Why no Residential Fridges?

[SV THIRD DAY]

Originally Posted by TeddyDiver

Ok, but the difference is in the speed controller circuit IMHO, not in the compressor itself.

Having a humble opinion is fine, but is it based on real life test data or your gut?

Look, I've tested dozens of brands of compressors.
I'm not a smarter guy, it's just what I do for a living and spend R&D money to do. Yes there is a difference in the compressor regardless of the speed controller. Data doesn't lie.

[Cadence]

Originally Posted by colemj

Isn't that called a "fuse" and not a "resistor"?

Mark

I'd call it a short circuit.

[SV THIRD DAY]

Originally Posted by Cadence

I'd call it a short circuit.

I won't tell you what my wife called it as she was taking the cover off our life raft!

[Scot McPherson]

My wife didn't call it anything, however I don't think I am allowed to tell you what she called me.


Sent from my iPhone using Tapatalk

[alansmith]

Use guys...like the Jersey way of saying it....are cracking me up. Like the time I asked my wife to hold the spark plug lead close to the engine while I pulled the rope to see if It had spark. I swear I did not know her hand was wet. She looked like Phyllis Diller hair style immediately. I saw murder in her eyes...no joke

after she stopped swearing she accused me of doing it to her on purpose. I told her with tongue in cheek that she always told me..."don't tell me what to do"...what can a man do sometimes?

[Cadence]

Originally Posted by alansmith

Use guys...like the Jersey way of saying it....are cracking me up. Like the time I asked my wife to hold the spark plug lead close to the engine while I pulled the rope to see if It had spark. I swear I did not know her hand was wet. She looked like Phyllis Diller hair style immediately. I saw murder in her eyes...no joke

after she stopped swearing she accused me of doing it to her on purpose. I told her with tongue in cheek that she always told me..."don't tell me what to do"...what can a man do sometimes?

That is a trip. Thanks for the humor.

[socaldmax]

Originally Posted by alansmith

Use guys...like the Jersey way of saying it....are cracking me up. Like the time I asked my wife to hold the spark plug lead close to the engine while I pulled the rope to see if It had spark. I swear I did not know her hand was wet. She looked like Phyllis Diller hair style immediately. I saw murder in her eyes...no joke

after she stopped swearing she accused me of doing it to her on purpose. I told her with tongue in cheek that she always told me..."don't tell me what to do"...what can a man do sometimes?

I'm amazed you're still alive! She must really love you!

[socaldmax]

I was doing some major electrical upgrades for a guy and he decided to start hooking up the huge battery bank one day before I arrived. Of course he had no idea what he was doing and apparently shorted it out with one of the cables.

When I got there, there was still the smell of burned insulation and heated metal in the air. He was sitting in the salon with a dazed look on his face and the end of the cable was vaporized off. After that, he had a much healthier respect for electrical knowledge!

[Dulcesuenos]

Originally Posted by kismet

As to the Edgestar. I had one, quite as soon as the warranty ran out, no help from the company. Chinese junk.

Our first one is over 5 years old still going strong. Current works great

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[StuM]

Originally Posted by Cadence

Lighten up. Every body knew it was per not divided by.

Sigh!

"per", "divided by", "out of", "for each" and "/" are virtually synonymous.

10 percent = 10 per hundred = 10 out of a hundred = 10 for each 100 = 10 /100 = 0.1

Once again:

Amp is an instantaneous measure of the rate of current flow. (As pointed out above 200CCA (cold cranking amps) is the maximum rate of discharge of the battery. It does not tell you anything about how many Amp hours or Watt hours the battery can store or deliver). It's like a pump's "gallons per minute".

Amps per hour or amps/hr is the rate of change of amps.

If I switch on my doofelaki and it initially draws 5 amps, but after it has been running for one hour it is drawing 7 amps, then the current draw is increasing at a rate 2 amps per hour. If it starts at 3 amps and increases to 5 amps over an hour, it is still 2 amps/hr. It tells me nothing about the amount of power used, just how it is changing.

That is then ONLY possible meaning of amps/hr or amps per hour. Anything else is nonsensical and a gross misuse of basic units.

[Jim Cate]

Originally Posted by StuM

Sigh!

"per", "divided by", "out of", "for each" and "/" are virtually synonymous.

10 percent = 10 per hundred = 10 out of a hundred = 10 for each 100 = 10 /100 = 0.1

Once again:

Amp is an instantaneous measure of the rate of current flow. (As pointed out above 200CCA (cold cranking amps) is the maximum rate of discharge of the battery. It does not tell you anything about how many Amp hours or Watt hours the battery can store or deliver). It's like a pump's "gallons per minute".

