If I understand the issue correctly, the inspector is requiring the
PV disconnect for the utility feed to be treated as a service. By
the definition in Article 100, it can not be a service, and therefore
should not be subject to the rules of a service.
The definition is quoted below:
Service. The conductors and equipment for delivering electric energy
from the serving utility to the wiring system of the premises served.
The comment from the NEC Handbook is quoted below:
The definition of service includes the statement that electric energy
to a service can be supplied only by the serving utility. If electric
energy is supplied by other than the serving utility, the supplied
conductors and equipment are considered feeders, not a service.
Energy supplied by an inverter is not coming from a utility.
Drake
At 12:13 PM 3/15/2009, you wrote:
<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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Drake Chamberlin
Athens Electric
OH License 44810
CO License 3773
740-448-7328
740-856-9648
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