Xantrex 4024 Software Issue? Can I disable the master/slave setup and separate them?

frank1998 · January 2013

What changes would I have to make to disable the master/slave setup and make both inverters operate independently? Can two inverters share a battery bank/PV array or must I break them up? The master/slave communication & software logic seem to be poorly written and frequently result in non-operation of the entire system. Separating them would allow one inverter to continue inverting when the other stops working. I frequently experience the AC1 breaker for the slave tripping and when the slave stops, the master stops inverting as well. The master and slave AC1 breakers are each larger than the "Grid" breaker in my residential panel (which never trips) so the issue appears to be a timing or similar issue between the inverters. Both inverters have the same (latest as of October) firmware revision.

Cariboocoot · January 2013

Re: Xantrex 4024 Software Issue? Can I disable the master/slave setup and separate them

Two inverters can share the DC side providing there's enough capacity there to handle the loads on both.
The Master & Slave configuration is only necessary when sharing the AC side. If the AC out of both are connected they must be configured this way otherwise the magic smoke comes out.

You should look in to why the input breaker on the slave is tripping; it shouldn't unless the circuit is overloaded.
What's happening here is that they are not inverting; they are relying on AC1 input to supply loads. Your slave's AC supplying is being dropped, so it tries to invert but is not allowed to because its function is integral to the master which is not inverting. ERROR!

Things that can cause this include having the GT functioning with Inverter 1 outputing and causing the input on Inverter 2 to go "high". I have vague recollection that their AC1 inputs are supposed to be tied together without separate breakers, but can't remember exactly.

Maybe I should add the Xantrex caveat: don't expect to find a solution to the bug.
Yeah, I've kind of given up on Xantrex.

Photowhit · January 2013

Re: Xantrex 4024 Software Issue? Can I disable the master/slave setup and separate them

So you have 2 4024 inverters and you want to use then independently? That shouldn't be a problem, other than not running them to the same sub panel, since they would no longer be in sync.

2 inverters can run off the same bank of batteries, but they need to "shake hands" to sync up their waves.

frank1998 · January 2013

Re: Xantrex 4024 Software Issue? Can I disable the master/slave setup and separate them

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I tried to attach a few pictures of where my system is. Note that I never connected the Slave output. I decided I didn't want the possibility to ever draw 8,000 watts from my battery bank so I did not make that connection. My intent with the system design was to allow use of a generation meter and to only use battery watts when the grid goes down. The strange parts of the schematic are to provide this. I welcome comments on potential improvements or bad practices I may have done.

Would I damage either XW4024 if I connected both AC1 terminals together without the breakers? I could then use a single breaker in the ePANEL to disconnect both from the residential panel. If I decide to make both inverters independent do I need to disconnect the sync cable?

I live in Michigan (not well known for solar power) and my system harvests 550-600KWA per month during the summer. I never see more than 6,000 watts inverting - is that much loss normal (7,800 nameplate watts input)? I am looking to add another 2,000 watts this spring. If I am willing to lose a few watts under rare "ideal" conditions, can I get by with just two inverters? I am assuming the charge controllers will just taper if more than 8,000 watts comes in.

Cariboocoot · January 2013

Re: Xantrex 4024 Software Issue? Can I disable the master/slave setup and separate them

Working backwards through your post with some observations ...
You've got 1800 Amp hours of battery and a maximum current potential of 250 Amps. That's not a good balance. You may be experiencing some trouble there.
6000 Watts from 7800 Watts of panel is about normal: typically the efficiency factor would be 77% and you're just about spot-on.
If you're going to run the two inverters separately you would disconnect the sync cable as well as uncouple the AC outputs.
With them separate, you probably would want a breaker for each AC in. You're going the opposite way from trying to make two inverters act as one to having them function independently (which includes dedicating loads to one or the other but not both).
Not having the slave's output connected to anything but otherwise having the inverters coupled is a mistake: the master will activate the slave when it sees fit but the slave's output never affects anything so the master would not be able to reconcile this.
Looks as though your second inverter has always been a useless appendix.
I can not see the images with my eyes and netbook screen. Perhaps someone else can do an analysis of them.

inetdog · January 2013

Re: Xantrex 4024 Software Issue? Can I disable the master/slave setup and separate them

Cariboocoot wrote: »

I can not see the images with my eyes and netbook screen. Perhaps someone else can do an analysis of them.

With most browsers you can enlarge the images with the View/Zoom menu option or by hitting Ctrl-Shift-+ repeatedly. But first you have to click on the image to get it to display all by itself in a new tab or window.

Here is what I see from it:

The two neutrals are permanently connected, the slave cable is permanently connected, while the AC1In's are fed through separate breakers from a common source and the ACOut's are fed through separate breakers to a common load point. The two DC - inputs are hard wired together while the two DC + inputs are fed through separate DC breakers from a common battery bank.

SolaRevolution · January 2013

Re: Xantrex 4024 Software Issue? Can I disable the master/slave setup and separate them

You would probably need two SCPs to use the two inverters seperately. Lots of data and controls are combined in the SCP. Even if you can get them to work, with two seperate systems on the same battery bank it could reach a stage where one is "selling" while the other is charging. (endless loss loop)

Do you notice any heat building up in the wiring at the AC1 breakers? Odd that it is tripping. Is the system shutting down or just disconnecting from the grid when this happens? Both inverters have to "qualify" a source in order to connect so it makes sense for them to both drop the grid if one set of breakers trip.

Looking at your diagram:
-The "Battery Breakers 60A". Are these for protecting parallel battery strings? If so, why only 60 amps? Are the terminals large enough for your battery cables?
-With two inverters linked as Master/Slave you need to wire the generator to the AC2 input of both inverters or else the XWs will never "qualify" and connect to it.
-The Master and Slave should probably have the AC Load outputs paralleled. It could be an issue of the XWs "trying" to balance their voltage and actually feeding power out the AC1 input of one and into the AC1 input of the other.

-Alex

Xantrex 4024 Software Issue? Can I disable the master/slave setup and separate them?

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