SB3800U inverter replacement

[ahultin]

I have a +-10yr old ground mount install consisting of 42 kyocera KC-167g panels in three strings of 14 connected to 2 SMA Sunny Boy SB3800U inverters. The inverters where chosen as to allow for an additional string of 14 if needed and when funds where available. When we got our highest ever electrical bill last month I inspected the system to discover that the inverter with two strings is dead. The original PV contractor is out of business and I am having difficulty getting information on replacement/upgrade. I am currently contemplating 2 replacement paths for the dead inverter:
1. Replace the dead inverter with a Sb4000us-12 , sourced for @950 and hope the second doesnt go anytime soon.
2. Replace both with a single sb 6.0-1sp-us-40-240, sourced for @1650 and have a new 10yr warranty

I have run through the sma sunny design web and it appears option two is workable without having to rewire the system.
Any issue I am missing with either of the solutions?
Last I have seen some mention of an upgrade program for the sb3800u but cannot seem to get any answers. SMA wont talk to me since I am not an installer (though I do have a general contractors licence) and all of the solar installers i have talked to thus far wont assist as they do not want to touch anyone elses install. Anyone have info on this?

[solarix]

I've been through this same scenario before and found that the string voltage of the SB4000 is fairly narrow and you may well have trouble using the existing string configuration. Check with the SMA string sizer to find this out. I would bet that your remaining SB3800 is not long for this world and your best move is to upgrade to the SB6.0 at this time. However, this is a transformerless inverter with non-grounded DC conductors. You may have to change the way your existing array is grounded to accommodate this.
I believe the SMA techline will be glad to talk with any homeowner that owns an SMA inverter. 877/697-6283

[ahultin]

Thank you for the reply,
I did call SMA tech and they immediately sent me to "2nd level support" which i have am now waiting on a return call from. Can you extrapolate at all on the ground issue? I am going to have to chase down the panel wires but from what I can see my dc conductors are not currently grounded. I do have a pair of pair wires bonding the racking which make their way through the dc disconnect and into the inverter on one end with the other going to a pair of ground rods (not fully driven I might add )
For now I have removed the dead inverter and moved the still working one over so as to connect it to the two strings. Better to be running at 2/3 than 1/3

[solarix]

Good luck having them call you back. Write down the ticket number they give you and use that every time you call.
If the conductors on your array are not presently grounded, then you are good to go on the new inverter.
Leave the ground bonding wiring in place although you may want to check if the bonding is still good after 10 years.
A lot of installers used the cheap aluminum ground lugs back then and the connections get all corroded.