Wire type and size-need to get this right

[hwy17]

Doesn’t this change my calculations pretty significantly? If I set at 130, there is no downside. Right?

I would still do your calculations at nominal voltage. I would size the feeders for 3% drop at 240v.

Then, if you have heavy 120v unbalanced loads and you are finding insufficient voltage at a particular load, you can use the inverter adjustment as an after the fact compensation. I have my inverter set at 124/124.

 

[Bluedog225]

Ok. I think I’m getting a better understanding.

1. Run aluminum, not copper. Except for the 2 feet between the inverter(s) and the main panel).

2. Make sure the inverters and main panel can accept the size line I use for the long run.

3. Adjust the Quattro so that the voltage at the subpanel is close to 120 volts after all is said and done.

4. Size L1 and L2 using 120 volts (up to 128), and 39 amps.

(Question-is this 39 amps at the end of the run per the calculator?-I think yes.)

5. I can safely size the neutral and ground wires at the same size as L1 and L2. Though it may be ok to make them smaller.

6. Use individual THWN because pulling bundled wires is going to be harder.

7. Use quality/name brand wire, not cheap stuff.


I hear the advice to size at 240 volts, and I don’t doubt you are right. But I don’t understand it well enough. It may be I have one Quattro and find it sufficient for all my needs. So I’d need to size for 120 volts.

Here’s where it stands

 

[AZ Solar Junkie]

Good callout. I was basing my figures above on 240 assuming the inverters were going to be split phasing. If the run is 120, lower voltage = more amps. The calculations would need to be for 86 amps for 120

edit: also one less wire at 120

2 x 120v hots @43 amps each. you shouldn't need to add the amps of each wire...

 

[AZ Solar Junkie]

Ok. I think I’m getting a better understanding.

1. Run aluminum, not copper. Except for the 2 feet between the inverter(s) and the main panel).

2. Make sure the inverters and main panel can accept the size line I use for the long run.

3. Adjust the Quattro so that the voltage at the subpanel is close to 120 volts after all is said and done.

4. Size L1 and L2 using 120 volts (up to 128), and 39 amps.

(Question-is this 39 amps at the end of the run per the calculator?-I think yes.)

5. I can safely size the neutral and ground wires at the same size as L1 and L2. Though it may be ok to make them smaller.

6. Use individual THWN because pulling bundled wires is going to be harder.

7. Use quality/name brand wire, not cheap stuff.


I hear the advice to size at 240 volts, and I don’t doubt you are right. But I don’t understand it well enough. It may be I have one Quattro and find it sufficient for all my needs. So I’d need to size for 120 volts.

Here’s where it stands

View attachment 198572View attachment 198573

I agree - each wire will only carry 120 volts, not 240 volts. The fact that the 2 combined are giving you split phase 240 volt is irrelevant to the individual wire specs.

 

[Bluedog225]

Yes.

From the manual:

AC-out-1 (see appendix A, maximum torque: 7 Nm)The AC output cable can be connected directly to the terminal block "AC-out". With its PowerAssist feature the Quattro can add up to 5kVA (that is 5.000 / 120 = 42A) to the output during periods of peak power requirement. Together with a maximum input current of 100A this means that the output can supply up to 100 + 42 = 142A. An earth leakage circuit breaker and a fuse or circuit breaker rated to support the expected load must be included in series with the output, and cable cross-section must be sized accordingly. The maximum rating of the fuse or circuit breaker is 142A.

So, take whatever you're going to feed the input and add 42A to it.

I missed this one.

Wow. That’s a huge change.

 

[Bluedog225]

Adding 42 amps to the 39 amps give me this.

 

[ricardocello]

I missed this one.

Wow. That’s a huge change.

Unless you don’t enable PowerAssist, then it won’t matter. I do not enable it on my Quattros, and use a 100A breaker.

But it is best to design it in now in case you do.