Amps per hour or amps/hr is the rate of change of amps.

If I switch on my doofelaki and it initially draws 5 amps, but after it has been running for one hour it is drawing 7 amps, then the current draw is increasing at a rate 2 amps per hour. If it starts at 3 amps and increases to 5 amps over an hour, it is still 2 amps/hr. It tells me nothing about the amount of power used, just how it is changing.

That is then ONLY possible meaning of amps/hr or amps per hour. Anything else is nonsensical and a gross misuse of basic units.

A good try, Stu, but compared to the task you have undertaken, Sisyphus had it easy! Folks just don't want to know these things, let alone use them correctly. Consider the frequent use of "knots per hour" Everyone should have to do Freshman dimensional analysis...

Jim

[StuM]

Originally Posted by sailorchic34

My though is that for a given box that the heat gain into the box will be the same at a given temperature, so that overall the same amount of work/ heat transfer has to happen. While the 12V VSD compressor can be more efficient, it also runs longer. where as the 120V compressor has only a few minute cycle time. So it can be less efficient, but if it only runs 1/3 the time of a 12V compressor, the overall loss to inefficiency is not so great.

???

The "overall loss to inefficiency" must be the same if the same amount of work/heat transfer has to happen regardless of how long it takes to do that work. You are just losing the same amount of energy faster if the less efficient compressor is more powerful and runs for a shorter time.

[RaymondR]

I have friends with domestic fridges on their boats but they tend not to go to sea too often.

[sailorchic34]

Originally Posted by StuM

???

The "overall loss to inefficiency" must be the same if the same amount of work/heat transfer has to happen regardless of how long it takes to do that work. You are just losing the same amount of energy faster if the less efficient compressor is more powerful and runs for a shorter time.

Lets take a hypothetical fridge. Say, oh a 120V 3.5 CF fridge that if it ran for an hour would use 15 Ah at 12.7v. But it only actually runs for 1/6th the time so uses 2.5 Ah or roughly 32 watt hr. Not a great number, but not that bad.

Mind you the compressor only runs for 2.5 minutes in 15 minutes with 13 minutes for the condenser to cool down between cycles. There is a improvement in heat rejection for about 1/3 the short run cycle time before the condenser reaches a higher temperature. For the first part of the short run cycle the condenser acts as a heat sink and then switches over to heat rejection as the temperature rises.

There is an improvement in heat loss efficiency for that first part of each run cycle due to that. That is one way a less efficient system could be a bit more efficient based on shorter cycle times.

Another hypothetical 12v fridge with might use only 1.8 Ah or 23 watt hr an hour, for the same work. It's more efficient in that it uses 9 watt hr less, but costs 5 to 10 times as much as a $140 120v fridge and $50 inverter. So, do you buy the fancy fridge or add one more 100 watt solar panel, for $120. Guess which I did....

I know that back in the old boat that did have a 12V fridge that the daily Ah used was just about what my 120V fridge uses, roughly 50-55 Ah.

Yes going with a variable speed 12V compressor and using a expansion valve in a small system can improve system efficiency. No question there. But for the poorer sailor without $1000 to $2500 for a compressor, expansion valve and holding plate, the 120V fridge can work well enough.

Mind you everything I read said you could not use a 120V fridge in a boat. But I thought for $140, lets experiment and find out. So I did. After 8 years on the boat, it still works well and has yet to show signs of rusting. Plus I've had zero maintenance. well other then replace the cooling fan in the inverter ($10 ebay)

[valhalla360]

Originally Posted by onestepcsy37

Amps per day is perfectly acceptable in this discussion. Most cruisers analyze their system needs based on that measure.

From someone who used to do a bit O'engineering.

Maybe "O'engineering" has a different meaning but amps/day would imply you your system starts drawing Y amps and it steadily increases by X amps over the course of a day.

Example: You start the day drawing 10amps and you are increasing by 30amps per day, so after 1 day, you are drawing 40amps.

Over the course of the day, you will average 25amps over 24hours or about 600amp-hours.

I don't know what situation would have the amps steadily increasing like that over the course of a day on a cruising boat so I see no situation where it makes sense.

In the engineering world, sloppy thinking like that leads to bridges that fall down and space ships that explode for no apparent reason. In the cruising world, it just costs you a lot of money when you build a massively oversized system because the guy builds you a system that will handle 600amp-hrs rather than the required 30amp-hrs.