NEC 690.64(B)(2)

[mike007]

I working with Sokar Gridtie systems here.

The explaination on the links isn't too clear. they state that during the daytime you will have current from both the power company and from the solar array across the bus bar.

I would have to ask if this has been tested. If my array lets say 5KW 240 volt is generating full power at noon and lets say 10.6amp 15 amp breaker across the 2 hot bars. That power is first going to feed the devices in the house and any excess would be pushed out to the grid. The dependancy on the grid has been reduced. How can you have both unless you aren't generating enough from an array in the morning and in the evening. Even then you wouldn't have competing power sources for the bus bar.


The requirement is that on a "dwelling unit"
the sum of circuit breakers feeding current to a conductor or busbar
cannot exceed 120% of the rating of the busbar [NEC 690.64(B)(2)
Exception]. What this means is that on a typical 200A residential
service the maximum sum of breakers is 240A. If the main breaker for
the service panel is 200A that leave a maximum of 40A for for SMA Inverters

 

[Flyersfan]

Re: NEC 690.64(B)(2)

You will "send Back" to the utility any net power that is available from your solar array. All of that is accomplished by the controller that is part of your installation. Do yourself a favor and sell the customer the "net metering option." This device will actually show what you have fed back from the solar array into the utility grid. Honestly, most utilities aren't going to read your net meter but the it's a great show and tell item for the customer. To simplify the whole process, let's say you are generating enough power from your array to supply the house's need and have some "left over." This left over amount will be fed back into the grid to be consumed on down the line. I know that's way too simple, but that's basically it. You can have both at the same time if your usage in the house is more than what your array is generating. That's more common than not. As a side note, I would stay away from the battery installs on a residential system. They take up too much space, they're heavy, they are expensive to purchase every few years and the hazardous nature of them is just too much to deal with in the average home. That's only my opinion, but I felt I would share.