# Question about wiring for Solar



## titiana (Sep 17, 2009)

I recently purchased a house, it's about 1200 sq foot, plus a attic and basement. I'm currently remodeling. House was built in 1900 +/-, so some parts are insulated, some aren't and who ever wired it :run:  (does have heat and running water, flushing toliets, and all that good stuff :thumbSo I have the downstairs to completely gut and insulate and I have to rewire the entire house. 

So in the future (goal to be self-sufficient) I want to place solar panels. Would love to start small in the next year or two. 

So before I wire the entire house, is there anything I should know about or do to prepare for solar?? Can I use standard wiring or do I need to put in something different? 

Thank you so much.


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## cowboy joe (Sep 14, 2003)

Here is a link to what inspectors might be looking for:

http://www.irecusa.org/fileadmin/user_upload/NationalOutreachPubs/InspectorGuidelines-Version2.1.pdf

http://www.solarsebastopol.com/PDFs/INSPECTOR_CHECKLIST_5-05__1.pdf

Please realize that most inspectors are not experienced when it comes to PV systems so the more documentation you have, the better.

NEC 690 includes all the requirements for a PV system. Full copies of the standard have to be purchased but you should be able to find related articles and breakdowns of each section on the internet.

In a nutshell, AC components (breakers, fuses, switches, etc) do not meet code for a PV system which is DC. Sadly, marine & automotive components also do not meet the strictest letter of the code. Improperly rated items are the easiest for inspectors to pick up on as the ratings must be visible or available via cut sheet. 

There are very few items that have both an AC & DC rating so plan on switching out many items if you try to convert from an AC system over to DC. IMO, you may be better off installing at least part of the PV system upfront rather than having to redo a lot of work later on.


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## TnAndy (Sep 15, 2005)

A lot depends on HOW you plan to use your solar.

1. Say you plan to grid tie it only...this is the most simple way to use it as far as your house re-wire goes.....all you need to do is leave a couple spaces in a breaker box to connect in the power from the inverter(s) off the solar to come later....and you can re-wire the house in the conventional way from there.

2. Grid tie with a battery backup, so if the grid power is down, you still have power. More complex, but during a re-wire is THE time to do this. You need to separate out certain house circuits that you consider critical ( say like the refrigerator, lighting, etc) and put those in a separate sub panel, then have a transfer switch wired so IF grid power goes down, you can switch ( auto or manually ) the transfer switch and those circuits in the subpanel will be the only ones that run....you won't be able to run the entire house unless you plan to put in a huge, and expensive, solar power system. This type re-wire would be exactly the same as if you were going to put in an emergency generator, with only the source of the emergency power being different, so any competent electrician should be up to the task. This has nothing to do with the wiring requirements for the solar power to come later, which are a whole different ball game, but don't really have anything to do with your current re-wire.

3. You could plan use the solar in a lower voltage DC manner.....like 12v.....instead of inverting it to 120/240AC as in the above two instances. This would require you running separate DC wiring, and a separate DC distribution panel, for the house, so you have 120AC and 12vDC receptacles side by side in places in the house, allowing you to use, for example, 12vDC appliances in the kitchen. This would be the most complex way to run an electrical system in your house, and describing all you'd need would be well beyond what I could tell you on a forum like this, other than it can be done....you're REALLY gonna have to learn electricity, codes, equipment, etc, or find someone that does......both are electricity, but they are two WAY different animals in about every other respect. Most electricians will not even have any idea how to do this right off the top of their heads.


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## Jim-mi (May 15, 2002)

In this day and age your better off wiring your house to code for 120/240 AC only.
At the breaker box keep the circuits well marked so that you can break out any circuits that you want dedicated to a separate AC source (Inverter-generator) when that happens.


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## titiana (Sep 17, 2009)

Jim-mi said:


> In this day and age your better off wiring your house to code for 120/240 AC only.
> At the breaker box keep the circuits well marked so that you can break out any circuits that you want dedicated to a separate AC source (Inverter-generator) when that happens.



So I can just wire my house for grid power and then as I add solar panels I can just take it from the breaker and wire it to the inverter for solar power. Is that correct???


