Friends:
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.
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 downstream from the fault.
See:
http://millersolar.com/MillerSolar/case_studies/ground_fauilt/_ground_fault.html
for some musings on the subject.
As they say on TV: "There had to be a better way!"
William Miller
At 05:54 PM 4/17/2012, Kent Osterberg wrote:
Nathan,
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.
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.
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.
Kent Osterberg
Blue Mountain Solar, Inc.
<http://www.bluemountainsolar.com>www.bluemountainsolar.com
On 4/17/2012 11:08 AM, Nathan Stumpff wrote:
Wrenches,
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.
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.
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?
Thanks,
-Nathan
--
Nathan J. Stumpff - Arctic Sun, LLC
NABCEP Ceritified PV Installer #091209-175
<mailto:[email protected]>[email protected]
Office: 907/457-1297
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