One PV feeding two meters/buidings

[OHHV]

I'm looking for some help to figure out if this senario meets code:

Customer has two stand-alone buildings on their propery. Each building is normally fed by it's own utility transformer and has it's own MP and meter. Building A will have the two independant PV systems installed on it. PV system 1 will feed building A and system 2 will feed building B with 120/240VAC, which is 600 feet away through an UG conduit into that MP and meter.

 

[Smart $]

Nothing described thus far is Code prohibited TTBOMK.

 

[Fulthrotl]

I'm looking for some help to figure out if this senario meets code:

Customer has two stand-alone buildings on their propery. Each building is normally fed by it's own utility transformer and has it's own MP and meter. Building A will have the two independant PV systems installed on it. PV system 1 will feed building A and system 2 will feed building B with 120/240VAC, which is 600 feet away through an UG conduit into that MP and meter.

you have two independent systems feeding two services....
just that both of the arrays are in the same place.

mark them accordingly, so nobody gets confused later, and rock on.

 

[GoldDigger]

you have two independent systems feeding two services....
just that both of the arrays are in the same place.

mark them accordingly, so nobody gets confused later, and rock on.

If the bills for both services go to the same person, the utility may offer virtual net metering, which would make it less important to balance the PV fraction to the consumption on each service.
I would look unto that option.

 

[jaggedben]

The only potential confusion I see here with respect to code is grounding. Your inspector may (and probably should) require you to ground the array for PV system 2 at building A, by connecting to a grounding electrode. (Also the inverter, since I presume it's located there as well.) They may or may not require you to use the same electrode to ground PV system 1 and to bond all electrodes at building A together (including the existing AC electrode).

In my opinion you should connect all equipment installed at building A to the grounding electrode system at that building, via GEC from the inverter(s) installed there. (Or GEC direct from the array for any solar panels whose inverter may be installed at building B, but I think you're saying the underground feed is AC.) Then run a normal equipment grounding conductor with the circuit going underground to building B. But your inspector may have a different interpretation, such as requiring additional electrodes and bonding jumpers between buildings. Depends partly on what code cycle you're on.

 

[Electric-Light]

If the bills for both services go to the same person, the utility may offer virtual net metering, which would make it less important to balance the PV fraction to the consumption on each service.
I would look unto that option.

Communism
http://www.cpuc.ca.gov/PUC/energy/DistGen/vnm.htm
:lol: :happysad: :huh: :happyno:

I think the concern here is to make sure you have absolute islanding protection that prevent each other from validating each other and back feeding when there's an outage.

 

[shortcircuit2]

If under 14 NEC, the Rapid Shutdown Function for each system on building A should be grouped.

 

[jaggedben]

...
I think the concern here is to make sure you have absolute islanding protection that prevent each other from validating each other and back feeding when there's an outage.

Virtual net metering has nothing to do with that.

 

[Electric-Light]

Virtual net metering has nothing to do with that.

It doesn't. I am addressing the topic of the thread.

 

[GoldDigger]

I think the concern here is to make sure you have absolute islanding protection that prevent each other from validating each other and back feeding when there's an outage.

By the design and UL listing of grid tie inverters you can be assured that two GTIs, even from different manufacturers, will not be able to satisfy each others anti-islanding checks. GTIs are paralleled all the time.
If only one service has grid power, then only that service's GTI will be operating. I do not see what you concern is.

 

[jaggedben]

...
If only one service has grid power, then only that service's GTI will be operating. I do not see what you concern is.

Now that you mentioned services...

An AHJ could say that this installation would run afoul of 230.2 and its one service per building rule. In my opinion a reasonable AHJ would allow this to be addressed with signage, especially if both inverters are installed outside such that no AC conductors from Building B actually enter Building A. Barring that, if the AHJ makes an issue, there could be a couple other ways around it...
- Don't actually install the inverter for PV system 2 in or on Building A. Put it on Building B and run DC over there, or put it on it's own structure (e.g. pole).
- Have a new service installed for PV system 2. Probably not a workable option for net-metering but it would be allowed by the NEC. Might be a last resort if the AHJ doesn't allow other options and there's still a lot of money to be saved for Building B.