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## greif (May 31, 2009)

if you want them on the roof run conduint up thruogh the walls into the attic then later you can just pass wires through to basement


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## roachhill (Jul 8, 2009)

No, I think the question no one has asked is are you planning on using the DC electricity that you get from solar panels or do you intend to invert it to 120 AC power as is used in most houses? If your planning to use DC it requires it's own wiring. If you plan to use regular AC power you can use standard wiring. You use the solar panels to charge batteries then use the batteries to power an inverter. The inverter output is standard 120 AC power and can be fed directly into your breaker panel in place of grid power (not in addition to).
The first thing you should do is buy The New Solar Electric Home it's the only book on solar power I've read so far that I would recommend. It should answer most of your questions.


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## Jim-mi (May 15, 2002)

The inverter would go to a second breaker box that contains your "dedicated" circuits . . . . .in other words the 'what ever' you choose to power with the inverter.

Thats why you do a very good job marking each circuit . . so that as you build your PV system you can then switch circuits from box to box . .
Another option is a pricy transfer switch........thats another story......

In days not so long ago it made some sense to wire for DC but not nearly so today. (let alone the cost of copper wire) Today there is a good range of sine wave inverters . . . .to better power every thing. 


Any body "not to sure about wiring" would be advised to seek some pro help . . . . .worth it in the long run.


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## roachhill (Jul 8, 2009)

I'm planning a DC off grid solar system myself if your near enough to PA to attend the campout at the Chapman State Park this summer I 'd be happy to compare notes. Not that I'm an expert by any means. Hopefully someone else will show up that knows what they are doing and can give better info.


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## SolarGary (Sep 8, 2005)

Hi,
As Andy says a it depends a lot on what kind of system you put in.
We put in this microinverter based grid-tie system:
http://www.builditsolar.com/Projects/PV/EnphasePV/Main.htm
See the page on wiring: http://www.builditsolar.com/Projects/PV/EnphasePV/Wiring.htm for the details -- its really simple.

If you were going to use this kind of system, which is good from the point of view of starting small and growing, then I'd do this in the rewire:
- Decide where the PV panels would go (good south exposure etc).
- Decide on where where the AC disconnect for the system is going to be. Usually you want this near the utility meter. 
- Provide a dedicated AC breaker in the breaker panel for PV, and then make a run from this breaker to the AC disconnect. This is a good thing to do in the rewire when things are torn up, since this wire will probably need to go through the house to get from breaker panel to AC disconnect.

I think that they would let you install the AC disconnect to terminate the wire in. You can then add the PV panel to disconnect wiring when you install the PV system. Usually this wire will be outside the house, so does not matter when you do it.

Going to efficient lighting and efficient appliances will save greatly on your eventual PV system size, so I'd give that some thought during the rewire as well. Efficiency = cheap PV = expensive.

Gary


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## 12vman (Feb 17, 2004)

My question would be..
Are you planning to live in this house the rest of your life or do you plan to sell in the future?

My house is totally against all codes but I know what I'm doing and I plan on croaking here. I couldn't care less about silly codes as long as things work in a safe manner. I have no thought of selling and if I did, I'm not expecting any huge profit. The value of the land alone would satisfy me.


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## roachhill (Jul 8, 2009)

I'm with 12vman but I agree with Jim-mi if you have a house already wired for AC and you want full featured house it would make the most sense to use an inverter and stick with AC power. Everybody has a different goal so it's not a one system fits all sort of answer. I'd still recommend the book it cover grid tied, off grid, AC and DC systems. Once you can identify exactly what you want you can develop a plan to get there.
Hey 12vman any chance your close enough to the PA border to make it to the campout at Chapman State Forest. I'd love to here more about your system. If you make it I'll see about bringing along an extra steak from our farm here to throw on the grill for you. Fair pay for picking your brain.


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## 12vman (Feb 17, 2004)

I agree.. If the house already has A.C. wiring, use it. Inverters are very efficient anymore so the loss factor will be low. 

Low voltage D.C. wiring can be expensive! And, IMO, there isn't any true low voltage codes to go by to satisfy anyone. I'll continue to use my cigar lighter outlets.. LOL

Roachill.. I'm sure I can fix you up. I'm not aware of this campout so fill me in.


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## roachhill (Jul 8, 2009)

Seedspeader has a post up in Countryside Families asking for votes on a best date for the campout. He's planning it at Chapman State forest which appears to be along the north edge of PA on the west side of the state. No other details yet. I was planning to have a campout at my place this summer for HT forum members but now that would seem redundant.


