Code Question: Replacing Inverter in 2013 System and Rapid Shutdown

The 3.6 kW Aurora inverter in our 2013 system has died. Apparently, there is a design flaw, and a lot of them do this... We have a string of 18 panels on the roof feeding it. I've tried to find a local contractor that can install a new inverter, and I'm getting a lot of mixed messages.

One of the big concerns they bring up is that our system pre-dates the rapid shutdown requirement. However, replacing the inverter doesn't require going anywhere near the panels, and I've found two references on-line that claim I don't need to bring the entire system up to current code if we aren't messing with the panels. The only quote I've received so far is for $17K to completely replace everything (including the roof, which will be trashed when they replace all the present panels & racking). I don't know if that is our only option, but I strongly suspect they are busy with full installations, and don't want to bother with a couple $K to just replace an inverter. One outfit just said they aren't doing "repairs" in our area, and two said they'd look into it and get back to me. That was over a week ago, and I haven't heard a peep.

My understanding is that the town electrical inspector can be as fussy as they want, and it may be a matter of how reasonable they are. Is contacting the inspector directly to get a ruling up front an option? We can't afford a complete replacement, and all the systems I've seen that meet the current code use electronics of one sort or another (optimizers or microinverters) installed on each panel, which isn't possible with an older system like ours.

I would think that a big relay up under the panels controlled by a rapid shutdown circuit in the inverter would do it, but I haven't found anything that simple. All of the DC wiring under the roof is in heavy conduit, and is mounted well below the roof itself, so It's not especially dangerous for firefighters as currently installed.

In the spirit of DIY, there are YouTube videos on how to repair the Aurora inverters. There's no guarantee that ours has died in the usual fashion, but if the only way to avoid a complete rebuild is to repair the inverter, I have the soldering skills to do it if I can get help disconnecting/reconnecting it.

Thanks for any comments and/or suggestions!

Gwhite

Why don't you just get a new old stock or used SMA Sunny Boy or Fronius string inverter and install that?
Compare maximum voltage specs, if at least as high, nothing else needed to do.

I try to pay $0.10/W for new old model inverters, e.g. $500 for 5kW.

Or look into hybrids, which would work with optional battery and back up critical loads.
Again be sure of max voltage, might need to rewire panels.

Thanks! That's an option I need to explore.

The Auroras are also available used, but I'd need to make sure they are properly repaired. The problem is that there is a relay connection that can overheat, and the thermal cycling eventually breaks the solder connection. The quick fix is to clean up the connection and resolder it. The proper fix is to beef up the solder joint so it won't overheat and break down in the future.

IMO this is a repair and you won’t be forced forward.

Can you just hire a standard electrician to swap in an electrically compatible UL1741 inverter? It is allowed under the licensing law in my state. Which is different from someone actually wanting to do it.

Installing it yourself should be “easy”, maybe you can find someone on a forum to mentor you.

Gwhite said:

I would think that a big relay up under the panels controlled by a rapid shutdown circuit in the inverter would do it, but I haven't found anything that simple.

Click to expand...

Eventually maybe but current code is captive to the RSD and microinverter lobby’s whims. The most widely adopted code requires every 30V or 60V to be individually isolated. Also you most likely do not have conduit in the HV wiring directly under the panel, that is bare PV to PV via MC4 style connectors

I would be very surprised if you can’t just put $30 RSD devices under each panel or every two panels worth, and use a RSD transmitter, those are easily available standalone from inverter. Worst case it would involve crimping on new MC4 style connectors. A lot of manual monkey labor involving unmounting each panel.