<I just found this sitting in my Drafts folder. Meant to send last week.> Hi Wayne, Grouping is a gray area in the NEC. Subject to the discretion and interpretation of the AHJ. Always has been since the concept of grouping was established. Certain conditions and occupancy classifications may allow different interpretations. Article 230 provides requirements for services. 230.2 Number of Services defines how many services are allowed to supply a building or structure. In general, only one is allowed unless one of several special conditions, occupancies, capacity requirements, or different characteristics are met. 230.2(A) Special Conditions stipulates that "Additional services shall be permitted to supply the following:" (1) Fire pumps; (2) Emergency systems; (3) Legally required standby systems; (4) Optional standby systems; (5) Parallel power production systems; and (6) Systems designed for connection to multiple sources of supply for the purpose of enhanced reliability. If you are doing a non-backup, grid-connected system, your application falls under 230.2(A)(5) Parallel power production systems. This is important for a couple reasons, primarily because it specifically allows the second service in the first place. It is also important because, as a Parallel power production system, this is a Special Condition and not a "normal" service. Requirements for Service Equipment Disconnecting Means are found in Article 230 Section VI. Article 230.70 General specifies that "Means shall be provided to disconnect all conductors in a building or other structure from the service-entrance conductors." (Keep in mind that little word "in".) Article 230.70 then goes on to list additional requirements for this service disconnect... Readily Accessible outside or inside nearest the point of entry, not in bathrooms, readily accessible again, marked as service disconnect, and suitable for use. Article 230.71 defines the Maximum Number of Disconnects. 230.71 says that the service disconnecting means for each service permitted by 230.2 shall not consist of more than 6 switches or breakers... In a single enclosure, group of separate enclosures, or switchboard. There also shall not be more than 6 sets of disconnects grouped at any one location. Article 230.72 gives us the Grouping concept. 230.72(A) General says, "The two to six disconnects as permitted in 230.71 shall be grouped. Each disconnect shall be marked to indicate the load served." There is NOT a definition of "grouped". 230.72(B) Additional Service Disconnecting Means specifies that the service disconnect for all of the Special Conditions listed in 230.2(A)(1) through 230.2(A)(4) "shall be installed remote from the one to six service disconnecting means for normal service to minimize the possibility of simultaneous interruption of supply." There is no direct mention of 230.2(A)(5) Parallel power production systems. It is unclear to me if this is intentional or unintentional. What is clear to me is that, if for no other reason than the 230.2(A) Special Conditions classification, it is not part of the "normal service". The explanation in the NEC Handbook (2008) says: The intent of 230.2(A) is to permit separate services, where necessary, for fire pumps (with one to six disconnects) or for emergency, legally required standby, or optional standby systems (with one to six disconnects), in addition to the one to six disconnects for the normal building service. Article 230 recognizes that a disruption of the normal building service should not disconnect the fire pump, emergency system, or other exempted systems. Because these services are in addition to the normal services, the one to six disconnects allowed for them are not included as one of the six disconnects for the normal supply. These separate services are permitted by 230.2 and are required to be installed in accordance with all the applicable requirements of Article 230. Notice that the explanation reiterates the "one to six disconnects" per service principle. What is more important is the concept of "remote from the normal service disconnecting means for the purpose of reliability". A couple of very important elements of the justification for FIT-subsidized DG PV are grid reliability and homeland security. In fact, the location of the DG disconnect in this case should be at the discretion of the interconnecting utility. This is generation, directly to and on behalf of the serving utility. Generation is treated differently than loads by grid operators and rightfully so. In the case of most utility distribution maps, meter locations for loads are mapped whereas generator disconnects are mapped. Note that, unless the customer's meter and service disconnecting means are located adjacent to or grouped with one another, the utility doesn't map (or even care) where the service disconnect is physically located. When you add generation, whether it's utility-side or customer-side connected, they map the generator disconnect. Quite different scenarios. There are fundamental differences between the need and use of each on the part of a utility operator. In utility-side configurations, the generator is 100% electrically isolated from and independent of the "normal" service. Their respective service disconnects should NOT be "required" to be located adjacent to or grouped with the other. Depending on the actual conditions and arrangements at the site, it may be prudent to provide a permanent placard at each service disconnect showing the location of the other. Personally, assuming otherwise "normal" conditions and appropriateness of the existing premise electrical system, I would present the AHJ with this rationale and explanation. It may even be prudent to have an earnest conversation with the local utility and see if they are willing to support this position. Try to find a line-crew somewhere and talk with them about it. Tell them that the local AHJ is trying to make you put the generator disconnect inside the house, next to the existing service disconnect. (This is one of the options the AHJ is presenting you with.) You will get one of two responses... If the person or crew you are speaking with has a jaw full of chew, you will most likely get a macho response like, "Shoot. That dinky solar system ain't gonna hurt us no-how. <spit> We just throw a chain over the line and take it to ground 'til we're done clearing the line. <spit> If your generator ain't ready when we pull the chain, then too bad for you." The other response you will get goes something like this: "They wanna what? Don't they know we don't wanna have to bust down somebody's door to have to lockout the generation? Man, it's our lives at stake out here. Who is this idiot building inspector?" You are far more likely to get the second response from a lone lineman. For some reason, when they are in groups, the macho comes out. I've had this conversation with these guys a few times over the years. For various reasons. It's funny to watch the whole group go from macho to pissed off when one of them says, "Wait a minute... He's right. That building inspector don't know what he's talking about. The customer's load don't have nothing to do with the generation... Generation is our business." Thought I'd pass it along. Matt Lafferty Solar Janitor _____
From: [email protected] [mailto:[email protected]] On Behalf Of Wayne Irwin Sent: Wednesday, March 11, 2009 7:56 AM To: [email protected] Subject: Re: [RE-wrenches] Line Side Feed In and Disconnects Wrenches, They are requiring us to install two service disco's. One for the PV (between the PV and the FIT (payment) meter) and one for the house (between the distribution panel and the standard utility (billing) meter). As Darryl stated, the reason is so that they are grouped together. They said it did not necessarily matter wether or not they were grouped inside or outside, so long as they are grouped. We normally install (batteryless) grid tie systems outside with discos within 10' of the utility meter. So as I see it, we must either install the inverter and PV disconnect inside next to the distribution panel, or install an additional disco outside between the house panel and the utility meter, next to the inveter, AC disconnect and FIT meter. Wayne Irwin
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