Solar Roof

http://al.howardknight.net/msgid.cgi?ID 9514290700
Does he know that most grid tie inverters will NOT function without the grid.
What that means in practical terms, he cannot use the electricity from solar during a power failure.
I think that is a travesty and the rules re inverter designs should be changed.
Right now this behavior is REQUIRED by the rules to prevent the possibility of backfeeding power to a dead power line.
At the time I wrote the post, I was not aware of any configuration changes in the clients setup. IE: As far as I was aware, they did not have a battery bank and were still using my modbox. My information wasn't accurate. Simple as that.
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On Thursday, May 18, 2017 at 8:09:26 PM UTC-4, Diesel wrote:

IDK what "rules" you're referring to. As I and Mike have pointed out over and over the fundamental problem with using solar to power a house without the grid and without batteries is the SUN. What happens to all the appliances, motors, etc when a cloud passes? How many customers are willing to put up with brownouts or total drop of power when clouds pass by, on a cloudy day, no power at night when you typically need it the most, etc?

That issue is certainly the most common issues that solar companies frequently cite when asked why it won't work without the grid. But I've provided you cites that also include the insurmountable problem outlined above. I suspect most solar companies go with the disconnect story because it's simpler and doesn't make solar look bad, but instead uses the safety issue. And you already said that it could be disconnected via an interlock, just like we do with generators. I agree with that, I don't see the isolation thing being the big, insurmountable problem. It's the sun and clouds, the inability to constantly keep up a given power level, without a battery bank, as Mike and I have pointed out.
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You're responding to the wrong individual. I quoted the individuals post, and included MID for you with the apology for having accused you of writing the nonsense.
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I do, but they need to be recharged each night.... ;-)
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Thu, 18 May 2017 01:12:48 GMT in alt.home.repair, wrote:

You're very welcome. Btw, for NEC code purposes, the series wiring is done on the internals of my modbox. In other words, you run both strings to it. And it's #12 for most of the power input side of the system. PV array strings, etc. The voltage is upto 600volts per string, but the amperage is low. The output on the modbox and the battery bank uses much larger wire as it's carrying lower voltage, but, MUCH higher amperage. The output side of the inverter is also a larger capacity wire, but not as large as the output side of the modbox or a battery bank. Since it's being tied into some switch gear (interlocks, disconnects, etc) and eventually winding up at your panel.
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On Tuesday, May 16, 2017 at 8:53:01 PM UTC-4, Diesel wrote:

More gibberish. If they are wired in series and installed that way, then it's a violation, because 600V is the max permitted voltage between any two conductors. If you wired them in series as an experiment, which sounds rather bizarre, then who cares what the voltage is? And we are talking about real residential solar systems, installed to code, not a hack job, are we not?
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Tue,

Are you sure you're an electrical engineer?

It *IS* installed to code, passed inspection just fine. Not a hack job, no. Far too much money spent in equipment alone to justify a half assing installation.
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On Wednesday, May 17, 2017 at 8:50:10 PM UTC-4, Diesel wrote:

It may have passed inspection, but it's not in conformance with NEC code, which almost all jurisdictions use, if it's generating voltages above 600V. What is the compelling reason to go above 600V anyway?
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alt.home.repair, wrote:

That it did.

Using both strings in a series wiring fashion, it can, yes.

Already explained.
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On Thursday, May 18, 2017 at 8:09:26 PM UTC-4, Diesel wrote:

Doh! A few posts ago, in series it was generating 1200V, now it takes using both strings in series to get to 600V. Pretty soon we'll be down to 120V.

I guess I missed that and it's too much to say it here? Reading what Mike was saying, I suspect the answer was that the miracle mod box required it? That the same amount of power supplied at the normal much lower voltage from the solar array just isn't good enough? Tell us why.

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Thu, 18 May 2017 14:41:11 GMT in

Hmm. You might wanna take a refresher course in english comprehension. Using both strings, it can easily exceed 600volts. Close to 1200, actually. Each string is capable of generating nearly 600 volts on it's own, and, I've never claimed differently.

