Refer power

[model 10]

I've been turning the fridge off at night, then back on when the solar starts in the morning. What I notice the most is the lack of noise from the damn refer unit cycling all night long. The refer temp does go up some, but is back down to normal temp by beer 30. I don't have a power meter to measure any of this, so I wonder, does it matter for just a refer?

[john61ct]

It is definitely using more power per 24hrs that way. But so long as the temp doesn't risk food safety. . .

Next time you overhaul / replace the reefer, consider putting in a holding plate setup.

[RainDog]

What temp does it get up to after being off all night?

[Stu Jackson]

Originally Posted by john61ct

It is definitely using more power per 24hrs that way. But so long as the temp doesn't risk food safety. . .

>>>>>>>>>>>>>>.

John, that makes little sense. Would you care to explain?


My experience, 21 years with a "not so well insulated if at all" box, with an Adler Barbour cold machine, is that once cooled down it stays pretty stable, and that the duty cycle after the first two or three hours is 50% at <5A or the standard 60 ah per day. This means nowhere the more power in 24 hours than if left running 24/7. I do this every short cruise I go on.


Do the math for leaving it off for 8 hours overnight and you simply can't use more in 24 hours than if you left it running.

[stormalong]

Originally Posted by Stu Jackson

John, that makes little sense. Would you care to explain?


My experience, 21 years with a "not so well insulated if at all" box, with an Adler Barbour cold machine, is that once cooled down it stays pretty stable, and that the duty cycle after the first two or three hours is 50% at <5A or the standard 60 ah per day. This means nowhere the more power in 24 hours than if left running 24/7. I do this every short cruise I go on.


Do the math for leaving it off for 8 hours overnight and you simply can't use more in 24 hours than if you left it running.

Actually it can and will use more power by turning it off for eight hours. The box will warm up and it takes more power to cool it down than to maintain it cold. Want to confirm that? Put an engine hour meter in the refer circuit and measure total run time per day in each configuration. Also, warming and cooling your food is less safe than keeping it at a steady cold temperature.

[Uncle Bob]

We used to have a number of actual refrigeration manufacturers here on this site that could have answered your questions with accuracy and possible improvement suggestions, however they have apparently been chased away or excommunicated, sadly a lost resource to us all.
Perhaps an email to one or more of them may get you the assistance required.

[john61ct]

With mainstream evaporators and systems designed for frequent & short duty cycling, maintaining a narrow range of hysteresis takes a **lot** less energy than letting temps rise over a long period of time.

With all fridges and freezers, leaving them plugged in so their control systems handle the duty cycling 24*7, will **always** be overall more energy efficient, than unplugging.

If the reason for unplugging is to lower DoD overnight, means you need a bigger bank.

Or as I said go for eutectic "cold energy" storage instead, but economically that only makes sense if you have "free energy" surplus production past the point of your bank's needs, most days.

And of course, your overall energy inputs must on average exceed your consumption, no way around that.

[model 10]

[QUOTE=RainDog;2981614]What temp does it get up to after being off all night?


I use a heat gun on the top of a beer can. I try to keep the beer about 38 deg. The water temp is always about 85deg. In the morning a beer can is usually about 48 deg sometimes as high as 54deg.
There is an amp meter for the refer, but it does not totalize. It usually starts out at 6.8a and never gets below 4.5a. and the refer is back down to temp by noon.

[sailorboy1]

Originally Posted by Ecos

I've been turning the fridge off at night, then back on when the solar starts in the morning. What I notice the most is the lack of noise from the damn refer unit cycling all night long. The refer temp does go up some, but is back down to normal temp by beer 30. I don't have a power meter to measure any of this, so I wonder, does it matter for just a refer?

Replace your refrigeration condenser fan with a good $17 one and you would hear it ever

[a64pilot]

Originally Posted by john61ct

With mainstream evaporators and systems designed for frequent & short duty cycling, maintaining a narrow range of hysteresis takes a **lot** less energy than letting temps rise over a long period of time.

With all fridges and freezers, leaving them plugged in so their control systems handle the duty cycling 24*7, will **always** be overall more energy efficient, than unplugging.

I don’t believe that is correct at all. In fact one of the primary ways a holding plate system gains efficiency is by extending on and off times, which is the same if you had a wider, not narrower hysteresis.
A system has some time after start up before good cooling begins, until that happens the power consumed is essentially wasted, reduce the frequency of start ups and you’ll increase efficiency.

Then your forgetting any excess Solar, which most have later in the day, if you can harvest that by having the compressor run continuously as opposed to cycling on and off, you will use less battery power.

Often using less energy from the battery bank is more relevant that system efficiency.

However I’m with SB, put a good fan on it, and leave it alone, a sealed compressor is nearly silent.

[john61ct]

Obviously if it's just for cooling drinks now worries about food poisoning, then not a big deal just wasting a bit of power.

Keeping the box **chock full** of high density stuff, like adding water bottles (bladders) as the other drinks gets consumed, will help a lot.

A high volume of low density stuff, particularly the worst case - air - means more frequent duty cycling (higher Ah consumption) is required.

[john61ct]

Originally Posted by a64pilot

I don’t believe that is correct at all.

Maybe you missed my qualifier:

>> With mainstream evaporators and systems designed for frequent & short duty cycling

Obviously, going to a eutectic plate system to reduce bank Ah capacity completely changes the dynamics.

Reducing the number of cycles per 24hrs is a fine goal, but food-safe concerns usually means wider hysteresis is not possible going upwards, and a lower bottom increases consumption geometrically not linear.

Excess solar is exactly what enables the greater overall efficiency of eutectic designs, but just putting in a bigger LFP bank is likely a better overall investment if your evaporator-based reefer is not currently in need of replacement.

[sailorboy1]

Originally Posted by sailorboy1

Replace your refrigeration condenser fan with a good $17 one and you would hear it ever

That’s “wouldn’t hear it”

[model 10]

I forgot to mention the other reason for turning the refer off at night, the batteries. Now I wake up to 12.8 or 12.9. Leaving it run all night, I would see 12.5 in the morning. A few cloudy, windless days and we could not recover.
We used to have self pumping water cooled set-up and I could hear that cycle also.

[john61ct]

>> If the reason for unplugging is to lower DoD overnight, means you need a bigger bank.


>> And of course, your overall energy inputs must on average exceed your consumption, no way around that.