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Old 04-10-2015, 18:52   #196
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Re: Why no Residential Fridges?

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Originally Posted by onestepcsy37 View Post
The only difference between "amp/hour" and "amp/day" is time. There is no other explanation.
I agree wholeheartedly. But we are not discussing the difference between Amp/hour and Amp/day.

The critical issue is the meaning of them compared to the true measurements of power consumption - which are Amp Hours or Amp Days.

Amps per hour IS NOT THE SAME as Amp-hours. And the difference DOES matter.
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Old 04-10-2015, 18:53   #197
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Re: Why no Residential Fridges?

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Originally Posted by StuM View Post
That is the fundamental mistake you keep making and is the cause of all of this discussion.

Gallons per minute has everything to do with speed. For a given pipe, the more gallons per minute you put through, the faster the water flows.
Stu the analogy of gallons per minute being a statement of speed it is not correct
GPM is a measure of volume
GPM Gallons per minute, a unit of volumetric flow rate.
https://en.m.wikipedia.org/wiki/Gallons_per_minute
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Old 04-10-2015, 19:33   #198
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Re: Why no Residential Fridges?

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Originally Posted by newhaul View Post
Stu the analogy of gallons per minute being a statement of speed it is not correct
GPM is a measure of volume
GPM Gallons per minute, a unit of volumetric flow rate.
https://en.m.wikipedia.org/wiki/Gallons_per_minute
WTF?
GPM is NOT a measure of volume.
Volumetric flow rate is not the same as volume.

Your wikipedia link doesn't say anything relevant to this. In fact it just redirects to the wikipedia page on "Gallons" which doesn't even contain the words "per minute".


I said analogous, not identical. Obviously volumetric flow rate is not exactly the same as speed. But given a fixed diameter of pipe, the speed of each single drop of water is determined by and proportional to the volumetric flow rate. The more GPM you push through a 1 inch pipe, the faster the water droplets travel.
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Old 04-10-2015, 20:00   #199
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Re: Why no Residential Fridges?

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Originally Posted by StuM View Post
WTF?
GPM is NOT a measure of volume.
Volumetric flow rate is not the same as volume.

Your wikipedia link doesn't say anything relevant to this. In fact it just redirects to the wikipedia page on "Gallons" which doesn't even contain the words "per minute".


I said analogous, not identical. Obviously volumetric flow rate is not exactly the same as speed. But given a fixed diameter of pipe, the speed of each single drop of water is determined by and proportional to the volumetric flow rate. The more GPM you push through a 1 inch pipe, the faster the water droplets travel.
I may have posted the wrong link was on way out the hatch. Will recheck that one if memory serves GPM is a measure of how many gallons used in a given time frame and your statement of "
The more GPM you push through a 1 inch pipe, the faster the water droplets travel " is a measure of pressure. Not volume per say to force more GPM through a given diameter pipe you must increase the pressure.
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Old 04-10-2015, 20:05   #200
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Re: Why no Residential Fridges?

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Originally Posted by onestepcsy37 View Post
I prefer, as do many others, to measure battery ins and outs in daily chunks.
Are you doing this measurement using a battery monitor or other similar meter?

If so, I would be very surprised if when you push the button (or whatever) to get your daily "amp number" chunk, that it is using "amps" and not "amp-hrs" as the unit of measurement.

On ours, the instantaneous draw at any time is labeled "amps", while the unit that comes up when I push the button for cumulative out is "amp-hr".

We even have some monitors on individual pieces of gear and they also use the same units in the same ways. Attached is a picture showing the instantaneous draw of a load, along with the cumulative total removed. Note the units.

If these units are not displayed on your meter, I'll bet they are described in the manual.

Mark
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Old 04-10-2015, 20:05   #201
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Re: Why no Residential Fridges?

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Now I have a question for you stu will a G1 CME with a c3 pulse have any affect on my pwm solar controller
Why duplicate. Just go here:
Solar Charge Controller and Solar Flares
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Old 04-10-2015, 20:07   #202
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Re: Why no Residential Fridges?

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Originally Posted by colemj View Post
Are you doing this measurement using a battery monitor or other similar meter?

If so, I would be very surprised if when you push the button (or whatever) to get your daily "amp number" chunk, that it is using "amps" and not "amp-hrs" as the unit of measurement.

