Installing Grid Tie, but have a question...

wilsonbh

I'm in the process of getting my new standing seam metal roof. It's beautiful! Immediately afterwards, I plan to begin my solar system. I have all the paperwork and the blessing of a local electrician to begin my DYI installation. I've identified just about everything needed and understand what needs to be done, with one exception on the actual wiring of the panels to the combiner.

I plan to buy 22 Evergreen 190w panels with a Fronius 4000 inverter. The plan is to physically install the whole setup, as much as I can, and then have the electrician do the finishing touches.

My question is I'm just a tad confused about the wiring coming off the panels going to the combiner box. I've read about several options in doing this but it is still confusing to me. The parrallel versus series wiring sequences has me confused. I'm not sure of the best way to wire these panels into the combiner.

Would it be as simple as taking all the negative and positive wires and route them to their respective bus bar in the combiner? Or do I need to route a positive wire to a negative wire on the next panel, ultimately having only two wires coming off the panels?

Any advice here?

Billy

Solar Guppy

Re: Installing Grid Tie, but have a question...

Use a Xantrex GT inverter, it has the built in disconnect that is NEC 690 compliant, otherwise you will have to have external disconnects, its also a much better inverter than the Fronius. Also did you check that the evergreens would work with the limited voltage range on the fronius?

The panels wires in series is done panel to panel and each string is home runned to the inverter. This is NO combiner

BB.

Re: Installing Grid Tie, but have a question...

The panels are series/parallel connected. For example, you might connect 11 panels in series, and the parallel the two strings together for a total of 22 panels. So, in this example, you would have two sets of wires running back to your inverter.

And, you need to check the spec. sheet for your panels for the series fuse rating. For example, a panel may have 5 amps Isc and require a 7 amp series fuse (or breaker)... In this case, two parallel strings do not require any protective fuses. But three or more strings would require a protective fuse in each string.

-Bill

wilsonbh

Re: Installing Grid Tie, but have a question...

Solar Guppy wrote: »

Use a Xantrex GT inverter, it has the built in disconnect that is NEC 690 compliant, otherwise you will have to have external disconnects, its also a much better inverter than the Fronius. Also did you check that the evergreens would work with the limited voltage range on the fronius?

The panels wires in series is done panel to panel and each string is home runned to the inverter. This is NO combiner

I will consider the Xantrex. Considering the 22 Evergreen 190 panels, which inverter would work?

BB.

Re: Installing Grid Tie, but have a question...

From the Fronius FAQ:

How much array can I put on a FRONIUS IG? Because of the FRONIUS IG series design, the most important factor is to be within the voltage window (150 V to 500 V). Your system size will depend upon your environment (latitude, irradiance and temperature), your array's orientation and how often your system should be at full load. Also, your modules typically do not output their rated power since they are usually not at those conditions (25°C, 1000 W/m2). If the total DC input, after conversion losses, would exceed the output ability of the FRONIUS IG, it will change the operating point from the maximum power point to a point where it draws less current, and can output the maximum possible power.

In some situations, you may be able to oversize a Fronius inverter by as much as 30% of the rated power output and never get 'clipping' losses from operating off the maximum power point. However, we typically recommend the following maximums: 2500 Wp for the IG 2000, 3300 Wp for the IG 3000, 3000 Wp for the IG 2500-LV, 5000 Wp for the IG 4000, 6300 Wp for the IG 5100, and 5500 Wp for the IG 4500-LV. Larger PV systems will work, but may not maximize the use of the array during peak conditions. Conversely, these estimates may be high for a site with optimal conditions and high-performance arrays.

From the Xantrex GT calculator for Evergreen 190's, an 11 panel string with 14F min and 90F typical high ambient:

11 panels cold: 405 volts
11 panels hot: 240 volts
2 strings: ~CEC of 3515 watts typical maximum output (using California's deratings)

The Fronius configuration program also shows that 11x2 Evergreen panels are OK for this installation (Xantrex calculator shows the actual voltage and CEC wattage numbers for various configurations/temperatures--a bit more useful information than the Green/yellow/red of the Fronius website).

