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I690.64 (B) (2008 NEC) permits connection "at any distribution equipment on the premises". Can this be a sub-panel at some distance from the service disconnect? Consider a barn with panels on the roof, can I connect (assuming other code conditions are met) to a a breaker panel in the barn, or do I need to bring the PV generated power, via a separate feeder, back to the house where the utility service disconnecting means is located?

There seems to be some ambiguity in the code which speaks of the inverter output being "connected to the load side of the service disconnecting mean" but then that connection can be "at any distribution equipment on the premises" (with some additional conditions). What is the meaning of this phrase "at any distribution ......" and why is it put in the code?

Can panels on the roof of a 9 story building connect via inverters to a breaker sub-panel on the roof, presently used solely to distribute power to the elevator motor? (assuming, of course, that requirements 1-7 of 690.64(B) are met?)
That would be a dramatic saving in costs if a separate new riser for the PV system is not required.
If what they are telling me about the system I am looking at that is true. You just pop a breaker in anywhere and hook it up. The IAEI news had an article that said you should hook up to the opposite end of the panelboard bus as the main connection.
Ensure that the inverter is listed for this type of connection. This means that if the utility cuts out for any reason the inverter cannot operate. Otherwise an automatic disconnect would be required at the service to avoid back feeding the power line. This also means that when the power drops out the solar also drops out. In otherwords the solar does not act as a power backup system and this is typical for the installation as I understand the question.
This is also how it was explained to me. I am seriously thinking about some kind of transfer equipment that would allow me to use my solars in a power failure. I am really surprised they don't offer that as an option. Since you are only transferring a fairly small supply and it could be a manual transfer, I don't see this being that big a deal.
I foresee putting a few critical loads into a small sub panel, with the inverter and transfer equipment integrated there but I don't know if that is actually available.
I still have not had the solar guy over here for that kind of chat.
Solar isn't practical to use during a power failure without a battery bank, which gets very expensive very quickly, and requires fairly frequent battery replacement. The more economical solution is almost certainly to leave the solar panels grid-tied, and install a generator for power failures. The inverters *may* work while the generator is running and save fuel bills; hard to say without more information on the model of generator and details on the interver.

I know my little UPS unit hates my portable generator with a passion, so there's something dirty going on that might not play nicely with the inverter(s).
I have over 600 A/H of battery storage in my golf cart. I would like to figure out how to use that. It is similar to those plans that use your electric car battery to supplement the grid in peak load situations. The trick is finding the appropriate inverter.
The reality is that most of the time our long term power outages are in the summer when you should be getting 14-15 hours of usable sunlight. My fridge will hold overnight if I can get it cold in the daytime. I am also looking at a separate system for the pool pump (all DC) that will keep my pool blue. If I have food, cold beer and the pool is OK what else do you need?
There are inverters available that are specifically not for grid tie. What this means is that you would have to have two separate systems as the non-grid tie type inverter is not compatible to feed the grid meter, it will not sync thus shorting out situations and destroyed equipment possible if tied to the grid.

You will effectively double your cost for little gain.

I also recommend a generator. And the inverter "may" as Steve put it, work while the generator is operating. For small loads I recommend an inverter type generator, often called a low speed generator, where the AC output frequency is created and has nothing to do with the speed of the motor. They save on fuel as the generator can slow right down and save fuel under low and no load situations. This is again as Steve mentioned.

UPS's and generators don't like each other. The UPS sees good AC, switches the load to the generator, the voltage dips as the generator ramps up to accept the load (unless a high speed generator oversized), mean while the UPS sees the voltage dip and removes the load back to it's battery, creating an endless cycle.
I see a generator as being a big cost for little gain too. One more engine that won't get used enough to be reliable when you need it. The last time I had an extended outage (Charley) we survived using inverters running off my car.
To be honest I have been thinking about 2 or 3 systems anyway. The solar contractor says he can work the loopholes so I can get the rebates on everything as long as some of it is grid tied. The collectors are the big thing and he can diddle the numbers to get all of them on the rebate.
I really like the direct drive pool pump idea. That is elegant without complication.
The grid tie part in necessary for the rebates and I would also like a battery system that uses my golf cart for storage and runs the tiki bar fridge and a few outlets.

My real problem at this point is available south facing roof. I may end up with collectors in ground racks.
Then go for it with the dual systems, just ensure there is no way to interconnect accidentally and you will need approval from your power company (at least we do here) if you want a net metering situation and for the grid tie portion. You will need to take care with how you handle the non-grid tie and make sure you program the battery charger correctly for golf cart batteries.

Finally, I would like to offer up my roof for any extra space you may need for south facing (I designed it specifically for panels 15 years ago thinking someday I might be rich or panels would be really cheap but neither have happened). I have even removed the 140 foot tall poplars that provided shading.
I was hoping this had already been done and I could find a listed solution but I do understand the need for real transfer equipment.
Some of the best equipment (costly but worth it in my opinion) I have found is from Outback Power. They manufacture both grid interactive and standalone inverters with a wide range of inputs. They have UL listed built solutions you can almost just hang on the wall. Whta I really like is the wide range the solar to battery chargers can handle, it allows for a build up over time of your system.

Trace and others are acceptable. I use them when there solution is the best fit. Be careful to ensure compatibility, some equipment is positive ground only while other is negative ground, at time poorly documented until you find the installation instructions. The good thing is most companies have the installation instructions online.
Tie all of your panels onto a DC buss. Then hang your battery string off of the DC buss, along with a grid tie and non grid tie inverter.

