Grid intertied PV house service

[Karl H]

Our Poco requires a lockable visible break disconnect switch per
thier specs. Mounted between the inverter and the service. It also has
to have a nameplate that reads,"PHOTOVOLTAIC SOURCE AC DISCONNECT."

 

[George Stolz]

Back to the drawing board. :roll:

When I went in to retrieve the meter socket (provided by POCO) and the specs for the service, there were no specs provided. So I asked the lady at the counter for the specs, and she called an engineer out to give them to me.

He was a nice guy, we talked for a bit and I pressed him about my plan, for which at this point the parts were purchased and sitting in the back of my van.

No, it's not right, he said. I need a service disconnect that the POCO can lock out, a real handle. So, I forwarded him the emails I had exchanged with the other guy at the POCO, encouraging them all to get on the same page (politely). :roll:

So, a $90 main breaker just evolved into a $350 fusible disconnect over the course of a fifteen minute conversation.

The only thing that really irritates me is I tried to do the right thing this time, learning from past mistakes, and actively hounded the AHJ and POCO to get it right the first time, and still almost wound up ripping things down and doing them over.

So, for the record (for future searches), the POCO in this instance required a fusible disconnect for a service disconnect in the case of an inverter on the load side of the service disconnect.

Edit to add: I realize that a couple people right now are thinking, "Well, duh - that's what we've been saying!" But the thing is, there are a few stops along the way between inverter and service disconnect on this one, and as the conversation progressed I was of the mindset that if the disconnect were misplaced, then it wouldn't do me any good anyway. Know what I mean?

 

[George Stolz]

I imagine my edit was too late, Bob's already writing.

 

[iwire]

George I strongly suggest that you do not take this persons word for it either.

Go to Google, type in the power company name and 'interconnections' I bet you will find a pdf with the real deal.

The fused disco sounds fishy.

 

[iwire]

I imagine my edit was too late, Bob's already writing.

Even with the edit ......... find the rules in writing, take no ones word for anything.

If you use the service disconnect as the utility PV disconnecting means, and the utility decides to exercises their right to open it and lock it they building will have no power at all.

We have always provided a utility PV disconnecting means that only disconnects the inverters, not the entire service.

 

[George Stolz]

George I strongly suggest that you do not take this persons word for it either.

Go to Google, type in the power company name and 'interconnections' I bet you will find a pdf with the real deal.

Gave it a shot, but I think the main problem is that there is no specification with this power company. My hounding them for specifications resulted in two occasions (two different guys) where the POCO presented me with specifications for a plain old 200A underground service.

Each time, I asked them flat out if they had a spec for grid intertie, and they said no.

Even with the edit ......... find the rules in writing, take no ones word for anything.

With that in mind, I intend to revise my drawing, and make both a rep from the POCO and the AHJ sign off on it. If/when one or the other changes their minds, I will beat them over the head with it.

If you use the service disconnect as the utility PV disconnecting means, and the utility decides to exercises their right to open it and lock it they building will have no power at all.

Do you think they will shut down the PV in other than an outage situation?

We have always provided a utility PV disconnecting means that only disconnects the inverters, not the entire service.

And if you think that there's a decent possibility that the POCO will want to disconnect the PV in other than an outage situation, I will strongly consider cancelling my order and revising the plan to inserting a disconnect inline on the 60A feeder to the inverter on the exterior wall.

I am not beyond revising my order for a fifth time, but at the same time I'd just as soon not have canned goods flung at me when I walk in the door the next time. I am really getting sick and tired of this house, and I haven't pulled an inch of rope yet.

I haven't even broached the other problems I've got yet.

 

[iwire]

Do you think they will shut down the PV in other than an outage situation?

I honestly do not know, but if it was to happen I picture a pretty unhappy customer.

 

[George Stolz]

You know that point in time you come to when you cease to care, knowing that the next EC would have stopped trying about a month ago?

 

[iwire]

You know that point in time you come to when you cease to care, knowing that the next EC would have stopped trying about a month ago?

I do and I am not an owner.

 

[George Stolz]

So, get this.

After thinking about it over the weekend, and mulling over the fact that Bob is usually right, I went ahead and canceled the order for the 200A safety-switch disconnect for the service disconnect, and opted for the 60A variety for just the inverter feeder. Cheaper, easier, better idea for the long haul.

Well, lo and behold, the POCO decided that after all this confusion, that they would go ahead and create a spec and get everybody on the same page.

The fershnecked spec looks just like what I just canceled buying.:roll:

I have a very thoughtful, well worded suggestion in to the POCO guy to see if he'll amend the spec before the ink dries, fingers crossed.

 

[George Stolz]

Afterword: In the end, after all these events, the requirement has revolved right back to where it began. The service disconnect is their disconnect, and as long as they can slap a padlock on the 3R panel cover, then they are fine with it, which is what their new spec shows. :roll:

 

[augie47]

George,
This is probably elementary, but there is something I don't understand.
I have inspected "stand alone" systems with batteries and "utility interactive systems", but I have not seen a "utility interactive" with batteries involved.
690.61 requires the inverter or AC module to de-energize its output when the distribution network looses power. Does your Panel PDP take care of this and allow Panel C to remain "hot" ?
On the "interactive" systems I have seen, the inverter wires directly to the utility (thru a disconnect) and all power is lost if POCO looses power.
Do we have solar charging the batteries which feed the inverter which feeds PDP and PDP provides the required disconnection ?

 

[George Stolz]

George,
This is probably elementary, but there is something I don't understand.
(snip)
690.61 requires the inverter or AC module to de-energize its output when the distribution network looses power. Does your Panel PDP take care of this and allow Panel C to remain "hot" ?

No, and I'm glad this has somebody else confused, because it threw me (and the solar gal) at the beginning too.

Eventually, we figured out that the input to the inverter from the utility is shut down, and the load side continues to send AC to Panel C. No physical change is required at PDP for this to happen, it's an automatic response at the inverter.

The solar gal actually had to change brands from her normal menu to get this feature, it must be cutting edge.

Once the POCO is called out to fix the outage, then they will have the ability to also come and lock out the service disconnect to ensure that they are absolutely disconnected from the PV system (double redundancy).

 

[augie47]

so PDP provides the "automatic" disconnect from the utility and the inverter continues to supply panel C thru PDP, correct ?

 

[George Stolz]

PDP doesn't automatically disconnect anything (overcurrent, short circuit, ground fault aside). It does manually disconnect just about every conductor you could ask for. The inverter (which is connected to the grid via PDP) does the automatic shutdown on power loss.

 

[augie47]

my confusion continues then. If the inverter shuts down, how does panel C get power in the event of a utility loss ?

 

[BillK-AZ]

Grid intertied PV house service- Inverter operation

Grid intertied PV house service- Inverter operation

The inverter does not shut down, it simply disconnects from the grid until it determines that the grid is restored and stable within specifications. The inversion part continues to supply the loads.

Some inverters have both a grid AC input and a generator AC input. Only one will be active at a time. In an extended outage the inverter can remote start and synchronize with the generator and use generator power to recharge the battery.

 

[weressl]

If I was being asked to I think I would want to talk to the inverter manufacturer to see if their unit has the sack to start a compressor that large.

The starting is not a problem, you have the Utility to take care of that. The PV just piddles along at a constant rate.

 

[George Stolz]

The starting is not a problem, you have the Utility to take care of that. The PV just piddles along at a constant rate.

Except if the utility is down.

 

[weressl]

Except if the utility is down.

I thought it is commonly understood that the PV's are designed to shut down when the Utility is down. So it is NOT a problem.:roll: