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Old 14-08-2016, 09:50   #1
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HOT weather Freezer/Fridge Amp use minimisation

Recent thread re someone using 8 amps continious 24 hours per day and having battery problems.

North USA currently has a "heat wave". (Well, if it was Australia 95deg F/35 deg C is just a normal warmish summers day... )

One of the big users of electricity is the fridge and freezer, but you may be able to cut usage down substantially.

The Dometic freezer I have is rated to -18c/0F BUT the minimum temperature cant be attained "if the ambient temperature is above +32C / 90 F". So on these 95 D days you are stuffed by at least 5 degrees (more as your air intake probably has a higher ambient temp due to the proximity of the compressor).

So a freezer striving for the recommended freezing temp for frozen food storage will run 24/7 and still not get down to -18/0.

I dont set it that low... Mine is about -7deg C / 20F and everything is solid as a rock. Meat will still keep for 6 months if I dont already fang it. Water, of course, starts freezin, in practice, at -.5c/30F.

So why do we need those very colds temps? ICE CREAM! The freezing point of liquid sugar and High Fructose Corn Syrup is much lower, and when you consider that ice cream is about 50% air the freezing point is lower again. Technically ice cream is a 'frozen foam'. Its just firm at -12C/10F and melts bloody quick in the the cockpit when its 95F outside.

To save a lot of electricity dump anything with sugar, HFCS, air, processed ingredients and stick with water intense foods like meats.
Meat will be quite solid at -4C/25F and will be quite safe to consume, no freezer burn etc for at least a few weeks.

The bad news maybe no icecream on the boat until the weather cools, but the good news is theres an ice cream shop not far away....


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Old 14-08-2016, 13:31   #2
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Re: HOT weather Freezer/Fridge Amp use minimisation

Ice cream is awesome! Our experience matches yours - we can't freeze ice cream effectively unless its close to 10 F.

The good news is that with our new frigoboat keel cooler and even in 100 degree weather, we are only seeing 53 Ah use over 24 hours. Here is our fridge stats for the last 24 hours:
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Old 14-08-2016, 13:45   #3
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Re: HOT weather Freezer/Fridge Amp use minimisation

I've rigged a couple of 12v computer fans to direct a *lot* of air over the heat exchanger. Won't help in realy high air temperatures but does wonders for my power consumption. When I bought my current boat it had an "inlet" for the three way fridge. This drew air, or was supposed to, from under the bridgedeck. To stop water coming into the boat in a seaway there was an aft facing cowling which made the inlet an outlet.

The three way fridge stopped working and I bought a compressor fridge. I now use fans linked to the compressor motor circuit to blow hot air from the fridge out and down which isn't especially efficient but seems to work.

I wonder if having a couple of strategically placed fans and a simple water evaporator might not save your ice cream?
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Old 14-08-2016, 14:02   #4
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Re: HOT weather Freezer/Fridge Amp use minimisation

Zboss, that's a cool display! What is it?
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Old 14-08-2016, 17:21   #5
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Re: HOT weather Freezer/Fridge Amp use minimisation

Yeah, Zboss. Spill the beanz.

Twohappence: Yep, i did exactly that on bith my fridge compressor and my freezer. Works much better.
I dont have a problem with ice cream, the advice was for others who cant keep their power up in hot times

Not that i have ice cream much Someone once said about diet "listen to your body it will tell you what it needs". I listened. It yelled ice cream, choccie shakes and PUDDING!


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Old 14-08-2016, 18:03   #6
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Re: HOT weather Freezer/Fridge Amp use minimisation

Quote:
Originally Posted by MarkJ View Post
Yeah, Zboss. Spill the beanz.

Twohappence: Yep, i did exactly that on bith my fridge compressor and my freezer. Works much better.
I dont have a problem with ice cream, the advice was for others who cant keep their power up in hot times

Not that i have ice cream much Someone once said about diet "listen to your body it will tell you what it needs". I listened. It yelled ice cream, choccie shakes and PUDDING!


Fridge optimizer

http://www.suremarineservice.com/ref...cessories.aspx

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Old 15-08-2016, 04:15   #7
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Re: HOT weather Freezer/Fridge Amp use minimisation

Yes, it's called a stainless lobster.

It has a built in circulation fan with a cool blue light. We have a spillover fridge and they recommend putting the fan/thermocouple in the fridge portion but we have been using it in the freezer.

Our frigoboat has both the keel cooler and the air cooler. The air cooler is set on a switch so it can be turned on when needed. I have yet to do so. I wonder how much it would help during very hot weeks.

FYI... This fridge only has 1 inch of 27 year old insulation in places. We added 5" of insulation to the bottom and an inch onto the bottom of the lid.


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Old 15-08-2016, 22:44   #8
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Re: HOT weather Freezer/Fridge Amp use minimisation

My Fridge used 17 AH overnight. No freezer, no ice cream and no pain. Oversize Bavaria box and basic machinery. And in very hot Ionion Islands, Greece ! The 260 AH of battery capacity are just strolling.

Cold enough for beer and keeps the milk fresh and meat OK for a couple of days.

All run by 2/80W panels.
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Old 15-08-2016, 23:14   #9
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Re: HOT weather Freezer/Fridge Amp use minimisation

Mark,

Do you have a shade over your boom? I find that shading the cabin top does keep it less hot inside perhaps by a couple of degrees and then your fridge and freezer don't have to work quite so hard.

I think you can make some energy savings by installing a digital temperature control to your fridge. Then you don't waste energy making the fridge colder than you need. Some people on the Jeanneau forum have fitted one of these and are happy with the result 10A 12V Digital Temperature Controller w/Sensor Thermostat Switch -40~120°C UK | eBay
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Old 10-02-2017, 07:18   #10
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Re: HOT weather Freezer/Fridge Amp use minimisation

Three words. Insulation, Insulation , Insulation. Don't think of upgrading anything until you re-insulate. Like Nike says , "just do it" if you are heading for the tropics and want efficient refrigeration you need to Re-insulate. R30 in the fridge R40 in a deep freeze . You can obtain these values using Polyiso board, (white board with foil on the outside) , Extruded polystyrene or blue/pink board , Expanded polystyrene, white board no foil , or a combination of all three. If you have deep pockets you could use Aerogel at R10 per inch .
This can been done through your existing openings , you don't have to destroy your cabinetry , but you will have to build a new liner. More then likely out of fiberglass. Some people have glued together plastic panels together but I don't see this as a long term fix , things shift in your box as you sail and plastic is brittle when cold and glued corners can let go. Fiberglass is a much more durable solution for this application.


I will be posting a "how to" video showing the process shortly on this forum and my website .

Regards John.
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