DR series inverter stacking problem

Tom T
9 Posts
Feb 1, 2008 02:46 pm
DR series inverter stacking problem


Looking for anyone who's got some experience with Xantrex's DR series inverters. 

I've got a problem with my power backup system which uses two Xantrex DR1524 inverters. 

The system uses the inverters in a stacked configuration to get 240V.  I bought Xantrex's DRI cable to connect the two.  I've got four 12V 92AH batteries in a series paralell configuration to both inverters.  The batteries are new.  The system will recharge them and I have run it in inverter mode. 

The problem is that the inverters, while charging the batteries, will randomly shut down.  They stop charging and all the lights go off on both units.  Typically, when I power the units on again they'll start charging, but again after anywhere from twenty minutes to several days, both units shut down. 

I can run a single inverter to charge the batteries with the DRI cable disconnected, and the single unit will stay on.  I just can't get the stacking setup to work. 

I've traded emails with Xantrex's tech support.  They had two suggestions:  make sure the systems are grounded and try a different stacking cable.  I've grounded the system seven different ways to Sunday with no success.  I thought I had something when I replaced the communications cable (looks like a phone cable) but after four days it happened again. 

Does anyone have any suggestions?

 
 
Jon C
97 Posts
Feb 1, 2008 04:41 pm
Re: DR series inverter stacking problem

Hi Tom T.  Just a thought about the shut down problem on the inverters.  I am using 48v inverters in a similar configuration to yours, and have experienced inverter shut down if the input voltage exceeds a preset maximum, which I beleive is somewhere around 31 volts on your inverters.  Are you charging the batteries at the maximum charge rate of 35 amps.........this would yield a charge rate of 70 amps with both inverters running?  I reset the charge rate on mine to 20 amps, and had to set the wind turbine dump voltage level below the preset maximum input voltage on the inverters to keep them from shutting down.  The panel shows an error light if input voltage is too high.  Could this be relevant to your problem?  Jon C.
 
 
Tom T
9 Posts
Feb 1, 2008 06:53 pm
Re: DR series inverter stacking problem

Hi Jon C,

I've got the charge rate turned down low as the battery bank is small.  And I haven't yet added any other charging source. 

At the moment I have the system charging the batteries.  Both inverters are float charging and the battery voltage is 27 volts.  I've never seen it go above about 28 volts. 

I don't think it's battery voltage as I can charge with a single inverter without a problem.  I'm convinced it has something to do with stacking the two inverters. 

I'm still scratching my head in puzzlement. 



 
 
Ron Stauffer
20 Posts
Feb 1, 2008 11:34 pm
Re: DR series inverter stacking problem

Tom T
We have lots of stacked DRs out there with no problems with battery charging from inverters.  Here is a couple of the most likely issues:
1
 
 
Ron Stauffer
20 Posts
Feb 2, 2008 12:08 am
Re: DR series inverter stacking problem

Tom T
We have lots of stacked DRs out there with no problems with battery charging from inverters.  Here is a couple of the most likely issues:
1  The + and - feeds to each inverter need to come from different terminals on the batteries.  If you feed both inverters from the same terminals, one will react to the others high charge voltage and shut down to float.  You should do what we call double opposing battery connections.  You need at least two parallel strings to do this which you have.   Feed one inverter from the + of string one and the - from the string two.   The other inverter gets - from string one and + from string two.
2  Verify that you have only one place in the system that AC neutral is bonded to ground.  Portable generators are notorious for being bonded.  Often subpanels are bonded in addition to the main panel - also bad.  Often multiple bonds in the system will show up with around a 60 volt measured reading on the neutral
3  The DC negative feeds to the inverters need to be bonded together with a few feet of each other.  We use Xantrex DC 175/250 disconnects next to the inverter conduit box.  In the DC 175/250 we bond both DC - from the inverters to a lug to a ground wire to a ground rod.
4  Charge rates may be set too high.  Adjust the battery capacity to 180 AHR.  Turn the charge rate down all the way on one inverter and halfway on the other.  If they both hold a bulk charge, then switch the settings.  This will verify that each are working.  Then try turning the charge rates of both to the midway point and see what happens.  Turn up the charge rate only as high as you can maintain bulk charging.  Small battery banks are more problematic for this
Most likely one of these should be a fix - hope this helps

Ron Stauffer
 
 
Tom T
9 Posts
Feb 2, 2008 12:44 pm
Re: DR series inverter stacking problem

Hi Ron,

1 I noticed all of the battery wiring schematics in the manual were drawn as you described.  So that's how I put my system together.  I got the sense that they were trying to balance wire length so that the longest positive lead connected to the battery with the shortest negative lead and vice versa. 

