Panel Wire Check

[Coydon]

Where do I look to find the best PV wire gauge info for connecting an array to the charge controller?

My 30A CC came with 10' of 10awg wire [edit: looking at receipts, I bought the wire separate]. The booklet for the Epever CC says 8awg is the max PV wire size. Does that just refer to what will fit in the screw connection terminals?

Will's Mobile Solar Power Made Easy book says 10awg is usual, unless it is over 25ft long which would require it to be 8awg. Is that 25' from panels to controller, or the full system length of positive and negative wires?

I've also been looking at this chart:

According to that, to carry the 30A (15A for 24V) my controller can pull 14' from the panels would require 10awg. But this says the length of the negative cable should be included, meaning a 28' total run and requiring 8awg. Does their statement about dividing amperage by two for a 24V system apply here? I thought the controller was still handling 30A at 24V since it delivers twice the W to the battery on 24V.

Also, does the controller limit the feed from the panels to 30A even if they are capable of producing 36A in parallel (39A Short)?

 

[fatjay]

It also depends on the insulation rating. A higher insulation temperature rating means you can go further with the same gauge wire.

If the panels are capable of producing 36a, and the inverter is capable of taking 36a, it will happen. If the controller is limited to 30a, then I would reduce the parallel string size.

 

[Coydon]

Specs on the iGreely wire say primary insulation is .65mm and secondary insulation is .85mm. Both are "125 degree irradiated cross-linked polyolefin". Is that better or worse than normal?

This is a 30A controller. If I go 2S3P instead of 6P on the panels, the total open V could supposedly reach 130V. The max rating on the controller is 150V and I am told that that combination could cause a fire?

I plan to upgrade the controller soon to Victron. Should I just go for 40A or is it worth getting one that can handle more than 150V OC for the 2S3P, keeping Amps down on the wire run? A quick glance looks like anything over the 150V rating pretty much more than doubles the price...

 

[MPPT Mike]

Good morning,

As fatjay said, wire insulation is a factor.

National Electric Code (NEC):
NEC Article 690 specifically covers solar photovoltaic systems. It provides detailed requirements for wire sizing based on:
Current-carrying capacity (ampacity).
Voltage drop limits (typically 2-3%).
Temperature and environmental conditions.


Also, Wire Sizing Calculators:
Solar Wire Size Calculator by Renogy:

Sizing Wires for PV Systems

Get guidance on selecting wire gauge based on cable length and current requirements for different components in your PV system, including solar panels, charge controllers, battery banks, and inverters. Ensure optimal performance and reduce risks by choosing the right wire sizes for your PV system.

www.renogy.com

 

[dopeassjackson]

That chart dosnt seam correct.

Also your PV voltage will be higher than your battery voltage. Higher voltage means less amps..less amps means smaller wire can be used. You didnt state your PV voltage so I can't comment any more.

 

[DougfromdaUP]

(Edited to remove charged language)

That chart cumbersome and misleading.


Use an online calculator, like Southwire’s.

 

[Coydon]

Also your PV voltage will be higher than your battery voltage. Higher voltage means less amps..less amps means smaller wire can be used. You didnt state your PV voltage so I can't comment any more.

My array of 6P Sunpowers are 54.7 max V, 64.9V OC.

 

[outboard1196]

My array of 6P Sunpowers are 54.7 max V, 64.9V OC.

You also need to calculate the low temperature VOC for the panels. Voltage will rise as temp goes down. Find your location historic low and use the panel specs to calculate it. 2s is could be over the limit.

Thread 'Maximum open circuit voltage calculator'

Feb 19, 2020

I'm posting this in a thread here since it might be useful for people. Please keep in mind that the below calculator contains bugs and doesn't do error checking - it's literally been 5 minutes to put together. Ok, so what does it do? It calculates the maximum open circuit voltage you would see on your solar panel string when the temperature drops. You just enter your Voc at 25C, the temperature coefficient (both should be available for panels in their datasheet, the former per panel and should be multiplied with the total panels per string in series, the latter is given as a percentage)...

• upnorthandpersonal
• Replies: 25
• Forum: Frequently Asked Questions

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[dopeassjackson]

My array of 6P Sunpowers are 54.7 max V, 64.9V OC.

54v would mean your PV wires are carrying about 7a with a 12v 30a charger controller.

 

[Coydon]

Or 3.5a on the 24V system?

 

[outboard1196]

Or 3.5a on the 24V system?

Would still be 7A