Supply Side Connection for Residential SolarPV

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rlamen

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Location
CT
When installing a SolarPV system in a home, many times the point of connection to the main service panel (MSP) is made by tapping onto the service feeders using 'bugs' ("Supply side connection" - see attached photo). (With the other method of connection, by back feeding via an OCPD (breaker) in the MSP.)

Are there any code restrictions that prohibit a "supply side connection" in the existing Main Service Panel? If so, where in NEC2011 (or older) does it state such a connection shall not be in the existing MSP?

Attached photo shows this connection in the MSP, but a local electrician stated recently that this connection can never be located in the MSP, and must be installed between the Utility meter and the MSP.

Thanks for your input, Rob
 

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Smart $

Smart $

Esteemed Member
Location
Ohio
No violation to tap the service conductors in a service disconnect enclosure. However, when you tap the service conductors, the tap conductors become/are service conductors. They require a service disconnecting means (w/OCPD) that meets the two-to-six disconnect grouping rule. Looking at it from the PV side of it, the output of utility-interactive inverters are only permitted to be connected to the load side of [a] service disconnecting means [705.12(D)].
 
Z

Zee

Senior Member
Location
CA
Code permits it,

I have done it many times,

never recently.

Many AHj's won't allow it any more. Not due to specific location in MSP, but no supply side taps for PV. period.
Up to them.
 
don_resqcapt19

don_resqcapt19

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Location
Illinois
Occupation
retired electrician
Zee said:
...Many AHj's won't allow it any more. Not due to specific location in MSP, but no supply side taps for PV. period.
Up to them.
Click to expand...
It is only up to them if they have officially amended the rule in the NEC that permits a supply side connection.
 
Smart $

Smart $

Esteemed Member
Location
Ohio
don_resqcapt19 said:
It is only up to them if they have officially amended the rule in the NEC that permits a supply side connection.
Click to expand...
Where is that rule BTW?


Anyway, if you tap and run taps to [another] service disconnect, connect the PV system to the load side of that service disconnect, the PV system is not connected to the supply side!!!
 
S

SolarPro

Senior Member
Location
Austin, TX
Smart $ said:
Where is that rule BTW?
Click to expand...

Section 705.12(A) allows for supply side connections. The capacity of the power production source is only limited by the rating of the service. Since load side connections are limited by the bus or conductor rating per 705.12(D), a supply side connection is useful if the proposed interconnected PV capacity is large relative to size of the main load panel.

If an AHJ doesn't want you adding big insulation-piercing connectors inside of a load panel, you may be able to use something like this, depending on the meter supplier:

http://www.milbankmfg.com/products/catalogs/CatalogFiles/PDF/K4977.pdf
 
P

PEDRO ESCOVILLA

Senior Member
Location
south texas
there may be concern with backfeeding power to utility lines in the event of an outage. how do you prevent that with the way this photo is shown ? is there a disco between the service panel and the meter, or does the ho pull the meter when power goes out.?
 
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don_resqcapt19

don_resqcapt19

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Illinois
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PEDRO ESCOVILLA said:
there may be concern with backfeeding power to utility lines in the event of an outage. how do you prevent that with the way this photo is shown ? is there a disco between the service panel and the meter, or does the ho pull the meter when power goes out.?
Click to expand...
Our utility would require a disconnect at the meter for the PV system, even when the connection is made on the load side of the service disconnect. The solar inverters will automatically shut down their output when they sense loss of utility power to prevent a back feed to the utility. This is required by the UL listing standard.
 
G

ggunn

PE (Electrical), NABCEP certified
Location
Austin, TX, USA
Occupation
Electrical Engineer - Photovoltaic Systems
don_resqcapt19 said:
The solar inverters will automatically shut down their output when they sense loss of utility power to prevent a back feed to the utility. This is required by the UL listing standard.
Click to expand...
Correct, but it's not just because of the listing. If an inverter did not shut down when the grid went away it would be trying to feed pretty much a dead short, since many/most of the loads on the grid would still be connected. You aren't going to power up the city from your 4kW inverter. :D
 
don_resqcapt19

don_resqcapt19

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Location
Illinois
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retired electrician
ggunn said:
Your ordinance calls out sections of the NEC to ignore? I guess that could happen though I've never seen it.
Click to expand...
Yes, there are some deletions. I think there were at least two states that deleted the AFCI rules when they first came out.
 
B

beechigby

Member
Location
St. Croix US Virgin Islands
supply side connections

supply side connections

What is the formulae, NEC rule, that limits the solar inverter(s) output that can be connected to a supply side tap?
It is not the 120% of the buss bar rule, correct?
 
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RICK NAPIER

Senior Member
Location
New Jersey
don_resqcapt19 said:
Yes, there are some deletions. I think there were at least two states that deleted the AFCI rules when they first came out.
Click to expand...

NJ was one of those states. 210.12 is now adopted but the 2005 exceptions in 210.8 (A) 2 and 5 for GFCI's are adopted into the 2011 code. You not only have to know your code you have to know the changes.
 
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