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Old 19-04-2016, 17:59   #1
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Simple Fridge Question

If I leave a marine fridge (say a small Engel) unplugged for several days at a time, will that damage the fridge in some way? I imagine it's harder on a fridge to go from 80F to 40F every couple days than to continually hover around 40F. Will I lose a lot of service life?

I ask because I'll only have enough power to run the fridge at anchor, so it would have to be turned off while underway for any significant period of time.

Thanks
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Old 19-04-2016, 18:49   #2
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Re: Simple Fridge Question

80 deg is no big deal. Very hot conditions do create higher pressures at startup which could potentially cause premature wear, but basically hours run are hours run.


FYI, you are better off with a better insulated danfoss cooled box energy wise. I run an approx. 3 cu fr fridge and 1.3 cu Ft deep freeze on about 25-30 amp/hrs in 80-85 deg ambient. 170 watts of solar is more than enough is sunny weather for all house loads. 80-100 watts would likely run the fridge/ freezer
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Old 20-04-2016, 15:57   #3
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Re: Simple Fridge Question

Quote:
Originally Posted by Boatguy30 View Post
80 deg is no big deal. Very hot conditions do create higher pressures at startup which could potentially cause premature wear, but basically hours run are hours run.
Thanks!

Quote:
FYI, you are better off with a better insulated danfoss cooled box energy wise. I run an approx. 3 cu fr fridge and 1.3 cu Ft deep freeze on about 25-30 amp/hrs in 80-85 deg ambient. 170 watts of solar is more than enough is sunny weather for all house loads. 80-100 watts would likely run the fridge/ freezer
The Engel 35L is *supposed* to draw 12AH/day at 77F, and 23AH/day at 95F, so a bit more efficient than yours (though yours is a bit larger). In any event, any of these high efficiency 12v'ers should work for my purposes.
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Old 21-04-2016, 05:37   #4
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Re: Simple Fridge Question

There is a basic issue with letting a fridge warm up:

If it is not propped open it can get mold and mildew and stink. In relatively dry climates you need to prop it open for a week.

Yes its a bit harder on the compressor to get the fridge down from 80 to 40 than to just keep it there... but if you load it with COLD food, you reduce the load. The food will cool the fridge liner.

A fridge or freezer is "happier" if its full. The food acts to moderate the temperature, not letting it have the huge temperature swings and frequent short compressor runs.

I worked in appliance repair and had the USA federal license for R-12, R-22 system charge/discharge and refrigerant recovery.
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Old 21-04-2016, 05:57   #5
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Re: Simple Fridge Question

The engel specs are based on a what 40 or so degree fridge? I keep my fridge closer to 35 and the freezer at 10 on that amp usage. I doubt you could keep an engel that cold if running flat out in the tropics.

My point is that if low power draw is your primary goal, it's easily possible to build a much more efficient system. But the Engel is convenient and since they are generally so small most people believe them to be "super efficient"
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Old 21-04-2016, 06:26   #6
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Re: Simple Fridge Question

It's sort of a toss up, I think.
Yes of course you can build a better insulated built in box in the boat, but that is a MAJOR project, I've seriously considered it myself and may one day do it. But most likely I will just end up adding a layer of insulation to the inside of my box.

Or you can install one more Solar panel for a whole lot less work and money that will more than offset the difference in efficiency

But leaving one unplugged for passages I don't see hurting it.
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Old 21-04-2016, 06:43   #7
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Re: Simple Fridge Question

Quote:
Originally Posted by Boatguy30 View Post
The engel specs are based on a what 40 or so degree fridge? I keep my fridge closer to 35 and the freezer at 10 on that amp usage. I doubt you could keep an engel that cold if running flat out in the tropics.

My point is that if low power draw is your primary goal, it's easily possible to build a much more efficient system. But the Engel is convenient and since they are generally so small most people believe them to be "super efficient"
3 years ago my main fridge packed up. I was at Port Dickson Malaysia and didnt want to hang around longer than need be to fix the fridge. So I purchased a Waeco to use temporarily until I did something about the main fridge. 3 years later I'm still using it. I know it shouldn't be efficient and I know its small but the reality is, it is efficient.. Ive used this through malaysia , Borneo, Philippines and now indonesia, very much the tropics. I suppose it depends on how big you want your fridge to be. Two smaller ones wo r k for me, as I only use both when out for a long time.
Ive just installed a ozefridge but are also keeping the waeco.

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Old 21-04-2016, 06:51   #8
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Re: Simple Fridge Question

Its really all must thermal dynamics. A portable unit with 1.5" of insulation and a large lid will be far less efficient than the same size box with R30 and a smaller lid.


On the IP the boxes are WAY to big. A friend last year in the winter on a IP 38 was turning it on turning it off, buying ice, anchoring far out into the harbor to keep the wind generator going just a bit more. What a pain! they look nice at the boatshows and when on shorepower but will totally hog the amps.
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Old 21-04-2016, 07:04   #9
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Re: Simple Fridge Question

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Originally Posted by Boatguy30 View Post
Its really all must thermal dynamics. A portable unit with 1.5" of insulation and a large lid will be far less efficient than the same size box with R30 and a smaller lid.


