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Old 28-01-2021, 07:44   #1
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Two questions about amperage draw

1) I have a Simrad 10 autohelm. The previous owner installed it with an on/off switch in an awkward spot. I'm not exactly certain why. Obviously they draw a lot of power when steering, but I can't imagine they have a sizable draw when on standby. Any thoughts?

2) We have one of those Costway 54 quart refrigerator/coolers. Someone on Amazon (not the best resource) says it draws 3.8 amps/hour. Does anybody have more confirmed data for that? Or does it at least sound plausible?
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Old 28-01-2021, 08:00   #2
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Re: Two questions about amperage draw

Do you have an ammeter on your dc panel? If so, turn everything else off and run your fridge to see what the draw is on the panel and do the same for the auto helm. If you have a battery monitor, you could do the same to see what the current draw is although less sensitive. You can buy a clamp on ammeter, and measure that way, too. The fridge will have a duty cycle when the compressor is running and then not. The current draw will be very different depending. Count on a 50% compressor cycle time, at least.

The reason to switch off the auto helm is it will still draw current even when not steering,came to guarantee your crew is actually helming. I switch mine off when not in use out sailing and at anchor, and when making a long passage. The last one so I am assured my crew are paying attention while I'm recovering from night watch and/or haven't fallen overboard while I was asleep while the boat keeps sailing along, tether not withstanding.

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Old 28-01-2021, 09:04   #3
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Re: Two questions about amperage draw

Quote:
Originally Posted by Tmacmi View Post
1) I have a Simrad 10 autohelm. The previous owner installed it with an on/off switch in an awkward spot. I'm not exactly certain why. Obviously they draw a lot of power when steering, but I can't imagine they have a sizable draw when on standby. Any thoughts?
I assume you mean Simrad autopilot? Autohelm is a trade name for autopilots made by Raymarine.

Regardless, yes you are correct. In standby mode the power usage is much lower but it is still significant. I have a Simrad AP and haven't checked the standby draw but I'm guessing at least an amp or more. But for me it's quite easy to power off the whole thing, either from my DC panel or on the AP control head. Don't know the details of the model 10 but isn't there an option in the menu to power off the unit directly?


Quote:
Originally Posted by Tmacmi View Post
1) 2) We have one of those Costway 54 quart refrigerator/coolers. Someone on Amazon (not the best resource) says it draws 3.8 amps/hour. Does anybody have more confirmed data for that? Or does it at least sound plausible?
Will depend a lot on the temp you set the thermostat to and how warm it is outside. Also, this kind of fridge cycles on and off and like the autopilot motor, when the compressor is running draws a lot, when the compressor isn't running draws very little.

So to better understand the power usage you should think about the average amp draw or better, amp hours per day.

That being said, even in warm weather an average amp draw of 3-4 amps seems a bit high. I would think more likely 4 amps when the compressor is running which might be anywhere from 40-50% of the time to 70-80%. So average might be more like 1.5-2 amps,
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Old 28-01-2021, 15:33   #4
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Re: Two questions about amperage draw

Quote:
Originally Posted by Tmacmi View Post
1) I have a Simrad 10 autohelm. The previous owner installed it with an on/off switch in an awkward spot. I'm not exactly certain why. Obviously they draw a lot of power when steering, but I can't imagine they have a sizable draw when on standby. Any thoughts?
Draw when on standby would be minimal.


Quote:
2) We have one of those Costway 54 quart refrigerator/coolers. Someone on Amazon (not the best resource) says it draws 3.8 amps/hour. Does anybody have more confirmed data for that? Or does it at least sound plausible?
No such thing as amps/hour.


Does it draw 3.8A when running or is it supposed to consume a total of 3.8 Ah per hour (91 Ah per day) ? They result in very different energy requirements per day.


The latter will be very much dependent on ambient conditions ( higher draw during the day than at night?) , what temperature you have it set at, how often you put things in it to be cooled down and how often you open it.


Added: Apparently it's 500W rated power, so 3.8Ah per hour (around 90Ah per day) would be a reasonable figure if it's getting heavy use.
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Old 28-01-2021, 15:51   #5
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Re: Two questions about amperage draw

Quote:
Originally Posted by skipmac View Post
I assume you mean Simrad autopilot? Autohelm is a trade name for autopilots made by Raymarine.

autohelm (lower case "a") has pretty much become a generic term like biro, hoover et al. It's actually a better description of the way it is commonly used than "autopilot"


And:
AUTOPILOT is a trademark of OPTIMA POWERWARE, INC )
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Old 28-01-2021, 16:05   #6
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Re: Two questions about amperage draw

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Originally Posted by Tmacmi View Post
2) We have one of those Costway 54 quart refrigerator/coolers. Someone on Amazon (not the best resource) says it draws 3.8 amps/hour. Does anybody have more confirmed data for that? Or does it at least sound plausible?

I have a similar one. I think you will find that to be the draw while it is running, which is ordinarily less than half the time. They draw a little more when it's hot.



