Thread Tools Search this Thread Display Modes
Old 04-18-2020, 02:29 PM   #1
3 Rivet Member
swilly43's Avatar
2016 Interstate Grand Tour Ext
escondido , California
Join Date: Nov 2017
Posts: 139
Sanity Check - Prewire

I have a 2016 AS Interstate Grand Tour Ext. I have previously upgraded with a 100W solar panel from AM Solar along with the factory flex panel. I wired these in parallel and it has been working fine.

I now want to add a third 100 W panel from Renogy and also will wire in parallel. The factory documentation indicates that the wire from the solar panel to the solar controller (Victron 100/30) is 10 AWG (stranded). The roof connection was an SAE connector and it has corroded to the point that I will eliminate it with a pass through and butt splice the solar wires to the existing 10 AWG cabling inside the coach.

I recognize the difference in parallel vs series approach but it is easier to add the third panel in parallel. My question is .... Is it safe to use the existing prewire 10 AWG stranded cable for the expected (max theoretical) current of <20 amps? The flex panel is old and likely not anywhere near 100w. The most I ever saw out of the current 200W set up is 10 amps so I am thinking that adding the third panel would yield ~ 17 amps maximum. I do not care about maximum efficiency. I tried to find the cable running from the roof to the solar controller but could not locate it easily from the roof.

Various sources indicate that max current in free air of 10 AWG solid wire is about 58 amps for insulation rated to 105C. I think all automotive wire insulation is supposed to be 105C and I noted that some of the wiring is marked. If I de-rate this for stranded wire by 30% and then de-rate again for a wire bundle by 20%, I end up with 32 amps. If by chance 12 AWG is used somewhere unbeknownst to me, the final de-rating is 25 amps. This appears to be a reasonable approach. The wire is fused at 30 amps at the controller.

All that being said, safety and property protection is important and many will not agree that this is a large enough safety factor but I am interested in your comments.

I guess I could rewire in series but the mismatch in panels may be too much to overcome.

Thanks in advance for constructive assessments.
swilly43 is offline   Reply With Quote
Old 04-20-2020, 07:22 PM   #2
Rivet Master
AirMiles's Avatar
2018 27' Globetrotter
Apollo Beach , Florida
Join Date: Feb 2017
Posts: 1,401
Three panels in parallel is fine. Some put four 100 watt panels in parallel on the factory prewire. Parallel is the preferred method for three panels on the prewire.
2018 GT27Q, 73 nights 12,177 miles, 600W Solar - 110kWh, PD4655L, 6V Batteries, Blue Ox, 16" tires, 2019 F250 PSD
Sold: 2017 FC25FB, 316 nights 40,150 miles, Propride, 400W Solar - 200kWh in 216 days
2013 Casita SD17 89 nights 16,200 miles
AirMiles is offline   Reply With Quote
Old 04-20-2020, 08:15 PM   #3
Rivet Master
2018 25' International
Slidell , Louisiana
Join Date: Sep 2017
Posts: 2,198
Your reasoning and logic looks very sound to me. I concur with you and AirMiles and also agree parallel is preferred.
BayouBiker is online now   Reply With Quote

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off

Similar Threads
Thread Thread Starter Forum Replies Last Post
Sanity Check on the Tommy Bahama 27FB marcesq Tommy Bahama Special Editions 64 07-29-2020 03:25 PM
Sanity check. Attaching Baseplates to floor to Frame bass-o-matic Repairing/Replacing Floor &/or Frame 0 05-07-2014 04:20 PM
Sanity Check PDigiorgio Electrical - Systems, Generators, Batteries & Solar 3 01-01-2014 07:29 AM
Sanity Check to Airstream or Not to Airstream? perryg114 Buyer Guidelines 8 09-09-2011 05:54 PM
Can someone reality/sanity check this plan for me? Slip7 Full-Timing 61 03-08-2011 05:43 PM

Featured Campgrounds

Reviews provided by


This website is not affiliated with or endorsed by the Airstream, Inc. or any of its affiliates. Airstream is a registered trademark of Airstream Inc. All rights reserved. Airstream trademark used under license to Social Knowledge LLC.

All times are GMT -6. The time now is 06:27 AM.

Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2020, Jelsoft Enterprises Ltd.