Max PV System Capacity to POC (Point Of Connection)

[pv_n00b]

I will and I have. I just won't try to defend my design to an inspector by saying "this is a switchboard not a panelboard".

Pointing that out works 100% of the time for me. The question that is a bit more difficult is, what does the NEC want to be done with switchboards?

 

[bendesa]

Nice conversation. Unfortunately no answers. That's ok guys, I appriciate all contributions.

Kind regards

Ben

 

[electrofelon]

Nice conversation. Unfortunately no answers. That's ok guys, I appriciate all contributions.

Kind regards

Ben

Post #2?

 

[bendesa]

Yes you're right

Thats a beginning of an answer. The guidelines to follow.
I need to look more into that.

For me it would be very helpfull if there was an example with calculation / explanation

But you're right

Take care!


Kind regards

Ben

 

[ggunn]

Yes you're right

Thats a beginning of an answer. The guidelines to follow.
I need to look more into that.

For me it would be very helpfull if there was an example with calculation / explanation

But you're right

Take care!


Kind regards

Ben

For a backfed breaker interconnection the calculation for the 120% rule (Article 705.12(B)(3)(2)):

(1.20)(bus rating) - (bus OCPD rating) >/= (1.25)(maximum inverter current)

 

[pv_n00b]

Yes you're right

Thats a beginning of an answer. The guidelines to follow.
I need to look more into that.

Unfortunately, once a debate about some part of the NEC that people do not share the same outlook on starts the chances of getting a straight answer to a question goes way down.

 

[pv_n00b]

Hi all,

This seems to be a nice foru, with a lot of available knowledge. I do have a question about the following.

When connecting a high capacity (1MW and up) PV System to the POC (Point Of Connection) how do you know if it is possible to the
available MDP (Main Distribution Panels)?

I've read about the 120% rule but it's not completely clear to me. I do have an example here of an distribution panel. What could be the maximum
PV System capacity to connect?

View attachment 2562014

I hope somebody can help me out on this

Many thx in advance

Kind regards

Ben

Let's talk theoretically. You have a 2500kVA transformer @ 400V, that limits you to about 3,608A back feed current, maybe the service conductor size limits that more but I'm not going to look that up. So you could do a supply side interconnection of a 2.5MW AC PV system. On the load side you are limited to 80% of the 4,000A main if it's not 100% rated, so maybe a 2.217MW AC system under engineering supervision. If someone talked you into the 120% rule then that would be 20% of 4,000A or 800A available back feed, assuming the SWBD bus is 4,000A. That would be a 554kW PV system.

 

[bendesa]

Let's talk theoretically. You have a 2500kVA transformer @ 400V, that limits you to about 3,608A back feed current, maybe the service conductor size limits that more but I'm not going to look that up. So you could do a supply side interconnection of a 2.5MW AC PV system. On the load side you are limited to 80% of the 4,000A main if it's not 100% rated, so maybe a 2.217MW AC system under engineering supervision. If someone talked you into the 120% rule then that would be 20% of 4,000A or 800A available back feed, assuming the SWBD bus is 4,000A. That would be a 554kW PV system.

Hi,

Thank you so much for your great answer!
I do appriciate it

Kind regards

Ben