Grouping of AC main PV disco

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hhsting

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Glen bunie, md, us
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Junior plan reviewer
Is it good idea to group the AC main PV disco that is tapped from line side of the building main service disconnect with the building main service disconnect or not?
 
augie47 said:
Does 705.31 not cover this ?
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Says to provide within 10 feet nothing about grouping.

We get plans that main service disco is inside the building wall and right opposite to the main service disco wall outside is the AC PV disco.


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I have plans that show main service disco is inside the building wall and right opposite to the main service disco wall outside is the AC PV disco.


When given comment to group them was told that NEC 2017 section 230.71(A) references 230.40 exceptions 1,2,3,4 or 5 and says for each set of service entrance conductors permitted in 230.40 exceptions need no more than six circuit breakers.

NEC 2017 section 230.72(A) says two to six disconnects in 230.71 need to be grouped.

Since there are two separate service entrance conductors one for solar AC disconnect and the other for main service building disconnect the two do not need to be grouped.

Does anyone agree with that?
 
I think it's a good idea where possible. Your utility may have specific requirements that they are grouped together and you have to request a waiver if they are not.
 
hhsting said:
Is it good idea to group the AC main PV disco that is tapped from line side of the building main service disconnect with the building main service disconnect or not?
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Why would it not? I always group them when and where I can.
 
hhsting said:
See post #4. What do you think?
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If I read it correctly you are saying why you think they might not need to be grouped rather than any reason why they shouldn't. Most of the AHJs I deal with want them to be grouped if it is possible to do so, and I don't know of any reason why they shouldn't be.
 
hhsting said:
I have plans that show main service disco is inside the building wall and right opposite to the main service disco wall outside is the AC PV disco.


When given comment to group them was told that NEC 2017 section 230.71(A) references 230.40 exceptions 1,2,3,4 or 5 and says for each set of service entrance conductors permitted in 230.40 exceptions need no more than six circuit breakers.

NEC 2017 section 230.72(A) says two to six disconnects in 230.71 need to be grouped.

Since there are two separate service entrance conductors one for solar AC disconnect and the other for main service building disconnect the two do not need to be grouped.

Does anyone agree with that?[\B]
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ggunn said:
If I read it correctly you are saying why you think they might not need to be grouped rather than any reason why they shouldn't. Most of the AHJs I deal with want them to be grouped if it is possible to do so, and I don't know of any reason why they shouldn't be.
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See bolded part thats why.
 
hhsting said:
I have plans that show main service disco is inside the building wall and right opposite to the main service disco wall outside is the AC PV disco.


When given comment to group them was told that NEC 2017 section 230.71(A) references 230.40 exceptions 1,2,3,4 or 5 and says for each set of service entrance conductors permitted in 230.40 exceptions need no more than six circuit breakers.

NEC 2017 section 230.72(A) says two to six disconnects in 230.71 need to be grouped.

Since there are two separate service entrance conductors one for solar AC disconnect and the other for main service building disconnect the two do not need to be grouped.

Does anyone agree with that?
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The ones I've seen will have in addition to that fused disconnect required within ten ft of the line side tap, disconnect(s) on outside within sight and a few feet of meter. Those disconnects are usually grouped. I suppose if 2020 requirements are in place the PV disconnect and the service disconnect are grouped near each other.
 
Fred B said:
The ones I've seen will have in addition to that fused disconnect required within ten ft of the line side tap, disconnect(s) on outside within sight and a few feet of meter. Those disconnects are usually grouped. I suppose if 2020 requirements are in place the PV disconnect and the service disconnect are grouped near each other.
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What I don’t like is what I call smart plans ones that reviewer has to scratch their head and say uh oh this is unusual because they do place two discos next to each other But they place it on opposite sides of building one inside wall and one outside wall of building but still within 10 feet

What do you do then? What does 10 feet measured from cable or actual person walking to disconnect? No guidance at all.
 
hhsting said:
What I don’t like is what I call smart plans ones that reviewer has to scratch their head and say uh oh this is unusual because they do place two discos next to each other But they place it on opposite sides of building one inside wall and one outside wall of building but still within 10 feet

What do you do then? What does 10 feet measured from cable or actual person walking to disconnect? No guidance at all.
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The AHJ's I deal with consider the 10' rule in 705.31 to mean the maximum length of conductors.
 
hhsting said:
What I don’t like is what I call smart plans ones that reviewer has to scratch their head and say uh oh this is unusual because they do place two discos next to each other But they place it on opposite sides of building one inside wall and one outside wall of building but still within 10 feet

What do you do then? What does 10 feet measured from cable or actual person walking to disconnect? No guidance at all.
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You struggle with this a lot. Yes there are things in the code that are vague or could be interpreted different ways. Just make a decision and move on.

Personally, if someone asked me how I came to a decision, I would much prefer to tell them that is the way I read the words rather than that's what people on an internet forum said.
 
electrofelon said:
You struggle with this a lot. Yes there are things in the code that are vague or could be interpreted different ways. Just make a decision and move on.

Personally, if someone asked me how I came to a decision, I would much prefer to tell them that is the way I read the words rather than that's what people on an internet forum said.
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Not really there are times its in the code not just opinion helps what most think though.

Do you think 230.40 exception no 2 would apply and make the PV ac disco and the building main grouped? Only thing if PV system would supply separate loads or not 230.40 exception no 2 apply or not
 
hhsting said:
What I don’t like is what I call smart plans ones that reviewer has to scratch their head and say uh oh this is unusual because they do place two discos next to each other But they place it on opposite sides of building one inside wall and one outside wall of building but still within 10 feet

What do you do then? What does 10 feet measured from cable or actual person walking to disconnect? No guidance at all.
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How would you see the measurement for reasoning of electrical codes, if you have the 2 disconnect only 2ft apart but you run a conduit to get around an obstacle ten ft? Is that 2ft or 10ft? To know first start with what is reason for a given measurement limitation?
I think in this instance the intent would be to limit the length of unprotected conductors. Length might be arbitrary (IDK) but some length limit probably needs to be placed. And somewhat seeming arbitrary numbers comes up elsewhere in the code like for when adding to a branch circuit that now requires AFCI but didn't when it was originally made. Why the number of ft on that one? Was there a reason or just needed some number?
I've had inspectors interpret it to require that same limit of length for service conductors entering a structure from the meter as a limit of the unprotected conductors.
 
electrofelon said:
.......rather than that's what people on an internet forum said.
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Just to be clear: There are lots of super knowledgeable people on here. I dont mean to diminish that....But unfortunately I tell some people about an issue that was discussed here and expect that since it was from MH forum so it should have some serious weight and sometimes they are like, "dont know that Mike Holt forurm...." :confused:
 
hhsting said:
Not really there are times its in the code not just opinion helps what most think though.

Do you think 230.40 exception no 2 would apply and make the PV ac disco and the building main grouped? Only thing if PV system would supply separate loads or not 230.40 exception no 2 apply or not
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I'm pretty sure that most AHJs would interpret that exception to apply only to multiple service entrance conductors from the same service, i.e., the utility.
 
ggunn said:
I still don't get what you are driving at, but it's OK.
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So I have had contractor tell me that PV AC main fused disconnect connected supply side of the main service disconnect is safer outside exterior wall of dwelling unit then inside grouped with main service disco.

This is because if their is fault the fused disconnect gets very hot and melted the exterior plastic sidings dwelling unit. If the PV AC fused disconnect is inside dwelling unit grouped next to main service disconnect in basement on open stud the damage would be much worse.

What do you all think?
 
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