Please check my design.

[tazmann]

My system is similar, I used 150 amp dc breaker off the battery and use it as a disconnect switch also. 4awg is a bit small for battery to inverter, I tried the original 4awg wires that came with the inverter, they were about 18" long attached to BB that was fed with 2/0 cable. The 4awg got pretty warm after about a half hour running 1600 watt load so I swapped the 4awg to 2/0

 

[tazmann]

Someone asked about the DC>DC converter wire gauge. I planned for the wire to be 8ga, but the wire coming from the converter is only 12ga and it is rated at 40a. How can the converter rated for 40A out use 12ga wires

Good question on the converter ,mine is the 30 amp model and it just seems to work, worst I did was run a 150 watt water heating element for 5 hours and other than the converter housing getting warm the wires were fine but the 12ga wires are only about 6" long

 

[svetz]

<Given THHN/THWN-2 wire, are the gauges correct given:>

• Panels 2S2P
• VOC: 37.6 V
• VMP: 30.3 V
• ISC: 8.85 A
• Max power current: 8.27 A
• Power Tolerance 0/+3%
• Maximum system voltage: 600V (UL)

Temperature correction factor? Probably moot (~1.5%?) since you're a Florida boy ;-)

How many amps are on each wire? A visual update would be nice.

For general 90°C Copper THHN:

AWG 4 - 95 amps​

AWG 8 - 55 amps​

AWG 10 - 40 amps​

AWG 12 - 30 amps​

• The 125 amp fuse for 4 AWG seems high, typically use see a lower slow-blow fuse... but probably depends on the inverter. The snapshot of the page in #9 shows 100 amps and AWG 6. But, you need to add in the amps for the converter, so it can't be determined yet.
• The SCC tracer is 40 amps, but the wire shown is rated for 95 amps and the circuit breaker is 50 amps
• Only 18 amps (2p x ~9) from the panels, so AWG 8 isn't needed
• Can't tell about the gauge of the DC fuse block or converter as you need to know the maximum draw

Hope that's of some help!

 

[Brewman]

I think you’re good to go brewman as long as the fuse block connected to that converter pulls less than 50 amps at 12v which is roughly 25amps @ 24v that fuse of yours shouldn't pop. Oh, also as long as your converter can handle an output of up to 12v at 50 amps and just in case you do pull 50 amps at 12vdc I hope it does pop because 12 wag will not handle 50 amps at 12vdc (I checked on that ampacity link posted above by svetz

The only thing coming off the fuse box will be LED lights and a few USB chargers. Total load should be no where close to its rated 40A.

 

[Brewman]

Is over sizing the wire an issue? I was doing this if future expansion happens. The converter is the one off Wills page, and I just noticed I got the gauge backwards, its 12 AWG is in and 10 AWG out. Ill update my drawing soon. @smoothJoey I update your drawings and use to show correction.

 

[Brewman]

 

[Brewman]

The nice thing about thhn is its relatively cheap.
I prefer to get white, then use red, black and green electrical tape to identify the wires.

I was able to get the black 4 AWG for free, Id rather have black and red but Ill just band it with colored heat shrink.

 

[John Frum]

I was able to get the black 4 AWG for free, Id rather have black and red but Ill just band it with colored heat shrink.

As you wish.

 

[John Frum]

Temperature correction factor? Probably moot (~1.5%?) since you're a Florida boy ;-)


How many amps are on each wire? A visual update would be nice.

For general 90°C Copper THHN:

AWG 4 - 95 amps​

AWG 8 - 55 amps​

AWG 10 - 40 amps​

AWG 12 - 30 amps​

• The 125 amp fuse for 4 AWG seems high, typically use see a lower slow-blow fuse... but probably depends on the inverter. The snapshot of the page in #9 shows 100 amps and AWG 6. But, you need to add in the amps for the converter, so it can't be determined yet.
• The SCC tracer is 40 amps, but the wire shown is rated for 95 amps and the circuit breaker is 50 amps
• Only 18 amps (2p x ~9) from the panels, so AWG 8 isn't needed
• Can't tell about the gauge of the DC fuse block or converter as you need to know the maximum draw

Hope that's of some help!

THHN is rated for 105C when used in for appliance wiring.

https://www.usawire-cable.com/pdfs/thhn_thwn.pdf

And 4 awg pure copper with 105C insulation is good for 160 amps.

Interactive Wire Size Calculator

Battery Chargers, Inverters, Solar Components, and Wiring Supplies for Boats, RVs, and Off-Grid Applications.

baymarinesupply.com

However, larger is better.

 

[svetz]

THHN is rated for 105C when used in for appliance wiring.

https://www.usawire-cable.com/pdfs/thhn_thwn.pdf

And 4 awg pure copper with 105C insulation is good for 160 amps.

Interactive Wire Size Calculator

Battery Chargers, Inverters, Solar Components, and Wiring Supplies for Boats, RVs, and Off-Grid Applications.

baymarinesupply.com

Exactly! It depends on what you get, for example, the bottom one is for a marine grade wire... and why you need to check the manufacturer's specs rather than any old well-meaning chart on the internet.
Use the charts for what you'll buy. For example, here's the southwire spec (available from homedepot)

 

[John Frum]

That's marine wire... and why you need to check the manufacturer's specs rather than any old well-meaning chart on the internt.

Copper is copper and the insulation temperature rating is its temperature rating.

 

[svetz]

Copper is copper ...

Except when it's not, e.g., oxygen-free copper.

... check the manufacturer's specs ...

Should have also said, don't trust the specs unless it's rated by an independent trustworthy source such as UL/ETL/CE.

 

[Brewman]

I'm going to place everything on a backboard today and show the distances between componets and wire run lengths.

 

[John Frum]

Assuming you are using compression lugs my concern is how well will they cold weld to thhn.
Thhn is thick strand, from memory there are only 19 strands in bog standard 4 awg thhn.

 

[Brewman]

Assuming you are using compression lugs my concern is how well will they cold weld to thhn.
Thhn is thick strand, from memory there are only 19 strands in bog standard 4 awg thhn.

I'm using a 10 Ton hydraulic crimper it that helps with your question.

 

[Brewman]

 

[BenQ]

Is over sizing the wire an issue? I was doing this if future expansion happens. The converter is the one off Wills page, and I just noticed I got the gauge backwards, its 12 AWG is in and 10 AWG out. Ill update my drawing soon. @smoothJoey I update your drawings and use to show correction.

Oversizing is usually only an issue for your wallet

 

[Brewman]

So here is what it should look like after its wired up. As you can see the longest run will be from the battery to the buss bars. The battery bank will sit right below the backboard so that run will be less then 6 feet one way.

 

[Brewman]

When it comes to the main fuse, it has to be able to handle the inverter and buck converter. As per the manual for the inverter it says 100A, the converter is 12V 40A out so that becomes 24V 20A in. Total is 120A, Should I up my main fuse to 150A or is 125A fine.

As for the PV circuit breakers, I should lower them from 40A to something like 20A. If the array is not big enough for really needing the breakers can I just leave the 40's as disconnects and if the array gets larger then resize them if needed?

 

[John Frum]

2000 ac watts / .85 conversion efficiency / 24 volts low cutoff + 20 dc amps / .8 fuse headroom = 147.549019608 fuse amps
That is pushing it for 4 awg wire.
It may be rated for 105C but I really doubt you want to get anywhere near that.