Not an expert, but unless you have some temperature extremes in your location that are different than those assumed above, your basic installation looks OK for either Xantrex of Fronius (that and $4.00 will buy you a cup of coffee).

-Bill

PS: While I liked the Xantrex unit before I "met" Solar Guppy because of the massive heat sink and no moving parts/fans--I don't know anything about Fronius.

SG was a designer that developed one or more GT/Solar controller programs for Xantrex and is very familiar with the major players in the market out there (and the strengths and weaknesses).

He is very proud of his contributions on these projects (rightly so)--In looking at your installation, take what SG has to say to heart and make sure that whichever brand/product you choose meets your needs.

And be very cost sensitive. With the major suppliers out there, solar panels and inverters/charge controllers are approaching commodity status.

If you end up paying a premium for your installation--make sure there is a reason for it (or work with the supplier and make them "work" to sell you their solution).

-BB

wilsonbh

Re: Installing Grid Tie, but have a question...

BB - Thank you for the insightful information. I respect SG and will take his advice to task. I evaluate every bit of advice that is thrown at me. I am very sensitive to cost as these things are expensive but am also sensitive to quality and will not buy junk. I've studied the Fronius and the Xantrex inverters and am trying to understand more, and at the same time juggling quality vs cost vs function in my final decision. The cost drivers are the panels and the inverter.

I'm sold on either SHARP or EVERGREEN panels and will probably go with the 190w EVERGREEN panels sold by sunelec.com in Miami, FL. They are about 3 hours away from me, south. I live near Cape Canaveral.

A local has a Fronius inverter up and running and has been running for 3 years with no issues. He has a 3kw setup and is very happy with it. I've been corresponding with a person in California that has the exact setup I'm moving towards, and it also includes the Fronius 4000 inverter. The reason I'm bending towards the Fronius is COST! The Xantrex probably is a better inverter but it's 33%+ more expensive too. I like BMW and Mercedes but can't afford or justify one of those either. Before I would buy the Xantrex, I have to see a cost benefit other than having an inverter that is labeled as "better" than the Fronius.

It's a shame the panels are so expensive. Every home in America should have a solar system setup to reduce their dependence on their local power company. Our culture needs to respond to our energy needs somehow and soon. We have a fragile economy that is far too dependent on foreign oil.

My motivations are not nobel as all I want to do is to save money and with the FL rebate, this actually becomes a smart thing to do. The "side effect" is less dependence on the power grid and support to the "Green Movement."

Every setup I've seen installed has made use of a combiner. I don't see how you can have more than 1 bank of panels and not use a combiner. It certainly would be easier to wire up the panels in series and then only have the 4 wires (2) from each bank of 11 panels wired into a combiner then have 2 more wires out from that to the inverter.

My last concern is the temperature. I live at latitude 28 degrees and it gets hot here in the summer time. It's common to see 95 degrees. I'm sure that these panels sitting on a hot tin roof will reach 100+ temps. I'll have to consider that in the voltage calculations I guess.

If you have any knowledge of the Fronius IG 4000 versus the Xantrex GT4 or 5, for comparisons sake, would be interested in that info. I've seen the specs on both but would like to know of anyone that has one functioning for their system. Like I said earlier, I have to juggle quality, cost and function. If the lower priced Fronius works, then why not go with Fronius?

Bill

wilsonbh

Re: Installing Grid Tie, but have a question...

Solar Guppy wrote: »

Use a Xantrex GT inverter, it has the built in disconnect that is NEC 690 compliant, otherwise you will have to have external disconnects, its also a much better inverter than the Fronius. Also did you check that the evergreens would work with the limited voltage range on the fronius?

The panels wires in series is done panel to panel and each string is home runned to the inverter. This is NO combiner

To wire the PV panels in this manner, then wire them back to the inverter, would the Xantrex GT4 handle the 4 wire inputs (two wires from each bank of PV Panels)?

I'm looking at something like this setup except I'll have more panels:
http://i275.photobucket.com/albums/jj301/wilsonbh/SolarSetup.jpg

Bill

BB.

Re: Installing Grid Tie, but have a question...

