[RE-wrenches] Xantrex SW 4048 grid tie mystery

[bob at midnitesolar.com]

You can test to see if both inverters are staying in sync by just 
watching the voltage between L1 and L2 of the

outputs for a while.  If they do not deviate much from 240VAC over 
several minutes, then they are probably

sync'd OK...  You can also help verify this by unplugging the sync cable 
and they should start to drift apart in

phase which will be seen eventually reflected in the 240VAC drifting 
around and through zero volts and back

up to 240V again.

Could be seconds or minutes depending on the internal clock stability.

boB


On 12/22/2019 12:57 AM, Jerry Shafer wrote:
> Well l would start simple and get a sync cable and make sure that they 
> are al least staying g in correct phasing, then look closely at the 
> programming, look at the grid voltages and settings, take it out of 
> IEEE for test purposes only, you might find out you have a board 
> that's out of calibration causing the issue but start simple
> Jerry
>
> On Fri, Dec 20, 2019, 9:44 AM Dave Tedeyan <dtedeyan at taitem.com 
> <mailto:dtedeyan at taitem.com>> wrote:
>
>     Hi All,
>
>     I am someone's last ditch effort to get their system working which
>     has been non-functional since a few months after installation, 13
>     years ago...
>
>     After getting some new batteries in there, I can at least fire it
>     up. It is a grid tie with battery backup situation with two
>     Xantrex SW4048 inverters. Each inverter is kind of like its own
>     system with two Outback MX60 CC's per inverter, and each inverter
>     powers its own 120V backed up loads panel. They do not see each
>     other until their 60A single pole breakers in the main panel.
>
>     What seems to be happening is that after turning on the inverters
>     the AC1 in good light will flash for about 30 seconds, then it
>     syncs up to the grid and the light stays on solid. But then after
>     a little bit, that light will start flashing, indicating that the
>     utility power has been dropped, when it has not actually been
>     dropped. Then at some point the backed up loads would lose power.
>     The customer says that every 1-10 minutes, they would lose the
>     backed up loads for 10-90 seconds. This happened all night long
>     until they bypassed the inverters.
>
>     There are a few other things of note:
>     1. There is a Xantrex GTI for each inverter.
>     2. I see in the manual there is information about stacking the
>     inverters, but I am guessing in this setup this not necessary or
>     would even be counter productive to stack the inverters. Not sure
>     if the inverters not being stacked could cause one of them to
>     unsync with the utility?
>     3. Neutrals and grounds are bonded in their main panel, but also
>     in each of the Xantrex DC breaker boxes. I was going to separate
>     them in the DC breaker boxes, but found that there is no way to
>     isolate the battery negative bus from the box itself, and figured
>     it would be dodgy to unground the enclosure. So I am also not sure
>     if the multiple N-G bonds could be causing these issues.
>
>     Does anyone have any ideas?
>     Cheers,
>     Dave
>
>     *Dave Tedeyan, PE*
>     Senior Engineer | Taitem Engineering, PC
>
>     110 South Albany Street | Ithaca, NY 14850
>     o. _607.277.1118 x121_  f. 607.277.2119
>     www.taitem.com <http://www.taitem.com>
>
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