Refigeration Amp Hour usage survey

[chala]

Originally Posted by Mike OReilly

in warmer climes.

It can happen that in warmer climes and on non stop running, the pressure in the high side (condenser) become too high and make the compressor inefficient then the unit only consume energy for not much cooling. For instance at over 45 deg C ambient, my Danfoss on the tow truck is unable to reach the set - 17 deg C and will run continualy. Set at -12 deg C it is able to cycle on and off and use fare less power and do more efficient cooling.

[crazyoldboatguy]

I have Kollman's book and have read his posts. He is clear that one should use the basic formula of 20 amp hours per cubic foot per day for freezers and 10 amp hours per cubic foot per day when estimated electrical power needs. Kollman clarifies the assumption of an r factor of 30 for the freezer and 20 for the fridge.

I read here some amazingly low usage from folks on this stream - far and away much lower than the guru asserts. I am in no way an expert on this - I will be building a system on my ketch in the near future. I would love to get the power usage that many claim here, rather than the calculations Kollman insists are basically inviolate.

Is there a parallel universe out there?

[SV THIRD DAY]

Originally Posted by crazyoldboatguy

I have Kollman's book and have read his posts. He is clear that one sh I would love to get the power usage that many claim here, rather than the calculations Kollman insists are basically inviolate.

Is there a parallel universe out there?

No...no parallel Universe, with all due respect for Kollman, his numbers are just a little outdated, his R-value assumptions a little low, and are intended to be Rule of Thumbs for worst case planning, not Laws of Physics.

Don't make the typical mistake to assume that a self selecting sample here on Cruisers Forum is in any way representative of the greater Cruising Community. Remember who you are dealing with here...people that pay attention. For example, when I talk to cruisers and ask what is the size of their battery bank, I routinely get the answer, "Oh..it's big...a bunch of big ass batteries". I then say, "good to hear, do you know the Amp hour size of your Big Ass Battery Bank?". After a pause, the answer back is "Ah...what's an Amp Hour".

After Cruising in Mexico for 4yrs living 100% at anchor followed by 4yrs now of living aboard on a mooring, I can almost tell my battery voltage by the color of my cheap LED lights and I remember my battery type, brand and Amp Hour rating easier than my kids birthdays and wedding anniversary. But I'm not "Normal" nor are the other Tech-nerds posting here. We are the type of folks that respond to these types of technical posts and threads. A self-selecting sample of people happy with and wanting to share their good low numbers.

Total daily power usage also is affected by other factors like size of crew, are you living aboard full time or only weekending? For example when we were in the Sea of Cortez for the summers each of our 4 crew members drank 2 Liters of Cold water per day. When we went to bed, we would then put 8 liters of warm water into the refrigerator for the next day. How many warm beers do you put in per day? Are you making ice in your Freezer compartment or buying ice and just keeping it frozen?

Unless you have a dedicated Amp Hour meter on your system or at least an hour meter, it's really a educated guess as to how much power you are really using in a 24hr period. Being a tech-nerd and in the Refrigeration industry I have an Amp hour counter and hour meter on both our refrigerator and freezer. But not everyone is going to be as anal, because I also have one on my solar panel output, battery charger output, alternator, and wind generator output, along with a battery bank total output meter...a scientist can't change his spots even when he becomes a Hobo Bozo cruiser.

[crazyoldboatguy]

Well, SV Third Day, with all due respect to those posting here I see numbers all over the map as far as consumption is concerned. As a person with relatively low experience I look to secure accurate info prior to installing twice the storage and generation capacity needed in my vessel - which (in your opinion, apparently) seems likely if I follow Kollman's advice.

Relying on anecdotal postings on CF just doesn't seem the best way to do that. It all seems more like the black arts and Alchemy.

[SV THIRD DAY]

Well enough Anecdotal examples and you get somewhere...but that's the hard part...getting an accurate sample of cruisers.

This I can tell you, add more solar until you have no room for more...then squeeze on more. Solar panels are like Garlic...you can't have too much. We went from 260W...to 430W...and now have 1300W...finally enough!

[crazyoldboatguy]

Originally Posted by SV THIRD DAY

Well enough Anecdotal examples and you get somewhere...but that's the hard part...getting an accurate sample of cruisers.

This I can tell you, add more solar until you have no room for more...then squeeze on more. Solar panels are like Garlic...you can't have too much. We went from 260W...to 430W...and now have 1300W...finally enough!

Yeah, well, my boat is a ketch rig - so I have that going for me!

