# how is net metering safe for utility workers?



## ace admirer (Oct 5, 2005)

so i agree with backfeeding your house from a large two pole breaker in a panel without a transfer switch is unsafe if someone makes a mistake.....

but how is the safety "problem" handled with solar systems that feed (net metering) the grid instead of using batteries? is there some type of automatic disconnect if the grid goes down? might anyone have net available information or a model of the actual safety device?

Thanks Fellows


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## farminghandyman (Mar 4, 2005)

the approved inverter has to meet a standard for electrical quality and disconnect proprieties, 

if the inverter does not meet UL and possibly some other agencies approval, and usually a IEEE Standard, or a series of them, most power companies will not allow you to connect,
some power company's require a large liability insurance policy as well,

the only way to actuly know is to contact your local power company and see the requiirments are for you to connect to the grid,

MY local power companys policy of grid tie power systems.


> The installation shall meet the requirements of the Institute of Electrical and Electronics Engineers (IEEE) 1547 &#8220;Standard for Interconnecting Distributed Resources with Electric Power Systems,&#8221; requirements of the National Electrical Code (ANSI/NFPA 70) latest edition, requirements of the National Electrical Safety Code (IEEE C2) latest edition, requirements of the State, requirements of the local municipality and the requirements of XXXXXX engineering department. The member shall certify that these requirements have been met and shall provide an electrical inspection by an inspector from the XXXXXX list of inspection agencies.


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## PD-Riverman (May 24, 2007)

To answer your question with a simple answer----If the grid goes down your grid tie system is set-up to disconnect from the grid automatically.



ace admirer said:


> so i agree with backfeeding your house from a large two pole breaker in a panel without a transfer switch is unsafe if someone makes a mistake.....
> 
> but how is the safety "problem" handled with solar systems that feed (net metering) the grid instead of using batteries? is there some type of automatic disconnect if the grid goes down? might anyone have net available information or a model of the actual safety device?
> 
> Thanks Fellows


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## TnAndy (Sep 15, 2005)

farminghandyman said:


> the approved inverter has to meet a standard for electrical quality and disconnect proprieties....


UL 1741, specifically. 

The inverter has to sense grid power, and shut down if grid power isn't on the output side. Without grid power, grid tie ONLY inverters are useless.

Interesting thing about grid tie with battery backup type inverters ( like Outback makes ), is when the grid contacts open, another set of contacts close, allowing you to continue to operate off solar with a separate set of wiring and appropriate transfer switching.....that's the way I set my system up.

Main panel is the white cover to left.....subpanel in the center runs with grid, or with solar only, depending on how the transfer switch ( far right ) is flipped.


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## DanielY (Aug 25, 2011)

If you are grid tied and the grid goes down when the sun is down. you lose power just like everyone else. The grid is basically your battery. Otherwise there is no more danger is a properly installed system than what you live with now. power is power. Now monkey around not knowing what you are doing and there can be problems. This is why the power company requires that the system pass an inspection. It reduces systems that where built by someone that "Thought" they knew what they where doing. You can do all the work yourself and then just have a final inspection done. Might want to find the electrician that will agree to that before you start though.


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## ace admirer (Oct 5, 2005)

Soooo.....the device that automatically disconnects the grid from net metering system is internal to the inverter itself.

other than outback can someone refer me to other brands of switch gear.

Thanks Fellows.


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## ace admirer (Oct 5, 2005)

I'm not sure i am explaining my request for information correctly.

its a sonny bright day. My family is at jobs and kids at school. my home solar panels are feeding power INTO the Grid. a car hits an electric pole a 1/4 mile down the line severing utility ties to my home/system. WITHOUT an AUTOMATIC disconnect system, my hourse is still feeding power INTO the downed feed to the break in utility lines. There HAS(?) to be an AUTOMATIC(?) disconnect point to prevent my system feeding the downed lines.....i would think anyway......if so is there specially equiped inverter or the device that does this..(one poster says yes its is the special inverter)..if so can someone give me model numbers of such an inverter or otherwise the automatic sdevice that will accomplish the disconnect?

