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Old 03-10-2015, 12:43   #166
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Re: Why no Residential Fridges?

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Originally Posted by valhalla360 View Post
If they were saying amp-days, that would be odd but as long as they follow with the correct math, it works fine. Likewise, you could use watt-hrs if you want to be voltage agnostic.

What is being proposed by several posters is amps/day, which makes no sense.
I have a friend evaluating solar for his house. I asked how it was working? I'm selling power back to the power co. KWHs but I'll let you know after a year after the sun has been at all angles to the panels. It's almost the same looking at a short timeframe doesn't tell the story. Granted amps/day is not common but could be a good way to look at it. Maybe ampere hrs/day would be.
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Old 03-10-2015, 13:01   #167
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Re: Why no Residential Fridges?

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Which as cruisers of course means ampere hours per day. Quite clear. Amperes per 24 hours, is very much like summing up 24 hours of ampere-hours loads. Its a unit of measuring ampere hours in a 24 hour range. Which is oddly somewhat important to many cruising sailors.

An ampere-hour is simply the number of amperes used or stored in a unit of time called an hour. We can also use units of milliseconds, femto-seconds, days, weeks or years. To say that we can only use ampere-hours to measure the consumption or production of electron's is somewhat limiting.

I could just have easily said my fridge uses 2.05 moles of electrons in a day, which would be clear to chemists and almost no one else. A mole being equal to 26.8 ampere hours. Lets not use moles though. Someone might confuse that with small burrowing insectivorous mammals.

We could also use milliampere-second or coulombs, 3600 coulombs equals 1Ah. Lots and lots of units. How cool is that.
You forgot joules and ergs?
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Old 03-10-2015, 13:11   #168
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Re: Why no Residential Fridges?

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You forgot joules and ergs?
LOL, Not really...

Joules and ergs don't convert to amperes. They convert to watts or volt amperes. But you knew that.
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Old 03-10-2015, 13:27   #169
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Re: Why no Residential Fridges?

I like ergs and bacon with toast. And a glass of orange joules.

I might not be using those words right
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Old 03-10-2015, 13:32   #170
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Re: Why no Residential Fridges?

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Originally Posted by sailorchic34 View Post
LOL, Not really...

Joules and ergs don't convert to amperes. They convert to watts or volt amperes. But you knew that.
Oh, hell we forgot BTUs. I think joules work for that and this whole thing started with refrigeration.

Let's start something about the new vs. the old refrigerants. R22 vs. R410A?
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Old 03-10-2015, 13:55   #171
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Re: Why no Residential Fridges?

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Oh, hell we forgot BTUs. I think joules work for that and this whole thing started with refrigeration.

Let's start something about the new vs. the old refrigerants. R22 vs. R410A?
Gee I can hardly keep up with all the new refrigerants. I remember when 134A was new. Though propane works rather well as a refrigerant. Cheap and easy to get too.
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Old 03-10-2015, 15:31   #172
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Re: Why no Residential Fridges?

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Which as cruisers of course means ampere hours per day. Quite clear. Amperes per 24 hours, is very much like summing up 24 hours of ampere-hours loads. Its a unit of measuring ampere hours in a 24 hour range. Which is oddly somewhat important to many cruising sailors.

An ampere-hour is simply the number of amperes used or stored in a unit of time called an hour. We can also use units of milliseconds, femto-seconds, days, weeks or years. To say that we can only use ampere-hours to measure the consumption or production of electron's is somewhat limiting.

I could just have easily said my fridge uses 2.05 moles of electrons in a day, which would be clear to chemists and almost no one else. A mole being equal to 26.8 ampere hours. Lets not use moles though. Someone might confuse that with small burrowing insectivorous mammals.

We could also use milliampere-second or coulombs, 3600 coulombs equals 1Ah. Lots and lots of units. How cool is that.
As I already stated in a previous post, you can use amp-days or watt-hrs or milliamp-femtoseconds. Some are a bit cumbersome, just like your examples that incorporate coulombs or moles but they have meaning in terms of the discussion.

You appear to be confusing the use of convenient but correct units of measurement with units of measurement that are not correct. If you want to use inconvenient units, that's odd but acceptable. If you use incorrect units, it leads to mistakes.

Amp/day has no meaning in this context. The only cruisers using X amps per day don't understand what they are talking about.
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Old 03-10-2015, 15:42   #173
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Re: Why no Residential Fridges?

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I have a friend evaluating solar for his house. I asked how it was working? I'm selling power back to the power co. KWHs but I'll let you know after a year after the sun has been at all angles to the panels. It's almost the same looking at a short timeframe doesn't tell the story. Granted amps/day is not common but could be a good way to look at it. Maybe ampere hrs/day would be.
What would amps/day tell you? In the morning, you will have positive amps/day. It will drop back to a low number mid day when the amp output is fairly steady then late afternoon it will turn negative as it drops back to zero. Overnight, it will sit at zero (assuming you don't shine a spot light or otherwise introduce a light source). Over the course of a year, it should average out to zero (or darn close with rounding errors).

Amp-hrs/day, is a totally different measurement. When averaged out over the course of a year, the time factors cancel out (with correct conversion between hours and days) and it will give you the average Amps produced by the system. Though in terms of battery storage, amp-hrs is a useful measurement and since the solar charging cycle is typically a daily cycle, amp-hrs/day can have a useful meaning.
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Old 03-10-2015, 16:19   #174
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Re: Why no Residential Fridges?

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As I already stated in a previous post, you can use amp-days or watt-hrs or milliamp-femtoseconds. Some are a bit cumbersome, just like your examples that incorporate coulombs or moles but they have meaning in terms of the discussion.

