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Old 07-21-2017, 04:53 AM   #1
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Capability of Newmar Solar Prewire

I'm fairly certain my 2006 Newmar has the older 10 gauge prewire, but I will verify that this weekend. I plan on putting 4 Renogy 100w panels on the roof for a total of 400w and about 25 amps maximum down the prewire. At an estimated 30' wire run I only get about 1.5volt drop on the wire to the charge controller.

I read a lot of posts here about upgrading to 6 gauge versus using the older prewire. From all my calculations the 10 gauge is more than capable of handling the 25 amps and the voltage drop is minimal. I do; however, think that is about the maximum that I would feed down the prewire at 5.1 amps per panel.

Am I missing something other than most folks must be putting a lot more than 400w on the roof?
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Old 07-21-2017, 07:30 AM   #2
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Split the panels into two strings, double the voltage and then half the current down the wire. You will need a MPPT controller to handle the higher voltage conversion. This would overall be a better system than four panels in parallel to a PWM controller. Else you should run a larger wire.

I have three strings, each with five 100w panels. Three pair of #10 from the roof.
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Old 07-21-2017, 08:00 AM   #3
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The 1.5 voltage drop is 10% of your voltage. That's a lot in the 12 volt solar world.

On the slightly overcast day when your panels are producing 14 volts, your getting 12.5. That's less then battery voltage of 12.6.

2% or maybe 5% is acceptable with solar.
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Old 07-21-2017, 12:26 PM   #4
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one of my two sets of panels runs on 12 gauge with 720w, but at 126v nominal (3 240w panels at 42v in series). no problem.

your panels are small in foot print. you can arrange them at the space(s) where there will be no shading between 10am to 4pm, in series. you can even install many more panels if you want to.

(the set of wires at 12g was been used prior to my ownership of the coach. when i set up mine, i installed a pair of 6g wires for 6 panels in parallel at 42v for 1440w. then added more panels using the unused pair of 12g for 720w in series. both of my controllers are mppt - one can handle 96a and another can do 60a).
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Old 07-22-2017, 05:29 AM   #5
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Quote:
Originally Posted by vsheetz View Post
Split the panels into two strings, double the voltage and then half the current down the wire. You will need a MPPT controller to handle the higher voltage conversion. This would overall be a better system than four panels in parallel to a PWM controller. Else you should run a larger wire.

I have three strings, each with five 100w panels. Three pair of #10 from the roof.
This sounds like the best way for me. I am going to use the Magnum charge controller which is a MPPT controller. I am quite confident the wire can handle 10amps and the voltage drop goes down to 0.6V or ~2.5%. I really don't want to rewire the solar. I'm worried enough about the conversion from cable to HDMI. LOL. Thanks VSHEETZ.
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Old 07-22-2017, 05:50 AM   #6
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Here is a site with some info about solar.

http://www.affordable-solar.com/sola...sizing-charts/
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Old 09-11-2017, 06:37 PM   #7
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You are correct, there are no issues with 10AWG while running multiple panels in series using a MPPT controller.

With a Renogy 400watt kit with Rover MPPT, I was seeing 72v and less then 6 amps to the controller.

Using an estimated 25' run, we were looking at .4% drop, which basically negligible.

Right now I'm to 600 watts - 2 parallel 300 watt strings - and I'm seeing more like 8-9amps at 56v...voltage drop again is way below 2%, though higher, at .9%.

Here is the site I use to make those calculations:
http://www.rapidtables.com/calc/wire...calculator.htm


There is a group out there that prefers running all panels in parallel @12V (really 18v) and running a PWM controller. As you can imagine with the low voltage, and potentially high amperages, wire size becomes much more important.
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Old 09-12-2017, 05:07 AM   #8
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Thanks!
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