[RE-wrenches] Combining Multiple Inverters

Thu Jun 26 06:18:38 PDT 2014

Jason, I agree completely. I'm curious which inverters you plan to use and I'm interested to see the cost benefit. There is so much "stuff" in a PV installation, and not all of it contributes directly to safety and serviceability. Especially now that we are seeing rooftop 1000V string inverters, it would be good to see solutions that simplify installation, reduce points of maintenance, reduce cost and maintain or increase safety.

Isaac Opalinsky | Technical Trainer | More Energy. For Life.
Desk 443-277-6286 | Cell 443-277-6286

-------- Original message --------
From: Jason Szumlanski
Date:06/26/2014 9:10 AM (GMT-05:00)
To: RE-wrenches
Subject: Re: [RE-wrenches] Combining Multiple Inverters

705.12(D) reads, "... the interconnection provisions for the utility-interactive inverter(s) shall comply with (D)(1) through (D)(7)." That's inverters - plural. The interconnection must be protected by dedicated OCPD, not each inverter individually. Microinverters comply because of this interpretation.

That said, I've never done it. An accumulator panel is pretty cost effective when you consider the alternative cost of an enclosure and the Polaris connectors. I guess if you are making the Polaris connections inside the main load center or inside an inverter you can eliminate the cost of a dedicated enclosure. There would be some material and labor savings.

If the inverter has a maximum OCPD rating, you will be limited by that. Microinverters "get around" that by the wire and inverter being sized/rated for the entire maximum string.

Jason Szumlanski

Fafco Solar

On Wed, Jun 25, 2014 at 10:40 PM, Isaac Opalinsky <David.Opalinsky at sunpower.com<mailto:David.Opalinsky at sunpower.com>> wrote:
Then how do we install microinverters?  705.12(D)(1) says OCPD for each inverter is required at the point of interconnection with distribution equipment.  But as long as the conductors are sized to the OCPD, we follow the branch-circuit/feeder tap rules, and the inverter’s maximum OCPD limit is not exceeded, what is the issue?  I’m assuming the inverter’s maximum OCPD is usually the limiting factor, but I’ve been intrigued by the fact that the ABB TRIO has an option for AC OCPD in the inverter – it seems like there must be a cost-effective solution for tapping a trunk cable with a string inverter just as we do with microinverters.  Has anyone tried this?

Isaac Opalinsky | Technical Trainer | SunPower Corporation
Desk 443-569-3476<tel:443-569-3476> | Cell 443-277-6286<tel:443-277-6286>

From: RE-wrenches [mailto:re-wrenches-bounces at lists.re-wrenches.org<mailto:re-wrenches-bounces at lists.re-wrenches.org>] On Behalf Of Glenn Burt
Sent: Wednesday, June 25, 2014 10:19 PM
To: RE-wrenches
Subject: Re: [RE-wrenches] Combining Multiple Inverters

Code requires OCPD on the output of each inverter, so not sure where the savings would be..
________________________________
From: Corey Shalanski<mailto:cshalanski at joule-energy.com>
Sent: ‎6/‎25/‎2014 21:19
To: RE-wrenches at lists.re-wrenches.org<mailto:RE-wrenches at lists.re-wrenches.org>
Subject: [RE-wrenches] Combining Multiple Inverters
I am curious about best practices for combining the output of multiple inverters:

  *   We are considering using an insulated tap "Polaris/Burndy" connector in lieu of a solar accumulation panel. We would then run the output of this tap connector through a fused disconnect and on to the interconnection. Does anyone else do this?
  *   In the above scenario, how should we size the wire between each inverter's output and the tap connector? Since there is no OCPD on this wire, would we have to use the same wire gauge as the combined output? or can we get away with sizing each wire according to its associated inverter output rating?
--
Corey Shalanski
Joule Energy
New Orleans, LA
[http://portal.mxlogic.com/images/transparent.gif]ᐧ

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