Frost and Ice Buildup: The Enemy eating your Amps

[SV THIRD DAY]

Something I see all the time is the Abominable Snowman taking up residency around the holding or evaporation plate. As a liveaboard cruise myself, I know that it is no fun to defrost and clean out the box…but once you get more than ¼” of frost and ice on your evaporator, the igloo affect takes hold. The ice and frost igloo will dramatically cut down on the efficient heat transfer from your box into the evaporation plate. That will cost you with a higher box temp and longer compressor run cycles. In other words, that Igloo is costing you battery power! How much power will vary of course, but in tests we have conducted we have seen up to a 30% increase in power usage with a badly frosted up holding plate.

Excessive frost and ice isn’t the fault of your refrigeration system, but typically an indication of poor hatch door seals. Since hot flows to cold, warm moist air is pulled through the hatch leaks (or a box drain hole) and the moisture condenses and forms frost. About that box drain hole…plug that hole asap!

On holding plates, which are usually made of stainless steel or cast aluminum, you can use a spatula to frequently scrape the holding plate and keep the frost/ice buildup down to a minimum. But on thin white rolled aluminum evaporator plates, you have to be much more careful or risk poking a hole. So turn them off and let the ice/frost break off in sheets with a little gentle help of room temperature water.

Keeping your refrigerator or ice box as frost and ice free as possible will not only keep your compressor happy with less run times, but your beer colder and your ice cream hard...now that my friends is worth the effort.

[a64pilot]

I have an icebox conversion, that of course has a drain.
I'm also lazy, so every couple of months I just let a water hose dribble over the plates, takes about ten minutes and I don't even turn the fridge off. When finished, lean over with a couple of paper towels and dry / clean up, put the frozen food back.
A WHOLE lot easier than defrosting a house freezer used to be.

On edit, Damn Son, put a shirt on

[senormechanico]

I use a heat gun on low setting.
Makes fast work and easy cleanup.
Overall, it's so fast it probably SAVES amp hours over scraping.

[Stu Jackson]

I have NO idea why anyone lets this stuff build up so much to begin with. All it takes is one short night to defrost if you don't let it build up so horribly to begin with, and most stuff in even the freezer will stay cold. Most of the smaller units can't hold very much anyway. If that's an issue, either schedule your "off" night for the day before you go shopping again, or buy a bag of ice and wrap the frozen stuff in it somewhere in the fridge. This is not rocket science, but some folks, based on the number of recurring "Oh, I punctured the tubing with my ice pick!" posts still think it is.

It's like preventative maintenance. Those who don't reap the results.

Good reminder for everyone, thanks for posting.

Unfortunately, the folks who need it the most probably don't read these kind of instructive missives.

[omc]

Thanks for the interesting post. Not only the igloo is costing lots of amps but also the ice is badly distorting the evaporator plus the bacterias proliferating.

[uncle stinkybob]

I thought the ice was for the booze in those nice decanters you have there? two fingers, one cube!!!!

[TurninTurtle]

The frost itself is not the problem.

Any mass that acts as a heat sink inside the fridge or freezer actually helps the refrigerator/freezer. Frost buildup is actually one of the best masses (ice) for this.
It does NOT alter the thermostat setting and therefore does not affect the temperature inside. (aside from the frost getting so bad that it makes the air leak worse)

The air leak is a problem. The exchange of air does make your refrigerator/freezer work harder and that is one reason we commonly have magnetic flexible door seals. Its an attempt to limit the exchange of cold air inside with warmer air outside.

Frost is frozen condensed moisture from the air.
Its essentially distilled water + air pollution. If you eliminate the air exchange you stop the frost.
That would mean never opening the door and having a perfect door seal. The unit is useless to you if you never open it...

Don't plug hole that the manufacturer put there on purpose. They had a good reason for it. You don't have to understand it.

The wasted space is a problem. The picture of extreme buildup has appx 3/4 of the freezer filled with frost buildup.
Note: in humid areas with a bad door seal you can get there in a month.

Self-defrosting units use a timer to turn on a HEATER and melt the frost out. These use a total of appx 2X the energy of a manual defrost (open it and let it melt out) of the same capacity and insulation rating.

We are used to the self-defrosting household units. They are convenient in not needing to be emptied out for defrosting every 1 to 6 months.

[El Pinguino]

'Don't plug hole that the manufacturer put there on purpose. They had a good reason for it. You don't have to understand it.'