 

[Electric-Light]

By the design and UL listing of grid tie inverters you can be assured that two GTIs, even from different manufacturers, will not be able to satisfy each others anti-islanding checks. GTIs are paralleled all the time.
If only one service has grid power, then only that service's GTI will be operating. I do not see what you concern is.

As long as it offers equally reliable positive lock out as a mechanical transfer switch on a generator, it shouldn't be an issue code wise and immune from missed trips. Code wise, same level of reliability as a breaker is expected...

http://www.nrel.gov/docs/fy05osti/37200.pdf

"Using a matched load, the inverter can be islanded (more than 2 seconds) without any
anti-islanding measures activated. In some cases, depending on load match and quality
factor, the inverter can run on indefinitely."

 

[jaggedben]

As long as it offers equally reliable positive lock out as a mechanical transfer switch on a generator, it shouldn't be an issue code wise and immune from missed trips. Code wise, same level of reliability as a breaker is expected...

Use listed inverters and this is not a concern. It is especially not a concern with the OP's situation as the two systems would be on different utility transformers.

http://www.nrel.gov/docs/fy05osti/37200.pdf

"Using a matched load, the inverter can be islanded (more than 2 seconds) without any
anti-islanding measures activated. In some cases, depending on load match and quality
factor, the inverter can run on indefinitely."

Funny. I don't recall ever hearing about a GE inverter brought to market. Perhaps this was a failed design.

 

[SolarPro]

As I recall, GE was more active in the wind industry, and had big inverters for wind turbines. I'm sure that had plans to use some of that technology in solar applications. They did get into the solar industry briefly. A company I worked for circa 2004 sold some of their modules. But they were never cost competitive, not even when module prices were high.

 

[BillK-AZ]

http://www.nrel.gov/docs/fy05osti/37200.pdf[/url]

"Using a matched load, the inverter can be islanded (more than 2 seconds) without any
anti-islanding measures activated. In some cases, depending on load match and quality
factor, the inverter can run on indefinitely."

Somewhat misleading quote. The above report covers tests with and with anti-islanding disabled for the tests. The extended run on was with anti-islanding software disabled.
After the test without anti-islanding, an anti-islanding scheme was enabled to demonstrate its effectiveness. Three schemes were tested.

From the report:

3.1 Findings
? Using a matched load, the inverter can be islanded (more than 2 seconds) without any
anti-islanding measures activated. In some cases, depending on load match and quality
factor, the inverter can run on indefinitely.
? With the recommended anti-islanding parameter settings, the schemes work
successfully (trip within 2 seconds) under all tested conditions, including worst-case
generation/load balance as defined in the IEEE P1547.1 testing standard.

 

[Richard66]

But what about inductive damage due to lighting or other events???

But what about inductive damage due to lighting or other events???

I have the same issue about feeding one PV array (well it will really be two PV arrays just mounted on the same roof next to each other) into two different meters and buildings. My thought was to do this as mentioned with just one ground for the array.
The issue at my location is that although the two meters (with two different transformers) are relative close to each other (about 300 feet) and the building which will have the PV installed upon it is in the middle, when you look at where the utility lines are run there is perhaps 5-10 acres of land within the loop made up from meter1 -> transfomer1 -> utility line -> transformer2 -> meter2 -> PV -> meter1. I am concerned that any and every lightning strike in the area will induce a voltage in this very large loop that will burn up some component in the loop.

I should say the reason for this is to prevent the customer from having to replace (upgrade) either of the two transformers using virtual metering and having all the PV on one meter. Ideally, I think it is best to just combine the two services into one with all three buildings on one meter. But that leads to a lot of added expense.