2 and 3 My AC neutral is only bonded at one place.  At the moment I'm grounding everything to the AC ground.  Would it be advantageous to sink another ground rod outside the wall were my inverters are and ground my inverters to that?  I do understand the importance of a single neutral bond, so this would only ground the battery negatives and the inverters.  I also set up the system with Xantrex's DC disconnect box (DC175) and DC ground block.

4 Last Sunday, I replaced the interface cable at the suggestion of the Xantrex tech.  The system stayed on until Thursday.  The longest they've stayed on yet.  On reading your notes, I went to check the charge rate settings.  In all the tweaking an toying, I had left one unit at max charge rate.  So, I'll set that to just above minimum and try again. 

 
 
Ron Stauffer
20 Posts
Feb 4, 2008 09:00 am
Re: DR series inverter stacking problem

Tom T

Only ground at one point whether it is DC - or AC, generator, etc.  You get differences of potential if you do.  It sounds like the charge rate is the likely culprit

Ron
 
 
Tom T
9 Posts
Feb 5, 2008 08:17 am
Re: DR series inverter stacking problem


No luck.

One of the two inverters shut down some time last night. 

Any other suggestions?
 
 
Tom M
462 Posts
Feb 6, 2008 10:52 am
Re: DR series inverter stacking problem

Tom T., just a quick question with regards to the inverter that keeps shutting down. Does the cooling fan come on?
 
 
Tom T
9 Posts
Feb 7, 2008 07:02 am
Re: DR series inverter stacking problem

Hi Tom,

When I power each unit up they both go through their self test and the fans briefly run at that point, but they're not running before the units shut down. 

 
 
Ron Stauffer
20 Posts
Feb 7, 2008 10:18 pm
Re: DR series inverter stacking problem

Tom T
Originally I thought the issue was the one inverter was shutting down charging to the float stage.  After rereading your original post, I know understand that the inverter is shutting down totally.   There could be many things to check/cover that would take many emails back and forth.  If you want, you can call me - 970 209 4764
Ron Stauffer
 
 
Tom T
9 Posts
Mar 6, 2008 08:17 pm
Re: DR series inverter stacking problem


I think I've solved the problem. 

Xantrex supplies a stacking cable with only 4 wires.  It's has a telco style modular connector at each end.  I replaced it with a similar cable but with 6 wires.  The extra two wires connect to the outer two contacts in the connectors on the inverters.  Both outer contacts are grounds and they add shielding to the communications signals between the two inverters.  Without those two extra wires, the inverters would lose communication with each other and shut down. 

I discussed the different cable with the Xantrex support tech.  He said there'd be no problem using the 6 wire cable instead of the 4 wire. 

The system ran for over three weeks and was still working when we had a power outage yesterday.  It supplied power when I needed it and charged the batteries when the power came back on. 

Thanks to all who offered suggestions. 
 
 
James Cormican
578 Posts
Mar 7, 2008 05:52 pm
Re: DR series inverter stacking problem

hey tom, i remember when you called in, i am glad that you finally found a solution to your problem. 

cheers,

james
AltE
"Making Renewable Do-able"
http://www.altEstore.com/

Tel: 877.878.4060 x107  or +1.978.562.5858 x107
Fax: 877.242.6718  or +1.978.562.5854
 
 

Disclaimer and Disclosure

The Alternative Energy Store, Inc reserves the right, within its sole discretion, to refuse or delete any posting or portion thereof, or terminate or block the access to this forum.

The opinions and statements posted on this forum are the opinions and statements of the person posting same, and do not constitute the opinion or act of the Alternative Energy Store, Inc (AltE). The Alternative Energy Store, Inc does not endorse or subscribe to any particular posting. No posting shall be construed as the act or opinion of the Alternative Energy Store, Inc.

Click here for BBB Business Review

McAfee SECURE sites help keep you safe from identity theft, credit card fraud, spyware, spam, viruses and online scams
Desktop Website | Mobile Website

Share

Click on an icon to share! If you don't see the method you want, hover over the orange "+".

Feedback

What can we do to help you?

Please enter a summary
Submit +
Sorry, the copyright must be in the template.
Please notify this forum's administrator that this site is using an ILLEGAL copy of SMF!
Copyright removed!!