On ours, the instantaneous draw at any time is labeled "amps", while the unit that comes up when I push the button for cumulative out is "amp-hr".

We even have some monitors on individual pieces of gear and they also use the same units in the same ways. Attached is a picture showing the instantaneous draw of a load, along with the cumulative total removed. Note the units.

If these units are not displayed on your meter, I'll bet they are described in the manual.

Mark
Excellent! Thanks for that very clear indication of the difference.
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Old 04-10-2015, 20:08   #203
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Re: Why no Residential Fridges?

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Originally Posted by StuM View Post
WTF?
GPM is NOT a measure of volume.
Volumetric flow rate is not the same as volume.

Your wikipedia link doesn't say anything relevant to this. In fact it just redirects to the wikipedia page on "Gallons" which doesn't even contain the words "per minute".


I said analogous, not identical. Obviously volumetric flow rate is not exactly the same as speed. But given a fixed diameter of pipe, the speed of each single drop of water is determined by and proportional to the volumetric flow rate. The more GPM you push through a 1 inch pipe, the faster the water droplets travel.
GPM IS a measurement of volume. Your confusing velocity of the water with the volume of water. A 2", 3" and 4" pipe will all flow 50 gpm but at different velocities. If I'm moving a 1000 gallons per minute through a pump it's a mass flow measurement not a velocity measurement. That is measured as feet per second or meters per second Not GPM. Yes change GPM flow rate and velocity does changes too. Your correct on that part. But No way no how is GPM a Speed or velocity measurement. It effects speed as does amp flow through wires, but it's not a speed measurement. It's mass flow, just as an Ampere is current flow.

I wrote hydraulic analysis software ages ago for water steam and gases. I may be a tad weak in electrical theory, but hydraulics, That sir, I have spent nearly 40 years working with and designing.
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Old 04-10-2015, 21:42   #204
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Re: Why no Residential Fridges?

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Originally Posted by sailorchic34 View Post
GPM IS a measurement of volume.

In that case: How many GPM does a standard fuel can hold?

Your confusing velocity of the water with the volume of water. A 2", 3" and 4" pipe will all flow 50 gpm but at different velocities. If I'm moving a 1000 gallons per minute through a pump it's a mass flow measurement not a velocity measurement.

I am not confusing anything. I have never said they were the same, I have repeatedly said that it is an analogy. (i.e. a similarity between like features of two things)

That is measured as feet per second or meters per second Not GPM. Yes change GPM flow rate and velocity does changes too. Your correct on that part. But No way no how is GPM a Speed or velocity measurement. It effects speed as does amp flow through wires, but it's not a speed measurement. It's mass flow, just as an Ampere is current flow.

.
At last: you almost get the analogy! GPM is analogous to Amp.

So if GPM is analogous to Amp, it follows that Gallon is analogous Coulomb.

And you DON'T measure a days usage of fuel in GPM you measure it in gallons. An in exactly the same way, you dont' measure electricity use in Amps, you measure it in Coulombs or Amp hours or Amp days
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Old 04-10-2015, 22:57   #205
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Re: Why no Residential Fridges?

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Originally Posted by onestepcsy37 View Post
Completely wrong. The only difference between "amp/hour" and "amp/day" is time. There is no other explanation.

I prefer, as do many others, to measure battery ins and outs in daily chunks. Makes much more sense because they can vary significantly during different times of the day. For instance, solar panels only charging during the daylight portion of the day.

The water analogy is helpful to people who don't or won't understand the practical application of this.
But no one is claiming they are different. Let's change the discussion to eliminate the confusion between second, minute, hour, day, year and call it "unit of time". It doesn't matter if its a second or an eon it's whether you multiply or divide by that unit that matters.

The claim by some poor misinformed souls is you measure battery storage using amps or amps/unit of time is flat out wrong.
- Amps is a flow rate. Without knowing how long the system has been operating at X amps, you don't know how much has been used.
- Amps/unit of time tells you how fast your amp rate is changing. Again without a duration and a starting amperage, you don't know how much has been used.

Amp-Unit of Time: Gives you the useful amount that is stored.
- Side note: coulombs is a unit that is defined by Amp-Unit of Time. It is perfectly acceptable to use either. Amp-Hr is in no way a bastardized unit. They are two units that measure the same property. Amp-Hr is more commonly used in this context as the source units are readily apparent making conversions easier.

