Just sprang for a 75dzw fridge and trying to wire it up now. I ran it off battery all night and the highest watt draw I got was about 63...so a little less than 5.5 amps at 12v DC. I have about 50 feet total circuit length so using a wire gauge calculator I should be fine for 10awg. However, the rated input current listed in website is 7.9 amps. Which would have been over 90 watts...which I never approached. So I'm confused now...what is rated input current? Why the big discrepancy between website and my actual measurements? I don't have tools to crimp 8awg and I have plenty of 10awg wire laying around so I'd really prefer to use that if at all possible.
Domestic fridge amp draw...rated current?
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highdesertranger
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I would go by what the manufacturers site says. they have tested the fridge in many different conditions and came to that number. you tested it once.
what type of crimpers are you using? I find that Klein crimpers work great for 8 gauge when using uninsulated terminals and then just use heat shrink.
highdesertranger
what type of crimpers are you using? I find that Klein crimpers work great for 8 gauge when using uninsulated terminals and then just use heat shrink.
highdesertranger
Trebor English
Well-known member
Could the difference be that the starting current is much higher than the normal running current?
bass_sears
Active member
50' with 5.5a still calls for 8awg wire, at least according to the calculator I usually use:
https://www.calculator.net/voltage-drop-calculator.html
... and that's still approaching 3% drop (2.88%). With 10awg you have 4.6% voltage drop on 5.5a.
I would go with the manufacturer's rated, it could do that in some heavy duty cycle when it's really hot outside or something, just when you don't want wires heating up / compressors being unhappy by not getting the voltage they want.
Plus, this is a pretty constant draw, the larger the wiring the more efficient the whole thing will be and that saves power in the end... I don't worry about that as much with an infrequent draw but fridges run frequently.
Using the calc for 6awg and 7.9a I get 2.6% voltage drop on 50', I would go with 6 gauge so you can handle the max draw without trouble and you'll be really efficient the rest of the time, even though I know the 6 isn't cheap.
I would love to have a set of Klein or something nice but I don't do enough big wiring to justify it. I'll share what I bought (no affiliation) when doing 6awg wiring for a solar setup at a cabin, certainly not tools you'd want to use every day if you were a pro but they will get the job done:
1) Most important item, hammer crimper: http://tinyurl.com/vwkbkp3 $20 Can handle all big sizes, works fine if you don't need to crimp in place. I mostly used it in a vice as it's much more controlled, but hammering works too.
2) If you don't have something that can strip wire larger than 12awg, these worked OKish (not most impressive ever but for price...) to strip up to 6awg: http://tinyurl.com/sr8ela2 $19
3) I needed big cutters too: http://tinyurl.com/u248v9q $29, not currently available anymore so don't want to guess at equivalent.
So for $20 - $70 you can have all the tools you need to do big wire, just buy some lugs and (preferably adhesive) heat shrink and you can make some really nice looking setups.
-- Bass
https://www.calculator.net/voltage-drop-calculator.html
... and that's still approaching 3% drop (2.88%). With 10awg you have 4.6% voltage drop on 5.5a.
I would go with the manufacturer's rated, it could do that in some heavy duty cycle when it's really hot outside or something, just when you don't want wires heating up / compressors being unhappy by not getting the voltage they want.
Plus, this is a pretty constant draw, the larger the wiring the more efficient the whole thing will be and that saves power in the end... I don't worry about that as much with an infrequent draw but fridges run frequently.
Using the calc for 6awg and 7.9a I get 2.6% voltage drop on 50', I would go with 6 gauge so you can handle the max draw without trouble and you'll be really efficient the rest of the time, even though I know the 6 isn't cheap.
I would love to have a set of Klein or something nice but I don't do enough big wiring to justify it. I'll share what I bought (no affiliation) when doing 6awg wiring for a solar setup at a cabin, certainly not tools you'd want to use every day if you were a pro but they will get the job done:
1) Most important item, hammer crimper: http://tinyurl.com/vwkbkp3 $20 Can handle all big sizes, works fine if you don't need to crimp in place. I mostly used it in a vice as it's much more controlled, but hammering works too.
