[RE-wrenches] AC coupled with grid and backup generator

[Mark Dickson]

Jeff, 

I had this same hesitation when we first fired up our AC coupled system.
When speaking with Steve at outback and he was pretty sure that the
generator would put out dirty enough power that the Fronius inverter would
not like it and shut down.  He was correct-it goes into an error mode as
soon as the geni kicks on.  Once the generator shuts down the Fronius senses
the frequency is back within range and resets itself.  Turned out to be a
simple solution and has been operating flawlessly for almost a year now.

 

Good luck!

 

Mark Dickson

Oasis Montana Inc.

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From: re-wrenches-bounces at lists.re-wrenches.org
[mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of Jeff Yago
Sent: Tuesday, July 28, 2009 6:55 AM
To: RE-wrenches
Subject: Re: [RE-wrenches] AC coupled with grid and backup generator

 


We are completing a residential 4 kW solar system that is on the grid, but
has backup battery-powered Xantrex 6 kW inverter, AC coupled Sunny-Boy
inverter, and a 17 kW Kohler generator.  The larger generator is to allow
operation of a ground-source heat pump during winter which is not supplied
from the inverter fed panel.  We have added a relay cut-out for the Sunny
Boy AC output to prevent over-charging the batteries during utility outage,
but have some concerns about back-feeding the generator through the 100 amp
240 VAC transfer switch when the Sunny Boy thinks the grid is still up.  

 

Will the Sunny Boy try to couple to the generator like it will the inverter
which will be feeding other house loads during an outage and if so, any
risk?   We have wired an aux. switch contact on the transfer switch to also
lock out the Sunny Boy output using the same relay control as being used for
high battery voltage cutout, but this is adding other issues related to
needing multiple relays due to different relay coil voltages.  

 

Anyone smoked a large generator by back-feeding from inverter when the loads
are reduced or shut off?

 

Thanks,

 

Jeff yago


 

  _____  

Netscape.  Just the Net You Need.

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