You appear to be confusing the use of convenient but correct units of measurement with units of measurement that are not correct. If you want to use inconvenient units, that's odd but acceptable. If you use incorrect units, it leads to mistakes.

Amp/day has no meaning in this context. The only cruisers using X amps per day don't understand what they are talking about.
He was keeping it simple. What comes out needs to go back in. I'll bet it works for him.

If I want to prove how smart I am, I'd have to find the books I through out a couple of decades ago. Knit picking is ridiculous.

This whole thread has been. Wanting to replace compressors. If it was a feasible idea, the companies with large R&D bucks would have done it.
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Old 03-10-2015, 17:27   #175
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Re: Why no Residential Fridges?

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Originally Posted by sailorchic34 View Post
I think everyone understands that. It's basic electrical. ...
An ampere hour is simply the number of amperes (amps, A) used or stored in one hour. One could also use Ampere-day ( amp-day or amps per day) to define the number of ampere-hours used in one day. It's simple and quite clear.
Utterly wrong again.

It's misunderstandings like this and incorrect use of the units that results in things like an earlier poster thinking that 1200 CCA is a measure of the capacity of his vehicle battery. (Both a tiny "emergency starter" and a big bank of trojans can have 1200 CCA, but you will get a lot more use out of the latter.)


OK, there is no use in trying to help the wilfully ignorant. I'm out of here too.
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Old 04-10-2015, 00:07   #176
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Re: Why no Residential Fridges?

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OK to me your numbers don't make any sense let's see you have a dorm refer running on an inverter so that looses efficiency right there first what is the power draw of your inverter in standby mode.
Now for the fridge. You state it uses 15 amps when compressor runs it runs 2.5 min for each. 15 min so it runs for 10 min per hour which means it runs for 1 hour in a 6 hour time frame which means 4 hours run time per 24hour day so we have 15 amps x 4 hours per day = 60 ah usage per day my fridge (a holding plate system uses 4 amps and runs for about 2.5 hours twice a day so uses 20 ah / day right now with mid to upper 60's and mid 50's water ( air cooled system ) so I use about 40 ah less than you not even calculating the static useage of your inverter ( not even looking at the inefficiency and power usage of the inverter itself)
AH, sorry for my the slow response. I missed your post. My usage and power draw were measured at 90 degree F cabin temperature in the California delta, where daytime highs can climb to over 100 degrees F. I've not tested at 60 degree cabin temperature, as it's not a problem then. That is, I wanted to make sure I had enough battery capacity to carry the fridge for 2 days worst case.

My inverter standby loss is about 1 ampere hours an hour, but that's factored in my daily load and in the 15 amp draw. The 2.5 ampere hour is worst case and drops quite a bit at night. I suspect I'm using ~50 amps a day with the fridge in 90 degree delta summer. At 60 degrees it runs much less.
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Old 04-10-2015, 00:11   #177
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Re: Why no Residential Fridges?

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He was keeping it simple. What comes out needs to go back in. I'll bet it works for him.

If I want to prove how smart I am, I'd have to find the books I through out a couple of decades ago. Knit picking is ridiculous.

This whole thread has been. Wanting to replace compressors. If it was a feasible idea, the companies with large R&D bucks would have done it.
But without a duration, amps by itself tells you nothing about how much came out or went back in.

Amps/day needs not only a duration but a starting amp draw to make the same determination.

It's like saying you burn 1 gal/hr, so how many gallons of fuel do you need? Without knowing how long you will be running the engine, you have no idea. Then along come poeple saying you need 10 gal/hr per day which has no meaning.

Your posts have clearly proven how smart you are no need to get the books out.
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Old 04-10-2015, 00:17   #178
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Re: Why no Residential Fridges?

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Now I'm not trying to be mean or any of that crap it works for you do it however a dorm fridge wouldnt'like being tilted 15 to 20 degree heel for a week or more straight like on a passage from here Washington to Hawaii. It works for you and I see no reason it wouldn't work great for anybody on a local sailing boat.
Ah but the Danfoss compressor design is practically the same as the larger 120V compressors. That being a electric motor driven piston compressor in an oil bath.. Mind you there is differences in displacement, but the basic design is the same.

But then I've only tested it short 4-6 hour sails. But the basic construction is quite similar. I find even when healed over at 20 degrees the boat rocks a bit so oil is still cooling and lubricating the compressor motor. TheyDanfoss /Socop don't actually make a marine compressor, its just an off the shelf 12v unit.
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Old 04-10-2015, 00:20   #179
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Re: Why no Residential Fridges?

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But without a duration, amps by itself tells you nothing about how much came out or went back in.

Amps/day needs not only a duration but a starting amp draw to make the same determination.
Ampere hours also need a amp draw and duration.
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Old 04-10-2015, 00:41   #180
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Re: Why no Residential Fridges?

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Originally Posted by sailorchic34 View Post
Ah but the Danfoss compressor design is practically the same as the larger 120V compressors. That being a electric motor driven piston compressor in an oil bath.. Mind you there is differences in displacement, but the basic design is the same.

But then I've only tested it short 4-6 hour sails. But the basic construction is quite similar. I find even when healed over at 20 degrees the boat rocks a bit so oil is still cooling and lubricating the compressor motor. TheyDanfoss /Socop don't actually make a marine compressor, its just an off the shelf 12v unit.
Adding some insulation to your refer install will improve your fridge power dynamic and I did say temps in upper 60's to low 70's for our fridge. Compressor is mounted in the engine room
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