2) If you don't have something that can strip wire larger than 12awg, these worked OKish (not most impressive ever but for price...) to strip up to 6awg: http://tinyurl.com/sr8ela2 $19
3) I needed big cutters too: http://tinyurl.com/u248v9q $29, not currently available anymore so don't want to guess at equivalent.
So for $20 - $70 you can have all the tools you need to do big wire, just buy some lugs and (preferably adhesive) heat shrink and you can make some really nice looking setups.
-- Bass
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MotorVation
Well-known member
"1) Most important item, hammer crimper: http://tinyurl.com/vwkbkp3 $20 Can handle all big sizes, works fine if you don't need to crimp in place. I mostly used it in a vice as it's much more controlled, but hammering works too."
That's pretty strange. I just ordered that exact crimper earlier today. I have to crimp some 8awg and 6awg cables with ring terminals to finish up my solar install :s
That's pretty strange. I just ordered that exact crimper earlier today. I have to crimp some 8awg and 6awg cables with ring terminals to finish up my solar install :s
ranger is right about being able to crimp a 8 gauge in the crimper when there is no insulation on the terminal. I did not have any un-insulated 8 gauge terminals on hand when doing some recent wiring so I just stripped the coating off an insulated 8 gauge terminal which I did have on hand. I did add some heat shrink. Seemed a waste of the more expensive insulated one but then again it saved me a trip to the store which would have interrupted my work flow and cost gas money too.highdesertranger said:
It is kind of funny about stripping larger wires. I learned to strip large stranded wires with an Exacta craft knife blade when I was working in the wire shop at Boeing. It is easy to do. If you are only doing a few wires then there is no real need to buy a wire stripper.
Get a scrap piece of wire or leave it extra long and practice the method on one end of the wire. You basically roll the blade around the wire trying to keep it inline with the starting point of the cut. Apply just enough pressure to cut through the coating. You can do it in two passes or more if you feel hesitant about how much pressure to use. Sometimes just one little area will be not have been severed and you can do a light cut on that area to release the covering. As long as you have a good feel in your hands and fingers for how much pressure you are applying with tools then you too can learn how to strip wires with a sharp knife or a straight edge razor blade. True for even smaller sizes of wiring, not just the heavy gauge ones.
Always nice to have alternative methods of doing a job when you are nomadic and have a limited amount of tools you want to carry.
Get a scrap piece of wire or leave it extra long and practice the method on one end of the wire. You basically roll the blade around the wire trying to keep it inline with the starting point of the cut. Apply just enough pressure to cut through the coating. You can do it in two passes or more if you feel hesitant about how much pressure to use. Sometimes just one little area will be not have been severed and you can do a light cut on that area to release the covering. As long as you have a good feel in your hands and fingers for how much pressure you are applying with tools then you too can learn how to strip wires with a sharp knife or a straight edge razor blade. True for even smaller sizes of wiring, not just the heavy gauge ones.
Always nice to have alternative methods of doing a job when you are nomadic and have a limited amount of tools you want to carry.
bass_sears
Active member
Hah, got my head wrapped into the numbers and didn't even think whether 50' was a reasonable distance. So yes, calc all the voltage drop on one way distances (at least with calculator I use).
If it were me I'd do 8 gauge just for efficiency and to cover worst case scenarios. What's the voltage input range for that Dometic... if you got the 7.9a draw with 3.29% voltage drop and a more depleted battery (right at 12v say) you're getting 11.73 volts at the fridge, will it run on that?
-- Bass
If it were me I'd do 8 gauge just for efficiency and to cover worst case scenarios. What's the voltage input range for that Dometic... if you got the 7.9a draw with 3.29% voltage drop and a more depleted battery (right at 12v say) you're getting 11.73 volts at the fridge, will it run on that?
-- Bass
bass_sears
Active member
maki2 said:
This is definitely true. As long as you're careful and don't start to lose strands of the big wire you're fine with a knife. I had a bunch to do and it is much quicker with a stripper just because you don't have to be as careful.
-- Bass
B and C
Well-known member
Here is the Blue Sea calculator: http://circuitwizard.bluesea.com/
Boaters use this one. They calculate the wire length each way. In this instance it is 50 feet.
Boaters use this one. They calculate the wire length each way. In this instance it is 50 feet.
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