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## TnAndy (Sep 15, 2005)

roachhill said:


> No, I think the question no one has asked is are you planning on using the DC electricity that you get from solar panels or do you intend to invert it to 120 AC power as is used in most houses?[


Actually, I laid out all 3 ways that solar power can be used in the house, including DC in my post above......and how re-wiring a house is affected by each of the possible ways one would intend to use solar power. 




roachhill said:


> You use solar panels to charge batteries then use the batteries to power an inverter.


ONLY in one type of solar/AC system....that with a battery backup. The vast majority of AC solar systems installed do NOT use batteries....they are grid tie only, and have no backup.....when the grid is down, solar production stops as well. Not an endorsement of that type system over the other, merely a statement of fact....systems without battery backup are far cheaper to install, which probably accounts for their popularity.....less components such as batteries, charge controllers, additional disconnects, heavy wiring from battery, etc.





roachhill said:


> The inverter output is standard 120 AC power and can be fed directly into your breaker panel in place of grid power (not in addition to).




Again, ONLY in the mode of 'grid down' and assuming a battery backup.....Normally, the inverted AC power is fed to the AC breaker panel ALONG WITH grid power....the home uses both at the same time, reducing the amount you purchase from the power company.....or if your solar is producing more than the home is currently consuming, the power company meter will run backwards ( and that varies by location.....not all installs use a bi-directional meter, or buyback power.....different power companies, different rules. )[/QUOTE]


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## roachhill (Jul 8, 2009)

Well the original post said the goal was self sufficiency so I was assuming the ultimate plan was to go off grid. Not necessarily a correct assumption but it seemed safe enough. Feeding power into a grid tied system is not a job for the homeowner so my only recommendation in that case would be to contact a licensed professional and get out the check book. I've noticed lately the Feds and most of the solar installers seem to be pushing the grid tied option. I think the fact that most Americans want convenience above all else would explain the popularity of grid tied systems. Install it, forget it, and use all the power you want. Being your own power company requires owner involvement and willingness to learn.


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## TnAndy (Sep 15, 2005)

Feeding power back to the grid is a far more simple process than running a totally off grid system. You simply connect the panels to an inverter, then to an AC disconnect, then into a breaker on your panel. Though many people aren't comfortable ( or allowed in some areas by code ) working with ANY electricity, it's not that complex.

An off grid system requires additional components such as charge controller(s), a DC disconnect on either side of the CC, additional wiring calculations for high amperage, load voltage loads, all kinds of choices in batteries ( and their maintenance ), heavy wiring from the battery bank to a LARGE DC fusing between the bank and the inverter, or a DC distribution system if going totally DC, and so on. YES, an education here is a definite.....and most electricians won't even have the necessary skills to set it up or maintain it.
I got NABCEP entry level certified while setting mine up.


Grid tie is actually a good way to go for most solar installs.....you use the grid as your storage medium even IF you have battery backup, by backfeeding to the grid.

In many cases, it makes good economic sense to do this as well....for example, our power supplier ( TVA ) charges us 9 cents per KwHr for power we buy, and pays us 21 cents per hour for all the solar we produce ( separate meters ) and throws in $1000 toward equipment costs when we connected. 1,000 bucks isn't much, but it IS a 1,000 bucks 


Here's my grid tied/battery backup system, by the way:

18-175watt Solarworld panels, mounted on two home built single axis powered trackers, 2 MX60's, 24v bank of Absolyte 2v AGM GNP II cells 1200amp/hr, 2-GTFX2524 2500w Outbacks producing 120/240 AC, Trimetric monitor.


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## roachhill (Jul 8, 2009)

Still it depends on your goal for the solar system. If your motivation is environmentalism or dollar saving grid tie is appropriate but if it's the more vague goal of self sufficiency then staying on grid defeats the intended purpose.


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## 12vman (Feb 17, 2004)

Personally I can't see any advantages of going alternative with the umbilical cord still connected. It's either one way or the other in my mind.

Jim-mi has the right idea if the zoning godz are out and around. In that case, one doesn't have any option then to appease them. It isn't going to cost a whole lot to wire a 1200 sq. ft. dwelling for a.c. A 100 amp service would suffice if no 220 volt appliances were being used or planned for. Install a propane or gas h/w tank with a gas range and furnace. This would be a benefit if the goal was to be totally off grid in the future. There wouldn't be any need for a larger power service with a solar powered system, IMO..