On the IP the boxes are WAY to big. A friend last year in the winter on a IP 38 was turning it on turning it off, buying ice, anchoring far out into the harbor to keep the wind generator going just a bit more. What a pain! they look nice at the boatshows and when on shorepower but will totally hog the amps.
The fridge built into my freedom is ridiculously large, ive cut it in half, much better.

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Old 21-04-2016, 07:13   #10
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Re: Simple Fridge Question

My Ice Box is 14 cu ft.
Remember it is and was meant to be an ice box, not a fridge, you can put a weeks worth of ice in the thing and still have room for food, but I wanted a freezer / fridge.
I contacted Rich Boren at Technautics and he built me a dual Cold Plate system with a larger than normal compressor and I have 750 W of Solar.
It works, but is not as efficient as it could be.
Remember though, you double the interior volume, you do NOT double the exterior surface area, sort of the 16" Pizza has twice the Pizza of a 12" argument. So being big isn't as inefficient as you might think, it's poor and old insulation not size that hurts my power consumption
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Old 21-04-2016, 11:02   #11
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Re: Simple Fridge Question

Quote:
Originally Posted by KISS View Post
If I leave a marine fridge (say a small Engel) unplugged for several days at a time, will that damage the fridge in some way? I imagine it's harder on a fridge to go from 80F to 40F every couple days than to continually hover around 40F. Will I lose a lot of service life?

I ask because I'll only have enough power to run the fridge at anchor, so it would have to be turned off while underway for any significant period of time.

Thanks
Sometimes when we get such a basic question it becomes harder to answer.

This is very true:
Quote:
Originally Posted by Boatguy30 View Post
80 deg is no big deal. Very hot conditions do create higher pressures at startup which could potentially cause premature wear, but basically hours run are hours run.
If you turn it off and it gets hotter inside the box, it takes longer for the system to cool it down, just like being in house with air conditioning.

The system doesn't know squat about what's going on regarding temperatures, all it knows is that it has to satisfy the inside thermostat. The hotter it is inside, the longer it takes to cool.

IT DOES NOT WORK ANY HARDER! It only has to work LONGER. It's either on or off.

Eventually, you might find it's actually less energy to run it longer than off and then on.

Your boat, your choice.

The other responses have covered a lot of the important issues, like insulation, box size, keep it full with cold stuff, etc.

Wanna learn more? Go here, THE place for boat refrigeration systems:

Kollmann Marine

Rich Boren is a contributor here, too, and does great work. Go find one of his posts using the search tool, and find his website.

Another approach is to add a battery or two or increase your charging sources. It's all an electrical system balancing act.
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Old 21-04-2016, 13:48   #12
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Re: Simple Fridge Question

WRONG: in a cap tube system the high pressure will be higher the greater the ambient. This will "work" the compressor more. It's best to avoid high temp starts when possible.
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Old 21-04-2016, 14:58   #13
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Re: Simple Fridge Question

In automotive AC systems, literally every maker says to run the system at least once per month (at least) in order to circulate the oil that is carried by the refrigerant gas. That oil keeps the O-rings pliable and prevents them from becoming leaking points that discharge the system. It also ensures that if there is any stray moisture or acid (formed when moisture is in the system) that other parts are lubricated, i.e. so the compressor is less likely to stick as well.


Not the same as a refrigerator...but I'd still suggest that running the system at least once per month, for at least 10-15 minutes, would be a good idea. Letting it sit "off" for a couple of weeks at a time? Should be no problem.
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Old 21-04-2016, 15:06   #14
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Re: Simple Fridge Question

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Originally Posted by KISS View Post
If I leave a marine fridge (say a small Engel) unplugged for several days at a time, will that damage the fridge in some way? .................. Will I lose a lot of service life?
I doubt it.

But you probably would be better off far as what you are planning to put in it to just run your engine a while each day to charge you batteries.
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Old 21-04-2016, 19:06   #15
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Re: Simple Fridge Question

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Originally Posted by hellosailor View Post
In automotive AC systems, literally every maker says to run the system at least once per month (at least) in order to circulate the oil that is carried by the refrigerant gas. That oil keeps the O-rings pliable and prevents them from becoming leaking points that discharge the system. It also ensures that if there is any stray moisture or acid (formed when moisture is in the system) that other parts are lubricated, i.e. so the compressor is less likely to stick as well.


Not the same as a refrigerator...but I'd still suggest that running the system at least once per month, for at least 10-15 minutes, would be a good idea. Letting it sit "off" for a couple of weeks at a time? Should be no problem.
Good point. I had a friend with an ancient Volvo station wagon. He was one of those "Berkeley types" who was so concerned about global warming 20 years ago he never ran his AC. I told him, I told him... One day it was SOOOO hot he was forced to. Guess what? He couldn't understand it. Seals has completely disintegrated.

I broke my leg skiing a few years ago and wasn't on the boat for 3 months. First thing I did was run the fridge. I use the boat once a week, normally, but that was the longest it's gone without use in the 18 years we've had our boat. Things are fine. It's a 30 year old Adler Barbour Cold Machine.

We always leave it off and the top open when not on the boat.
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