[ColdEH]

I have zero solar and don't plan on adding any . I don't plug in at the dock either . Just run my generator for 2hrs every 4 days or less and I am good to go. When I am sailing using all the electronics I run 2 hrs every 2 days , maybe . That's if I'm using 200 ah a day .
Design your systems properly , make sure they are running right .
No black arts needed. 🤓

Regards


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[a64pilot]

I'm still trying to understand how flying pig Skip can use 250 AH a day.
I'm at the boat now and made a point to check the amp meter when I came aboard, the battery charger was putting out 6.3 amps at float voltage, fridge was the only thing on. Later with other stuff on, I turned off the fridge and noted amp drop, 5.8 amps at float voltage.
So I'm pretty certain my BD80 compressor with cooling fan pulls 6 amps, assume it runs continuously and never stops for 24 hours, that is only 144 AH? A little more than 100 short of 250?


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[SeaSon]

4.4 cu ft ref-frzr. 120v. Home Depot as I was in a fix.

Draws 5.5amps @12v. Runs approx 60-70% in 85deg day, much less at 70deg night. So estimated 50% for 70AH per day.

[a64pilot]

Originally Posted by crazyoldboatguy

I have Kollman's book and have read his posts. He is clear that one should use the basic formula of 20 amp hours per cubic foot per day for freezers and 10 amp hours per cubic foot per day when estimated electrical power needs. Kollman clarifies the assumption of an r factor of 30 for the freezer and 20 for the fridge.



I read here some amazingly low usage from folks on this stream - far and away much lower than the guru asserts. I am in no way an expert on this - I will be building a system on my ketch in the near future. I would love to get the power usage that many claim here, rather than the calculations Kollman insists are basically inviolate.



Is there a parallel universe out there?

No parallel Universe, though if you follow Richards numbers, use them to plan on consumption, you'll be a happy camper almost certainly, if you go one some of these very hard to achieve numbers, you will almost certainly be unhappy, as it is very likely your consumption will be much higher, and if you used them to determine amount of Solar you needed, you'll be short.
I assume Richard used numbers with a little "fudge" or based on experience, people on average have poor insulation and or are often adding hot items.
Wanna put a hurt on your fridge? Put a case or two or maybe three of 90 degree beer in in


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[Mike OReilly]

Originally Posted by chala

It can happen that in warmer climes and on non stop running, the pressure in the high side (condenser) become too high and make the compressor inefficient then the unit only consume energy for not much cooling. For instance at over 45 deg C ambient, my Danfoss on the tow truck is unable to reach the set - 17 deg C and will run continualy. Set at -12 deg C it is able to cycle on and off and use fare less power and do more efficient cooling.

Thanks again Chala, I really think there must be a fault with the thermostat. I did have the compressor cycling about a week ago. We then went into some really hot weather (low/mid 30C, and high humidity). Since then it's refused to cycle off. Our whole setup is old, and I'm sure we're not as well insulated as we could/should be. The radiator is also caked in some plastered dust. It's in an inaccessible area, so hard to get at and clean ... but I'll try that next.

Anyway, we're on board all the time now. And with sun in the sky we can keep up with the draw, so we're basically running all day and shutting off overnight. Things stay cool enough. Once we're done for the season I'll take a stab at some real testing/maintenance/surgery. Hard to do when the box is full of beer .

[ColdEH]

Originally Posted by a64pilot

I'm still trying to understand how flying pig Skip can use 250 AH a day.
I'm at the boat now and made a point to check the amp meter when I came aboard, the battery charger was putting out 6.3 amps at float voltage, fridge was the only thing on. Later with other stuff on, I turned off the fridge and noted amp drop, 5.8 amps at float voltage.
So I'm pretty certain my BD80 compressor with cooling fan pulls 6 amps, assume it runs continuously and never stops for 24 hours, that is only 144 AH? A little more than 100 short of 250?


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I know . I wish I was close to him , I would really like to see where all those amps are going . There is definitely a few gremlins in his system .

I looked up the specs on the bd80 and your estimate is spot on .

Regards


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[SV THIRD DAY]

I agree....Skip's Unit's power usage is just crazy a water cooled BD80 with his box size and type of insulation just shouldn't be using those type of numbers. I've spent lots of back and forth time trying to help...but just had to admit that I couldn't figure it out without being on the boat myself. Heck if Skip will have cold beer for me, I will offer to do that the next time I am in Florida!

[ColdEH]

The last two dayshave been very hot up here . With the inside of the boat at 35 Celsius . These turned out to be my worst amp hour days . 38 Ah . No alchemy here . Just counting . I have yet to insulate my two top doors which I will do this week with aerogell . The doors actually feel cold to the touch so there is a lot of btu's going up up and away from there .

Regards


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[ColdEH]

Originally Posted by SV THIRD DAY

I agree....Skip's Unit's power usage is just crazy a water cooled BD80 with his box size and type of insulation just shouldn't be using those type of numbers. I've spent lots of back and forth time trying to help...but just had to admit that I couldn't figure it out without being on the boat myself. Heck if Skip will have cold beer for me, I will offer to do that the next time I am in Florida!

Lol beer for me too , meet you there Rich . 😀


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