I guess you should consider accessing usenet via a real client.
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On Friday, May 19, 2017 at 6:08:59 PM UTC-4, Diesel wrote:

You might want to take a refresher course in keeping your story straight. You just confirmed again exactly what I posted above.

Typical, now trying to start a diversion into what is totally irrelevant.
Still waiting for some simple answers that the designer of a "mod box" should have been able to answer instantly.
1 - Give us the specs for the caps that you say are used as part of a design to "emulate" a battery bank. How large are they?
2 - Why would anyone design a "mod box" using caps instead of just using a battery bank? No batteries in TN? And why would any real, reputable solar company have one of it's employees hacking around, building special gear to install at a customer site instead of just using a very simple battery bank, which the Conext install manual clearly says must be used? And note that the battery bank could also provide power when there is no sun too.
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I'm loosing faith in Usenet.
This is one of the few threads in AHR that is on topic.
AHR is being attacked by spam.
You both are knowledgeable guys so lets end the pissing context and try to help some newbies.
Else this newsgroup is going to die.
m
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On Monday, May 22, 2017 at 9:16:59 AM UTC-4, snipped-for-privacy@yahoo.com wrote:

I don't see the relevance to your comment. What is or isn't going on in this on-topic thread has nothing to do with the new spam and I have been responding to other legitimate posts. Actually, if you're paying attention, the sudden increase started with the arrival of certain posters, who brought some "friends" with them. I agree that it's under attack, that it's probably finished, but IDK how to solve it. Someone suggested creating a moderated group.
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On 5/22/2017 12:15 PM, trader_4 wrote:

I don't like the idea of moderation. Sadly, this group has a lot of crap now. I do find that putting a half dozen posters in the bozo bin gets rid of a lot of the nonsense. Just added another this morning. Ignoring them may help.
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Tue, 23 May 2017 16:02:18 GMT in alt.home.repair, wrote:

NewsProxy. <G>
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right, I'm saying this thread is NOT spam, and is on topic...
So lets keep it civil even if we have disagreements.
My point being, if we can't keep the on topic threads between knowledgeable folks civil, we have no chance against the spam.
m
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On 5/16/2017 3:25 AM, Diesel wrote:

