Dave:
I don’t have a definite answer for you, but I do have my suspicion: The GTI units may be at fault. As you probably know, these units were an afterthought add-in to try and meet IEEE and/or UL testing. How the GTIs work is a bit of a mystery to me, and I would like to learn more about them. I had an interesting experience with the GTI: I have a GTBB customer without GTIs. They were having a billing dispute with the local utility (PG&E). I disabled the Sell function for a few months, but I later learned the SW inverters (2 SW5548) were selling about 1 kWh per day even with Sell disabled. I can imagine this would violate the listing and is likely why the GTIs were invented. You might try bypassing the GTIs, if only for a limited time test. Then you can judge if you want to recommend a system without GTIs. There is a risk without them of being unable to defeat sell and of violating a building permit (if one exists) by modifying the system. Good luck and please keep me informed about how this works out. William Miller Miller Solar 17395 Oak Road, Atascadero, CA 93422 805-438-5600 www.millersolar.com CA Lic. 773985 *From:* RE-wrenches [mailto:[email protected]] *On Behalf Of *Dave Tedeyan *Sent:* Friday, December 20, 2019 9:45 AM *To:* RE-wrenches *Subject:* [RE-wrenches] Xantrex SW 4048 grid tie mystery 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 Solar • Sustainability • Energy • Design Certified B-Corporation since 2013
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