[RE-wrenches] Xantrex SW 4048 grid tie mystery

[Lloyd Hoffstatter]

Dave,

Guessing it’s a synchronization problem between the two inverters.
Depending on the placement of the grid tie breakers, the two inverters are presenting themselves as either in parallel (2 x 120v sources on the same leg) or “series” (120 / 240 on two 120V legs).
The attached manual excerpt and tech note talk about both.  Seems that you need a synch cable in either case, recently did a rebuild on an SW 5048 (pm for internals rebuilder info) and needed cable to get both inverters to work properly.

Have at least one grid-tie / backup system that has been running for years with dual SW / GTI’s – time for battery replacement, rest of system still going…

Best regards,
Lloyd
Lloyd Hoffstatter
Sunstruck Consulting

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From: Dave Tedeyan<mailto:dtedeyan at taitem.com>
Sent: Friday, December 20, 2019 1:03 PM
To: offgridsolar at sti.net<mailto:offgridsolar at sti.net>; RE-wrenches<mailto:re-wrenches at lists.re-wrenches.org>
Subject: Re: [RE-wrenches] Xantrex SW 4048 grid tie mystery

Dave,
Sorry, misspeak on my part. It is DC negatives and grounds that are tied together. No neutrals in the DC box.
Cheers,
Dave

Dave Tedeyan, PE
Senior Engineer | Taitem Engineering, PC
[https://www.taitem.com/signatures/logo.png]
110 South Albany Street | Ithaca, NY 14850
o. 607.277.1118 x121  f. 607.277.2119
www.taitem.com<http://www.taitem.com>

Solar • Sustainability • Energy • Design
Certified B-Corporation since 2013


On Fri, Dec 20, 2019 at 12:57 PM Dave Angelini Offgrid Solar <offgridsolar at sti.net<mailto:offgridsolar at sti.net>> wrote:

Why would neutral be in the DC conduit box? This just wrong but I doubt this is the problem.

Since this never worked properly or has not in 13 years, I would suggest replacement with modern equipment. SW from xantrex has been out of support for around 15 years and always was a headache grid tied, in my opinion.

Dave Angelini Offgrid Solar

"we go where powerlines don't"

http://members.sti.net/offgridsolar/

e-mail  offgridsolar at sti.net<mailto:offgridsolar at sti.net>

text 209 813 0060

On Fri, 20 Dec 2019 12:44:42 -0500, 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
[cid:image001.gif at 01D5B73F.05B24710]
110 South Albany Street | Ithaca, NY 14850
o. 607.277.1118 x121  f. 607.277.2119
www.taitem.com<http://www.taitem.com>

Solar • Sustainability • Energy • Design
Certified B-Corporation since 2013
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