You don't have a commercial installation. You have a bunch of auction acquired stuff cobbled together to make something that works for you. Nothing wrong with a hobby project; I do it all the time. But that's not something you can do with a commercial installation. For general use, you'll find your customers more demanding.
You've described a situation where you have grid tie. You have decided that you can tolerate a 30-second loss of power when the grid is down. You replaced battery storage with diesel LOCAL storage and a generator to convert it to electrical energy. You have not described what happens when the generator is running and the cloud has passed, or the load dropped below what solar can supply, or what happens when a new cloud arrives.
Take a look at the curve here: https://www.wholesalesolar.com/solar-information/solar-panel-efficiency
When solar becomes insufficient, the operating point is past the knee of the curve. Small changes in load current can change the voltage dramatically. If the refrigerator starts, the current surge can drop the voltage below your threshold and shut down your system. That lets the panel voltage rise above the threshold. What do you do? With the grid down and insolation low, you will see a lot of those cycles. They can happen way short of 30 seconds apart. They'll probably happen every time you turn on the electric stove or air conditioner when insolation is low. Do you start the generator? Do you let the fridge try to restart every few seconds?
Engineering is a process of defining a problem and providing a ROBUST solution that meets the needs of your entire customer base. Sure, you can restrict your customer base to those who want a generator in their back yard and tolerate limit-cycle oscillations in their utility supply. A commercial supplier cannot do that.
Engineering is a process of recognizing, meticulously defining a problem and solving it. You must predict and evaluate the performance of your solution for situations at the limit that most people would not even consider. It requires empathy, putting yourself in the shoes of your target audience. That's something sorely lacking in the engineering community. It's almost non-existent in the newsgroups where everybody talks, few listen and even fewer have a clue. You can't just look at the 10KW on the label and assume it's all good. It ain't.
Many people reading this will conclude that they could tolerate your solution. People over in that other group posting pictures of their cat would find it totally unacceptable. There are way more of them than us.
In summary... You evaded the issues. You DO have grid tie. You DO have local storage, just not batteries. You tolerate interruptions that many would find acceptable in a system that cost them big bux.
Nothing that you have said debunks my assertion that widespread use of rooftop solar without local storage is a fool's errand. Nothing wrong with a hobby project. It's just not a solution for the masses.
One thing that just occurred to me. How does rooftop solar deal with 240V appliances in locations. where 2X 120VAC is the norm, like the USA. Seems like a huge complication to generate two separate 120VAC outputs and try to figure out how to load share a house designed with the ability to use either phase indiscriminately. But, if you don't, the clothes dryer or electric stove won't work. Converting water heating, HVAC, clothes dryer, etc, from electric to gas is not feasible for existing houses.
The hobby project rolling around in my mind would consist of about 17 RV batteries in series. Or maybe an electric car battery. Buck convert it to 170VDC and use that to create 120VAC. Problem is that neutral not directly connected to ground probably violates all manner of safety codes. Existing inverters have solved that problem. On the input side, panel voltage set to something near max battery voltage (~250VDC) at max insolation. MPPT buck/boost controller to charge batteries. May also want a second buck controller to bypass the batteries and feed the 170VDC directly when insolation and load are high. The objective is to keep voltages as high as possible everywhere to minimize current-related efficiency losses.
Depending on usage patterns, it may be cost effective to dump excess back into the grid, but that's not the objective here. The objective is to create a scalable solution to unload the grid without destabilizing their generation and pricing models.
There are lotsa gotchas in the above concept that need to be addressed. That's the fun of engineering. With the 60' trees all around me, the project will never get past the fantasy stage.
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May 2017 21:21:11 GMT in alt.home.repair, wrote:

I don't have ANY installation, myself. But, the client does. I shared pics previously of some aspects to its installation. The pics were originally taken for 'promotional' purposes: advertising for one of the companies I work for. I was provided copies.

No, I do not. The home owner doesn't either. The panels, inverter, wiring, etc (except for my 'modbox') are sourced from actual companies, directly purchased from them and/or authorized resellers. Nothing from auction, ebay, etc. Installed by properly licensed electricians. We aren't jake legs.

It wasn't a hobby project...And wasn't my customer, either. I don't own the company I did the work for.

To reduce the clients electrical bill, yes.

I didn't make any of the executive decisions. The client made that decision.

Well, as I said, the generator comes online if no power is detected on the mains, for 30 seconds. As long as the PV array is up, and my box was working (or the battery bank now), that doesn't happen, so, the generator doesn't run. The generator is propane, btw. Not Diesel.

Sorry, I thought some of this was self explanatory. It would be to most other electricians I know. I'll humour you though.
It's done by a few automatic interlock switches. If it detects a load present from the grid and/or inverter for more than a preset amount of time, it disconnects the generator and re-establishes connection to the inverter and/or grid, depending on which unit has resumed providing power. IF the power remains 'stable' for a preset period of time after switch over, the generator is shut down. This prevents unncessary switching and gen shutdown/restart when the power grid and/or inverter is trying to come back up, but continues to fall back out.
The inverter has one, the generator has one, too. And, of course, the inverter has a manual switch that the home owner can access which will disconnect it from the grid, whenever they want. I personally wouldn't, since when it's up and running, it's able to save him a power bill, but, that's his decision to make, not mine.

If the refrigerator starts? Well, you see, the problem with your question is this:
It's a propane driven refrigerator. It *DOES* have a small battery to provide power to the internal LED lighting, though. But, that doesn't have anything whatsoever to do with the panel in the house. Infact, it doesn't use *any* power from the house. Not a bit. No way to plug it in, infact.

