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Old 21-08-2013, 12:35   #1
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How Much Power does your Fridge Draw?

What kind of fridge is it?
Where do you have the compressor? Ventilated?
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Old 21-08-2013, 12:47   #2
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Re: How much power does your fridge draw?

35-60 watts for a danfrost 35
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Old 21-08-2013, 13:50   #3
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Re: How much power does your fridge draw?

Adler Barbour, 60 ah/day, compressor is located in the stern lazarette, no extra cooling.
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Old 21-08-2013, 13:58   #4
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Re: How much power does your fridge draw?

Adler Barbour air cooler, averages around 60AH/day, installed under settee and draws air from the salon and discharges into the space uder the settee that has a vent on one end
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Old 21-08-2013, 14:11   #5
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Re: How much power does your fridge draw?

Does 60AH/day work out to be 30 watts?
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Old 21-08-2013, 14:14   #6
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Re: How much power does your fridge draw?

Air cooled AB very small fridges (less than 2 cu ft) at least 70-80 AH per day in the tropics.
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Old 21-08-2013, 15:04   #7
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Re: How much power does your fridge draw?

Quote:
Originally Posted by o_q View Post
Does 60AH/day work out to be 30 watts?
no ........... yes ...............maybe

watts = volts X amps

watts is power but most people are more interested in how many amps per day something uses
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Old 21-08-2013, 15:09   #8
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Re: How much power does your fridge draw?

Quote:
Originally Posted by Don L View Post
no ........... yes ...............maybe

watts = volts X amps

watts is power but most people are more interested in how many amps per day something uses
I ask because one of the replies here was in watts

Assuming we're all running at 12 volts, and at 24 hours a day, I calculated 30 watts. IDK if I'm right.
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Old 21-08-2013, 15:20   #9
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Re: How much power does your fridge draw?

Quote:
Originally Posted by o_q View Post
I ask because one of the replies here was in watts

Assuming we're all running at 12 volts, and you're running 24 hours a day, I calculated 30 watts. IDK if I'm right.
My system is big, I use about 50 watts when the system is running (4 amps at 12.5V), but the unit cycles and uses abut 60AH/day on my 12V system. If it ran continous because I left the lid open all the time it would use 96 AH/day.
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Old 21-08-2013, 15:24   #10
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Re: How much power does your fridge draw?

Your fridge's manufacturer label MAY give you the Wattage (W) power rating, the max current load (A), and the voltage for your fridge (V). If you have two values, you can obtain the third; W = V x A. Amp-hour is a unit that Electrical Engineers do not usually work with; it is a "relative" calculated number used to compare/assess the current flow per hour from batteries and solar cells, among other devices.

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Old 21-08-2013, 15:35   #11
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Re: How much power does your fridge draw?

Quote:
Originally Posted by Don L View Post
My system is big, I use about 50 watts when the system is running (4 amps at 12.5V), but the unit cycles and uses abut 60AH/day on my 12V system. If it ran continous because I left the lid open all the time it would use 96 AH/day.
This is how I understood it, but this makes it clear that since devices aren't necessarily in use all the time, amp hours doesn't necessarily equate to watts. I think I was more focused on if my calculation was correct. Of course there are factors IRL that are unknown, but I was asserting values to fill in the blanks.
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Old 21-08-2013, 15:41   #12
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Re: How much power does your fridge draw?

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Originally Posted by Teknav View Post
Amp-hour is a unit that Electrical Engineers do not usually work with; it is a "relative" calculated number used to compare/assess the current flow per hour from batteries and solar cells, among other devices.
Yeah. I figured amp hour is merely used as a practical way of measuring limited power resources. Unlike being on land where you have the luxury of practically unlimited power.
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Old 21-08-2013, 15:51   #13
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Re: How much power does your fridge draw?

I was wondering if the price of this Norcold SCQT4408 Icebox Conversion Kit is typical.
$699.99

Quote:
Features: Converts up to a 6 cubic foot insulated ice box into an automatic electric refrigerator Reduced current draw (2.5 Amp) Reduced noise level
Power: Multi Volt
12 Volt DC, Draw: 2.5 Amp
24 Volt DC, Draw: 1.3 Amp
120 Volt AC, Draw: 0.71 Amp
Kit Includes: Single compressor and evaporator Power ventilation package Temperature control 12 Feet of Pre-charged copper tubing for convenient placement of compressor / power supply away from evaporator plate
I didn't search extensively. This is first I found. I was wondering from those in-the-know if there was better/cheaper.
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Old 21-08-2013, 15:55   #14
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Re: How much power does your fridge draw?

The error in using amp hours as an indicator of power usage is not large where the voltage the system is running at is relatively constant as is the case when using nominal 12v batteries and recharging systems in a boat. However this would not be the case with say a large installation like a multi kilowatt solar power installation back feeding to the grid.

If you put an amp meter on the power supply to your fridge you will notice that when you first load the fridge and start the process of pulling down the temperature the compressor will pull high ampage, then as it cools the ampage will reduce. Where it settles eventually will depend upon the temperature setting of the thermostat.

How often the compressor cycles will depend upon how often you introduce warm material and how effective the insulation is. Opening the box regularly allows warm air into it and poor insulation allows lots of heat to bleed in so the compressor will cycle often.

The load that the compressor works against depends upon the temperature in the condenser. If you have a poor condenser which is not pulling the heat out of the compressor discharge vapor the compressor will have to work harder than it would with an efficient condenser and consequently will draw more amps.

My BD-50 compressor pulls about 8.5 - 10 amps with a warm box and drops back to about 4.5 - 5.5 once the temperature pulls down and the compressor starts cycling. I am at present changing the system from an air cooled condenser to a water cooled one in an attempt to reduce the head pressure and amps draw of the compressor. I mostly cruise in the tropics where air cooled condensers are not very effective.
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Old 21-08-2013, 16:09   #15
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Re: How much power does your fridge draw?

My 3.5 CF magic chef, 120V A/C run off a 700 watt inverter, at the moment is using about 50 amps per day. In the 95 degree heat of the delta it will use 60 amps a day or so. Mind you when its running its pulling 14 amps. But it only runs 10 minutes an hour at 90-95 degree cabin temperature. Plus the whole thing costs me less then $200..
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