An analogy (not exact conversion) is
- Amps ~ Gal/Unit of Time ~ Flow Rate
- Amps/Unit of Time ~ Gal/Unit of Time Squared ~ Rate of Change of Flow Rate
- Amp-Unit of Time ~ Gal-Unit of Time/Unit of Time ~ Gal ~ Volume

How is this used:
- If you want to know how fast you are drawing your battery down, you want the Flow Rate (Amps).
- If you want to know how much of your battery capacity, you have used, you want the Volume (Amp-Hr)
- I don't have a practical use for the Rate of Change of Flow Rate in terms of a typical cruising boat electrical system. If you start looking at induction and some more complicated electrical analysis, there can be a use for it but not in a typical cruising battery bank analysis.
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Old 04-10-2015, 23:03   #206
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Re: Why no Residential Fridges?

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The more GPM you push through a 1 inch pipe, the faster the water droplets travel " is a measure of pressure. Not volume per say to force more GPM through a given diameter pipe you must increase the pressure.
There is a correlation with pressure. It is not a measure of pressure. Pressure does not have a volume component (ie: lbs/square inch is a unit of pressure)

In fact, you will find if you take a 2" pipe put a reducer on to a 1" pipe and measure the pressure at a particular flow rate, the pressure will be higher in the 2" pipe even though the water is moving much faster in the 1" pipe.
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Old 04-10-2015, 23:04   #207
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Re: Why no Residential Fridges?

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Stu the analogy of gallons per minute being a statement of speed it is not correct
GPM is a measure of volume
GPM Gallons per minute, a unit of volumetric flow rate.
https://en.m.wikipedia.org/wiki/Gallons_per_minute
So when someone asks how big your water tank is, do you tell them it's 100GPM?
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Old 04-10-2015, 23:26   #208
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Re: Why no Residential Fridges?

Back in 1885 Sir Edmond Burbank was the first to discover that the longer an argument goes, the further is drifts from the topic.

I hope everyone has now learned a good lesson in how internet chat rooms work.

Ask about an apple...get answers on how to make a fruit salad.
Enjoy.
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Old 05-10-2015, 04:57   #209
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Re: Why no Residential Fridges?

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Originally Posted by StuM View Post
Everything you said is quite correct with the exception of the part in red
Hmm… I see you are thinking that the part in red equals "amperes divided by day where as I see it as equals "amperes multiplied by day". We are on the same side as I concur that "ampere hour" is correct while "ampere/hour" is not. I won't argue which view on the red bit is correct
There is no such thing as "the number of Amperes used in a day". You cannot "use" Amperes. ………....
I like to think we can use amperes. Otherwise there is no point in designing electrical circuits that result in current flow, it would be a waste of time if the lights didn't work or stuff didn't get heated or moved or whatever. Yeah, we use amperes


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Originally Posted by StuM View Post
……...

So if GPM is analogous to Amp, it follows that Gallon is analogous Coulomb.

And you DON'T measure a days usage of fuel in GPM you measure it in gallons. An in exactly the same way, you dont' measure electricity use in Amps, you measure it in Coulombs or Amp hours or Amp days
[/COLOR]
Totally correct
A gallon is a measurement of quantity of a fluid (usually a liquid) and a Coulomb is measurement of quantity of electricity.
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Old 05-10-2015, 05:06   #210
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Re: Why no Residential Fridges?

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One safety concern that hasn't been talked about is how home appliances are usually wired in a way that is considered dangerous for boats. As I understand it, the negative and green ground wires are usually connected in home appliances. On boats, they are supposed to be kept separate. Numerous wiring manuals I've read say that combining them presents a shock hazard to people on board. I won't try for an explanation why because I would probably mangle it. Maybe there is someone on the list who is better schooled in the reasoning behind this
It is indeed unsafe to use appliances that have the frame and safety green wire connected to the neutral wire. If the neutral drifts away from ground and some other things happen you could get zapped by the door of the fridge ot someone could get zapped outside the boat while the boat is ashkre.

That is tolerated in US land code (NEC) in certain cases where the wiring of the house is old and has no green wire.
Most importantly, I am sure it is possible to undo that link and install a proper 3-wire cord in which the green wire connectes the frame to the green wire in the boat's wiring.

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