Six handle rule

ggunn

PE (Electrical), NABCEP certified
Location
Austin, TX, USA
Occupation
Electrical Engineer - Photovoltaic Systems
I just got a response from my AHJ regarding the installation of a PV system connected to the line side of a service where there is a MLO MDP with breakers feeding subpanels in the building. They told me that it would be OK as long as the PV did not constitute a 7th handle. I watched a Mike Holt video a couple of weeks ago that said that this was not the case. In addition, the note in the 2014 NEC Handbook at the end of 690.14 says, "...no more than six disconnects for each source of power are permitted...", emphasis mine, seems to agree with that. Thoughts?
 

GoldDigger

Moderator
Staff member
Dereck's general rule applies here:

1. The inspector (AHJ) is always right.
2. When the inspector is wrong, see rule 1.

The question is whether the chance of prevailing is good enough to justify the hassle and delay.
I tend to agree with MH on this, but the whole area of PV disconnect is badly muddled.
 

jaggedben

Senior Member
Read 230.71(A) really carefully...

The service disconnecting means for each service permitted by 230.2, or for each set of service entrance
conductors permitted by 230.40, Exception No
.1, 3, 4, or 5, shall consist of not more than six [handles]...
Emphasis mine.

If you are installing a new set of service entrance conductors, you get six more handles.

If you are adding a breaker to the existing MLO panel, you don't.
 

ggunn

PE (Electrical), NABCEP certified
Location
Austin, TX, USA
Occupation
Electrical Engineer - Photovoltaic Systems
Read 230.71(A) really carefully...



Emphasis mine.

If you are installing a new set of service entrance conductors, you get six more handles.

If you are adding a breaker to the existing MLO panel, you don't.
Mike Holt appears to disagree. How would that be different from this? In the video he referenced the same section of code that I did.
 

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ggunn

PE (Electrical), NABCEP certified
Location
Austin, TX, USA
Occupation
Electrical Engineer - Photovoltaic Systems
Same service entrance conductors in latter... different in former.
I'm sorry, but can you elaborate on that a little for me? Former, latter, same, different, conductors where... sorry, but that's not clear to me.
 

Smart $

Esteemed Member
Location
Ohio
I'm sorry, but can you elaborate on that a little for me? Former, latter, same, different, conductors where... sorry, but that's not clear to me.
MH graphic shows 7 disconnects with a wireway above them. Assuming there is one large set of service entrance conductors (SEC) running though the wireway, then tapped to supply each disconnect, so you have a multi-enclosure scenario under 230.40 Exception No. 2. However, the tap to the PV disconnect falls under 230.40 Exception No. 5. From there, refer to 230.71(A).

NOTE: I do not agree with the MH graphic in that I believe there has to be at least a little more space between the 6th service disconnect and the PV disconnect to set the service grouping apart.

With this explanation, can you now see how 7 handles in an MLO panel is a violation?
 

ggunn

PE (Electrical), NABCEP certified
Location
Austin, TX, USA
Occupation
Electrical Engineer - Photovoltaic Systems
MH graphic shows 7 disconnects with a wireway above them. Assuming there is one large set of service entrance conductors (SEC) running though the wireway, then tapped to supply each disconnect, so you have a multi-enclosure scenario under 230.40 Exception No. 2. However, the tap to the PV disconnect falls under 230.40 Exception No. 5. From there, refer to 230.71(A).

NOTE: I do not agree with the MH graphic in that I believe there has to be at least a little more space between the 6th service disconnect and the PV disconnect to set the service grouping apart.

With this explanation, can you now see how 7 handles in an MLO panel is a violation?
Actually, no, I don't. In those wireways there are usually a set of busbars, just like in a MLO panel. The only difference I see is that in MH's drawing there are conductors between the busbars and the switches where in an MLO the breakers land directly on the bus. Why would that make any difference?

In MH's video, he says that the reason you don't count the PV as a seventh handle is because it's not a service disconnect under 230.82(6).

I will go read the sections you reference. The way you see it, could someone mount a switch on the wall next to the MLO and run tap conductors to the bus in the MLO and be OK?
 

jaggedben

Senior Member
Oh man, here we go again with whether or not the PV disconnect is a service disconnect or not. You remember how that came out the last time around? You want to chime in now that you have a stake in the answer? :D

For the record, I simply disagree with Mike Holt, notwithstanding Smart$'s explanations above. We happen to agree in some situations, but not others, because our reasoning is totally different. But until the code gets revised on this matter, the answer is ... ask your AHJ.:cool: I guess from what you said in the first post, they agree with me and not Mike Holt.

Also, FWIW, most of the gutters I've seen that resemble Mike Holt's drawing are full of tapped wires as described by Smart$. Actually my own building is wired that way. (It's very out of date). If it were a meter bank, it would have busbars.
 
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Smart $

Esteemed Member
Location
Ohio
Actually, no, I don't. In those wireways there are usually a set of busbars, just like in a MLO panel. The only difference I see is that in MH's drawing there are conductors between the busbars and the switches where in an MLO the breakers land directly on the bus. Why would that make any difference?

In MH's video, he says that the reason you don't count the PV as a seventh handle is because it's not a service disconnect under 230.82(6).

I will go read the sections you reference. The way you see it, could someone mount a switch on the wall next to the MLO and run tap conductors to the bus in the MLO and be OK?
In an MLO panel, you will have only one set of service entrance conductors serving 7 handles in one enclosure. That's a violation of 230.71(A) because you only have one set of service entrance conductors. If you tap the bus or the service entrance conductors, you are creating another set of service entrance conductors, so a switch to the side would be compliant.

