Finally got through to Outback. They said the GVFX could be wired with a genny
line-side of the inverter in order for the genny to charge the batteries and
that this configuration could potentially cause problems for the genny. The
likelihood of the PV sending power to the generator is extremely small as the
inverter needs to see 5 minutes of perfect power in addition to sensing a near
full battery bank before it will attempt to "sell" power back to the AC source.
Additionally, when the genset is connected with the AGS the generator will turn
on automatically when the batteries require absorption and automatically turn
off when the batteries are "full" (according to set points). The moment when
the batteries reach that "full" set point is when the inverter may attempt to
"sell" power back but this is when the AGS will shut down the generator.
I have, on my house, an older Xantrex SW4024 and it works fine with my Kohler
8.5kW genset but then again, it has two AC-IN inputs which operate in mutual
exclusion. Outback mentioned that while the FX series inverters do not enjoy
this feature, the Radian inverter re-introduces this configuration. Hallelujah!
So, it sounds like the solution for the Outback grid-tied BB system is to
install an AGS...which is part of the plan as soon as the homeowner completes
some required genny repairs.
The solution for the grid-tied Enphase system, it seems, will have to be asking
the homeowner to shut off his PV when the grid goes down...Ugh.
But reading back through the older posts in this thread, pretty much all
recommending against configuring the genset supply-side of the inverter, the
question remains, for me at least, how does the generator charge the batteries
if the genny is load-side of the inverter?
Eric
SunHarvest
----- Original Message -----
From: SunHarvest
To: RE-wrenches
Sent: Wednesday, January 16, 2013 8:47 AM
Subject: Re: [RE-wrenches] off grid PV connected to generator
For claification, the two installs with which I'm concerned are:
1) Grid or 8.5kW Genset ---> Manual transfer switch ---> FlexPower One
w/GVFX3524, FM80, Mate ---> transformer to 240vac ---> Residential Loads.
This set up also has batteries and an old 600Wstc PV array tied in to the FP1.
2) Grid or ~10kW Genset determined by auto transfer switch, all located at
utility main panel/meter located
about 400' from main residence ---> Subpanel and sub meter at main residence
<--- PV-designated subpanel <--- 8.4kW PV array w/Enphase micros.
It's good to hear (thanks Phil) that PV doesn't auto disconnect when the
genny kicks on (didn't think this was the case) but if the PV does not
disconnect don't we end up with PV potentially backfeeding to the genset??
Isn't this thread discussing how PV backfeeding to a genny is a dangerous
configuration??
David, I can't disconnect the GVFX when the grid is down and the genny on as
both grid and genset supply the AC-IN to the inverter via the manual transfer
switch. But your comment begs the question: Why do you recommend disconnecting
the inverter?
Still trying to connect to an Outback tech (Katee Wood)...
Eric
SunHarvest
----- Original Message -----
From: David Katz
To: RE-wrenches
Sent: Wednesday, January 16, 2013 8:12 AM
Subject: Re: [RE-wrenches] off grid PV connected to generator
Phil,
If Eric is using the FX ot GTFX in an AC coupled mode, he would need to
disconnect the grid tie inverter when the generator was running. >From the
thread, I cannot tell if this is his situation.
David Katz
Sent from my HTC smartphone on the Now Network from Sprint!
----- Reply message -----
From: "Phil Undercuffler" <[email protected]>
To: "RE-wrenches" <[email protected]>
Subject: [RE-wrenches] off grid PV connected to generator
Date: Tue, Jan 15, 2013 8:07 pm
Eric,
Good questions, and you hit on a number of topics so let me see if I can
address them one at a time, not necessarily in chronological order.
Yes, the optimal application for the GTFX / GVFX inverter series is grid
tie with battery backup. If you just want backup to the grid, the traditional
FX is a great solution. If you need extended run-time and want to integrate a
generator, then the Radian series is a better solution because it can not only
integrate both grid and generator, but it can change its operating parameters
based on which input it's connected to.
The SW, XW and Radian inverters are all capable of operating on-grid
(grid-interactive or backup) or off-grid (with or without a generator).
However, none will automatically disconnect the PV when the genny auto-starts,
nor would I suggest that they should. Realistically, the system should only
start the genny when the batteries are near depletion -- if it's started, the
batteries need all the help they can get. Rather, the generator should only be
disconnected (turned off) when the batteries reach the absorb setpoint. BTW, I
can't speak for everyone but none of those inverters have that functionality,
at least not yet.
With 600 Watts of connected PV, I wouldn't worry about disconnecting the
PV. Even with a small battery bank, the sun will set before that size of array
drives the bank anywhere close to an absorb voltage. Add another zero to the
PV size and my answer would be different, of course.
Also, if you do wind up installing an automatic transfer switch with a
battery-based inverter system, don't allow the ATS to control the generator
starting, even if that flies against every tradition of the generator sales
guy. You don't want the genny running through every minute of the power
outage, you want the system to start the genny only when the batteries are low.
Good luck with it, and enjoy the sun!
Phil
On Tue, Jan 15, 2013 at 1:50 PM, SunHarvest <[email protected]> wrote:
Further, I recently installed a GVFX for a customer. I'm hearing from
certain sources that the grid-tied line of inverters from Outback are not
designed to interface with a generator. Really??
I was told by Outback to install a transfer switch line/supply side of
the inverter; that this was the only way to interface the genny with the
inverter; that the AC Hot In could come from grid or a genset. And indeed, this
is the only way I can figure out how to get the genny to charge the batteries
when the grid goes down. But then again, I don't have the extensive electrical
background that allows me to think outside the box as often as I would
like...that's why I'm posing my query here for the pros. In this Outback
install I have to again advise the homeowner to open the PV breaker to the
inverter during generator operation, right? Even though he has a modest 600W
(STC) array and an 8.5kW Kohler genset. Hardly the opportunity for solar to
feed back to the genny under the most sunny and cool of days. I'm more
concerned with the Enphase install.
The Xantrex SW series inverters are fully capable of operating on-grid or
off-grid with a genset. So do those inverters automatically disconnect the PV
when the genny auto-starts? And with the Outback, is the Mate supposed to do
the same (as long as the genny is operated by the auto-start and not a transfer
switch)?
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