Beginners Grid Tie Question

2Guido · May 2014

Recently picked up a Fronus IG 3000. I have already setup an off grid daylight system which auto-disconnects from the grid, but have become interested in adding Grid -Tie as well. I have scoured the forums, but still have questions. Does this inverter simply tie directly into the house grid main breaker ?? And I assume I need about 150v DC from the panels in series. So does the inverter simply shut off when the panels are not producing ?? To many of you these are perhaps simple questions, but I really want to experiment with this..
THANKS !!!!

mike95490 · May 2014

Re: Beginners Grid Tie Question

2Guido wrote: »

.......To many of you these are perhaps simple questions, but I really want to experiment with this..
THANKS !!!!

Don't experiment with the grid. Sorry. You just don't know enough about the gear to be competent.

If something goes wrong, best case, your electric company slaps you with a fine or pulls your meter. Worst case, the coroner loads up a body bag and fills out a bunch of papers and you go to jail.

solar_dave · May 2014

Re: Beginners Grid Tie Question

Before you do anything, stop!

Grid tie has specific connection requirements to attach to the grid.
1. Usually there is an interconnection agreement with the utility
1a. the utility may have special requirements, like with mine it required a solar production meter.
2. Usually there is a requirement of a permit.
2a. the permits generally requires at least a line drawing for the attachment. There may be other requirements for the drawing, solar AC disconnect, engineers sign off, roof load calculations ...
3. There are NEC requirements to attach to a main service entrance via a back feed breaker. The 20% of bus bar rating has to be observed.
4. There are grounding requirements for the panel frames and all equipment.
5. My AHJ requires a 3ft setback for the panels from the roof peak for fire department access to vent the roof in case of fire.

Requirements varies by region but generally the panels are connected in series to produce a higher voltage input to the controller. The controller is then wired to a double pole split phase breaker in the service entrance panel (with perhaps the above mentioned requirements included). Strings of panels are run to a DC combiner box with the properly rated DC breakers or fuses and then with heavier wire a run is made to the inverter. Grid tie inverters generally run at fairly high DC voltages. That inverter has a DC input range of 150V to 500V. Nothing to mess around with, has the potential of quite a shock hazard and definitely the possibility of a sustained arc fire hazard.

Here is the sizing chart for the fronus inverter:
http://www.fronius.com/cps/rde/xchg/SID-05807842-8029BBDE/fronius_usa/hs.xsl/2714_8236.htm

Yes the inverter shuts off for many out of spec conditions, like no line voltage present (anti-islanding safety), low input voltage, line voltage doesn't make the qualification (out of whack frequency or excessive line voltage) and I am sure many more. Most inverters take 5 minutes of qualification of all parameters to get the production to start.

What ever you do don't experiment, make a plan, get it reviewed and approved then execute it.

Edit: oh yeah I forgot one important one, having the proper meter to account for the back feed to the grid, with an improper meter you may even get charged to supply power to the grid. This all relates to the interconnection agreement and the net metering plan of your utility. While I am mentioning the net metering plan, it is possibly the most important part of the system, it can be advantageous to you, no one or the utility. Understand it completely before you make a plan.

Skippy · June 2014

Re: Beginners Grid Tie Question

solar_dave wrote: »

Before you do anything, stop!
Grid tie has specific connection requirements to attach to the grid.
1. Usually there is an interconnection agreement with the utility
1a. the utility may have special requirements, like with mine it required a solar production meter.
2. Usually there is a requirement of a permit.
2a. the permits generally requires at least a line drawing for the attachment. There may be other requirements for the drawing, solar AC disconnect, engineers sign off, roof load calculations ...
3. There are NEC requirements to attach to a main service entrance via a back feed breaker. The 20% of bus bar rating has to be observed.
4. There are grounding requirements for the panel frames and all equipment.
5. My AHJ requires a 3ft setback for the panels from the roof peak for fire department access to vent the roof in case of fire.

Requirements varies by region but generally the panels are connected in series to produce a higher voltage input to the controller. The controller is then wired to a double pole split phase breaker in the service entrance panel (with perhaps the above mentioned requirements included). Strings of panels are run to a DC combiner box with the properly rated DC breakers or fuses and then with heavier wire a run is made to the inverter. Grid tie inverters generally run at fairly high DC voltages. That inverter has a DC input range of 150V to 500V. Nothing to mess around with, has the potential of quite a shock hazard and definitely the possibility of a sustained arc fire hazard.

Edit: oh yeah I forgot one important one, having the proper meter to account for the back feed to the grid, with an improper meter you may even get charged to supply power to the grid. This all relates to the interconnection agreement and the net metering plan of your utility. While I am mentioning the net metering plan, it is possibly the most important part of the system, it can be advantageous to you, no one or the utility. Understand it completely before you make a plan.

I would definately agree with everything you just said. . . don't mess around with the grid ! Here is my experience so far, that I hope others can learn from :

(1. - 1a.) I found out that my utility does do "net metering" . . after the panels were all up on the roof . . it will cost me between 300 and 500 $ . . but they will come out and install the proper meter that runs backward, and sign me up with an agreement. . . but they have already told me that they will send out a person to "have a look" at my system.

(2 - 2a) I had to get a permit for the shed, and had the shed "signed off" fairly easily, but then I had to get the engineer in too have a look at the panels or else take em down... no if's and or buts about it. Get this step done BEFORE you build anything. . going back in and making changes is a pain in the (part you sit on).

For the rest of the requirements, I can only hope that I meet the standard. The guy who sold me the solar panels is willing to help me to a certain extent in making sure the wiring is up to my areas standards, but I have no signed agreement as of yet.

Get it all planned out before you do anything !

Beginners Grid Tie Question

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