 

[sunshine_eggo]

Ok. I think I’m getting a better understanding.

1. Run aluminum, not copper. Except for the 2 feet between the inverter(s) and the main panel).

Ugh... if you have to.

2. Make sure the inverters and main panel can accept the size line I use for the long run.

Yep

3. Adjust the Quattro so that the voltage at the subpanel is close to 120 volts after all is said and done.

Remember, that's load dependent. Sitting there running a few hundred Watts means you'll still see near 128V @ panel.

4. Size L1 and L2 using 120 volts (up to 128), and 39 amps.

(Question-is this 39 amps at the end of the run per the calculator?-I think yes.)

I feel like we're picking fly turds out of pepper at this point. It was intended to be illustrative.

5. I can safely size the neutral and ground wires at the same size as L1 and L2.

Yes.

Though it may be ok to make them smaller.

No. 0A on either leg means the N is carrying whatever the hot wire is carrying.

6. Use individual THWN because pulling bundled wires is going to be harder.

Probably.

7. Use quality/name brand wire, not cheap stuff.

I'm flexible on this...

 

[ricardocello]

No. 0A on either leg means the N is carrying whatever the hot wire is carrying

only the ground conductor is allowed to be smaller.
The Neutral carries current and must be the same size as the hots.

 

[Bluedog225]

Ugh, you're not a fan of aluminum?

Can I turn off power assist? That 42 amps extra just put me off the charts.

 

[sunshine_eggo]

Ugh, you're not a fan of aluminum?

Can I turn off power assist? That 42 amps extra just put me off the charts.

Yes.

 

[hwy17]

If you buy 1000ft of 4awg copper black THHN and cut it into 4x 250ft and pull all of those together you will probably already be cursing.

Larger wire will lead to more cursing.

 

[Supervstech]

That voltage drop calculator is appropriate for subpanel feeders. It is not using main feeder allowances.

Correct.
I guess i should have worded it, that calculators for load dont have the allowances a main feeder gets.

 

[Bluedog225]

only the ground conductor is allowed to be smaller.
The Neutral carries current and must be the same size as the hots.

Got it.

Do I size the ground for the sum of the max amperage of L1 plus L2?

Thanks

 

[Sennen]

Ground conductor can be smaller
https://up.codes/s/size-of-equipment-grounding-conductors

Use this for ground sizing

 

[Supervstech]

Got it.

Do I size the ground for the sum of the max amperage of L1 plus L2?

Thanks

No.
Just main breaker size

 

[740GLE]

Yes.

Ugh, you're not a fan of aluminum?

Can I turn off power assist? That 42 amps extra just put me off the charts.

I also don’t like wine, but that doesn’t mean I don’t get tippsy on it in a pinch

Aluminum is used 99% more than copper over the entire grid. There’s nothing wrong with it, just know the couple extra steps and you’ll be fine (and a thicker wallet too).

 

[ricardocello]

Aluminum is used 99% more than copper

I used 220’ of AWG 2 Aluminum direct-burial URD duplex for my 40A solar DC feed from the ground mount to the house. it was the least expensive way to keep the voltage drop way down at the time.

But then I chose to put it in PVC conduit. That was a really painful pull, so half way in I cheated and assembled some of the conduit around the cable. Never again.

 

[Bluedog225]

Good info. Thanks. Too late for me to cheat. Conduit is buried.

Are you saying you would go with individual conductors or that it’s going to be a pain either way?

 

[ricardocello]

Good info. Thanks. Too late for me to cheat. Conduit is buried.

Are you saying you would go with individual conductors or that it’s going to be a pain either way?

Individual THHN/THWN2 conductors with lube is by far the easiest. Over 200’, “easy” is of course not that easy.
You did 2” conduit? should be ok.

For me, the duplex URD was twisted around itself, making the pull even harder than it needed to be.
Also, I had a separate single ground wire 8 AWG that was getting caught up in the twists.