Thanks Fellows


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## Wanderer (Aug 22, 2011)

You want one with an integrated automatic disconnect. Look at this one:
http://shop.solardirect.com/product...=1036&osCsid=b22b3c7241d2e1d7be334dc93af4b7ea


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## trkarl (Dec 15, 2009)

TnAndy said:


> UL 1741, specifically.
> 
> Without grid power, grid tie ONLY inverters are useless.


That is not entirely true. Some SMA grid tie only inverters, some of the SunnyBoy models, when used in conjunction with the Sunny Island battery based inverters, are able to continue to produce power in a grid down situation. Basically the Sunny Island performs the UL 1741 spec instead of the Sunny Boy when used together and programmed to do so.

A friend of mine has a 10.2 kw setup with 2 grid tie Sunny Boy 5000 inverters and 2 Sunny Island 5048u inverters. When the power goes out it works flawlessly.

But if all you have are grid tie only inverters then yes you are pretty much sol when the grid goes down.


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## wy_white_wolf (Oct 14, 2004)

ace admirer said:


> I'm not sure i am explaining my request for information correctly.
> 
> its a sonny bright day. My family is at jobs and kids at school. my home solar panels are feeding power INTO the Grid. a car hits an electric pole a 1/4 mile down the line severing utility ties to my home/system. WITHOUT an AUTOMATIC disconnect system, my hourse is still feeding power INTO the downed feed to the break in utility lines. There HAS(?) to be an AUTOMATIC(?) disconnect point to prevent my system feeding the downed lines.....i would think anyway......if so is there specially equiped inverter or the device that does this..(one poster says yes its is the special inverter)..if so can someone give me model numbers of such an inverter or otherwise the automatic sdevice that will accomplish the disconnect?
> 
> Thanks Fellows




Net metering really has nothing to do with it.

What your asking about is called anti-islanding. UL-1741 requires grid-tie inverters to have anti-islanding built into them. Basicly it's an internal switch that shuts them down when there is no longer grid power supplied to them. One could think about it alone the lines of the exciter on an alternater. It will quit producing power if the exciter is no longer supplied power. To find such an inverter you only need to find one that is UL-1741 compliant.

WWW


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## ace admirer (Oct 5, 2005)

Please explain, is there another reason to be tied to the utility grid if i were not net metering?

Thanks Fellows for the information


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## Bluesgal (Jun 17, 2011)

ace admirer said:


> Please explain, is there another reason to be tied to the utility grid if i were not net metering?
> 
> Thanks Fellows for the information


Then unless you had sufficient batteries you would have no power at night, the grid provides nighttime power and you "net" with the power produced during the day.


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## Jim-mi (May 15, 2002)

trkarl; . . go ask your friend with the Sonny Islands about the $$$$$$ he has invested in that system . . . . . .????

That is a great way to go if your pockets are deep . . . . . . . . .

I get the feeling that the OP person would not go that kind of $$$$$

The same can be done with a couple Outbacks----IF YOU KNOW WHAT YOUR DOING-----------


By being tied to the grid is an easy way to keep your battery bank topped off when the sun and wind are hideing.

Those who think they are going to make money from being grid tied only have not done their math properly......

Folks like TnAndy have the best of both . . . . . . .reducing their grid bill . ..AND . . .electrical power when the grid goes away..........

But get to know them before you ask for the $$$$ investment......

I don't care to put a price tag 'here' about my investment........


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## ace admirer (Oct 5, 2005)

ok let me try again.....

would my solar system be backfeeding the utility in any way if i were not net metering?

if so how?

i dont see how unless i would be back feeding as if i were running a generator and did not disconnect the main breaker...

if i am using an inverter that feeds from batteries until low batt then acting as a load pulling power from the grid to charge....there is no chance of back feeding is there?

is there any way that a properly installed system feeds into the utility grid unless it is designed for net metering?

and isn't net metering all about using grid at night? what other purpose is there for net metering on a home sized system? sell if possible during daylight,,,purchase during night? the only monetary advantage is not haveing to purchase and maintain a battery bank....

i am asking for educational reasons only. i have no horse in this race,,,,i just need correct information.


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## trkarl (Dec 15, 2009)

Jim-mi -
He has a HUGE investment in the system. I know what he paid for it. I helped him with the system before the install. And unless electricity rates skyrocket ( gee where have I heard that before) he will never get it back. Just like me I will never get it back as far as investment is concerned at todays rate but I never built the system to save money.