In MH graphic, you actually have seven sets of service entrance conductors... six (or should I say five) of which are permitted by exception because the "handles" are in six separate enclosures [230.40 Exception No. 2]. The seventh handle is supplied by yet another set of service entrance conductors permitted by a different exception [ 230.40 Exception No. 5]. However, 230.71(A) prohibits the seventh (PV) disconnect in the service grouping... IMO ...but literal interpretation of the first paragraph, last sentence opens the door to his interpretation.
 

ggunn

PE (Electrical), NABCEP certified
Location
Austin, TX, USA
Occupation
Electrical Engineer - Photovoltaic Systems
In an MLO panel, you will have only one set of service entrance conductors serving 7 handles in one enclosure. That's a violation of 230.71(A) because you only have one set of service entrance conductors. If you tap the bus or the service entrance conductors, you are creating another set of service entrance conductors, so a switch to the side would be compliant.

In MH graphic, you actually have seven sets of service entrance conductors... six (or should I say five) of which are permitted by exception because the "handles" are in six separate enclosures [230.40 Exception No. 2]. The seventh handle is supplied by yet another set of service entrance conductors permitted by a different exception [ 230.40 Exception No. 5]. However, 230.71(A) prohibits the seventh (PV) disconnect in the service grouping... IMO ...but literal interpretation of the first paragraph, last sentence opens the door to his interpretation.
OK, but all the lawyerese notwithstanding, what difference does it actually make of you take power from or put power into a seventh handle when it is a separate switch versus another breaker in a MDP? Or from a tapped conductor versus a busbar? What could go wrong in one scenario that couldn't in the other? Electrically it all looks the same to me.
 

ggunn

PE (Electrical), NABCEP certified
Location
Austin, TX, USA
Occupation
Electrical Engineer - Photovoltaic Systems
Also, FWIW, most of the gutters I've seen that resemble Mike Holt's drawing are full of tapped wires as described by Smart$. Actually my own building is wired that way. (It's very out of date). If it were a meter bank, it would have busbars.
What difference does it make? Tapped conductors or tapped busbars, I mean. the only reason I brought it up was to accentuate the similarity of a gutter full of busbars and an MLO MDP.

And yeah, I remember how it turned out last time, with much wailing and gnashing of teeth and nothing being settled. Do I want to wade into that morass? Nope. I'm going to make an appointment with the AHJ and work with them to find the most cost effective and code compliant solution to my client's interconnection problem. I'm going in with all the information I can pull together and get the matter settled in there where it makes a difference. In here, it doesn't, though I appreciate the discourse. Pass the popcorn. :D
 

Smart $

Esteemed Member
Location
Ohio
OK, but all the lawyerese notwithstanding, what difference does it actually make of you take power from or put power into a seventh handle when it is a separate switch versus another breaker in a MDP? Or from a tapped conductor versus a busbar? What could go wrong in one scenario that couldn't in the other? Electrically it all looks the same to me.
I hear ya'. Electrically it is all the same. I didn't make the rules.
 

jaggedben

Senior Member
...And yeah, I remember how it turned out last time, with much wailing and gnashing of teeth and nothing being settled. Do I want to wade into that morass? Nope. ...
Glad to hear it. When I put the question to you it was rhetorical. :D
 

jaggedben

Senior Member
As far as how it is electrically, or safety-wise...

I always took the six handle rule to be about ensuring that someone (say, a first responder) could shut down power to a building quickly and without confusion. By that token, I don't understand why an extra set of service conductors should buy you another set of handles; electrically they are all the same. The same goes for a PV disconnect, or six. But I didn't make the rules either.
 

ggunn

PE (Electrical), NABCEP certified
Location
Austin, TX, USA
Occupation
Electrical Engineer - Photovoltaic Systems
As far as how it is electrically, or safety-wise...

I always took the six handle rule to be about ensuring that someone (say, a first responder) could shut down power to a building quickly and without confusion. By that token, I don't understand why an extra set of service conductors should buy you another set of handles; electrically they are all the same. The same goes for a PV disconnect, or six. But I didn't make the rules either.
The thing is, to me at least, that the rules should reflect some safety and/or fire prevention measure. The rules are much easier to learn when that is the case; like anything else, if you understand the underlying principles you don't have to memorize nearly as much.

As a small example, one of the rules surrounding solar installations is that a fused AC disco must have the inverter feed on the load side and the utility connection on the line side. Inspectors have told me that getting this wrong is one of the most common mistakes they find in installations. If you think about why this is (if you get it backwards the fuses are hot when the switch is open), you don't have to memorize the rule.
 

jaggedben

Senior Member
I have a related question...

I've run into quite a few different service panels of an 'MLO' type. That is to say, they are designed to have multiple service disconnects, a.k.a 'handles'. Notwithstanding a few situations where someone has violated the instructions on the label, it seems to me that I've never seen one that was designed for more than six handles. It's very common to find them where they would accept at most two poles for a standard sized breaker and four poles of tandem or quad breakers, hence six poles at most. I have recently encountered one Square-D model where you could put up to 12 single-pole breakers, but the label says to install no more than six, and clearly the intention is for 6 two pole breakers.

Is this likely to be generally true? Is it part of a UL standard?

Granted, 95% of my work has been residential, and at the moment I can't recall seeing a commercial service panel of this type.
 

Smart $

Esteemed Member
Location
Ohio
I have a related question...
...
Is this likely to be generally true? Is it part of a UL standard?
...
I don't know about UL Standard playing any part of this, but I'd think the manufacturers of such panels would have to make unique-design breakers and panel receiver to limit panel usage to two- or three-pole breakers and no single pole. That's likely not going to happen.
 
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