Utility Interconnection

ike5547

Senior Member
Location is in Butte County California.

Installing (2) strings (circuits) on a residential roof using micro-inverters. Is there any problem (code or otherwise) with installing (2) circuit breakers directly in the service panel as the disconnect? Or must they be fed through a combiner so that the utility interconnection consists of a single switch?

Looking around the area I see a lot of these systems with their micro-inverter AC output circuits running through a combiner (just a load center) and then over to the interconnect location.
 

PaulMmn

Senior Member
There was a thread here not too long ago where an AHJ was insisting on a combiner so there was only one feed to the main panel.

I don't remember the consensus of this group, and if the AHJ should have been taken to task or not.
 

ike5547

Senior Member
There was a thread here not too long ago where an AHJ was insisting on a combiner so there was only one feed to the main panel.

I don't remember the consensus of this group, and if the AHJ should have been taken to task or not.
Thanks. I found it.
 

ggunn

PE (Electrical), NABCEP certified
There was a thread here not too long ago where an AHJ was insisting on a combiner so there was only one feed to the main panel.

I don't remember the consensus of this group, and if the AHJ should have been taken to task or not.
The AHJ can require that if they want. I don't believe you can take them to task if that is their policy. They can be more restrictive than the NEC.
 

pv_n00b

Senior Member
The AHJ can require that if they want. I don't believe you can take them to task if that is their policy. They can be more restrictive than the NEC.
They can be more restrictive but only by local ordinance adoption. The building department can't just decide to be more restrictive without going through the correct process. An inspector can't just make up their own rules that are more restrictive and apply them where they want. If they could the construction industry would be a mess.
 

ggunn

PE (Electrical), NABCEP certified
They can be more restrictive but only by local ordinance adoption. The building department can't just decide to be more restrictive without going through the correct process. An inspector can't just make up their own rules that are more restrictive and apply them where they want. If they could the construction industry would be a mess.
That's technically correct but not always true in the real world. It's one thing to say "they can't do that" but it's another to win that fight in the field when the inspector has the power to fail your installation. Some things are just not worth fighting about.
 

ggunn

PE (Electrical), NABCEP certified
They can be more restrictive but only by local ordinance adoption. The building department can't just decide to be more restrictive without going through the correct process. An inspector can't just make up their own rules that are more restrictive and apply them where they want. If they could the construction industry would be a mess.
Actually, we have one of these right now. We do a bazillion microinverter installations all over Texas, most of which require a 40A or less interconnection breaker. To simplify things for our installers we set a minimum conductor size of #6 copper back to the solar load center and a minimum interconnection breaker size of 40A.

We have an inspector in one jurisdiction that is telling us that if the minimum breaker size per 690.8(B)(1)(a) is 35A we have to use a 35A breaker and no larger, even though the derated ampacity of the wiring is 68.3A and even though there is no article in the NEC to back up his assertion. We have appealed to his boss and the chief electrical inspector for the city, and rather than allow an inspector to lose face, they have pulled the wagons in a circle and stand behind him (sorry for the mixed metaphor). The inspector is making up his own code, and he can't do that, right?

By the way, I know a lot but I don't know everything. If any of you guys can show where this inspector is correctly interpreting the NEC, I'd like to see it.
 
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jaggedben

Senior Member
Location is in Butte County California.

Installing (2) strings (circuits) on a residential roof using micro-inverters. Is there any problem (code or otherwise) with installing (2) circuit breakers directly in the service panel as the disconnect? Or must they be fed through a combiner so that the utility interconnection consists of a single switch?

Looking around the area I see a lot of these systems with their micro-inverter AC output circuits running through a combiner (just a load center) and then over to the interconnect location.
If it's PG&E territory and the meter is rated for 320A or less you don't need a combiner or disconnect per se, unless you run into some egotistical newbie inspector like in that other thread.

Reasons you might see combiners (Enphase in particular) when you might think they're not needed:
  • Avoids possible arguments over the 'opposite end' rule with multiple breakers
  • Saves time on the monitoring device install for Enphase specifically, and also helps monitoring communications to be more reliable and easier to troubleshoot
  • Designers and installers who don't have a solid electrical background or are swayed by manufacturer literature may not realize they can save on materials with standard electrical components.
  • Larger companies in particular are likely to 'streamline' their operations by using a combiner on every job because it will work about 100% of the time, rather than try to keep track of the solutions and deal with the inventory necessary to save a hundred bucks on this job and that. They are also likely getting the combiners cheaper.
 
Location is in Butte County California.

Installing (2) strings (circuits) on a residential roof using micro-inverters. Is there any problem (code or otherwise) with installing (2) circuit breakers directly in the service panel as the disconnect? Or must they be fed through a combiner so that the utility interconnection consists of a single switch?

Looking around the area I see a lot of these systems with their micro-inverter AC output circuits running through a combiner (just a load center) and then over to the interconnect location.
I've installed a ton of these, although the Enphase box is pricey, it provides some nice features.
1) Avoid installing a new plug just so the Envoy can "see" the microinverters.
2) You can reduce service calls by adding the Cellular modem, 90% of Enphase service calls are because someone changed their router or password.
3) Provide a clean install.
4) You don't have to create your own sub-panel.
5) Most of the installs you are seeing in Butte County are AES/sunpower and they have the envoy and cellular monitoring in that box also.

My 2 cents.

Michael
 

pv_n00b

Senior Member
Actually, we have one of these right now. We do a bazillion microinverter installations all over Texas, most of which require a 40A or less interconnection breaker. To simplify things for our installers we set a minimum conductor size of #6 copper back to the solar load center and a minimum interconnection breaker size of 40A.
I agree that it can be a problem, how far up can you take something? Once I have been turned down by the head building inspector I can technically take the city building department to court and win the case but by that point, it's more expensive than either doing what they want or just not doing any work in their area. So they win by default that it's not worth fighting them after a certain point. There was a local building department in Silicon Valley that was so hard to work with that PV contractors just stopped taking jobs there for a long time.
 

pv_n00b

Senior Member
2) You can reduce service calls by adding the Cellular modem, 90% of Enphase service calls are because someone changed their router or password.


Michael
I can't change my WIFI password if I install an Enphase system? Is that a service call to fix or can the owner update the Envoy?
 
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