whats minium lengh from AC disconent to Panel?

[scancool]

I submitted my plans for solar and got rejected cause of this error does anyone know what it means?
what's the correct value?

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[J.P.M.]

Seems to me that someone who claims to be qualified to design PV systems would know. I'd start by asking the system designer. Failing that, I'd ask the authority who rejected the plans what they meant.

[scancool]

Thanks that's what I did , I asked the person who design the plans they told me they didn't know, I asked the person who rejected the plans twice and no email back in the pass week. this forum is my last resort.

[foo1bar]

Seems to me that someone who claims to be qualified to design PV systems would know. I'd start by asking the system designer. Failing that, I'd ask the authority who rejected the plans what they meant.

I agree.

I'd also like to know what you find out from the designer/AHJ.
I didn't calculate a minimum length for conductors after the breaker panel for my installation.
And I know mine are much less than 4', so I'm curious what this is referring to (or if it's irrelevant because this wire is between the breakers and the inverter and the text box was mistakenly left on a copy of plans adapted from something else.)

[SunEagle]

I would say that the length of a cable is based on it's resistance value used in the formula to determine the Short Circuit Current value to be less than 10k amps. The longer the wire length or smaller the wire size increases the resistance value but the wire size needs to be big enough to handle the current of the load.

[foo1bar]

Thanks that's what I did , I asked the person who design the plans they told me they didn't know, I asked the person who rejected the plans twice and no email back in the pass week. this forum is my last resort.

So the person who did the design doesn't understand the design that they created for you. (and has typos in the plans besides)
They *should* be able to tell you what that text box means.
If they can't tell you how they calculated the 4', or "AFC below 10K", and they aren't willing to talk to the AHJ to fix the problem with their plan then I would not pay them.

[scancool]

@foo1bar The company is boxedsolar where I got the plans, and they refund the money because they can't figure it out. is just I have to pay to get it review, so I'm wasting time and money when the plans are not good

@suneagle so if the resistant for 1 foot of a 8 gauge wire is 0.0006282 ohms times 4 is 0.0025128 ohms
240V / 10K amps is 0.024ohms
then the length we are providing should be good or what am I missing?
if they want to keep the current below 10K wire should be 38.2 Feet but that's seems too long

[bob-n]

8 AWG copper is 0.6282 ohms per 1000 feet of SINGLE conductor. You have a two conductor cable, so need to double that resistance. In other words, to get >0.024 ohms, you need >19.1 feet of two 8 gauge conductors.

As others have said, you really need to hear from the AHJ. Rather than email, perhaps you can show up in person early in the morning before they've started out on jobs, act polite, and beg for someone who can tell you what to change to make this pass. In my little town, that worked for me.

I'm going out on a limb here, but my wild guess is that the AHJ is simply telling you that the calculation is wrong. If that's all he/she is saying, then all you need to do is change the plans to show the entire cable length from Solaredge to Main Panel is at least 20'. All of that wire is in series and would limit the current. Fortunately, that's not a lot of extra cost. Home Depot sells each conductor of 8AWG Copper for ~$25/50' length, so if you had to add 15 feet of additional wire 2 conductors, you're adding <$50 to the total cost.

Disclaimer: I'm not an electrician. Don't act on my advice.

[foo1bar]

If that's all he/she is saying, then all you need to do is change the plans to show the entire cable length from Solaredge to Main Panel is at least 20'.

I'd probably put the actual distance you expect it to be. ex. '10 feet of 8AWG wire, contained in 3/4" PVC conduit' (or whatever you're going to use)
And bring that to the building dept. as your new plans, and leave off the "AFC below 10K" text.

I'd be honest with the plan reviewer. Explain that the guy who drew up the plans couldn't explain to you why that text was there. And that you didn't understand the note the reviewer added. But if he can tell you which code section your plans aren't meeting, you think you'll be able to make sure the plan is redone correctly.

Disclaimer: I'm not an electrician. Don't act on my advice.

Ditto.

[Mike90250]

I'd guess at typos
An arc-fault circuit interrupter (AFCI) No idea what AFC is

There may be a minimum length needed to keep nuisance trips from happening.

[bob-n]

Going based on exactly what is written, "...to keep AFC below 10K" could mean "to keep arc fault current below 10K amps". But I'm just guessing.

I didn't see an AFCI breaker anywhere in the diagram.

The spec on standard Square D Qo breakers is 10kA interrupt rating. My understanding of that is that the breaker will safely interrupt a fault as high as 10kA, so if you can keep fault current below 10kA, a standard Qo breaker will protect you.

[SunEagle]

Going based on exactly what is written, "...to keep AFC below 10K" could mean "to keep arc fault current below 10K amps". But I'm just guessing.

I didn't see an AFCI breaker anywhere in the diagram.

The spec on standard Square D Qo breakers is 10kA interrupt rating. My understanding of that is that the breaker will safely interrupt a fault as high as 10kA, so if you can keep fault current below 10kA, a standard Qo breaker will protect you.

That 10k rating is usually for the "short circuit amp" capability. The lower the resistance the higher the short circuit amps a system sees during a "short". Usually you can protect the system by increasing the resistance between where the short occurs and the over current device that protects it or change out the over current device to one that has a higher short circuit amp rating.

With the addition to AFCI ratings of home equipment there may be another factor to what the AHJ is looking for. Hard to tell exactly what they want changed and why.

[J.P.M.]

Thanks that's what I did , I asked the person who design the plans they told me they didn't know, I asked the person who rejected the plans twice and no email back in the pass week. this forum is my last resort.

Wherever you get the answers, your actions, designs and drawings will still need to satisfy the AHJ. Cut out all the flailing about and get to the source who rejected the design. All else is opinion that, while nice and perhaps/probably well informed, means precisely squat with respect to getting your design approved.

As for lack of response from the AHJ, nothing can replace persistence. Show up at the building dept. with a polite, contrite and penitent attitude, and smile all the while you ask for answers that you can understand. You'll get more flies with honey than vinegar, but stay professional. Also get the nane of everyone you speak with, and take lots of notes.

If necessary, be prepared to start climbing the chain of command while keeping in mind that the AHJ is not your enemy and probably more on your side than the outfit that did the design that got rejected. This is the part of the process where the names and information you wrote down will come in handy.

After you understand what the AHJ wants to see added/removed/changed with respect to the design, find someone more competent to effect those changes that the bonehead outfit that did those drawings.

Welcome to the forum of few(er) illusions.