Where to use 2/0 wiring?

[WorldwideDave]

I know that Will says he oversizes wires and solar arrays often, but I made a mistake. My system design was going to use 2 gauge wire, and I bought 2/0 wire instead.

Where would someone normally use 2/0 wire anyway? It is so thick, and hard to bend. Presume between say a 200 amp panel and a 200 amp generator disconnect box or something? It is THICK!

Also, if I were to use in my setup, I think between a battery and a battery bus bar or battery and fuse or battery and on/off switch or bus bar and inverter, but I don't think I'll find 2/0 lugs anywhere - think they are normally torqued down with screws to main panels. The wire seems thicker than the wire coming to my house from the grid for my 100 amp panel.

 

[chrisski]

Any time ampacity demands it.

The Installer used 2/0 from each 5 kWh battery to the inverter for a 48 volt system. Could be required for a 12 volt system with a moderate sized inverter.

 

[WorldwideDave]

you went straight from battery to inverter - no fuse, no bus - on a 48 v system? Asking because I'm new to all this.
When you say moderate inverter, you mean a 5000 Watt low frequency inverter, or like a big 6K wall mount system like the EG4s Will talks about so much?

 

[Brett V]

Well I wouldn’t use it between my batteries and the inverter, I used 4/0.

You size your cables accordingly for potential current at maximum power from the inverter, and fuse appropriately to protect the cables from an over current situation. My 12k Growatt could potentially pull in excess of 275 amps. My cable run between the battery rack and the inverter is 12 feet.

 

[registered-bum]

.... The wire seems thicker than the wire coming to my house from the grid for my 100 amp pane

This is as it should be.

Power through the wires is a combination of Voltage and Current.
( P = V * I - Power is equal to Voltage * Current, with Power in Watts, Voltage measured in Volts and Current measured in Amps)

Your household is likely wired for 220V Split Phase. In this model, there are 2 hot wires delivered with 220v between them. These are labeled L1 and L2, and typically one is Black and the other Red. There is also a Neutral wire, and is White, and of course a ground wire - Green.

Between L1 and L2 is the 220v (for stove, dryer, water heater, EV car charger, etc.).
Between L1 and Neutral is a 120V feed for lights and outlets.
Between L2 and Neutral is a second 120V feed for lights and outlets.
Yes, two feeds for the 120 outlets and lights.

Because the voltage is higher (120v AC) than a 12v or 48v DC inverter/battery setup, you need much larger wires for these.
Eg, a hair dryer will use about 1,500 watts on the high setting.

* For a 120v AC circuit this 1,500W is about 12-14 Amps. (household wiring is typical 14/2 or 12/2 Romex)

* For a 12v inverter to power this, the inverter has to pull the 1,500w from the battery. 1,500w / 12v = 125 Amps
(simplified math - not counting for losses due to inefficiencies)
To move that much current, you would much larger wires ...

Ampacity tables will provide guidance for these, with other considerations such as length of run and temperature.
For example:
https://www.cerrowire.com/products/resources/tables-calculators/ampacity-charts/

 

[Hedges]

2/0 can be good for battery to inverter, in the 200A range, but limber fine-strand wire is preferred. That's what I'm using for 6kW inverter at 48V.

I used 3/0 for 200A utility service connection. 2/0 is allowed there (for split-phase, 2 current-carrying conductors plus Neutral, not for 3-phase.) 3/0 would normally be used for 200A branch circuits.

You could use something like Polaris multi-port connectors to attach pigtails of battery cable, same gauge or smaller, to connect at inverter and at battery. If a significant length is needed and you want to use the wire you already bought.

 

[chrisski]

you went straight from battery to inverter - no fuse, no bus - on a 48 v system? Asking because I'm new to all this.
When you say moderate inverter, you mean a 5000 Watt low frequency inverter, or like a big 6K wall mount system like the EG4s Will talks about so much?

The battery I had installed for the house, 48 volts, has an internal class t installed at the factory. The battery is attached to a load center that has an additional circuit breaker for each battery bank.

The moderate inverter is a 12 volt inverter, 2000 watts, that runs at 1000 watts constant with brief time to 2000 watts, a couple minutes at a time 5 or 6 times a day. That couple minutes pulls 200 amps at 12 volts, so 2/0 territory.

 

[JRH]

I know that Will says he oversizes wires and solar arrays often, but I made a mistake. My system design was going to use 2 gauge wire, and I bought 2/0 wire instead.

Where would someone normally use 2/0 wire anyway? It is so thick, and hard to bend. Presume between say a 200 amp panel and a 200 amp generator disconnect box or something? It is THICK!

Also, if I were to use in my setup, I think between a battery and a battery bus bar or battery and fuse or battery and on/off switch or bus bar and inverter, but I don't think I'll find 2/0 lugs anywhere - think they are normally torqued down with screws to main panels. The wire seems thicker than the wire coming to my house from the grid for my 100 amp panel.

1st ) Make everything bigger.. you already bought it…I’ve done it..use it .. No prob …
Everything will run cooler ….and when you up-size , it will already be installed..