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## roachhill (Jul 8, 2009)

Amen Brother, I went to an alternative energy/ energy efficiency gathering on Saturday and I noticed the government and all the solar installer companies are now pushing grid tied systems. They are actively preaching against going off grid. Heaven forbid your not beholden to the power company for the rest of your life.


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## gusty60 (Jan 18, 2010)

Solar heating and hot water is also a great way to save money and be less dependent on the grid.


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## TnAndy (Sep 15, 2005)

roachhill said:


> Amen Brother, I went to an alternative energy/ energy efficiency gathering on Saturday and I noticed the government and all the solar installer companies are now pushing grid tied systems. They are actively preaching against going off grid.


I believe it has more to do with cost than a conspiracy to make us slaves to the power company. The cost of a battery system is much higher than the cost of a grid tie only system, and even the cost of a GTO system is enough to make most people choke. The lower they can keep the initial costs, the more folks that will install some solar. Given the current costs of solar, I suspect it's never going to be more than a tiny, novelty source of power production.....I rather doubt the solar industry has the utility companies too worried. Our local power system has 75,000 customers....and last I knew of, there were 5 of us doing solar.....what fraction of 1% is that ?

If you REALLY want to "stick it to the man", install a system big enough to generate all your own + a bunch, and have them send YOU a check.....that's my plan !




roachhill said:


> Heaven forbid your not beholden to the power company for the rest of your life.



Fact of the matter is, NOBODY is 100% self sufficient.....or probably even close.....heck, Laura Engles Little House on the Prairie wasn't 100% "off grid".....they still shopped at the general store. 

Every off grid person I know of uses propane ( and is beholden to the propane company ), or some type of liquid petroleum fuels for their vehicles/chainsaws/heating/etc, ( and is thus beholden to the oil companies ) and buys at least some basic supplies such as sugar/salt/etc, ( and thus is beholden to whoever sells those ), their internet access is supplied by someone else, and so on and so on.

I totally understand the desire to be MORE self sufficient.....we raise way more than 1/2 what we eat ( virtually ALL our meat proteins )....our heating fuel comes from our own timber.....same timber that built my house and every shed/barn/building on the place....( and the labor wasn't hired out either ), our water system is gravity fed spring, sewage is septic system I installed, and so on and so on.

By the same token, I generally avoid cutting my nose off to spite my face....I'll take 21 cents/kwhr for my solar production when they charge me 9 cents for what I buy, secure in the knowledge that my system was set up so IF the grid goes away, I have enough capacity to have a shot at producing at least enough energy to keep me somewhere in the mid-20th century....some lighting, some refrigeration, and an electric clothes washing machine....the rest of what we use over our production is what I consider convenience/entertainment.....things like microwave, or TV, etc....that IF it comes to NO GRID, I won't miss them. Who wants a TV picture of just snow ?


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## roachhill (Jul 8, 2009)

I don't know where your at but our electric company pays 1 cent a kwhr which is clearly just a token payment. The cost of grid tied systems is more reasonable because both the Federal and State government subsidize it. Also the Feds are requiring the electric company to produce a certain percentage of their power through environmentally friendly means or by credits from someone who does. So in yet another way the Feds are subsidizing grid tied systems. It's obvious by there actions they are discouraging off grid systems and encouraging grid tied systems. Not an argument just an observation.


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## TnAndy (Sep 15, 2005)

I'm in Tennessee (the Tn part of TnAndy ) and we're on the TVA system.

Federal law requires utilities to buy back power for at LEAST wholesale generation costs, which though well under retail, is well over 1 cent.

As to the Feds subsidizing solar, I assume you mean the 30% tax credit. From my reading of the tax code, and my tax guy's concurrence, the credit is available on or off grid.....grid tie isn't mentioned. Have no idea about State tax subsidies, as Tennessee doesn't have one for homeowners ( nor do we have an income tax )


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## Jim-mi (May 15, 2002)

TnAndy is fortunate to be getting his stated deal--9 out &21 in.
Here in Mich. we finally got net metering --9 in & 9 out. . . . . whoopee doo......

With the old style meter I did have net in/out........
bills of zero . . . . . . . .those were the days.....

The >"fancy"< meter now does not allow that. . . . .sigh....

Yes the "new guys" on the block are touting grid tied . . . . much easier.

I'm from the old school "with batterys" . . . . . . .I like it that way.

When and if the grid goes down for a who knows how long period . . .I will still have power for my well pump, lights fridg's and freezers, tools, etc. etc.


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