I built it as insurance against power outages period. Unfortunately when I built mine grid tie was not allowed where I live. Now it is but I would have to jump through all kinds of hoops just to get approved which I won't do. For me it's all about self sufficiency as much as possible.

When the power goes out in my neighborhood mine never does. I don't need the grid to survive. It is a luxury I like however.

As far as making money on solar you are correct. That is the first question most people ask me when they see my setup. Then they say it's not worth it. I always reply that people spend way more on all kinds of junk toys and expensive vacations that they never get their money back. 

One thing about my friends system is during nice sunny days he produces over 60 kwhrs of power from it. I wish mine could do that. I think our biggest usage days run up in the mid thirties and that is when DW is running the clothes drier all day. 

The most I've ever produced from mine is 25 kwhrs. Since my system is totally off grid I had to keep using as much power as I could all day, cooking, vacuuming, tv, computer, etc all day. It's a whole other ball game running and off grid system than a grid tie with back up. You get skilled in using power to it's fullest when it's available. It's kinda fun.


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## TnAndy (Sep 15, 2005)

trkarl said:


> That is not entirely true.


Yeah, actually it is. I specifically said "grid tie ONLY", not grid tie with battery backup. Two different types of inverters.

The inverter you're talking about is a grid tie with battery backup, which IS what I have in my Outback inverters.


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## greg273 (Aug 5, 2003)

Ace, I've got an older model inverter, non-grid tie, so I am no expert. But from what I have read, the newer grid-tie inverters pretty much take care of all that safety switching automatically. For the price, they should...


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## trkarl (Dec 15, 2009)

TnAndy said:


> Yeah, actually it is. I specifically said "grid tie ONLY", not grid tie with battery backup. Two different types of inverters.
> 
> The inverter you're talking about is a grid tie with battery backup, which IS what I have in my Outback inverters.



Well my point is that a Suunyboy, which is a "grid tie ONLY" inverter will work when the grid goes down IF it is paired with a sunny island battery based inverter.


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## wy_white_wolf (Oct 14, 2004)

ace admirer said:


> ok let me try again.....
> 
> would my solar system be backfeeding the utility in any way if i were not net metering?
> 
> if so how?....


Net metering only has to do with how or if you get compensated for any power you may backfeed to the grid. It's only a paper agreement between you and the power company with the basic terms of it set by the state regulation. 

It really has nothing to do with whether your equip can physically backfeed to the grid.

You question is like asking if one can drive a car without insurance. Yes one phyically can drive that car but is only legal to do a few instances. Such as if you never leave your property or post a bond in lew of insurance.

Now yes your equipment can back feed to the grid but it may only be *legal* to do so with a net metering agreement. You would need to find out the laws in your state covering this.


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## ace admirer (Oct 5, 2005)

Let me try this again,,,,
net metering has much more to do with being electrocuted than a paper agreement. a paper agreement does not feed electricity into a grid,,,EQUIPMENT feeds electricity..i am asking a hardware/equipment question only...my question has ONLY to do with backfeeding/safety..PLEASE don't give me advise about if its worth it or what state allows what payment.....its a simple question...its a hardware question ONLY... 

"It really has nothing to do with whether your equip can physically backfeed to the grid."

we cannot be communicating,,,how can one net meter if your system does not physically feed current into the grid?

in the car example above,,,,i am not asking if i can get insurance on a car,,,i am asking how the transmission works.....

I just want a hardware answer, or a net page that can answer my hardware question

can someone guide me to a page that will give me hardward/equipment that is used to net meter,,,,Thank You..


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## Jim-mi (May 15, 2002)

. . ."Net Metering" is strickly a term. . . . . The agrement between you and your local utility.

'Net' means the same $ "in" or "out"
All utilitys have differing amounts of 'payback'

. ."Net Metering" has nothing to do with feeding your self produced power into the grid.

What I think you mean is the little black box that senses when the 'grid' is up and running.
When that little black box (circuit) finds that the grid has gone away it instantly shuts down the inverter. . . . . . . . .

Using an inverter that does not have that circuit ( to back feed the grid) is very illegal.


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## ace admirer (Oct 5, 2005)

thank you


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