22 enphase micro invert

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SAP

Senior Member
Location
Fresno Ca
We are adding 8 enphase micros to a existing 14 micros with a existing 20 amp backfeed breaker wire size 10 AWG. The system will have 22 micros at 19.8 Amps 1.25=24.75 Amps.The plans call for 40 AMP backfeed breaker with 10 AWG, Feeding a solar subpanel with a 15 Amp and 20 Amp Solar CKTS,I'm I missing something 10 AWG on a 40 AMP breaker, Is there a Exception like the air conditioning,should I just change that 40 to a 25 or 30 Amp,thanks
 
Smart $

Smart $

Esteemed Member
Location
Ohio
Seems crazy, don't it...!!! :blink:

690.6(D) says ac modules shall be permitted to have ocp and wire sizing per 240.5(B)(2)...
(2) Fixture Wire. Fixture wire shall be permitted to be
tapped to the branch-circuit conductor of a branch circuit in
accordance with the following:
(1) 20-ampere circuits — 18 AWG, up to 15 m (50 ft) of
run length
(2) 20-ampere circuits — 16 AWG, up to 30 m (100 ft) of
run length
(3) 20-ampere circuits — 14 AWG and larger
(4) 30-ampere circuits — 14 AWG and larger
(5) 40-ampere circuits — 12 AWG and larger
(6) 50-ampere circuits — 12 AWG and larger
Click to expand...
 
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SAP

Senior Member
Location
Fresno Ca
Thank you,Correct me if I'm wrong, But I'm reading 240.5(B)2,let me give you a real life example,A fluorescent lay in fixture that has the factory Whip installed I'm not sure what AWG the wire is but I know it's smaller then 12 awg,Years back I connected fixture to fixture,My Forman made me redo it and hit a Jbox above the fix that went all the way back to the lighting panel ,I'm guessing that I'm tapping into the branch CKT when I hit the jay box?
 
Smart $

Smart $

Esteemed Member
Location
Ohio
SAP said:
Thank you,Correct me if I'm wrong, But I'm reading 240.5(B)2,let me give you a real life example,A fluorescent lay in fixture that has the factory Whip installed I'm not sure what AWG the wire is but I know it's smaller then 12 awg,Years back I connected fixture to fixture,My Forman made me redo it and hit a Jbox above the fix that went all the way back to the lighting panel ,I'm guessing that I'm tapping into the branch CKT when I hit the jay box?
Click to expand...
Given the factory whip was made up of fixture wire, yes. That's a very common scenario.

The point of a 'tap' is, the tap's ampacity is less than the branch circuit's ocp rating.
 
Smart $

Smart $

Esteemed Member
Location
Ohio
SAP said:
The 40 amp breaker is the backfeed breaker in the main Feeds a solar subpanel on the roof using 10 AWG
Click to expand...
A feeder (conductor between two panels) cannot have an ampacity less than its ocp rating... in general. And in many cases may even be required to meet the 120% rule of 705.12(D) when interconnected power sources are involved.

The requirement of 690.5(E) only applies to the module-to-ocpd wiring.
 
mwm1752

mwm1752

Senior Member
Location
Aspen, Colo
So per the manufactures instructions on the m250 micro inverter (per 20 amp branch circuit) ---- single pahse 240v @ 1 amp max limit to 16 on one string 3 phase 208v @ 1,15amp max 24 on one string -- I can only assume they are rated to be installed at 20 a branch circuit increments. Older spec sheets are more direct.
 
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SAP

Senior Member
Location
Fresno Ca
It's the enphase 250 single phase,I guess I have only two options for the feeders run number 8 or go to the city and see if I can redline the plans to a 30 Amp , I don't understand why the engineer would put a 40 Amp breaker feeding the solar subpanel
 
mwm1752

mwm1752

Senior Member
Location
Aspen, Colo
SAP said:
It's the enphase 250 single phase,I guess I have only two options for the feeders run number 8 or go to the city and see if I can redline the plans to a 30 Amp , I don't understand why the engineer would put a 40 Amp breaker feeding the solar subpanel
Click to expand...

Are you implying the strings can be combined without OCPD for each string?
 
S

SAP

Senior Member
Location
Fresno Ca
Not at all . Main panel with the 40 amp breaker feeding a sub panel on the roof for my solar Circuits one 15 and one 20 amp.my question was the plans call a 40 amp breaker in the main panel with #10 wire feeding the solar subpanel on the roof
 
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jaggedben

Senior Member
Location
Northern California
Occupation
Solar and Energy Storage Installer
Breaker should have been 30A instead of 40A. 40A breaker needs 8awg wire but neither are necessary.

Some people are making this thread more complicated than it is. We are not talking about the branch circuits.
 
S

SAP

Senior Member
Location
Fresno Ca
It could be the way I wrote it, sometimes I write to fast, type feeders when I really mean (feeder) confusing,I need to work on that ,Thanks
 
mwm1752

mwm1752

Senior Member
Location
Aspen, Colo
SAP said:
We are adding 8 enphase micros to a existing 14 micros with a existing 20 amp backfeed breaker wire size 10 AWG. The system will have 22 micros at 19.8 Amps 1.25=24.75 Amps.The plans call for 40 AMP backfeed breaker with 10 AWG, Feeding a solar subpanel with a 15 Amp and 20 Amp Solar CKTS,I'm I missing something 10 AWG on a 40 AMP breaker, Is there a Exception like the air conditioning,should I just change that 40 to a 25 or 30 Amp,thanks
Click to expand...

jaggedben said:
Breaker should have been 30A instead of 40A. 40A breaker needs 8awg wire but neither are necessary.

Some people are making this thread more complicated than it is. We are not talking about the branch circuits.
Click to expand...

You have a micro string of 22 - 250 emphase micro inverters terminating into a 20 amp OCPD ( manufactures installation specs max out the number of inverters for single phase 240v as 16) - ?
You are not feeding from the combiner subpanel that contains the individual string OCPD to the proposed 40 amp main backfeed breaker in which you question using 10# AWG as being properly proteceted . ( 690.6(D) requirement ends at the combiner sub panel where each string is individually protected --
We are talking about feeders 240.4(D) would apply -- 240.4(D) a 10# AWG CU limits OCPD to 30 amps -- 8# AWG AWG CU limits OCPD to 40 amp
Why would you put 22 inverters on a single string @ 1 amp apiece with a continuous load of 27.5 amps on a 20 amp breaker? Base load of 22 amps could still open the 20 amp OCPD
 
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