Operational Quirks of AC Coupling inverters

[sboat]

Operational Quirks of AC Coupling inverters

Dual XW Pro with (45) 415-watt 144 cut Mono cell PERK PV panels, (45) Enphase IQ-7+ micro inverters and (12) 48 vdc 100 ah Lithium Phosphate batteries so 61.8 kWh of storage.

We are 100% OFF GRID, but with 250 amps @ 48 vdc of battery charger power available from the grid if we needed it.

This home has terrible all day shading issues so even with 18,600 installed watts of PV at peak we only see 11.5kW. But, in the microinverters defense we see a usable 220vac power from 7:30 AM to 7:30 PM, and better than expected power on cloudy days. So, here in Florida and now with March sun our average daily harvest ranges from 62-66 kWh per day. This system has been up for over 6 months. This is a poorly insulated ocean access house on the water carrying 9.000 watts of heat we have use perhaps 20 times in six months or 6,000 watts of AC cycling on and off vertually every day and or night has never gone off on low battery so the 61.8 kwh we are happy with.
By the way, Ive worked with alot of inverters. Far as raw power invert or charge, these Scheinder Elect 6848's are awsome!

So quirks. Fearing unstable power I installed (6) Costco Cyber Power 1350 VA ups back ups on all (6) hi power graphics computers here. These UPS units are a plesent supprise as they change over perfactly. Not so much as screen flicker. However, apparently, these UPS units do use internal mechanical relays to swap line to battery back up and back to line. Every day AND night, for no apparant resaon, we sudenly hear all six relays clicking in perfect unison. at the same time the power display on each UPS changes from line to backup and back to line. On average they will do this dance 10 or more times in a session then they go back on the dual sinced XW Pro''s somtimes for hours with no change over. Again all (6) cycle in perfact unision so if nothing else Cyber Power has done a great job of matcing unit to unit charastics. The XW Pro must be feeding some kind of voltage ripple. At first I suspected frequency shifting caused be eather the IQ-7+ units or the XW Pros but it happens at night as well so I blame the dual Schneider 6848's. Sometimes it will happen when either of our dual zone Inverter drive AC units come on but not always. And Ive seen clouds passing start the change over. But again is just as bad at night unless the moonlight on the PV is causing it, LOL.
Any ideas?
All the best
SBoat

 

[wheisenburg]

Well I am glad to see that you have gotten AC coupling all worked out on your system. I did notice that you have twelve 100 ah batteries. I have a similar system, but mine is used for backup only and uses IQ8+. I also only currently have 3 batteries. Perhaps that is not enough for AC coupling to work.

How much trouble did you have getting the AC coupling to work? I still don't really have mine working.

Also the max continuous power rating of the IQ7+ is 290 watts. So you should not expect more than 13,050 watts ever. Your panels are a little large for your inverters. They recommend the IQ7+ for panels up to 335 watts. It is normal for panel watts to exceed the inverter watts.

As far as your UPS issues. Do you have any other large loads on the same circuit? It could be the start up of a large load either on this circuit or even somewhere else is causing voltage sag. Maybe your car charger cycling on and off. Maybe a motor starting up (like sump pump). Motors are notorious for large startup surges. Maybe even the heating element on a oven or water heater cycling on and off. You might want to check the connections on all the wiring for the computer circuit. I recently tracked a nuisance trip on an arc fault breaker to a lose connection in my breaker box.

If it really bothers you, you could turn off 1/2 of your breakers, but not the one to the computers. See if it still happens. If it does not turn off the other half. If you figure out if it is in one half of the breakers, and then a quarter and so on, you might be able to figure out where the problem is coming from. If you know that, maybe it can be fixed. It is is related to a motor, you might be able to add a soft starter.

If you start with turning off all large motors with automatic start, like air compressors, sump pumps, air conditioners and any heavy 240 volt loads you might be able to track it down faster.