Runtime varies widely though depending mainly on ambient temperature. They aren't that well insulated. Mine is somewhat smaller but I find it runs around 50% of the time on hot days (but it's in the shade), and less than that on cooler days.
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Old 28-01-2021, 16:07   #7
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Re: Two questions about amperage draw

FWIW, the Costway website says:

The 50W works out reasonably close to 3.8A while running (50W = 3.8A@13.16V), so that makes some sense.

The rated energy usage of 160Wh/day comes in at a duty cycle of 13%, meaning it runs about one hour out of every 8. I have a hard time with that but that is the spec.

Then again, the site says "55-Quarts Portable Thermoelectric Electric Car Cooler Refrigerator" and "This energy-efficient refrigerator USES compressor cooling technology" and those are not the same thing, so don't know what to believe.

[Edit] Found a review that says:

Quote:
We aren't blown away by the insulatory capacity of the Costway. It's constructed of similar materials as the other compressor units we tested but gained the most heat over our 36-hour insulation test. In that amount of time, this cooler went from a frosty 34.7 F to a warm 62.6, crossing the USDA food safety line of 40 after just 1.5 hours of being disconnected from power. And this was in a roughly 70 room!
Based on that I'd predict you'll use the 3.8A at a lot more than the 13% duty cycle, I'd plan on 50% or more unless you're up in the chilly north.
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Old 28-01-2021, 17:23   #8
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Re: Two questions about amperage draw

Quote:
Originally Posted by StuM View Post
autohelm (lower case "a") has pretty much become a generic term like biro, hoover et al. It's actually a better description of the way it is commonly used than "autopilot"
Guess that could be so but haven't heard it used generically in my neighborhood but then I don't get out much.

Quote:
Originally Posted by StuM View Post
AUTOPILOT is a trademark of OPTIMA POWERWARE, INC )
That I didn't know. Did a little internet snooping and found more companies using Autopilot as a trade name for their products. However since it's a common, English word, I'm pretty sure no one can prevent the use of the word in the context of it's generally accepted meaning.
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Old 28-01-2021, 17:35   #9
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Re: Two questions about amperage draw

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Originally Posted by skipmac View Post
............
Did a little internet snooping and found more companies using Autopilot as a trade name for their products. However since it's a common, English word, I'm pretty sure no one can prevent the use of the word in the context of it's generally accepted meaning.
FWIW autopilot (all lowercase) is very widely used in aviation.
I concur it is a common word and its meaning is (or should be) unambiguous!
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Old 29-01-2021, 09:19   #10
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Re: Two questions about amperage draw

For about us$ 50, you may purchase clamp meter and measure the actual amperage going to any equipment. Just pay attention that the tool is D/C enabled (the cheaper tools measure only A/C).
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Old 29-01-2021, 09:25   #11
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Re: Two questions about amperage draw

Thank you to all who answered and those who did some internet digging. Here are my follow on questions.

Let's say that the refrigerator is cycling 50% of the time. When running its at 3.8 amps when off its at .5 amps (made that up for the example). That would suggest it would draw 129 amps in one hour?

As it regards the autopilot/autohelm/Otto. The positive ran to a 10 amp fused switch. Between the fused switch and the autohelm it had another inline 10 amp fuse. Isn't that redundant or should there be a lower amp use in-line?
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Old 29-01-2021, 09:29   #12
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Re: Two questions about amperage draw

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Originally Posted by meirriba View Post
For about us$ 50, you may purchase clamp meter and measure the actual amperage going to any equipment. Just pay attention that the tool is D/C enabled (the cheaper tools measure only A/C).
I am considering that. Though I find that the DC enabled ones are more expensive.

The most helpful would be to know how many amps are drawn in an hour. I wonder if those things track average draw over a period of time.
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Old 29-01-2021, 09:55   #13
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Re: Two questions about amperage draw

Quote:
Originally Posted by StuM View Post
autohelm (lower case "a") has pretty much become a generic term like biro, hoover et al. It's actually a better description of the way it is commonly used than "autopilot"


And:
AUTOPILOT is a trademark of OPTIMA POWERWARE, INC )
I've personally never heard "autohelm" used in reference to an autopilot; and I do get around a lot. But, I do agree it's a better description for a boat.

"AUTOPILOT" is a registered trademark of Optima Powerware. "AutoPilot" is also a registered trademark of AquaCal AutoPilot, Inc. (I'm sure there are other companies that use the word "autopilot" in their logos and product names.

These trademarks do not restrict the use of the generic word 'autopilot' (a contraction for automatic pilot), which is commonly used throughout many industries and came into common use sometime in the 1930s.
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Old 29-01-2021, 10:54   #14
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Re: Two questions about amperage draw

Back in my youth ( mid fifties) we called it the iron mike, or just mike.
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Old 29-01-2021, 11:17   #15
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Re: Two questions about amperage draw

Why don't you move the autopilot switch to a more accessible location? It's not hard to do.
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