You will end up with solar to PoCo system, along with an independant system to power up the pool pump and charge your batteries. When the PV panels output more than what the batteries and pump can take, the excess will go to the PoCo. Pump the cool pool water thru heatsinks mounted behind the PV panels to increase their output. A transfer switch to switch on the non grid tie inverter when the PoCo goes away and you are all set.
Since Todd pointed out the solar rebate program is broke I am on my own again so I will be going with a scaled down system.
At this point, if I can pump my pool water and keep my golf cart charged I will be happy. I am probably looking for a 120/240 inverter that runs off of 36v. I assume somebody makes one.
This has really been pushed to the back burner tho.
36 volts is an odd duck. I can not look things up for I am at home and do not want to use up my neighbors generosity in bandwidth. Outback may have a charger that could be set at 36 volts, but I a fairly certain the inverters won't do. I could be pleasantly surprised. You may need to look at a specialty place like Atkinsons. I am unsure if they have anything, but they do engineer things like 3-wire starters for generators.
I wondered about that. I know there is a lot of 36v on ships (old war ships) but that was 400hz.
The reason I chose 36v was that is what my golf cart is and I don't want any extra batteries around if I can avoid it.
If 36 is a non starter, maybe 48 is better. Then it becomes a question, is it cheaper to buy a 36v inverter from some specialty house or convert the golf cart to 48v. (several hundred bucks). The up side of that is you get a very fast/powerful golf cart but I am really not in that big of a hurry.
As I said, when the Fla rebates are not in the picture this is not as important to me so I have time to shop around and see what I can do on the cheap. I assume the feds will still honor their 30% rebate since they don't care if they are out of money.

edit
The top hit on a google search was this
http://www.powercomplete.com/36VoltInverterwithCharger/TrippLiteAPS3636VR.html

I am not exactly sure how I would integrate this into a solar system but, at least, 36v equipment is available.
Originally Posted by sabrown
I recommend an inverter type generator, often called a low speed generator, where the AC output frequency is created and has nothing to do with the speed of the motor. They save on fuel as the generator can slow right down and save fuel under low and no load situations.

How does that work?
Through most of an electricians training, we are taught that the output frequency of an alternator is based upon it's rotational speed, could be 50Hz, could be 60Hz, but the prime mover still has to be moving at a constant speed to achieve that frequency, all the time, not speeding up and slowing down.
Trumpy,
You are correct for the standard generator.

A an inverter generator can use a DC generator (see http://micro.magnet.fsu.edu/electromag/java/generator/dc.html ) or an unregulated AC generator with a full bridge rectifier (half bridge does not make economical sense as you would only get half the available power out). This output is then inverted to AC using a timer for the frequency (same as a stand alone solar inverter).

Yamaha, Kawasaki (I think), and Honda (if they still manufacture there own generators) should have one. I have not looked for one above about 10KVA so I don't know if large ones exist. It seems unlikely as a DC generator, but maybe as the dual conversion AC style. I don't often find myself above the 30KVA size where I am looking at standard generators.

An advantage to these styles is that they can be easily paralleled. One serving as the master providing the frequency for the others to follow.
I am really avoiding getting a generator. That is just one more engine that won't start in an emergency and if the outage lasts for more than a few days fuel becomes a problem.
My friends up in Punta Gorda (ground zero for Charley) called it "feeding the monster". They had to go out on a foraging trip every day looking for an open gas station and hauling cans of gas back to the house. In recent years, more people get killed by generators than by the actual storm.
The other option is a propane powered generator but once you empty that tank you are stuck until the propane supplier comes back around. In a disaster situation, that might be a while.
I found that the economically critical element is pre-existing south-facing collection space.

In my neighborhood only about 1 in 8 homes are suitable.

Lacking this attribute one must accept a great plunge in performance, so much so that the numbers don't work even with the subsidy.

Because of life safety issues none of the current generation of inverters is suitable during outages. Installing a back-up plant just for outages is brutally expensive since it's utility is so low. Our Poco is too reliable to back-up. Way up in the hills, that's another matter.

BTW the nasty weather that leads to outages is normally the type that is a stinker for solar collection, too.

Hence, I'd also recommend using a gen-set.

I get away from using a UPS for my Mac by using a Laptop. UPS is built-in at the factory and the load is so low that any gen-set is untroubled.
I suppose it all depends on where you live and what the weather actually is.
After a hurricane we usually have sunny days for at least a week because it blows all the weather away. (water is cooler etc)
The guy I was talking to was guaranteeing his collector system up to 150 MPH.
I do have the south facing roof on my addition and I put an extra membrane under the shingles to mitigate problems with mounting collectors.
This is not intended as "life safety" just quality of life.
Originally Posted by gfretwell
I am really avoiding getting a generator. That is just one more engine that won't start in an emergency and if the outage lasts for more than a few days fuel becomes a problem.
Despite the drawbacks, it's really hard to beat a generator. It doesn't need to be big- a 3500W gen (15A/240V) will power every light, fridge, computer and TV in the house and still have power to spare. You don't need to run it 24/7 during an extended outage, just a few hours a day- a single tank will probably last you a week if you only run it 2 hours a night. A couple 5 gallon cans, and you're up for days. I like to store mine dry to keep the gas from going bad; I keep gas in 5 gallon cans I slowly cycle through our lawnmower over the course of the summer. The deaths are from people doing stupid things, like running their generator in their living room (or in the garage with the door shut) and with no CO detector in the house. If you're smart about it, there's virtually no risk.

The next step down is an inverter. Small inverters are VERY cheap and have enough juice to charge a laptop and your cellphones, but not much else. For about the cost of a generator, you could get a more powerful inverter mounted to your car that would let your car function as the generator; you still have the same gas problem as with a portable gen, though. You could get a 12V inverter and move it from one battery to the next on your golf cart.
I installed one of the little Generac units a few years ago.

Fed it from the house natural gas supply and set it to automatically start, test and transfer.

It's been working fine; but now I need to get it a new battery so it starts easier.
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