Contact US

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

PV system sizing as per main electrical service

PV system sizing as per main electrical service

PV system sizing as per main electrical service


I'd appreciate some feedback on the following PV system sizing scenario:

The main electrical service for the building is 400A, 1-phase, 120/240V. The main CDP is rated for 400A, 1-phase, 120/240V. Based on the 20% power feedback rule, I'd be permitted max. of 80A (19.2 kW PV system) of feedback into the electrical distribution system.

The CDP has limited number of spare spaces to install circuit breakers, so I intend to install a 100A,1-phase, 120/240V sub-panel via 100A/2P circuit breaker in the CDP. Would this configuration meet the 20% feedback rule or do I need to size the sub-panel to 400A so I'll be compliant with the feedback rule?

Thank you.

RE: PV system sizing as per main electrical service

Quote (OP)

Based on the 20% power feedback rule
Is this a utility rule or a CEC rule?
Can you post a copy of the rule or the CEC rule number?

"Why not the best?"
Jimmy Carter

RE: PV system sizing as per main electrical service


It seems to be a utility rule. But the CEC Section 64-112 c & 64-112 d, mentions the following:

"The sum of the ampere ratings of the OCP in source circuits supplying power to a busbar / conductor shall be permitted to exceed the busbar / conductor ratings to a maximum of 120% of the ratings of the busbar or conductor"

RE: PV system sizing as per main electrical service

Seems to me that you are misinterpreting the condition. Your solar isn't going to add to the utility current, it'll substitute for it and whatever is not consumed by the load is fed to the utility.

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert! https://www.youtube.com/watch?v=BKorP55Aqvg
FAQ731-376: Eng-Tips.com Forum Policies forum1529: Translation Assistance for Engineers Entire Forum list http://www.eng-tips.com/forumlist.cfm

RE: PV system sizing as per main electrical service

80 Amps total feed into a 100 Amp panel.
100 Amp rate conductors from a 100 Amp panel to a 100 Amp breaker in a 400 Amp PDC?
I don't see a problem, but the last word is the AHJ.
Remember, even if the AHJ makes a mistake, he is still the AHJ.
If a load fed by a 100 Amp breaker is shifted to a 100 Amp sub panel fed by a 100 Amp breaker and the solar power added into the 100 Amp panel it gets more complicated.

"Why not the best?"
Jimmy Carter

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members! Already a Member? Login


Low-Volume Rapid Injection Molding With 3D Printed Molds
Learn methods and guidelines for using stereolithography (SLA) 3D printed molds in the injection molding process to lower costs and lead time. Discover how this hybrid manufacturing process enables on-demand mold fabrication to quickly produce small batches of thermoplastic parts. Download Now
Design for Additive Manufacturing (DfAM)
Examine how the principles of DfAM upend many of the long-standing rules around manufacturability - allowing engineers and designers to place a part’s function at the center of their design considerations. Download Now
Taking Control of Engineering Documents
This ebook covers tips for creating and managing workflows, security best practices and protection of intellectual property, Cloud vs. on-premise software solutions, CAD file management, compliance, and more. Download Now

Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close