The Xantrex GT series directly supports connections to 2 parallel strings and does not need an external combiner (GT 5.0 supports 3 parallel strings but you probably need to add external series fusing to each string to protect against panel shorts).

2 parallel strings home run'ed back to the inverter is how mine is connected (GT 3.0).

I have 2x10 BP 4175 (20 total x 175 watt) panels running behind a 2.5 year old Xantrex GT 3.0 inverter (no problems at all). No combiner box--just a standard j-box where the UV rated wire from the roof is connected to the two home runs of 12 awg wire in metallic conduit). The connection from the the UV to 12 awg wire was some sort of swaged collar by my electrician (instead of wire nut--better/smaller connection?).

I don't know anything all all about the Fronius so I cannot speak to its strengths or weaknesses.

And the Xantrex--since I have not taken it apart--I can't tell you much more about its virtues other than it works fine (plus runs cool and does not have a fan).

-Bill

wilsonbh

Re: Installing Grid Tie, but have a question...

Well, I'm beginning to bend towards the Xantrex GT4 now. Looks like it would save me a little money by not requireing a combiner. I downloaded the manual from the Xantrex site and liked what I read. It does have an appeal by not needing a fan. Convection cooling makes sense to me.

I still plan on 22 Evergreen 190s. Two strings of 11 panels each. I'll have to dig through the specs of the Xantrex GT4 but at first look, it appears ok for these panels.

Bill

Roderick

Re: Installing Grid Tie, but have a question...

It may be irrelavant by now, but if you plan to monitor your array by computer, the Xantrex protocol is more open, and you can easily get a free program (I think Solar Guppy wrote it, but I could be wrong) to do the monitoring.

With the Fronius, you need to accept their software, and any hardware accessory they additionally require for monitoring.

mike95490

Re: Installing Grid Tie, but have a question...

Roderick wrote: »

It may be irrelavant by now, but if you plan to monitor your array by computer, the Xantrex protocol is more open, and you can easily get a free program (I think Solar Guppy wrote it, but I could be wrong) to do the monitoring.

I agree with Roderick, and I have mine set up & working.

The free program from Solar Guppy http://www.solar-guppy.com/forum/viewtopic.php?t=548
A $5 serial DB9 cable (only 3 wires needed)
A computer with DB9 serial port, or get a $7 USB to serial port adapter.
GT series inverter.

wilsonbh

Re: Installing Grid Tie, but have a question...

mike90045 wrote: »

I agree with Roderick, and I have mine set up & working.

The free program from Solar Guppy http://www.solar-guppy.com/forum/viewtopic.php?t=548
A $5 serial DB9 cable (only 3 wires needed)
A computer with DB9 serial port, or get a $7 USB to serial port adapter.
GT series inverter.

I've reconsidered the Fronius and now plan to buy a Xantrex GT 4000. I will be running two parallel strings, each with 12 Evergreen ES190 panels. I have the plans drawn up and will be buying the panels in the next couple of weeks from Sun Electric in Miami. I need to locate a source for the Xantrex.

I plan to submit my stamped drawings to the county this week for the permit. Should only take me one weekend to install this "tinker toy" system. Hardest part will be running the wires and conduit through the attic. It's hot up there!

I'm really excited about this. Still can't fully believe the rebates are what they are.

mike95490

Re: Installing Grid Tie, but have a question...

wilsonbh wrote: »

two parallel strings, each with 12 Evergreen ES190 panels.

-snip-

Should only take me one weekend to install this "tinker toy" system.

I'd suggest you plan on longer. My install, with a crew of 2, took them 2 full days, and they ran conduit outdoors, not thru the attic. And the roof brackets were preset earlier, when the roof was re-shingled.

wilsonbh

Re: Installing Grid Tie, but have a question...

mike90045 wrote: »

I'd suggest you plan on longer. My install, with a crew of 2, took them 2 full days, and they ran conduit outdoors, not thru the attic. And the roof brackets were preset earlier, when the roof was re-shingled.

The roof brackets are designed for my roof type so it's just a matter of tightening screws. I do things slowly. I was speculating that it could only take a weekend to do but I concede that it may take longer.