The recommended sizes for most everything they publish are a minimum…the bare minimum to be leagal and to do the job…the bare basics…
(Quoting mike holt) …

So many problems are caused by using wire and connections that just barely meet real world loads….

2nd). you wont do that again as you learned the old “measure twice -cut once lesson.”

We all learn this lesson at some point in whatever you build ….

A mistake is never a mistake if you learn a good lesson for the future…

Jus sayin…J.

 

[time2roll]

2/0 feeds a 2000 watt inverter nicely on 12v. Probably go 4000w on 24 volts.

 

[WorldwideDave]

We are all talking about 2/0 AWG wire, that is 0.364797 thick, right? Not 2 AWG wire, that is 0.257626 thick, yes?
In the example above - a 2000 watt 12v inverter - what low-frequency inverter has posts *that* big?
what about a 4000 watt inverter on 24 volts?
You saying that for an 8000 watt inverter on 48 volts this would be good for short distances?
I'm mostly curious about the 12v example, as I have a 12v setup today (will have 48v later).

 

[time2roll]

Posts? There is a bar to bolt the lug to. I have an old discontinued Go Power 2000w sine wave inverter. But any brand will connect with 2/0.

Quality 2/0 marine wire is good for at least 280 amps and a 2000w inverter will pull 170-190 amps as it approaches peak rated power.
I installed 4/0 and in hindsight if spending money today I would go with 2/0 wire.

Mine is in an RV and I have no intention of upping to 24, 48 volts. All works just fine at 12v.

 

[740GLE]

What style of wire did you buy? There are many different types of conductor that meet 2/0 awg rating.

2/0 THHN is mighty different than ultra fine stranded welding cable.

I assume you bought it online, not at a local store? Mind sharing the link to where you purchased it from.

 

[JRH]

Posts? There is a bar to bolt the lug to. I have an old discontinued Go Power 2000w sine wave inverter. But any brand will connect with 2/0.

Quality 2/0 marine wire is good for at least 280 amps and a 2000w inverter will pull 170-190 amps as it approaches peak rated power.
I installed 4/0 and in hindsight if spending money today I would go with 2/0 wire.

Mine is in an RV and I have no intention of upping to 24, 48 volts. All works just fine at 12v.

Mine is an FOR an RV and I like 24… it does all I need + ….easy… …I don’t need 48 unless I build a house or somthing…

 

[WorldwideDave]

What style of wire did you buy? There are many different types of conductor that meet 2/0 awg rating.

2/0 THHN is mighty different than ultra fine stranded welding cable.

I assume you bought it online, not at a local store? Mind sharing the link to where you purchased it from.

Home Depot. Thhn is what I got.

 

[time2roll]

THHN will be very stiff. Will still take a lug and connect. Going to be an effort to get the wire bent to avoid stress on the component terminals.

 

[740GLE]

How many feet did you buy?

I’d say you got your self a nice souvenir, maybe make some art work/jewelry with it?

I would not use THHN 2/0 for anything DC related, just not worth the headaches and so much can go wrong. Just cut your losses as part of the education al journey and move on.

 

[WorldwideDave]

I have 2 pieces at 4 feet each. For the DC side if no good, then when I buy an all-in-one inverter in the future, I can use this to go between it and a wall-mounted panel, then (which I already own)?

 

[chrisski]

I would not use THHN 2/0 for anything DC related, just not worth the headaches and so much can go wrong. Just cut your losses as part of the education al journey and move on.

Why not? This is a 600 volt rated wire. If not THHN, then what type wire?

I would not want to use THHN as a connection to a #10 stud, or whatever the studs size is on a 280 ah cell, in a mobile build where the battery could be bouncing up and down such as a mobile build. If it were a thicker stud like on a lead acid battery, then properly secured, the THHN would be fine.

Thick THHN is a pain to bend and route, and great care needs to be done on the crimp because there won't be flexibility, but still can be done.

 

[WorldwideDave]

Thick THHN is a pain to bend and route, and great care needs to be done on the crimp because there won't be flexibility, but still can be done.

I have not done cuts or crimps on it yet. Just carrying it to my car was a workout. That's some hefty wire. My plan was to lay it out perfectly first. I thought I read in the Victron PDF that this was good for my application as well (THHN) vs solid core or the super thin stuff. Didn't cost to much, so if I have to replace it, I will. Adding the victron PDF because man everyone should have a copy of this thing. It's like a PhD in wiring - learn so much every time I review it. OOPS says PDF too large to attach. Trying to ZIP it, it is also too big. Oh well. Download it from them

 

[740GLE]

Why not? This is a 600 volt rated wire. If not THHN, then what type wire?

I would not want to use THHN as a connection to a #10 stud, or whatever the studs size is on a 280 ah cell, in a mobile build where the battery could be bouncing up and down such as a mobile build. If it were a thicker stud like on a lead acid battery, then properly secured, the THHN would be fine.

Thick THHN is a pain to bend and route, and great care needs to be done on the crimp because there won't be flexibility, but still can be done.

I mean yeah it can work, it’ll carry current. With a lot of effort and frustration I can also pound a round peg through a square hole.