Realtime-Why am I getting 240 volts between the 2 neutrals running split phase?

[farroffgrid]

We are working with Ian at Watts247. We started with the 3kw Growatts running them in split phase and we had the following issue. Then we upgraded to the 13kw Mpp solar inverters and the same issue is occurring in both cases... The issue is that even though the two inverters are programmed correctly when testing the voltage between the two units the numbers are very strange. When you test the voltage between leg 1 on 2p1 and leg 2 on 2p2, we get a reading of 110 volts. When we test the voltage between the two neutrals we get a voltage reading of 240 volts. Also when we test the voltage between the two grounds we get 240 volts. When the two neutral wires are connected in the neutral bus bar and/or when the two grounds are connected into a common bus bar the system with throw a fault code and shut down.

I have spoken with Ian for a number of hours going over everything without coming to a resolution. I have had a master electrician come out and look over everything with no resolution. The really interesting thing is that the Growatts that were having the same issue once returned to Ian and tested proved to be perfectly fine but now we have these Mpp's and they are doing the exact same thing!.. Everything on the battery and solar input side seems perfectly normal. We are running Tesla Model S batteries, 4 batteries, 2 in series for 48 volt system. We have a 6kw solar array with Voc of 180v. I have a large positive and negative bus bar that the batteries are wired into using 2/0 wire. The 2/0 cables are then ran into two 175 amp breakers and then 2/0 cables from those breakers are ran positive negative to the first inverter and then positive negative to the second inverter. The PV is ran in via 6 gauge wire. The solar panels are wired into the combiner box in two groups producing 180Voc each. These four wires are brought into a breaker panel with two 80 amp breakers. Positive negative from one group of panels and positive negative from another group of panels. From the breakers the wires are ran into the inverters positive negative from one breaker and positive negative from the other breaker. Actually it's just the two positives that go to and from the breakers, the two negatives just go directly to the inverters. Again, the problem arises when we try to put the two neutrals together. It always throws a fault. For some reason it seems that when these inverters come into my solar shed, they just don't want to work together LOL!

Please help!! We are way behind on getting this up and running! Thank you!

 

[schmism]

some model numbers of what you have and photos of your install might help.

 

[farroffgrid]

2 x LV6548 13KW split phase bundle 120v 240v Solar inverter 8kW -2 x 4kW 250V MPPT UL1741​

I'll try to post some pics tomorrow.

 

[newbostonconst]

Are both Growatts running off the same battery or do you have two sets of batteries?

 

[farroffgrid]

We are no longer using the Growatts we exchanged them for the MPP Solar found on Watts24/7 website

2 x LV6548 13KW split phase bundle 120v 240v Solar inverter 8kW -2 x 4kW 250V MPPT UL1741​

But YES, when I was working with the Growatts and now with the MPP Solar both inverters are connected to the same battery bank.

 

[farroffgrid]

Here's a link to what we purchased from Watts24/7

2 x LV6548 13KW split phase bundle 120v 240v Solar inverter 8kW -2 x 4kW 250V MPPT UL1741 – built in Wifi- Clearance see conditions*** – Watts247 Wholesale

watts247.com

 

[farroffgrid]

Here's some pictures of the installation. Please overlook my messy wires but after this issue with the Growatts I wanted to make sure that this MPP will work or will we have to go with some other system?? until we know it's not a priority.. Also this is a temporary placement of our system. Once we get our house up we'll be moving it out of this shed and into the house.

 

[farroffgrid]

 

[BMcL]

Did you watch Will Prowse's video and compare his wiring to yours ?
He had some trouble setting the inverters to work together correctly.

 

[740GLE]

My guess is settings issue

 

[schmism]

My guess is settings issue

same. I also dont note any load side wireing attached. Are you just testing with a DMM on the terminals or have you wired in a complete service panel with with double pole breakers and put loads on the system to measure actual voltage under use.

 

[farroffgrid]

THE ISSUE HAS BEEN RESOLVED!

I mistakenly wired up all the negatives from my solar panels into one buss bar in the combiner box. I have two banks of solar panels and each bank/group has their own designated negative buss bar because they have to remain separate.? Basically I wired it like it was A/C rather than D/C and the negatives were like neutrals and could all be together... ?
Thanks for the help!

 

[schmism]

I mistakenly wired up all the negatives from my solar panels into one buss bar in the combiner box.

As the DC side is entirely seprate from the AC side this seems likely an extremely unlikely cause for your AC issue.