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then add 10-20 percent for the " what did I forget clause".
Tim.
Do this on any new type job, and put that money away as " Oh [email protected] I forgot to put this in money" That way you may never lose on a job, this fund covers you.
If you never use it, it becomes retirement fund.

Cowboy
 

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I thought the system was designed so that the solar backfeeds the utility grid and therefore should only work in conjunction with the utility power. That’s why it’s line side tapped before the main.
Solar systems insert power into your electrical panel. That power is used by your local branch circuits. If your local circuits are not using it all, the excess flows back into the utility grid.

The solar system is designed to shut off if it doesn't sense utility power. This is just a safety measure to keep line crews safe in case of an outage. The solar system doesn't care if you have utility power or not otherwise.

The solar system also can't tell the difference between utility power and power coming from your local generator.

Not all solar systems are line side tapped. A backfed breaker can also be used but it requires the panel to have sufficient ampacity on its buss bars and space for the breaker. Breakers are easier and will usually be used if possible.


But I still don’t understand exactly how they sync up and work together.
The inverter changes the DC coming from the solar panels into AC at 60 hz. It does this electronically so it's simply a matter of tracking the sine wave of the utility power and outputting a sine wave that matches it's timing.

If you really want to blow your mind consider that all the giant generators on a power grid are also in sync. When a generator comes online it is not connected to the grid at first. First it is brought up to speed (60 hz here in America) then the sine wave of the generator is compared with that of the power on the grid. The speed the generator is tweaked (changed minutely) until the sine waves are in alignment. Then the big disconnect is closed and the generator is connected to the grid.

Once connected to the power grid, the generator is locked into the sine wave. If the generator stops producing power for some reason like a mechanical failure of its prime mover, it will be backfed with power from the grid and start to act like a motor i.e. it will be pulled along at 60 hz until it is disconnected from the grid for repair. If the rotor is slowed down due to mechanical failure, bad things will happen.
 

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And good luck getting that job, I’d be interested to see if anyone beats you out and does it for cheaper.
The job is about 1/2 mile from my office so I will see how it pans out. I haven't heard back from the homeowner yet. Next time I will bump up my price and see what happens. Some contractors can afford to wait for the higher prices, I cannot. I lost two large jobs due to Covid cancellations so I have to take what I can right now.
 

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Discussion Starter #24
Does anyone know a good place to order warning labels for the meter and panel stating there are three sources of power onsite? (Utility, PV, and portable generator). I know the inspector for that town always looks for the appropriate warning label and I didn’t see any great options when I did a quick google search.
 

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Get some stickers made up that also have your company name and number.
Spend the extra couple of bucks to get a UV and weather resistant ones. They will last years and help drive business.

Tim
 

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Just trying to get home
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Reading through these posts and not having done a solar system myself, I'm thinking that protecting the stupids is working against us.

The solar system on my house would actually be part of the grid as it feeds, on bright sunny days, the system when I use only a little to none...the excess goes to the grid.

Now, when the grid goes down so does my bright sunny day backfeed so as to prevent powering the grid during repairs...great. But my solar doesn't feed me during that outage and now I need a generator to keep my freezer working instead of using my battery bank?

Am I interpreting this correctly?

Why wouldn't we design a smarter control system to lockout the grid and still use solar without needing the generator, say at night, with no solar or battery storage?

I understand the frequency shifting with the load (and the source)...but a smarter system should be in design by now.
 

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Reading through these posts and not having done a solar system myself, I'm thinking that protecting the stupids is working against us.

The solar system on my house would actually be part of the grid as it feeds, on bright sunny days, the system when I use only a little to none...the excess goes to the grid.

Now, when the grid goes down so does my bright sunny day backfeed so as to prevent powering the grid during repairs...great. But my solar doesn't feed me during that outage and now I need a generator to keep my freezer working instead of using my battery bank?

Am I interpreting this correctly?

Why wouldn't we design a smarter control system to lockout the grid and still use solar without needing the generator, say at night, with no solar or battery storage?

I understand the frequency shifting with the load (and the source)...but a smarter system should be in design by now.
Most solar set-ups do not have expensive batteries. If you have a battery set-up you can use solar during a power outage.
 

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Just trying to get home
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Hmmm...that makes sense. I guess I was assuming there was a battery setup there, like boondocking in an RV to ride through the passing clouds.
 

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The Accidental Welder
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Does anyone know a good place to order warning labels for the meter and panel stating there are three sources of power onsite? (Utility, PV, and portable generator). I know the inspector for that town always looks for the appropriate warning label and I didn’t see any great options when I did a quick google search.

I order mine online here:
https://www.myengravedsign.com/


Oh, and don't forget the extra one at the meter.
 

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