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<font size=3>Dick:<br><br>
We are gong to install HU361 disconnects at the PV. Touch-safe fuse
holders are one way to apply disconnecting means rated at 600 VDC to a
Sola Deck device. Fusing at an array and GFDI at an inverter do not
de-energize PV feeders. Combiner fuses, if required, protect only
adjacent arrays. They will not open if a feeder is violated.
In my humble opinion, this is one of the serious, unrecognized hazards of
the PV industry.<br><br>
Burial tape is always a good idea, but it is only effective if the
backhoe is taking shallow scoops. I don't believe it is required so
it does not always get installed. Most of our run is already in the
ground without tape.<br><br>
If a PV array were present, I would hope an operator would be more
cautious, but without surface marking, it is difficult to be cautious
over an unknown distance. If I was digging near an array, I would
examine the perimeter of the array looking for a disconnect and/or a
telephone number for the installer.<br><br>
Never thought about dumping fill over arcing leads. I'm not sure
this is SOP.<br><br>
Each scenario is different, but I like working on de-energized leads and
it is standard in other electrical trades to require that it be possible
to do so. Without disconnecting means, how is this
accomplished? I like avoiding the expense of disconnecting means as
much as anyone else, but I do want to leave a legacy of safe
installs.<br><br>
Lastly, a 1Kw array at 550 VDC is just as lethal as a 100KW array at
550VDC.<br><br>
This conundrum is new on my radar and I'm still working this out in my
own mind. It was brought up by a recent post regarding PV feeders
through an adjacent building and also this job with conduit-finding back
hoes. I think the issue is warrants discussion. Thanks for
participating. I enjoy your view point and the camaraderie of this
list.<br><br>
<br>
William Miller<br><br>
<br>
At 11:34 AM 12/20/2009, you wrote:<br>
<blockquote type=cite class=cite cite>William,<br><br>
Not sure I understand how buried PV runs protected by touchsafe fuses
in<br>
combiner boxes at the array and GFCI protection at the inverters
constitute a<br>
fire hazard.<br>
That's not saying I disagree with your disconnect here. I don't. If it
was a 1kW<br>
system, would you still install one? I would not.<br><br>
Would not a deeper trench with properly located burial tape have been a
good<br>
call? If the array was installed and visible, maybe the excavation
operator<br>
would have thought to ask about underground utilities. <br>
They should have anyway. Would not common sense imply the operator would
drop a<br>
bucket of fill on any sign of arcing. Would they know to look for a
disconnect<br>
at the array in any case?<br><br>
Common sense can be slippery.<br><br>
Dick <br>
Solarwind Electric<br><br>
<br><br>
<br><br>
--- You wrote:<br>
Friends:<br><br>
I am embarking on a 10 Kw ground mount grid-tie installation. The
client <br>
prepared for this installation some time ago by stubbing a PVC conduit
<br>
underground towards the future location of the PV array. Prior to
<br>
beginning this job, an excavation contractor intercepted the empty
conduit <br>
with a backhoe.<br><br>
No harm was done because this conduit was empty. Had this conduit
been <br>
filled with PV feeders, it would have been very necessary to be able to
<br>
disconnect the PV arrays, both for safety and to prevent a brush fire in
<br>
our very dry climate.<br><br>
The inverters will be located in a pump house about 130 feet from the PV
<br>
arrays. I would not normally put disconnects at the array and they
are not <br>
required. This scenario, however, has caused me to
reconsider. The design <br>
now calls for a disconnect at each row of modules. I feel that it
would <br>
not be prudent to delete this important safety item.<br>
<br>
I wish there were a better selection of compact, low profile
disconnects <br>
suitable for a roof-top installation. I have put external handle
<br>
disconnects on roof but they look terrible. I may specify
touch-safe fuse <br>
holders inside of a Sola Deck for future comp roof jobs. I am not
sure <br>
what we will do with tile roofs.<br><br>
It seems to me that every source of power should have a means of <br>
disconnection as close to the source as possible. This is just
common sense.<br><br>
William Miller</font></blockquote></body>
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