4/0 cable: Pushing Over the Current Limit

[timselectric]

This is a crazy conversation in my opinion.
I never run anything hot on purpose, no matter what it's rated for.
Any heat generated is lost power. I want everything to run close to room temperature. I want all of my production to get to my loads. And I don't want to put any unnecessary stress on anything. If I touch anything that feels more than slightly warm, I'm looking for a solution to my mistake.

 

[DPC]

This is a crazy conversation in my opinion.
I never run anything hot on purpose, no matter what it's rated for.
Any heat generated is lost power. I want everything to run close to room temperature. I want all of my production to get to my loads. And I don't want to put any unnecessary stress on anything. If I touch anything that feels more than slightly warm, I'm looking for a solution to my mistake.

Sometimes you have to run hot.
If you already in a very hot environment you need to run even hotter to effectively cool.

Imagine you had to wire something in death valley.
I wired things in hotter places...

 

[timselectric]

Sometimes you have to run hot.
If you already in a very hot environment you need to run even hotter to effectively cool.

Imagine you had to wire something in death valley.
I wired things in hotter places...

I have wired things in very hot conditions. This is why the conductors and insulation have temperature ratings.
But that still falls under my analogy for "room temperature".

 

[DPC]

I have wired things in very hot conditions. This is why the conductors and insulation have temperature ratings.
But that still falls under my analogy for "room temperature".

My places are hotter than your places lol. ( boy that sounds like a gay pick up line )
I agree, I'm just making a point that sometimes your ambient is so high its nuts, you need those special cables.

BUT sometimes you need to deal with heat.
Like in an electrical encloser for a transformer for example...

 

[ricardocello]

This is a crazy conversation in my opinion.
I never run anything hot on purpose, no matter what it's rated for.
Any heat generated is lost power. I want everything to run close to room temperature. I want all of my production to get to my loads. And I don't want to put any unnecessary stress on anything. If I touch anything that feels more than slightly warm, I'm looking for a solution to my mistake.

That’s right. Who wants to give up 157W to heat when you could be storing that in the batteries?
Why would you let cables get uncomfortably hot? If they are not comfortable, I’m not comfortable.
Upgrade to >400 MCM or run a parallel 4/0 (reducing the heat wattage to about 80W).

 

[AntronX]

I have 21kw of PV and 3 EG4-6000xp inverters. I have a battery bank of 14 rack mount 100Ahr batteries connected with 4/0 cables (length of 10'... I'm wondering how much I can push over the 230A rating ?

21 kW solar * 0.85 = 17.9 kW / 54v = 331A
That's only 1.43x over NEC rating. I say let it rip. NEC is stupid conservative.
Voltage drop calc shows 0.32V drop for 10' run of 4/0 at 331A.
That's 106w loss / 17.9kW = 0.6% loss = 99.4% cable efficiency.
Your inverters lose 6 - 8% in comparison when charging batt from PV.

 

[SomethingAppropriate]

Heat has to go someplace...

9 watt LED.
View attachment 260447
Put it in a closed or semi closed light fixture and it could set you house on fire, but its only 9 watts...
Old fixture may have been rated for 100 watts of incandescent but they never caught fire.
Its what else might be cooked with the device in that localized heat you need to consider

That is a great way to say it.

 

[timselectric]

That’s right. Who wants to give up 157W to heat when you could be storing that in the batteries?
Why would you let cables get uncomfortably hot? If they are not comfortable, I’m not comfortable.
Upgrade to >400 MCM or run a parallel 4/0 (reducing the heat wattage to about 80W).

Yup
I'm running 500 kcmil between my banks.
They will almost never carry more than 250a. But they will never create heat either.

 

[ricardocello]

Does anyone remember 1974’s “‘the Towering Inferno” movie?
I was young and impressionable.

What was the cause?
Undersized power cables not in conduit!
Cables getting too hot!

The Towering Inferno (1974) - Horror Guys

Directed by John Guillermin Written by Richard Martin Stern, Thomas. N. Scotia, Frank M. Robinson Stars Paul Newman, Steve McQueen, William Holden, Faye Dunaway Run Time: 2 Hours, 45 Minutes Trailer: https://www.youtube.com/watch?v=nch1URmJvMA Spoiler-Free Judgment Zone...

www.horrorguys.com

 

[J.H.]

Headroom is your friend …..in most everything…always have some..sleep well.

J.

 

[DPC]

Does anyone remember 1974’s “‘the Towering Inferno” movie?
I was young and impressionable.

Even better...

 

[DIYrich]

You have 3 6kW inverters (140a each) and 2 racks of 700ah batteries.

Get a 1000a busbar, and connect as follows:
I - B - I - B - I
where "I" is an Inverter, and "B" is a rack of 7 batteries.

Each battery rack will discharge 210a (140a from the I on the outside, and 70a from the inverter in the middle). Max charge rate is 188a per rack (125a max charge rate per inverter).

Each battery cable will only see 188a charging, for a total of 375a charging.

 

[GeeGee]

How about split the bank of batteries into two stacks of seven. Feed each with 230 amps from the common bus.
One more battery would go three stacks of five bringing the rate to 690 amps. Need a bigger bus.

Clever......have you tried such a setup/design yourself?

 

[time2roll]

Clever......have you tried such a setup/design yourself?

Not at this scale and yet the math works out nicely. Just two batteries limited to #4 wire. Single would have limited my power same as you.