Author Topic: Common neg for panel wiring  (Read 4728 times)

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Jason Wilkinson

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Common neg for panel wiring
« on: September 18, 2014, 02:52:23 PM »
I want to add another string to the existing two strings of panels,but my conduct won't allow 6 wires (i know i can  but should i) run 3 red pos and 1 black neg to the combiner box  located in the house? Each string will have 3 panels  9 in all
  Jason

Mary B

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Re: Common neg for panel wiring
« Reply #1 on: September 18, 2014, 04:18:33 PM »
What are you running for a charge controller? If it is MPPT series more panels into 2 strings.  Otherwise your ground wire has to be sized to carry the return current of all 3 strings, 3 times current rating  of the other wires. Not sure if there would be issues with ground loops either.

lifer

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Re: Common neg for panel wiring
« Reply #2 on: September 18, 2014, 05:19:52 PM »
Why don't you use just two (thick) wires, connecting the three strings in parallel right at panel location? Do you have a separate charger for each string or something?

southpaw

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Re: Common neg for panel wiring
« Reply #3 on: September 19, 2014, 10:01:39 AM »
If you only run 4 wires, use the largest 4 that will fit in your conduit, combine the strings of panels at the panels and use 2 wires for + and 2 wires for -. This will give you the most power to your batteries.  Using 3 wires for + and one for - will result in a larger voltage drop as the current in a series circuit is the same in all parts of that circuit, meaning the single - wire will have to carry the same current as the 3 + wires and will waste power.

XeonPony

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Re: Common neg for panel wiring
« Reply #4 on: September 21, 2014, 09:10:20 PM »
simple answer: NO
Ignorance is not bliss, You may not know there is a semie behind you but you'll still be a hood ornimant!

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Jason Wilkinson

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Re: Common neg for panel wiring
« Reply #5 on: September 28, 2014, 03:03:49 PM »
[ <Why don't you use just two (thick) wires, connecting the three strings in parallel right at panel location? Do you have a separate charger for each string or something?
[/quote]
Won't that eliminate the use of the combinerbox which is in the house ? i want a separate fuse/breaker for each string

gww

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Re: Common neg for panel wiring
« Reply #6 on: September 28, 2014, 03:59:54 PM »
I put my combiner out by the solar.  Due to the increased amps, it may affect your wire size.  Just threw this out there incase it helps.
gww

Jason Wilkinson

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Re: Common neg for panel wiring
« Reply #7 on: September 28, 2014, 10:17:41 PM »
In our harsh enviroment (I'm 1/2 mile from the atlantic ) a combiner box won't last as long as  ice cream on a sunny summer 's day. I have to lower my turbine  3 to 4 times a year for servicing, you won't believe how fast/much rust can accumalate. You guys who are located miles inland don't know know the half of what the weather does, so all electrics/electronics must be inside
  Jason
 

Frank S

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Re: Common neg for panel wiring
« Reply #8 on: September 28, 2014, 10:41:52 PM »
I may have done mine wrong by everyone's standards but for my 8 panel set up I just bolted all 8 of the + panel leads to a single 2AWG and the same for the - leads then straight to  my PWMs I actually paralled 2 60 amp PWMs then down to the connection that connects the bank  both inverters  and a 60 amp Shumacher charger those bolts are 1/2" stainless with a dozen cables bolted to them.
 I know I should have a better means of disconnecting the bank from the system but currently the only disconnect is in the 2AWG from the array  its been like that for a year and a half with no problems.
 I couldn't see the need for a combiner box as such
I live so far outside of the box, when I die they will stretch my carcass over the coffin

gww

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Re: Common neg for panel wiring
« Reply #9 on: September 28, 2014, 11:05:19 PM »
Frank
I have every thing, fused and breaker, on my house system but still use the stainless bolts as my battery buss bars with turbines, inverters, batteries etc. all together.  I put a small system at the creek with just an extension cord to a  parked rv.

Jason
 I am glad that I don't have salt water to deal with and I am sure you still have lightning.
gww

southpaw

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Re: Common neg for panel wiring
« Reply #10 on: September 29, 2014, 11:34:16 AM »
A 1" pvc conduit will hold 4 4AWG copper conductors, and each pair will carry about 40A 100 ft with less than 3% voltage drop giving you about 80A capacity. the same conduit will hold 6 6AWG conductors, and each pair will carry about 30A 100ft with less than 3% voltage drop, giving you about 90 amp capacity.
There are plenty of online calculators which you can use to find the number of wires that will fit in your conduit for a given size.

 As a rule if the conduit is the limiting factor; more conductors of a smaller size at maximum fill will conduct more power. Plug your conduit size into a conduit fill calculator and find the max wire size for 6 conductors, this will allow you to use your existing combiner box in its present location.

Jason Wilkinson

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Re: Common neg for panel wiring
« Reply #11 on: September 29, 2014, 05:48:30 PM »
Well said Southpaw, that's providing you're starting anew , but what if the conduit & wires are already in place , to add just one more wire the existing wires must first be taken out ----- calculators can't help  ,  but thanks for the post