I made a big mistake and didn’t realize it soon enough

[Phil Timmons]

Can you split the system and only make 1/2 be Grid-Tied?

 

[BackCountry]

Can you split the system and only make 1/2 be Grid-Tied?

I think that’s essentially what I’d accomplish if I use export limiting — it’ll throttle the output down to the max allowable 13kw, plus any additional to cover that meter’s load.

The second problem with <30kw and PG&E, is there is no one to talk to on the phone. It’s all by email and all through a shared inbox, no actual person to help you figure out a solution.

 

[BackCountry]

If there is one thing I have learned after 20 years in the electrical trade is utility construction costs are all over the place. Had one service upgrade a few years ago that required a new 3 phase pole bank and drop and the POCO paid for all of it. Then another new 480 200 A OH service that was $16k. You just never know.

Agreed. PG&E won’t go over 125A in 2” conduit for service wire (we place the pipe, they do the pull). I had to abandon a 30’ 2” conduit with existing #1 service wire and go to overhead service wire on a 200A upgrade. They are completely inflexible. It took 9 months to approve, and cost $800 for them to abandon the service wire at a joint pull box at the base of the pole, aka snip snip and that’s it.

On another job, they showed direct burial AL 4/0, 600’ length, and wouldn’t allow it for a 200 to 400A upgrade for obvious reasons.

We waited 6 months, trenched 750’ of conduit, put in transformers all on the customer side, when they came to abandon their existing “direct burial” service wire, they discovered it was 10’ of direct burial 4/0 into a 600’ run of 350’s in 3” conduit the whole way. Good one.

 

[jaggedben]

On another job, they showed direct burial AL 4/0, 600’ length, and wouldn’t allow it for a 200 to 400A upgrade for obvious reasons.

We waited 6 months, trenched 750’ of conduit, put in transformers all on the customer side, when they came to abandon their existing “direct burial” service wire, they discovered it was 10’ of direct burial 4/0 into a 600’ run of 350’s in 3” conduit the whole way. Good one.

Oh man, I'm sorry. I have some stories but none top that.

 

[msheets]

PG&E is stipulating either $21,000 to upgrade the transformer, or…? I’ve never tried to export limit before, has anyone done this with SMA inverters, if so — do you need the data manager to do it? And finally, any experience with PTO using export limiting?

I'm a little late to the party here, but I just recently set up a system with zero export with SMA inverters and the Data Manager M. It isn't very difficult at all. As someone else said, you need a meter that the data manager can communicate with. In our setup, we had to add the energy meter as a device in the data manager, and the data manager polls the meter's Modbus registers for the total power. The Grid Management settings in the data manager allow you to dictate how much power can be exported.

If I did export limit, it would likely not be a huge difference — this system maxes at 19kw during testing, and PG&E would limit me to 13kw.

It might seem like not a big deal, but just make sure the client knows that when you curtail the power for limiting export, it can reduce the total amount of energy generated. I know that sounds obvious, but we had that problem with the project I mentioned above. We thought we had explained it well enough during the design phase, but after the system was up and running, someone higher up in the client's company, who hadn't been involved in the earlier discussions, made a bit of a stink when the zero-export system wasn't generating as much as they hoped.

 

[ggunn]

We discussed this sort of thing earlier in the thread; it comes down to whether the utility will accept it as a solution.

 

[BackCountry]

If there is one thing I have learned after 20 years in the electrical trade is utility construction costs are all over the place. Had one service upgrade a few years ago that required a new 3 phase pole bank and drop and the POCO paid for all of it. Then another new 480 200 A OH service that was $16k. You just never know.

Final update here — final cost came back at $7,800. The $21,000 original estimate must have been their boilerplate language.

At that price, while expensive — it’s better than the alternatives.

 

[winnie]

Thanks for the update. All too often we don't get the end of the story.

 

[BackCountry]

Thanks for the update. All too often we don't get the end of the story.

Agreed. This forum is an incredible resource for my company.

 

[gadfly56]

Thanks for the update. All too often we don't get the end of the story.

Paul Harvey would definitely not approve!

 

[solarken]

Well, I have to admit when I’m wrong: and I made an error that I should have caught, and now I’ve got a potential $21,000 loss if I can’t figure out some way to mitigate it.

Background: 23kw (three SMA7.7’s) single phase 240v PV system that we built that’s in the PTO process with PG&E, it’s NEMA with one generating meter and 4 load meters. All of the load meters are at least 3-500’ away.

I never thought to pre apply or check the transformer on the generating meter, it’s an ag property and the pole is around the corner, it has an existing 200A service — I never looked up. I should have, it’s a 10kva transformer.

PG&E is stipulating either $21,000 to upgrade the transformer, or…? I’ve never tried to export limit before, has anyone done this with SMA inverters, if so — do you need the data manager to do it? And finally, any experience with PTO using export limiting?

If I did export limit, it would likely not be a huge difference — this system maxes at 19kw during testing, and PG&E would limit me to 13kw.

The other option is to re permit, and trench 500’ to another meter with a 25kva transformer, pull 4/0 to that and re submit.

I’m all ears, and I’ll be looking up more often. I for some reason mistakenly thought that PG&E was on the hook for lower than 30kw, and I was wrong.

I would think the Data Manager and a TCP modbus meter (and CT's) would be needed. I never configured export limiting on the DM but remember seeing the options to do so. Looks like they may have a Data manager Lite now for residential which may be cheaper.

 

[BackCountry]

I would think the Data Manager and a TCP modbus meter (and CT's) would be needed. I never configured export limiting on the DM but remember seeing the options to do so. Looks like they may have a Data manager Lite now for residential which may be cheaper.

You’re right on both counts. We elected to pay for the transformer upgrade and eat the cost, the solar generator meter has practically no load on it, so it wouldn’t have been fair in the long run.

The data manager lite can do it, you can also limit the active power if you don’t want to base it on consumption.

This was a big lesson for me moving forward.