A GFDI fault requires an EMU (Envoy) to clear the fault. Or the
inverter must be replaced. There is sound reasoning behind this:
1. UL1741 requires the GFDI to "provide an indication of the fault".
It does not stipulate how to indicate, or where to indicate.
2. Further, the requirement states that the GFDI "shall not be capable
of automatic reclosure". This means some form of human interaction is
required to clear the fault indication to allow the inverter to restart.
3. The inverters are mounted under the module, often up on a roof and
inconvenient to gain access to.
While some indication of the fault at the inverter can be helpful in
verifying the "culprit", it is impractical to rely solely on a rooftop
annunciation. Who wants to crawl around on a roof looking under modules
to see an LED or listen for a buzzer? Because the EMU and inverters
talk to each other via powerline communications, it becomes practical to
also annunciate the fault thru the EMU (Envoy).
Once you know there is a fault, you know the serial number of the
offending unit, and you know the location on the roof (because you were
so diligent at filling out the install map!), it is relatively easy to
find the actual fault.
Two brief comments on GFDI:
1. Micro deployments see far fewer GFDIs than string installations.
The DC wiring is localized at each module and is not strung across the
roof. Far fewer opportunities for pinched wire and compromised insulation.
2. If there is a GFDI, its' precise location is identified. You do not
need to search thru a string (or strings) of 10 or 12 modules to find
the problem.
Clearing the fault from the Envoy is a simple matter of "checking a
check box" on the Envoy webpage interface. Certainly easier than
climbing up on a roof and fumbling around for a button or a switch. A
button or a switch, by the way, costs money and is a point of failure.
We are striving to minimize both.
So, for full functionality an Envoy is required. By the way, it's also
required to get the California rebate, as it is the only means of
displaying 5% metering information as required by the CSI program. And
yes, you probably want to have a laptop computer with you on the job site.
All other faults (over/under voltage/frequency, anti-islanding, etc.)
are automatically reset. The Envoy and the Enlighten Web application
allows you to see all faults, but only the GFDI requires human
intervention to reset.
Any other questions, just drop me a line. Or call our excellent
Customer Support folks at 877 797-4743.
See Ya!
Marv
Enphase Energy
707 763-4784 x7016
Travis Creswell wrote:
I really appreciate the responses to my questions. Marv, can you address
Bill L's comment that some faults could require the EnPhase EMU unit to
clear? That's good point about shading which isn't a problem on this roof.
Regarding the "wasted glass" and "third module" of the KC120's. Currently
these 3 modules charge a battery bank with only a few rarely used lights on
it. Is used to be more frequently used but not now so the batteries are
spending most of their time at float thus the glass is already wasted. The
third module will continue to charge the same battery bank.
Best,
Travis Creswell
Ozark Energy Services
-----Original Message-----
From: re-wrenches-boun...@lists.re-wrenches.org
[mailto:re-wrenches-boun...@lists.re-wrenches.org] On Behalf Of Marv Dargatz
Sent: Tuesday, April 07, 2009 7:32 PM
To: RE-wrenches
Subject: Re: [RE-wrenches] Enphase Application
Travis,
You are exactly right. As long as you do not exceed the max open
circuit voltage or short circuit current rating you're perfectly fine.
Even if you put 300W of module on the inverter, it will just hit power
limit until the irradiance declines enough to let the MPPT work again.
No problem. No damage to the module or the inverter. The "smoke
threshold" voltage is many volts above our stated maximum input voltage.
Of course, it probably doesn't make economic sense to waste that much
glass.
In your case, two Kyoceras in series will work just fine. Depending on
the age of the modules, soiling, etc., you'll probably have less than
240W peak. I'd guess you will seldom see the inverters hit power limit.
This configuration will have no impact on MTBF or reliability.
Do be aware that if you shade one of the two modules, you'll limit the
output of both modules in the series string. No worse than a standard
string inverter.
We chose a Tyco CPC connector for cost, reliability, and environmental
reasons. If you can find a connector that meets the demanding NEMA6
requirements at a better price, please let me know. We're constantly
looking for ways to reduce product cost without degrading reliability.
Hope this helps.
See Ya!
Marv
Enphase Energy
707 763-4784 x7016
Travis Creswell wrote:
Greetings Wrenches,
I have customer with a three module array made up of 120 watt Kyocera's
that
charge the battery bank underutilized of “hobby system”.
It spends most time in float plus were adding a 5.5 kW direct grid tied
array that require us to move the existing array so the customer is
interested in putting an EnPhase inverter on two of the Kyocera 120’s.
I’ve looked over the EnPhase specs and don’t see a reason why I can’t wire
two KC120’s in series and feed the EnPhase with them. I do see them
listing
it’s compatibility of up 225 watt modules but am having a hard time
getting
much further. I didn’t find a max input wattage so what happens if I put
240 watts to the EnPhase? Does the magic smoke come out on day one or
does
MTBF drop from 32,895 years to 80 years?
Even is the EnPhase's max output is 200 watts it's still more kWh/day then
the hobby system that spending most of it's time in float. I can see no
difference between one 72 cell module and two 36 cell module in series.
Also it looks like there is unique connector coming off the AC side of the
module. How do I deal with that?
Best and thanks in advance!
Travis Creswell
Ozark Energy Services
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