[RE-wrenches] NEP PVG wiring

[William Miller]

Lloyd:



Thank you for your reply.  That is how I read the instructions for all of
the aforementioned MLPE devices.



I think there is a flaw in the logic here, at least for the NEP and Tigo
products.  It is because both manufacturers offer rail or frame mounting
options.  This is significant for this reason:



If you are frame-mounting an MLPE device it is convenient to connect PV
leads to the MLPE first and you can easily comply with the instructions.



If, however, you are rail-mounting the MLPE it is quite inconvenient to not
be allowed to interconnect the MLPE devices before connecting the PV. You
really need to complete all of the hardware and wiring infrastructure
associate with your mounting system before you bring your modules to the
roof.  It is very awkward to be juggling a panel on the roof to connect it
to rail-mounted MLPE before you are allowed to interconnect the
rail-mounted MLPE devices.



It is my opinion that if your MLPE devices cannot be interconnected, you
should not offer a rail-mount option.



It is important that we use proper terminology for these parts of the
system. “Interconnecting” and “home-runs” are different things:
Interconnecting leads are between devices.  Home-runs are leads run between
the ends of strings of devices and the terminating equipment.  NEP equated
these in their quick start guide and this caused confusion.



I spoke to George with NEP today about this.  I presented this dilemma and
he seemed to understand the conflict.  George told me the concern is that
if an installer connected a PV panel to the series-string output of the PVG
units, damage to the MLPE unit could occur. They do have the same MC4
connectors so this is possible.



I get the concept that even the dumbest mistakes are possible, but it would
be hard to confuse the different connections.  The PV inputs are quite
short and the series-string connections are abundantly long.  Also they are
clearly labeled.  George told me that as long as the home-runs were left
unterminated, the interconnecting leads can be connected prior to
connecting PV without risking damage to the PVG units.



As always, the devil is in the details.  Success is achieved in
understanding and dealing with the details.



William Miller



Miller Solar

17395 Oak Road, Atascadero, CA 93422

805-438-5600

www.millersolar.com

CA Lic. 773985





*From:* Lloyd Hoffstatter [mailto:lloyd at sunstruckconsulting.com]
*Sent:* Tuesday, November 12, 2024 7:44 AM
*To:* william at millersolar.com; RE-wrenches
*Subject:* RE: [RE-wrenches] NEP PVG wiring



Hi William,



The RSD installation instructions mirror those of TIGO and APSmart per
connection order of PV to RSD first.



Best regards,

Lloyd



Lloyd Hoffstatter, M.S. Applied Solar Energy

Director, Sunstruck Consulting

*lloyd at sunstruckconsulting.com <lloyd at sunstruckconsulting.com>*

845-657-8132 (office)

914-844-3404 (cell)



*From:* RE-wrenches <re-wrenches-bounces at lists.re-wrenches.org> *On Behalf
Of *William Miller via RE-wrenches
*Sent:* Monday, November 11, 2024 11:30 PM
*To:* RE-wrenches <re-wrenches at lists.re-wrenches.org>
*Cc:* William Miller <william at millersolar.com>
*Subject:* [RE-wrenches] NEP PVG wiring



Friends:



I am repairing a site with NEP PVG RSD devices.  We will be removing all of
the modules and finding out why the system is underperforming and why 2 of
the units are not reporting.



The quick start guide includes this line:  PVG’s PV-lead pairs must be
connected to PV modules before connecting homerun cables between RSD device.



I find this wording confusing.  Homerun cables do not connect between RSD
devices, home runs connect to the PV input on an inverter (Soul-Arc in this
case).



I wish to rail mount the PVG RSD devices, connect the series wiring between
these modules and then connect the PV.  Can I interconnect the PVG units
prior to connecting the PV modules?  This sure would make the process
easier.



Thanks in advance for in any input on working with these units.





William Miller

Miller Solar

17395 Oak Road, Atascadero, CA 93422

805-438-5600

www.millersolar.com
<https://urldefense.proofpoint.com/v2/url?u=http-3A__www.millersolar.com_&d=DwMFaQ&c=euGZstcaTDllvimEN8b7jXrwqOf-v5A_CdpgnVfiiMM&r=p2tHyHEAjVe2zSh4C_236V4KkHnn0z0ynUvWz0mobds&m=Sj6SvGiGAeDHb1dV0napuS0qhQ9nlBiveGTpGaibMKwEylmjU3_fIw0-VKruQ-jo&s=DC5TfZLJCY1FTLE0G9RSxAQIvPgwzSR54I9_gSu5gJM&e=>

CA Lic. 773985
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