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Comment by grecy | Hacker News Reader

So don't backfeed the grid when the grid is "off"

That has nothing to do with powering you own home from you own solar panels.

When the grid-tie inverter senses the grid is down (it could even be scheduled outage for maintenance) - it stops feeding the grid and only powers the house. When it senses the grid is back it ties to the grid again.

If you need to work on the house, there can be a master switch where the panels come into the inverter (law in Australia) so you can manually turn them off, thus ensuring none of the house has power.

Simple.

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The spark for the article, so I understand, is that regulation advocated by FPL made it illegal for homeowners to access that switch. So, in the wake of the hurricane, it was explicitly forbidden for folks with solar systems to power their own homes.

You are describing a rational, reasonable regulatory system. :) Sadly, not the one in force.

That's incorrect. To install a generator, which is legal, you are required to have and to use a manual transfer switch.

I don't know where the full building code which would require this is, but this describes it in part:

> Florida State Generator Law 526.143 > Alternate generated power capacity for motor fuel dispensing facilities

> As of June 1, 2007, all retail outlets selling motor fuel must be able to operate its distribution loading racks using an alternate generated power source ... Installation of appropriate wiring, including a transfer switch shall be performed by a certified electrical contractor.

You can't run loads from cells directly, you need a battery and inverters. Or every cloud will fluctuate the voltage and watts massively and your electronics will fry. In the olden days, flickering incandescent would be fine.

Not exactly accurate. My Dad has a 7kw array grid-tie no battery system in FL.

It has a single emergency outlet that will provide up 1500w when the grid is down. With the power being down last week from Irma it was able to output at least a 1000w load even with heavy overcast. It will off course shut off if it can't provide the attached load.

If you have a solar system for home its going to have an inverter, but most likely no batteries, some inverters can provide emergency power without them.

Batteries obviously work much better for that scenario allowing them to buffer energy. But nearly all grid tie systems installed do not have batteries due to extra cost and maintenance.

Does his system meet code?

If so, it demonstrates that the article is, uh, not well researched.

Yes it was completely done to code. Here is the explanation of his inverter: http://www.smainverted.com/how-to-explain-secure-power-suppl...

The inverter doesn't backfeed for emergency power, it just has a separate output wired to a single outlet for emergency power.

Yeah I linked that page a few days ago (https://news.ycombinator.com/item?id=15247172 ).

But the article would have us believe that it is illegal to use those inverters in Florida.

True but look at the percentage, a smaller setup would have very little useable load

7kw? Amazing! How large is the array? (sq ft) How much did that set him back?

Its half a barn roof, I believe its was around $15k installed.

Main issue I have seen with the law in FL for them is that they are net metered but the power bill can't go negative. So if they produce more than they use the power company doesn't have to pay them for it, also they always get a service charge no matter what. So their power bill ends up being about $20 a month no matter what which is just the service charge.

That's how net metering works for me in Oregon, too - I earn credits by over-producing all summer, and then use some of them up until Jan 1, as they won't roll over year-to-year. As a result I gave power away for free to the grid for several years, but now I have a plug-in hybrid to soak up the surplus.

In Australia 5kw is extremely common (20 250 watt panels) - out of pocket it's ~$5000 AUD.

Now that 280 watt panels are becoming common, up to 7kw is a "standard" install.

But you need three phase to go beyond 5kw if I understand correctly

I think you have to get permission to ensure that not too many people in your immediate area have over 5kw, otherwise the grid in that area might not be able to handle so much being pushed back in without upgrades.

I don't know about three phase.

As the other reply says, it's quite possible to power electronics from the cells (but not directly). What you need to look for are the types of regulators and batteries used in caravans. Of course you cannot connect such a system directly to the grid.

You don't need inverters, strictly speaking. For some applications the battery voltage is just fine.

Except the normal solar inverter can't do this. It doesn't see the grid, it doesn't produce power.

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