Current Capacity of Copper Wire Chart

[Boyntonstu]

This chart may be of use:

 

[Wabbit]

Any idea what the colors mean?

 

[Boyntonstu]

Any idea what the colors mean?

Yes, the colors separate the wire sizes.

Every box is valid.

For example;  #10 wire can safely pass 140 Amps for 2 feet.

I am not sure whether or not the graph denotes a pair of wires as opposed to a grounded negative.

A round trip has twice the wire resistance.

The Devil is in the details.

 

[John61CT]

Blue Sea app "Circuit Wizard", takes all the variables into account, lets you play with tolerable voltage drops until you can maybe get a more reasonable gauge.

 

[MikeRuth]

For our purposes, I would agree that the Blue Seas Calculator would be a safer chart to use.

http://circuitwizard.bluesea.com/#

 

[Weight]

That chart could cause problems. example; that chart 200 amps at 10 feet needs 1awg. Most wire charts show 1awg safe for up to 250 amps, so that's ok.
Voltage drop would be 4 1/4 %. That is fine for lower uses but not for inverters and other voltage sensitive devices. I would not want to lose 4% of my charging voltage. My inverter instruction calls for 2/0awg cable and a 200 amp fuse. I would not trust 1awg.

 

[John61CT]

The Blue Sea app is better than **any** chart, it takes more (and very relevant) factors into account like insulation rating, bundled or not, time factor etc.

At large currents, safety is rarely the relevant factor, requires a **much** smaller gauge than what you need to reduce voltage drop, often 3-5 wire sizes apart.

Put the app on your phone rather than using the web site.

 

[sephson]

A chart is a good reference, but is no substitute for load calculations. If you either don't understand or don't feel like doing the load calcs, it's a good idea to upsize your conductors on longer runs in order to minimize voltage drop. Another good rule of thumb is to never run more than 80% of the rated current capacity through any conductor.

 

[Boyntonstu]

That chart could cause problems. example; that chart 200 amps at 10 feet needs 1awg. Most wire charts show 1awg safe for up to 250 amps, so that's ok.
Voltage drop would be 4 1/4 %. That is fine for lower uses but not for inverters and other voltage sensitive devices. I would not want to lose 4% of my charging voltage. My inverter instruction calls for 2/0awg cable and a 200 amp fuse. I would not trust 1awg.

"Voltage drop would be 4 1/4 %. "

Is that for a round trip or for a grounded Negative?

https://www.cirris.com/learning-center/calculators/133-wire-resistance-calculator-table

Plug in 10 feet and #1 wire and you get 0.001 Ohm

The IR drop would be 200 x 0.001 = .2 Volts

.2 / 12 x 100  = 1.66% Voltage drop.

Would you accept 12.5 Volts dropping to `12.3 Volts?

Double check my calculations.

 

[jimindenver]

There are a number of good places to catch up. I suggest checking them all out honestly. Some like Handy Bob's could stand to be updated. I also suggest our own Bobs blog here as well as the 12v side of life #1 and 2. There is. also Jack Mayers write ups

http://redirect.viglink.com/?format...m&txt=http://www.marxrv.com/12volt/12volt.htm

http://redirect.viglink.com/?format...&txt=http://www.marxrv.com/12volt/12volta.htm

http://redirect.viglink.com/?format....jackdanmayer.com/rv_electrical_and_solar.htm

 

[akrvbob]

Would you accept 12.5 Volts dropping to `12.3 Volts?

No, that would be totally unacceptable. If my batteries are full and reading 12.8 and I turn on my microwave it drops down to 12.0 or even 11.9. I lose .2 and I'm at 11.7 and dangerously close to the inverter shutting off because the battery is too low. 

If my battery is even a little low, that .2 drop means I can't use my microwave even though it is nearly full.

My cables are 2/0 and only 4 foot long, but I wouldn't consider anything less.

 

[Boyntonstu]

No, that would be totally unacceptable. If my batteries are full and reading 12.8 and I turn on my microwave it drops down to 12.0 or even 11.9. I lose .2 and I'm at 11.7 and dangerously close to the inverter shutting off because the battery is too low. 

If my battery is even a little low, that .2 drop means I can't use my microwave even though it is nearly full.

My cables are 2/0 and only 4 foot long, but I wouldn't consider anything less.

You are using 4 feet.  The .2 calculated loss was for 10 feet.

Using #10 wire would result in a 0.08 V loss.

11.9 - .8  =  11.82 Volts

Would a 0.08 V loss be a problem?

 

[John61CT]

2/3rds of 1%, of course not.

But other factors like CP, connectors, busses all have their drops, it all adds up.

In the end your system your call.

Being more demanding and precise gives more leeway before things start not working.

 

[Boyntonstu]

2/3rds of 1%, of course not.

But other factors like CP, connectors, busses all have their drops, it all adds up.

In the end your system your call.

Being more demanding and precise gives more leeway before things start not working.

"But other factors like CP, connectors, busses all have their drops, it all adds up.

"Yes, to about a zero Voltage drop, unless of course you have contradictory data.

Electrical design takes all factors into account.

The AWG wire chart is a reasonable guide IMO.

 

[highdesertranger]

I am curious, Boyntonstu do you have a vehicle that you put into practice all this advice you are trying to give us? highdesertranger

 

[Boyntonstu]

I am curious,  Boyntonstu do you have a vehicle that you put into practice all this advice you are trying to give us?  highdesertranger

I am curious,   Highdesertranger do you have a vehicle that you put into practice all this advice you are trying to give us about  which appliances are sensitive to a chassis ground?

 

[highdesertranger]

yes I do and there are plenty of pictures of my vehicle on this forum. also anybody who has been to RTR the last 2 years knows my vehicle. my refrigerators, my inverter, my front winch, and my 2 way radios all get wired to the positive and negative of my batteries, all other loads get wired to chassis ground. now I answered your question. I only asked you because it seems to me you are giving advice based on second hand information not actual experience. highdesertranger

 

[Boyntonstu]

yes I do and there are plenty of pictures of my vehicle on this forum.  also anybody who has been to RTR the last 2 years knows my vehicle.  my refrigerators,  my inverter,  my front winch,  and my 2 way radios all get wired to the positive and negative of my batteries,  all other loads get wired to chassis ground.  now I answered your question.  I only asked you because it seems to me you are giving advice based on second hand information not actual experience.   highdesertranger

 my refrigerators,  my inverter,  my front winch,  and my 2 way radios all get wired to the positive and negative of my batteries,  

Have you tried them with a negative to chassis and had them fail?

 

[highdesertranger]

on my refrigerators, inverter, and 2 way radios I followed the manufacturer instructions, they said to do it that way and do not use chassis ground. on the front winch I did it for minimum voltage drop as it is capable of drawing 480amps. the rear winch I use chassis ground because its maximum draw is much less. highdesertranger

 

[John61CT]

> Have you tried them with a negative to chassis and had them fail?

Are you seriously advocating that?

Really, talk to some serious DC electric professionals, not talking car mechanics but people that know what they're talking about, aviation, marine and high-end RV specialists.