proper genny wiring for dual inverter off grid

bekahsnow

I did a 6 hr round trip drive ot troubleshoot a system; I didn't install it.  I've never done an AGS with a dual inverter system so I'm not sure, but I feel like the wiring was wrong and wanted to check before I tell the homeowner their installer is liable.

It is 2 Magna 4448 inverters wired as master/slave with a decent amount of production and storage, AGS set for a Generac.  The genny was wired into both of the inverters (L1,L2,N,G) and the slave inverter burned out.  The installer disconnected the slave and told the owners that they simply didn't need it.  Eh.  I reconnected (RJ45 into the comm center for remote, batt sense) and fired up the system (no genny on) and teh slave is clearly faulting.  No smell of ozone or burn just loud, creating surging in circuits, clearly busted.  Is this an issue that could have been caused by improper genny wiring?  My gut tells me that only the master inverter would be wired to genny charge; more info if needed.

Estragon

I have Outbacks in a 120v master/slave stack, which is likely similar.

IIRC, both inverter are connected to genny AC so both chargers can be used.  In my case, I use a 4kw diesel or a honda eu2000i, and have to adjust charger max on both so as to not overload whichever genny is in use.

My pair can be either parallel master/slave 120v, or 120/240v series stacking though (not 120/240 on each).  It may be different with both doing split phase?  Presumably both the genny and inverters are wired and configured the same for either 120v or 120/240 split?

bekahsnow

Ok, that definitely gives me pause on my initial thinking.  Granted I am grasping a little since I do more on grid than off, and I didn't install this system so reverse troubleshooting is rough.  Thanks for input, I'll holster my suggestion to the homeowners that they installer messed up and will gather more info. Def don't wanna start a ruckus.

bekahsnow

THe 8x8 box splits the genny feed (generac 16kw) into the individual breaker discos to backfeed the inverters.  THey both are wired with L1,L2,N and ground...THe one on top is commissioned as master and lower is slave and has been disconnected because of malfunction.  When the genny was on once they heard it revving quick and smelled burning but taking it apart didn't show any damage.  Fault say a relay error on the comm screen.  Is this proper wiring for this do ya think?

Estragon

To clarify, is this a new system which the installer walked away from, or a previously functional system which has now failed?

bekahsnow

it's been functional for about a year, I was called in for a troubleshoot because they couldn't get him back to check the system.  Various hums and haws, waiting for tech support to call him back for a month.  So, it's been functional but the second inverter only worked for a brief time before it burned out.  I got to the site after asking all of the common questions and getting an affirmative that the system was functional, the batteries were charging and had been watered, and production was good.  The installer had told them he'd watered batteries in october when he adjusted the modules; I looked in one of the bank of 16.  So, after putting about 7 gallons into the bank, I continued a basic check out.  I'm really not sure if this is wired correctly or not, but there are enough inconsistencies in what he's told them about maintenance that I told them I'd check around to let them know if it looks like an inverter warranty malfunction, an installation error or other.  The genny was running a LOT to try to keep up with the dehydrated batteries (every day at least 2 hrs, often 7 hrs, often multiple times and installer suggested more production or more batteries).  SO, there's the rundown.  It's a pretty install, but I know the guy is new at off grid and pretty doesn't mean right.  But I am new at AGS systems so don't wanna sick them on their installer with no cause.  ya know?

thanks

Estragon

7 gallons on a fairly new bank?   How big, 16 x L16s for 2 strings, ~700ah@48v?  Sounds kinda high.  Might be worth looking at other stuff once you get past the acute stuff.

Anyway,  from MS install manual FWIW...

"CAUTION: If there is a communication issue, the ME-RTR’s top line will show the inverter’s status (e.g., Off, Inverting, Searching) rather than identifying that port’s connected inverter as a master or slave unit. In that case, the router mistakes the unit as a standalone inverter, will not sync properly, and may result in damage to that unit— possibly causing damage to the other inverters in the system as well."

It isn't all that hard to make or develop a bad rj45 connection in my experience.  From the above, it sounds like a comms failure could result in the sort of fail (burnt relay?) you seem to have?

Doesn't seem like a graceful way to recover from a comms failure to me, but...

bekahsnow

interesting.  Definitely sounds like what they described to me; thanks for bringing that paragraph.  They've got a kid (like, 28?  so still a kid, right?) learning about the system (i met with him and talked him through a lot of it while doing the site visit) and he's waded through a lot of the settings to fix issues.  But, they've been through two generators (first one burned out from lack of oil) and the system was connected then, and the generator they bought was actually the wrong type so they had to modify to allow for the AGS.  Enough issues with it that any of those could have caused the relay failure, now that I know that comm errors can do that.  The batteries were unfortunate; I think that the installer had told them he'd filled the batteries and hadn't in the however long (isn't clear to me exactly when the system was installed) so every battery/every cell was at least 1/2" to a full 1" below the fill line; some with the top of the plate clearly dry.  I've seen worse come back to life so I'm pretty sure they'll be okay on that end now that they have a fill schedule, an easy-fill set, and know the proper water to use. 

I appreciate your help here; like I said I know enough to know when I need an extra set of eyes and a more informed brain!