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William,<br>
<br>
There have been too many fires where GFP failed to operate correctly
to argue that they are really good at what they are supposed to do.
But, I think it is inappropriate to say they don't really work at
all. How many fires could have or would have happened without the
GFP devices? Does anyone have stats?<br>
<br>
In every PV system I've installed, and since you do high quality
work, I'm confident that in every one that you have installed, the
mounting framework is securely grounded. The GFP device does not
change that circumstance. Every junction box, conduit, mounting
rail, and PV module is grounded and safe to touch regardless of what
the GFP does. If someone removes <i>the </i>module grounding while
looking for a ground fault, then it is possible to have an energized
module frame, but the GFP didn't create this risk. The system could
be solidly grounded with no GFP device and the module frame would be
just as energized. It's important that every PV installer understand
that risk and also understand that every properly grounded component
of the system is still perfectly safe.<br>
<br>
My major complaint about the GFP is that, in battery systems, they
expose the homeowner to unsafe conditions. 690.5(C) requires that a
GFP hazard warning be located within site of the batteries.
Unfortunately, the person servicing the 12-volt or 24-volt
refrigerator or lights isn't going to see that warning. In the event
of a ground fault that opens the GFP device, the negative wire going
to the lights or refrigerator or any other dc load may be energized
to -150-volts to ground. Or maybe -300 volts or -600 volts with some
of the new charge controllers. Ground, the green wire running
everywhere, is connected to the positive PV wire someplace in the
array and the negative wire is connected to every negative wire in
the system. If the unexpected voltage isn't a bad enough risk, the
current may be worse. There is nothing to stop the arc from the
shorted PV array if someone accidently connects negative to ground.
This is actually a preventable circumstance: the GFP simply needs to
open both PV+ and PV-. The manufacturers need to step up and correct
this. The NEC needs to be changed to require it. This won't reduce
the risks at the PV array, but it is certainly worth it to design
components that don't but homeowners at unnecessary risk.<br>
<br>
<pre class="moz-signature" cols="72">Kent Osterberg
Blue Mountain Solar, Inc.
<a class="moz-txt-link-abbreviated" href="http://www.bluemountainsolar.com">www.bluemountainsolar.com</a>
</pre>
<br>
On 4/17/2012 6:42 PM, William Miller wrote:
<blockquote
cite="mid:6.0.1.1.2.20120417180352.02904358@millersolar.com"
type="cite">
Friends:<br>
<br>
Here is a related problem: If we use an 80 amp GFD (ground fault
detection) breaker, even for a very small array, we have to use
3AWG CU
wire from the battery buss to the breaker and from the breaker to
the FM
or MX60. This seems like a big hassle for 5 or 10 amps of
charging. A variety of sizes of GFD breakers would be
helpful.<br>
<br>
Here is a bigger problem: GFD breakers don't really work. All
they do is turn off the charge function in hopes that someone will
find
the problem. In the meantime, the negative-to-ground bond is
removed and module mounting framework could be energized. PV GFD
breakers are completely different from standard AC GFDI (ground
fault
detection and interruption) receptacles and circuit breakers. The
AC versions interrupt power upstream, the PV versions interrupt
power
<i>downstream</i> from the fault.<br>
<br>
See:
<a moz-do-not-send="true"
href="http://millersolar.com/MillerSolar/case_studies/ground_fauilt/_ground_fault.html"
eudora="autourl">http://millersolar.com/MillerSolar/case_studies/ground_fauilt/_ground_fault.html</a>
for some musings on the subject.<br>
<br>
As they say on TV: "There had to be a better way!"<br>
<br>
William Miller<br>
<br>
<br>
<br>
<br>
<br>
At 05:54 PM 4/17/2012, Kent Osterberg wrote:<br>
<blockquote type="cite" class="cite" cite="">Nathan,<br>
<br>
I don't think anyone makes a 100-amp PV GFP. The panel mount
breaker model that's being used for the PV GFP doesn't include a
100-amp breaker.<br>
<br>
The Classic has a built-in GFP so you shouldn't need an external
GFP for it. You will need to add a GFP for the FM60 - a single
80-amp GFP would work.<br>
<br>
You can use the dual 80-amp GFP and shut down both PV arrays at
the same time if the GFP is wired to disconnect the PV array
from the charge controller input. That's where Outback's
instructions used to show the GFP, and it is a better place for
it than on the charge controller output anyway. Midnite's
instructions show the GFP on the charge controller input, but
their 80-amp GFP is a single.<br>
<br>
<pre>Kent Osterberg
Blue Mountain Solar, Inc.
<a moz-do-not-send="true" href="http://www.bluemountainsolar.com">www.bluemountainsolar.com</a>
</pre>
<br>
On 4/17/2012 11:08 AM, Nathan Stumpff wrote: <br>
<blockquote type="cite" class="cite" cite="">Wrenches,<br>
<br>
In a job coming up I have a customer with an existing FM60
controller, 520 watt (!!) array. We are doing a ton of work,
including adding a 4 kW solar array with Classic 150 charge
controller. I am trying to figure out how to handle the GFP.<br>
<br>
For the Classic, I need a 90 or 100 A output breaker minimum.
80 A is not an option. The OutBack dual GFP is 80 A, and so it
not an option.<br>
<br>
Is there a 100 A GFP breaker assembly I have just never seen?
Is there a way to use the Classic’s GFP to run an external
relay via AUX (to trip the FM60 output breaker at the same
time)? Any ideas?<br>
<br>
Thanks,<br>
-Nathan<br>
<br>
--<br>
Nathan J. Stumpff - Arctic Sun, LLC<br>
NABCEP Ceritified PV Installer #091209-175<br>
<a moz-do-not-send="true"
href="mailto:nathan@arcticsun-llc.com">nathan@arcticsun-llc.com</a><br>
Office: 907/457-1297<br>
</blockquote>
<br>
</blockquote>
<x-sigsep>
<p>Miller Solar<br>
Voice :805-438-5600<br>
email: <a class="moz-txt-link-abbreviated" href="mailto:william@millersolar.com">william@millersolar.com</a><br>
<a moz-do-not-send="true" href="http://millersolar.com/"
eudora="autourl">http://millersolar.com<br>
</a>License No. C-10-773985<br>
<br>
</p>
</x-sigsep></blockquote>
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