480/277 Backfeed [RE-wrenches]

Matt Lafferty mlafferty at universalenergies.com
Thu Oct 19 08:25:49 PDT 2006


All,

Jeff C asked about GFCI 480 Service requirements.

It is not "480" specifically... And it is not "all"... Here's the NEC lingo:

230.95 Ground-Fault Protection of Equipment
Ground-fault protection of equipment shall be provided for solidly grounded
wye electrical services of more than 150 volts to ground but not exceeding
600 volts phase-to-phase for each service disconnect rated 1000 amperes or
more. The grounded conductor for the solidly grounded wye system shall be
connected directly to ground without inserting any resistor or impedance
device.
The rating of the service disconnect shall be considered to be the rating of
the largest fuse that can be installed or the highest continuous current
trip setting for which the actual overcurrent device installed in a circuit
breaker is rated or can be adjusted.  <End of NEC reference>

The nutshell version is that 277/480 service disconnects rated 1000 Amps or
more need to have ground-fault protection.

What may be in Jeff's mind is a post from a month or so ago related to
service requirments in a Flood Zone and the local AHJ saying that the whole
thing would have to be GFCI protected if below the Base Flood Elevation.  It
turns out that the AHJ's initial interpretation was subsequently revised...
Go figure!  The new, and more appropriate IMHO, interpretation was that a
service cannot be located at an elevation less than 1 foot above Base Flood
Elevation (100 Year Flood Height), regardless of GFCI...  Services located
in these Flood Zones need to be elevated.  Permanent service platforms &
stairways need to be provided.  Loads connected to the elevated service are
allowed to be located below the BFE+1 height as long as they are GFCI
protected. 

For those who care... The case that originally put this issue on my radar
came out as follows:  We paid a licensed surveyor $850 to determine and
certify the BFE for the area of the parcel which was affected by our work.
The county charged an additional $288 to look at the form (standard 4 page
FEMA form).  The outcome of the survey was that, as long as all serviceable
equipment was located 3' above grade or higher, no additional mitigation was
required.  Since there were no walls or stem-wall footing/foundations
related to the trellis-structure and it was deemed "non-dwelling", the
County backed off their requirement that "in-progress" and
"post-construction" certifications be provided by the surveyor.  This saved
us $650 in potential additional fees.

The system is installed and signed off by the County.  Awaiting Utility
inspection and net-meter set.

Hope this helps,

Matt Lafferty
mlafferty at universalenergies.com


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