Wire type and size-need to get this right

[sunshine_eggo]

I’m past my knowledge here as well.

I thought with two Quattros I would run two lines (L1 and L2) at 120 volts each. Plus a neutral and a ground for 4 wires total.

I don’t think I understand how two Quattros and split phase works. In the short term, I was going to use one Quattro and see how it goes.

@sunshine_eggo Would you mind shedding some light? I’ve looked at the Victron info and the Victron forum but am still unclear.

I have two Quattros working in split phase. Q1 provides L1-N-G connections and Q2 provies L2-N-G connections. N and G are common between them. The N-G bond is provided ONLY in the L1 inverter.

With one quattro, you are limited to 120V, L-N-G.

Anything unclear?

 

[Bluedog225]

That is perfectly clear.

When calculating line size, I need 4 conductors.

And I need to size L1 and L2 each using 120 volts and 42 amps.

And I will size the neutral and ground to match the L1 and L2.

Is this correct?

Many thanks.

 

[ricardocello]

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

 

[hwy17]

Subpanel feed cable uses a different calculation than main breaker wire.

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

 

[hwy17]

Here is another debate of the question at hand here:

voltage drop, 1-phase, stupid question,

www.electriciantalk.com

Basically, it is common practice to size feeders for 240v voltage drop, and yes if you run a totally unbalanced load you will get twice the voltage drop.

So if you were running 120v loads and you really want only 3% voltage drop you would input 120v in the calculator. But normally, a subpanel is sized for 3% at 240 and the greater voltage drop in the case of 120v unbalanced full current loads is tolerated.

 

[hwy17]

@sunshine_eggo Does Victron provide easy access to a voltage output adjustment?

If you have 120v a 6% drop won't hurt anything. But if they're locked at a franken-Euro 115/230 then voltage drop is a bit more crucial.

 

[sunshine_eggo]

That is perfectly clear.

When calculating line size, I need 4 conductors.

And I need to size L1 and L2 each using 120 volts and 42 amps.

And I will size the neutral and ground to match the L1 and L2.

Is this correct?

Yes, but output may need to be oversized due to passthrough and powerassist.

N will never carry more than L1 or L2. If current is used on both legs, N is actually reduced to the difference between the two.

Manual specified gages consider the transfer switch rating + powerassist. If you are setup to provide less at the input, you can size accordingly at the output.

I'm inputting only 13A via generator, so 55A max output - using 6awg.

 

[Bluedog225]

Thanks for the link.

I guess I don’t know how to balance the load given the 240 volt will the the intermittent mini split. I can split the circuits with best guesses between L1 and L2 but it will be rough justice.

 

[Sennen]

That is perfectly clear.

When calculating line size, I need 4 conductors.

And I need to size L1 and L2 each using 120 volts and 42 amps.

And I will size the neutral and ground to match the L1 and L2.

Is this correct?

Many thanks.

Keep in mind as mentioned above, you can get the wire bundled. Using HD as example, local electrical supply would likely be cheaper.
https://www.homedepot.com/p/Southwire-500-ft-2-3-Black-Stranded-CU-W-G-Tray-Cable-44342401/202316565 (They also sell by foot)

Southwire 500 ft. 2/0-2/0-2/0-1 Gray Stranded CU SER Cable 27083501 - The Home Depot

Southwire Type SE, Style SER service entrance cable is primarily used as panel feeder in multiple unit dwellings. The cable may be used in all applications where Type SE cable is permitted. SER may be

www.homedepot.com

 

[ricardocello]

Does Victron provide easy access to a voltage output adjustment?

Yes, the inverter voltage setting is in VEConfigure. It can go up to 128V i believe. be careful

 

[sunshine_eggo]

@sunshine_eggo Does Victron provide easy access to a voltage output adjustment?

If you have 120v a 6% drop won't hurt anything. But if they're locked at a franken-Euro 115/230 then voltage drop is a bit more crucial.

Yes.

 

[Bluedog225]

Yes, but output may need to be oversized due to passthrough and powerassist.

N will never carry more than L1 or L2. If current is used on both legs, N is actually reduced to the difference between the two.

Manual specified gages consider the transfer switch rating + powerassist. If you are setup to provide less at the input, you can size accordingly at the output.

Sorry, I don’t know how to operationalize some of this.

Are you saying I need to upsize the conductors account for pass through and power assist?

I read the N line as saying N will never need to be larger than L1 or L2. Great.

 

[Bluedog225]

I do see that voltage at the inverter can be adjusted up to 130 volts.

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

Edit-I see that 130 doesn’t help as much as I thought it might.

 

[sunshine_eggo]

Sorry, I don’t know how to operationalize some of this.

Are you saying I need to upsize the conductors account for pass through and power assist?

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.

 

[sunshine_eggo]

I do see that voltage at the inverter can be adjusted up to 130 volts.

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

Edit-I see that 130 doesn’t help as much as I thought it might.

128V is the actual limit in the software.

If 128V is what it takes to show 120V at the end of your wires, no problem. You will still be current limited to the VA, i.e., 5000/128 = 39A.

Most equipment is happiest at the rated 120V.

 

[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.