supply side PV connection

[tritium]

I believe with most POCO's where two or more meters are on one account, each meter is itemized separately. With net metering, it is just one meter, one reading value. But you are correct in that the net balance for multiple meters is calculated.

I cannot speak for most utility companies, but after much debate over it all, interconnection departments from the two major players in SC require a separate production meter alongside their net meter for all DER net-metering customers. Strangely, they are at odds on whether the production meter should be allowed to be placed before or after the disconnect switch. :blink:

 

[tritium]

Also, I posted this in another thread on supply-side tap questions, but it seems more appropriate here:

I have an installation coming up that will be roof-mounted to an "adjacent" structure (read: a building on the same property, but a couple hundred feet from inverters to the meter where the required utility disconnect will be) which has a separate service from the house, but the inverter outputs will only be tied to the main residence's service. The system is large enough that we can't interconnect on the load side, so here I've stumbled trying to figure out the new language of 2014's 705.31 and rules for connecting to the supply side of the service disconnect.

The conductors for the run were sized for the voltage drop (running 4/0 aluminum) and per 705.65(A) Exception (2), an OCPD "shall not be required" for the inverter output conductors if the "short circuit currents from all sources do not exceed the ampacity of the conductors".

Well, 4/0 aluminum's ampacity is 205, and the panel combining the two inverters' output has OCPD for each of those smaller branches. If the conductors and equipment are out of harm's way here, and the disconnect allows for the opening of the circuit regardless of fusing, then isn't the code intention of 705.31 (which is specifically stated in the informational note following it) satisfied?

Still putting in a fused disconnect at the end of the day for peace of mind here, but I see these as contradictory given certain circumstances (and interpretations).

 

[Smart $]

I cannot speak for most utility companies, but after much debate over it all, interconnection departments from the two major players in SC require a separate production meter alongside their net meter for all DER net-metering customers. Strangely, they are at odds on whether the production meter should be allowed to be placed before or after the disconnect switch. :blink:

In doing so, have they had an account prove that they did lose more revenue than was produced? I ask because I imagine unwarranted loss of revenue is their biggest concern.

 

[Smart $]

...The conductors for the run were sized for the voltage drop (running 4/0 aluminum) and per 705.65(A) Exception (2), an OCPD "shall not be required" for the inverter output conductors if the "short circuit currents from all sources do not exceed the ampacity of the conductors". ...

The short-circuit current contribution from the POCO side will most likely exceed conductor ampacity. Did you obtain an available short-circuit current value from the POCO for the service in question? [110.9, 110.10]

 

[tritium]

The short-circuit current contribution from the POCO side will most likely exceed conductor ampacity. Did you obtain an available short-circuit current value from the POCO for the service in question? [110.9, 110.10]

Nope. Do you really have to if you there are circuit breakers at the panel combining the inverters with the same AIC as the MCB for the residence if you consider the conductors to be service conductors (as you have mentioned, which you must because feeder OCP requirements are flimsier)?

Circular logic here: the inverter output conductors, as defined in 705.2 ("Utility-Interactive Inverter Output Circuit"), already have OCPD that is adequate for the I-sc of the utility, unless you doubt the capacity of the MCB as being sufficient. (Both have a rated AIC of 22kA) This is then the equipment you've referenced in 110.9, and since they are set to trip above 60A at the nominal circuit voltage of 240, and it complies with Article 230. Then the disconnect for the PV system at the house is for utility convenience and not for OCP.

In no way am I stating that this is SOUND design, but my point here is until there is total clarity on what rules actually apply to the conductors and the disconnect equipment's classification, even if what results is a new set of definitions, then there's plenty of room for interpretation to muddy the Code waters that are already thick.

 

[Smart $]

Nope. Do you really have to if you there are circuit breakers at the panel combining the inverters with the same AIC as the MCB for the residence if you consider the conductors to be service conductors (as you have mentioned, which you must because feeder OCP requirements are flimsier)?

Circular logic here: the inverter output conductors, as defined in 705.2 ("Utility-Interactive Inverter Output Circuit"), already have OCPD that is adequate for the I-sc of the utility, unless you doubt the capacity of the MCB as being sufficient. (Both have a rated AIC of 22kA) This is then the equipment you've referenced in 110.9, and since they are set to trip above 60A at the nominal circuit voltage of 240, and it complies with Article 230. Then the disconnect for the PV system at the house is for utility convenience and not for OCP.

In no way am I stating that this is SOUND design, but my point here is until there is total clarity on what rules actually apply to the conductors and the disconnect equipment's classification, even if what results is a new set of definitions, then there's plenty of room for interpretation to muddy the Code waters that are already thick.

I'm just saying OCPD is required within 10' of your supply-side point of connection because the available short-circuit current at any point on that set of conductors exceeds its ampacity. In effect, Code is forcing consumers to not have service conductors extending more than 10' from the point of connection. In contrast, the panel could be set up as a service to a separate structure, i.e. load-side connected PV system (e.g. add a load or receptacles).

 

[tritium]

I'm just saying OCPD is required within 10' of your supply-side point of connection because the available short-circuit current at any point on that set of conductors exceeds its ampacity. In effect, Code is forcing consumers to not have service conductors extending more than 10' from the point of connection. In contrast, the panel could be set up as a service to a separate structure, i.e. load-side connected PV system (e.g. add a load or receptacles).

I get it. I just think it's ambiguous to put out any literature applying rules of one conductor classification to another without expounding on how exactly it applies, what instances necessitate it and what code articles/sections we are modifying such that it is clear when they are used in a DER that there is little or no debate as to how to treat them. THIS is an example of a potential safety issue derived from the interpretation of the muddle here, more so than to bond or not to bond the neutral and ground conductors in both disconnects or one only, though how the definition process shakes out should have an impact on both questions.

And yes, the panel could be set up as a service, but if it is a service disconnect connected via service conductors to utility equipment that is at it's "supply" side, then isn't already (especially if it has an MCB and not simply MLO)? At least I think they tried to separate the definition of the supply in 705.2, but the literature in 705.12(A) and (D) and 705.31 could use some "esplainification" as my astrophysics prof was fond of saying. Otherwise, MCB in the panel is the "integral" OCPD equipment and is in full compliance with 705.20-31