[RE-wrenches] Utility Side Feed In and Disconnects (was "Line Side")

Matt Lafferty gilligan06 at gmail.com
Sun Mar 15 10:13:29 PDT 2009


<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: re-wrenches-bounces at lists.re-wrenches.org
[mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of Wayne Irwin
Sent: Wednesday, March 11, 2009 7:56 AM
To: re-wrenches at lists.re-wrenches.org
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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