Go Back   EcoRenovator > Improvements > Solar Power
Advanced Search

Blog 60+ Home Energy Saving Tips Recent Posts Search Today's Posts Mark Forums Read

Thread Tools Display Modes
Old 04-18-17, 02:30 PM   #1
Join Date: Jan 2011
Location: Mpls,MN
Posts: 315
Thanks: 2
Thanked 17 Times in 17 Posts
Default Wire size for solar array???

Want to preinstall a conduit run for future PV roof array from my attic to basement main box during new construction. What gauge main feed wiring and how many would be required? I have 30'x20" of south 45deg pitch clear roof exposure.

Drake is offline   Reply With Quote
Old 04-18-17, 04:14 PM   #2
Steve Hull
Join Date: Dec 2012
Location: hilly, tree covered Arcadia, OK USA
Posts: 827
Thanks: 241
Thanked 165 Times in 123 Posts

Well, lets calculate . . . .

You have some 600 sq feet of roof size (20 x 30 ft). Assume you fill the roof completely with panels with each panel being about 18 sq feet each. About 33 panels (600/18).

Assume net output of 300 watts (high estimate per panel ) gives you about 10 kW (300 W x 33). P = Ei so the wattage is about 40 amps at 240 V.

Now the kicker is how far your wire run is. This current load is likely going to need 6 G stranded copper (NOT aluminum) and maybe 4G if it is a long run (> 75 feet).

Remember that L1 and L2 (each being the 120 V legs) need to be fat and thick (6 or 4 G). The neutral can be 8 or even 10G with 10 G for the ground (four wires total). The extra $ cost for thicker G wire is small considering safety and lower voltage drop .

I would use 1 inch conduit with a pull string installed. The above four wires can easily fit in this size conduit.

GREAT idea to do this now. Also excellent roof pitch for your latitude.

Hope this helps.

consulting on geothermal heating/cooling & rational energy use since 1990

Last edited by stevehull; 04-18-17 at 04:23 PM.. Reason: clarity
stevehull is offline   Reply With Quote
Old 04-21-17, 04:17 PM   #3
Join Date: Jan 2011
Location: Mpls,MN
Posts: 315
Thanks: 2
Thanked 17 Times in 17 Posts

It will be a direct run from basement to attic two stories, about 25'. As I plan to grid tie if I'm doing any PV I might as well cover front of roof. I have to cross a couple of top and bottom plates so I'm not sure I have clearance for 1" but will try for it(may have to flattened it in some places). Is a ground wire required? I am still very uneducated in the wiring world of PV. Am concentrating currently on building of structure and learning hydronics for infloor heating.

Drake is offline   Reply With Quote

Thread Tools
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

Forum Jump

All times are GMT -5. The time now is 08:41 PM.

Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2022, vBulletin Solutions Inc.
Ad Management by RedTyger
Inactive Reminders By Icora Web Design