mlennox
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| 07/07/2009 7:44 AM |
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We're about to start construction of our new home and I will be laying out 2" Carlon PVC conduit prior to the footings for 200A service (from the meter base to the electrical panel).
We would like to be prepared for putting in a future grid-tie PV system, so I'm wondering if I need to plan for extra wiring from the panel back to the meter base. Or does a grid-tie system simply use the same service wire to push electricity back to the grid?
Any other recommendations would be very helpful. I'm planning to run 3 separate 3/0 wires + ground through the 2" rigid PVC. I've understand some people use 4/0 for 200A service.
Thanks.
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Brock
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| 07/08/2009 10:35 AM |
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| A 200 amp service should be fine. Most of the time grid tie systems (without batteries) will go to its own meter installed by the utility out near your existing one. But sometimes it is wired back to your main panel. It should NOT go to a sub panel off the main panel. |
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Green Bay, WI. - 4 ton horizontal, 16k gallon indoor pool, 1.8kw solar PV setup, 3400 sq ft |
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mlennox
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| 07/08/2009 11:38 AM |
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| So it would use the existing 200A wire connecting my meter to my circuit panel? Or would I need separate wiring to the outside of the house from my circuit panel? |
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Brock
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| 07/10/2009 12:17 PM |
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| It could go either way. If your utility requires a second grid tie meter they will do that part, nothing you have to do or pre plan for, other than maybe the space it might take up at that location. If it is back fed in to you main panel, you don't need to change anything with the feed from the meter to the panel. All that would be needed is a wire from the inverter to the main panel. |
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Green Bay, WI. - 4 ton horizontal, 16k gallon indoor pool, 1.8kw solar PV setup, 3400 sq ft |
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flyingfish
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| 07/18/2009 11:33 AM |
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| Interesting Brock,you would say that the PV system should not be connected to a sub-panel. My 5kw system is connected to my hangar subpanel where the inverter is located by the subpanel. It was reviewed and approved by the PV man at Florida Power &light. The system has been operating since last Sept and I could not be happier with results. I only have one meter which is upstream of mainpanel. My old meter with wheel was changed to digital meter for no charge by FPL. It increases the positive number when FPL is sending me power and the negative number increases when we're sending them our excess. |
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Brock
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| 07/18/2009 9:34 PM |
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| There are certian ways to tie back in to a sub panel and still falling under code, but it is easier to suggest mst people just go back to the main panel. But yes it can be done it things are sized right. |
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Green Bay, WI. - 4 ton horizontal, 16k gallon indoor pool, 1.8kw solar PV setup, 3400 sq ft |
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flyingfish
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| 07/19/2009 12:20 AM |
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| Brock, I would like to convert my PV system to be able to use the Xantrax type inverter that can run with grid tie normally , but be able to run with generator or a small bank of batteries in emergency ( read hurricane or terrorists). Do you have any ideas of why I should not do this? |
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Brock
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| 07/19/2009 8:17 PM |
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You can do it. What do you have right now?
The big catch with grid tie battery-less systems is they usually run the solar array's at a much higher voltage, typically 300 to 500 vdc at 5-10 amps. A battery-based system typically runs the panels from 60 to 84 volts at higher amperages; this is because the battery bank is typically 12vdc to 48vdc. Basically it would mean a total re-wire of the solar panels where ever they are mounted, adding a charge controller (or two), batteries and finally a "hybrid" inverter that can run with or without the grid.
The trade off is you also loose about 10% of the energy created because of the charge controller losses and battery losses that don't exist in a battery less system. But then again if the grid goes down, everything keeps on running.
The other option is to get a stable source to feed your existing grid tie inverter so it can "turn on" and power loads in your home. |
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Green Bay, WI. - 4 ton horizontal, 16k gallon indoor pool, 1.8kw solar PV setup, 3400 sq ft |
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flyingfish
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| 08/04/2009 5:55 PM |
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Hi Brock,
Thanks for the info! I would hate to give up 10% for controllers etc. Rewiring would be a snap, it is in my hangar and everything is accessible.
Can I install a 2nd smaller bank of PV cells and inverter with batteries that someway runs in parallel to the current system so that the smaller system provides the sign wave to keep the original larger system functioning off grid but without the 10% loss on the original??
TIA,
bernie
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Brock
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| 08/07/2009 10:10 AM |
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Yes you can use a battery based pure sine wave inverter to trick a grid tied inverter in to thinking the grid is alive. I can be a dangerous thing to do since there is really only one fail safe in that type of system and I wouldn't recommend it unless you understand what it is doing.
The main problem is if you have more solar power than you’re using and your batteries get full. There is no additional place to dump power so the battery based inverter will keep trying to push the power in to the battery bank, even if it is beyond full. Then the only real cut out is a max battery bank voltage which would shut off the battery based inverter and in turn the grid tied inverter.
You would need an inverter like a xantrex XW to be stable enough and supply 240vac most grid tied inverters want to see. But the battery bank could be smaller, just enough to support the XW inverter.
There is some great info in this thread over on Wind & Sun |
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Green Bay, WI. - 4 ton horizontal, 16k gallon indoor pool, 1.8kw solar PV setup, 3400 sq ft |
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