keeping the frost down can make for a big energy savings.

[Cheechako]

At least I'm learning something! But isn't a holding plate the same as a parasitic plate? Part of it is frozen, part of it is not.
For example; I put a block of ice in my picnic cooler. I drink drinks out of it and it may last a few days. By your logic, it's better to just put cold drinks in with no ice and then introduce cold later...? somehow it's just not logic-ing out for me I guess. I do understand the penalty for freezing the jugs/ice at the onset... btu's in/btu's out.

[SV THIRD DAY]

Originally Posted by Cheechako

But isn't a holding plate the same as a parasitic plate? Part of it is frozen, part of it is not. For example; I put a block of ice in my picnic cooler. I drink drinks out of it and it may last a few days. By your logic, it's better to just put cold drinks in with no ice and then introduce cold later...? somehow it's just not logic-ing out for me I guess. I do understand the penalty for freezing the jugs/ice at the onset... btu's in/btu's out.

Actually no.
The holding plate is filled with a eutectic solution which can change temperatures without going through a phase change, so a block of ice isn't equilivant to a block of holding plate. You don't want to ever let your holding plate defrost because then you have to spend a LOT more energy to go from a liquid to a solid again....but this isn't the issue and none of that really matters to the "Energy Usage Question" we are talking about here. Holding plate or Evaporation plate...it's all the same from a BTU in/BTU out point of view.

We are confusing the holding plate, block of Ice, or frozen food with be ability to Remove Heat from the Box on a temporaty basis (until the BTUs of the ice or holding plate or food are gone) to a continuing basis. That is the logic flaw. You have to look at the box in equilibrium, and this will all be an issue of having to pull out the amount of heat going into the box to maintain the equilibrium. Regardless of what is in the box.