I would like to understand... I'm funny like that.

Mine is blocked... I empty all the tucker out of it every now and again ( once a week or so) and clean it out...mainly cos I'm looking for beer or gin when times are grim... but cleanout includes any spills and stuff in the bottom.

[TurninTurtle]

Also... Differences in insulation, including insulation breakdown, can result in more than 50% difference in energy use for the same capacity fridge...

Changing the thermostat setting also affects efficiency. Its just easier to keep the freezer at -5 c than -20 c. (-20 C is about as far as you'll reasonably go with an R-134a system)

"Heat loss" is based on difference in temperature and insulation value. + air exchange.
Hotter outside and colder inside = more heat transfer.
R2 insulation vs R22, obviously the R22 will have less heat transfer.

And then there's the efficiency of the refrigerant system and its mechanical condition. Modern systems in excellent condition can be very good. Short on refrigerant aged systems near end of life can be very inefficient.

[poiu]

On the subject of making the seals good, I have some seals where the corners have come apart. I have no idea what plastic/rubber material is used. What is the best way or what types of glue might be best for gluing them back together?

[TurninTurtle]

There is no glue that really works well on fridge door seals. You end up replacing the seal. (for some fridges you can't replace the seal without replacing the door)

E-6000 craft glue can buy you a bit of time.
Apply plastic wrap as smoothly as possible to the frame where the seal will meet. Apply glue. Close the door. Wait for the glue to dry. The wrap lets you open the door again.

[sailing_gal]

I defrost my freezer holding plates in 5 minutes. Empty it out, hot tap water after running the engine, spray on the holding plates. It melts the frost, dry the fridge up and food goes right back in.

[a64pilot]

Frost is a problem, ice is actually a good insulator or Igloos would be full of dead Eskimo's, and they aren't.

You can't prevent ice build up, you can slow it down of course, but if you ever open the freezer, you let in moisture every time you do, bad seals obviously make it worse.
I need to plug my drain, common sense tells me I need to, I just keep forgetting

[a64pilot]

Originally Posted by sailing_gal

I defrost my freezer holding plates in 5 minutes. Empty it out, hot tap water after running the engine, spray on the holding plates. It melts the frost, dry the fridge up and food goes right back in.

I keep telling myself to extend the hose on the sink sprayer so it will reach, but I haven't yet, I'm still using the hose that I fill the water tank with

[SV THIRD DAY]

Originally Posted by TurninTurtle

The frost itself is not the problem.

Any mass that acts as a heat sink inside the fridge or freezer actually helps the refrigerator/freezer. Frost buildup is actually one of the best masses (ice) for this.
It does NOT alter the thermostat setting and therefore does not affect the temperature inside. (aside from the frost getting so bad that it makes the air leak worse)

With all due respect...that is Absolutely 100% bogus information.

I have test data going back to the founding of Technautics in 1968 showing just how wrong these statements are...one of the advantages of having the company founder being a PhD in Thermodynamics and a data nerd. This is how Dock and Cruise Rumors get started and the next thing you know I will be talking to cruisers with 1ft of frost around their holding plate thinking they are doing good....ahhhhh....

Lets just take the easy one first:
The compressor thermostat is not located in the Box to measure the box temperature, but rather the temperature of the evaporator. So the Ice/Frost engulfing the evaporator and thermostat will insulate it from the actual box temp, thus your compressor will turn off while your real box temperature is higher than inside your Igloo.
Bingo...warmer beer and soft ice cream will result.

Next...
The driving factor governing the uptake of heat from your Box into the evaporator (Holding plate or rolled aluminum) is the Delta T, or temperature difference. Greater the temp difference then faster the uptake of heat and lower the temperature difference then slower the heat uptake...basic physics here folks. So when you have Frosty the snow man surrounding your evaporation unit, the heat in the box is not seeing the 0 to -20 degree F temperatures of your evaporation unit...but rather the much warmer temperatures of the frost and ice engulfing the evaporator. This slows down the heat uptake...and make the compressor have to run longer, but as mentioned above, since the thermostat is mounted ON the evaporator, it will be fooled into thinking your box is already cold.

Plugging the Hole...
The hole was put there to drain the melted ice out from the bottom of the box, the was the purpose. But since we are not using block ice but rather a refrigeration system, all that hold is good for now is to allow a path for warm moist air to be sucked into the Box.