Isuzu npr 4wd

[gator70]

So... what size cable did you run over what length?

4 awg - 13 ft

 

[gator70]

In Utah, So Cal, Arizona, New Mexico, and Baha sur, the days get 90-95F. A/C is necessary at night after the sunsets.

I needed two battery circuits for this engineering.

1) For one interior light and the 12v refrigerator
2) The main at 600 amp hr to keep the A/C running until 4 am after sunset.

 

[SkiFreak]

4 awg - 13 ft

You obviously size cabling very differently than I do...

At 80 amps with 4AWG wire that is 13 feet long (actually 26 feet, as you need to calculate using both positive and negative) you will get a voltage drop of 0.52 volts, which is 3.92%.
That is beyond what I would consider acceptable, especially when driving a motor, which is what an AC compressor is.
This will also be a continuous load, not an intermittent load, so I am guessing that your wiring is going to get pretty hot when running at full load.

All of my camper wiring has been designed to have less than a 2% voltage drop and most of the wiring that powers a motor is around 1% (fridge, actuators etc.).
As the voltage drops, the current increases, as the load tries to draw the power it wants. If the wiring is undersized this additional current draw will result in more heat being generated.
Also, if your cabling is run inside your walls, or inside conduit, then you need to derate the current capacity of the wire, as any generated heat cannot escape as easily.

My main concern with this unit is the size of the cabling you need to run to it.

The setups that I have seen with this specific AC unit have used much thicker cable that you plan to use, hence my original comment.

 

[gator70]

You obviously size cabling very differently than I do...

At 80 amps with 4AWG wire that is 13 feet long (actually 26 feet, as you need to calculate using both positive and negative) you will get a voltage drop of 0.52 volts, which is 3.92%.
That is beyond what I would consider acceptable, especially when driving a motor, which is what an AC compressor is.
This will also be a continuous load, not an intermittent load, so I am guessing that your wiring is going to get pretty hot when running at full load.

All of my camper wiring has been designed to have less than a 2% voltage drop and most of the wiring that powers a motor is around 1% (fridge, actuators etc.).
As the voltage drops, the current increases, as the load tries to draw the power it wants. If the wiring is undersized this additional current draw will result in more heat being generated.
Also, if your cabling is run inside your walls, or inside conduit, then you need to derate the current capacity of the wire, as any generated heat cannot escape as easily.


The setups that I have seen with this specific AC unit have used much thicker cable that you plan to use, hence my original comment.

Thanks for the comment

This is the AWG recommended, and also the same stub cable mounted on the unit

I think your math is based on the fuse, not the actual amp load

Based on most folks use, 45 amps is the draw in the boost mode, while 19 amps is the draw in the eco mode.

Boost mode is rarely run for more than 20 minutes duration.

While eco mode is run most of 65% of the time

Not concerned

 

[SkiFreak]

This cable must support 12v - 80 amp load.

I based my comment on the information YOU provided.