No, they don't.

Again, no. The stove isn't electric. It's propane, too.

The air conditioner is propane, too. As is the heating system. They do require a small amount of electrical energy to run blowers, but, it doesn't put the drain on the panel you seem to be expecting it to. They have very efficient motors for that...so, you don't even see the lights dim for a second when one switches on.

The fridge is a self contained unit, that has a gas line fed to it. It doesn't make use of household power and could care less if power is even available to the house. It doesn't even need to be plugged in for ignition purposes.

I don't know what they can tolerate or not tolerate. This system along with the house, etc, was custom built to the home owners specifications. They wanted it done this way, they got what they wanted. Would I personally do this myself? No.
I like the grid and all it affords. I'd require a hell of alot more electrical power than he needs to run my computer lab, let alone my work shop, or the house itself. (The shop and house are seperate buildings). It would cost me a fortune, even with the people I know and access to materials I have to be able to harness enough 'sunlight' to power my stuff. I'd have to factor in additional power for my welding equipment, tube benders, etc in the shop.
They aren't exactly gentle when it comes to electrical power consumption. Neither is my computer network for that matter. it wasn't built with tree huggers in mind. It's very kilowatt friendly. And, NONE of my appliances are so called 'off grid' ones. They ALL use electricity. I have gas and electric heat, and, I'm not willing to give up my electric comfy heat.
Then there's battery/generator maintance, additional costs in safe wiring for the interlocks, etc. I see no real benefit to this for my situation. I don't want to live 'off grid'; been there and done that when I was alot younger than I am now. Fuck that shit, I like creature comforts and modern technology and I'm not nearly as financially 'fuck it all' as the client is. I've got enough tied up in nearly instant on emergency power for this place as it is. And, I only need that because of the computer equipment here. Some of it MUST be able to function 24/7/365 days a year. UPS ensures computers remain online and okay while the backup power switches online, in case you were wondering, in MY house configuration. While there is a small delay in generator coming online for me as well, there's NO waiting for power to resume for these machines; they *never* noticed power dropped out.
And, my generators are more than adequate to run my entire property, at full power if I wanted to do so; without lag, hesitation or strain on them. I planned ahead. Overkill, according to some, but, more amps than you need is ALWAYS better than not enough.
I don't mind electricity at all, but, I have this unreasonable fear personally about gas. I don't like the idea of an explosion.

I recently found the other newsgroup, myself. I was keeping tabs on someone who's dead set on stalking me and punishing me for what he feels are wrongs against him. But, heh, he initiated the problem with me, he's simply bitten off more than he can chew.

This should be fun.

I've evaded nothing of the sort.

I'm personally tied to the grid, yes.

Last time I checked, generators didn't store power. I have generators, no batteries here. You're confusing me for the client. They have both.

The client tolerates an interruption in power, yes. I do not.

It's not a hobby project.

Do you think the inverter is tied into a single leg? :) Think again. It's a 240volt AC output device.

The house was built new with the intention of using gas appliances. So...

That's an issue the client and myself, don't have. OTH, I do have a huge dust problem here. I've planted some grass seeds recently though, so I'm hoping that will become an issue of the past.
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On Tuesday, May 16, 2017 at 5:22:41 PM UTC-4, mike wrote:

Even residential customers can't. So far, Diesel hasn't provided us with examples from all the solar installers that offer a residential grid-tied system that also supplies power to the house when the grid is down, without a battery bank. If this was possible, practical, it would be a powerful selling point. But it isn't, with the cloud problem, the rainy day problem, etc, being the major, insurmountable problem. Like you say, customers aren't going to tolerate brown outs, total outages, from passing clouds. And during a power outage, when do you need power the most? Typically at night, when the sun isn't shining. That's why you don't see installs that offer power without the grid or batteries.
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