AC-coupled Xantrex XW-6048 cycling on/off

aj164

In the evenings, sometime during the last hour of sunlight, the XW inverter starts to "hiccup", turning on/off the output. There are no (noticeable) power glitches on the grid side. It cycles on/off a few times, and then turns back on.

The Xantrex XW-6048 inverter was installed recently with existing grid-tied PV. There is an SMA and an Aurora (Power One) inverter. To get the benefit of PV when the grid goes down, both grid-tied inverters are wired into the output side of the Xantrex XW. There is roughly 6kW PV on the SMA and 3kW on the Aurora, for a total of 9kW.

The system has been working fine for a couple of months. About three or four weeks ago, I set a schedule on the XW to disable charging at night. (When the charger is off, the display shows dashes.)

The owner says the fault logs are clear. I will check the fault logs tomorrow and post back here. Any ideas what this could be?

Thanks - AJ

aj164

Re: AC-coupled Xantrex XW-6048 cycling on/off

Update: There are no faults or warnings on any device. The event log for the inverter shows a series of events, all with the same timestamp of 19:06.
559 inverting
636 ac good
523 qualifying ac
548 qualifying aps
549 invert to bypass delay
559 inverting
603 engaging inverter
636 etc...
549

aj164

Re: AC-coupled Xantrex XW-6048 cycling on/off

Did it again; two on/off cycles in a row. It is becoming like clockwork: every night after 7pm. This is the weirdest thing. The grid itself is not going down, but the AC output "critical loads" turns off and on again in the space of a minute or two.

RCinFLA

Re: AC-coupled Xantrex XW-6048 cycling on/off

Sounds like a software glitch associated with deactivation of charger, maybe coupled with GT inverter sputtering out as sun sets.

Try to make sure the charger does not get disabled until a safe margin of time after GT inverter has shut down for the evening.

When you disable charger, the inverter is shut down and unit just does AC passthru. I am not 100% sure, but the inverter may need to run in parallel when there is backfeed from GT inverter to ensure a load regulation if grid goes out. At near sunset, the GT may shutdown and reactivate a few times before it finally fizzles out for the evening. If charger is set to disable, XW may shut down its inverter when GT goes down, then have to reactivate when GT comes back online.

The control board should maintain grid syncronization even when inverter is off and be able to reactivate inverter in a couple of cycles. Should be able to handle a couple of bounces of GT inverter but you cannot ignore the observation that the issue did not start to happen until you deactivated charger function.

XWGuy

Re: AC-coupled Xantrex XW-6048 cycling on/off

Did you try calling tech support?
1-866-519-1470

Jeff

aj164

Re: AC-coupled Xantrex XW-6048 cycling on/off

I spoke to someone at tech support. He did not have an answer, but he suggested to look for loose wiring (DC and AC). He also said it could be a software glitch, and I could try a "restore factory defaults", reboot, and reconfigure.

I did both of those things (found no loose wires), and I also set the charge block begin time to well after sunset. So far, so good. I couldn't afford multiple return trips to change one thing at a time, so I suppose I have no idea what exactly went wrong.

aj164

Re: AC-coupled Xantrex XW-6048 cycling on/off

The gremlin is back. Sometime before 7pm (I will know definitely when I can check the logs), the XW burped again. The main grid did not go down; only the XW and critical loads. Also, the inverter is making a once-per-second ticking sound, as though it is in search mode, but the relays are in AC pass-through.

There is 9kW AC coupled through this 6kW XW inverter. I just read another thread in which someone posted that there should not be more than 6kW AC coupled on an XW-6048. While this makes sense (6kW on a 6kW-rated inverter), it doesn't explain why this problem occurs just before sundown rather than in the middle of the day during peak power.

RCinFLA

Re: AC-coupled Xantrex XW-6048 cycling on/off

aj164 wrote: »

I just read another thread in which someone posted that there should not be more than 6kW AC coupled on an XW-6048. While this makes sense (6kW on a 6kW-rated inverter), it doesn't explain why this problem occurs just before sundown rather than in the middle of the day during peak power.

The reason for GT power not to exceed XW6048 capability is because during no grid the XW6048 is pushing excess PV to batteries or shuts down GT by moving AC freq outside GT range. If batteries have not reached full charge and AC loads cannot consume PV power then inverter pushes remaining power to batteries, within the limits of the XW inverter power capability. Batteries must also be capable of taking the full PV push as there will be no charge current regulation. If pushed power exceeds XW inverter capability it is just like an overload on the inverter. XW will likely shut down as it does for an overload.

I agree this probably has nothing to do with your problem. Shutting off XW charger at night isn't going to save that much grid power. Probably something like 200 WH's/night for batteries depending on AH size of batteries and about 200 WH's/night to keep inverter running for charging. With inverter active you will get a bit faster AC load pickup on any momentary grid outages.

I still think it has something to do with the inverter going to standby (inverter chopping stops) and having to get woken back up again. There are some intertangled setting but I think there is one to keep the inverter running while not charging batteries. That would at least save the battery floating power consumption.

If problem only happens when you set charger to disable at night seem the path of lease resistance is to not disable charger at night.

aj164

Re: AC-coupled Xantrex XW-6048 cycling on/off

When we arrived on the scene, we found half of the grid power was down at the XW wiring panel. The breaker in the main panel opened up internally on one leg (it was not tripped). The connection at the bus bar shows discoloration from overheating. Either the breaker was bad, or the connection at the bus was loose.

An explanation for the odd behavior right around sunset could be from thermal expansion-contraction. The breaker panel gets afternoon sun until late evening. A loose connection could have been opening up from the thermal contraction as materials cooled at sunset.

I suppose time will tell whether the bad breaker was the cause of the XW cycling.

lelson

Hmmm. I'm having somewhat similar symptoms to those in this very old post. In my case, I know the cause: failure (pegs high) of the utility's voltage regulators at the substation (1000# behemoths). In my case, the Xantrex XW-6048 disconnects/connects from the grid when the voltage gets too high (early morning). In your case, the voltage might be getting too low (late evening). In neither case does the grid "fail" and, oddly, there are no warnings or events in the log. I do get a fault when the inverter side encounters a grid voltage that it can't match. I've never had this situation occur before in 17 years and it took awhile to figure out what's going on. YMMV.

BB.

In Puerto Rico, a few years(?) ago, there was a large GT Solar array installed (local military base?) and the generated current from the solar farm caused the local line voltage to rise (out of spec.) on sunny days...

So, with increasing solar farms in your area, it is possible for the local line voltage to go out of specification. Especially if you are at the "end of the power grid" (remote city/farm/etc.).

If the line voltage is going out of specifications (say 104 to 132 or 208 to 264 VAC for "240" nominal power), You should be able to call your utility and have them monitor your AC line power.

I guess you are around Gardnerville Nevada?

-Bill

lelson

Yes, near Gardnerville. I wasn't speculating on the cause (utility regulator failure) of the high voltage. I've been in touch with them. Solar farms don't play a role in the failure here.