First I wanted to ask a couple questions about the MX60 and GVFX3524. I saw that MX60 sometimes had problems with Radio Interferance. We currently have a Trace C40 and DR3624 inverter and we had to move phone wires and computer networking cable away from it after installation due to interferance. We no longer have problems, but my father runs a Ranger 2995DX Ham Radio in the same household about 25 ft away and the wiring never gets any closer than 25ft. If we were to upgrade to an Outback system, would that be too close? Or would EMI be about the same?

Next I wanted ask about MX60 Wiring. By my understanding of the MX60's limitations, if you have a rated VOC 0f 47.7volts and weather that could drop as low as -20 Degrees Fahrenheit. It would not be wise Use series strings of 3 as the VOC could reach 143.1 volts, which exceeds the charge current of the MX60. In reality though, how often would it reach that voltage if it were -20 degrees, with a clear sky and fresh snow?
I was going to wire the panels I have at 80volts (95.4 VOC) in series strings of 2. I have 14 of these Sunpower SPR-215-BLK panels, and yes Im aware they are positive ground. From what I understand they still work, they just might be up to 30% less efficient than they could be.Anyway this gives me 7 Strings at 95.4 VOC & 5.9Amps Short Circuit Current. I am planning on wiring the first 4 strings at 2 strings each to 2 MX60 charge controllers at 860 watts max per MX60 and the last 3 Strings to 1 MX60 at 1290 Watts max. The arrays are 150ft away with 3 seperate runs of 4 Gauge Aluminum Wire.

Does anyone see anything wrong with this setup of have anything that they would like to point out? Is there a more efficient way to do this without upgrading the battery bank to 48volts? (They need to be 24volts for other charging devices.) This will be a grid tied setup by the way and we have now 16 6volt 400ah batteries from US Battery. Also, is there any reason I should seriously consider the new XW4024 system from Xantrex?

How long can you hold your breath ?

Series strings are better for less copper loss.

I would have used copper for the wire runs as we did on our original array 10 years ago, but it is overpriced due to china's high copper consumption. Only aluminum was available in 4 gauge wire. They had 4 guage aluminum and 8 guage copper for the same price. But 8 guage wasn't going to do it at 150ft. Also it was direct burial capable wire but we burried it inside 2.5 inch conduit FYI.

what mike meant was that you will lose less power through your wires when higher voltages are used. aluminum wire cannot handle as much power for the same gauge # as copper can handle. aluminum has a higher resistance is the reason why. also note that when copper and aluminum mix, as in your connection points, that it sets up what they call galvanic reactions so you need to be sure that the controller you get can accomodate the aluminum wire or you will have to make an adaptive provision approved for that purpose. fires have occured during the 60s and 70s because of aluminum wire used on copper only connections. on this point maybe solar guppy can add to my post by saying of the xw60's possible compatibility with aluminum wires.
as to reducing the rfi/emi, the xw is obviously better for it. keep in mind that interference is a 2 way street as the radio may interfere with the controller's operations too. any that is proven to be in compliance on outgoing interference will also reject interference getting into the controller to that same degree. you may or may not have a problem with using the mx60 with that radio, but for about the same money why not get the xw60? i don't mean to scare you, but even with an approved controller for interference there are no guarantees of being interference free as that approval only indicates that it is sufficiently reduced in strength, but look at what it might be otherwise without that reduction.
you may have read the thread on the interference, but these steps and measures do apply to nearly all items emitting or receiving interference. http://www.solar-guppy.com/forum/viewtopic.php?t=568 you may not be familiar with these steps and may not have to be in most cases.

Ok, so if I understand you correctly, the MX60 is rated for copper wire not aluminum? Arggg. I never noticed that in the users manual. Ok, well I can make accomodations for that, Im sure someone at the Electrical Engineering firm that I work at would be familiar converting aluminum wire to copper, being that all our ground wires for High Voltage transmission lines (115,000 kV+ 3 Phase AC) use aluminum static wire and are bonded to copper ground wires on each pole.

Also, there are 2 reasons I would go with the MX60 over the XW. For one if I buy the GVFX3524, I want to be able to network them and control them with the hub. Second is price, on most sites the XW is $100 more. I will need 4 MPPT controllers for 3.7kw because we are using 24volts. I don't want to dish out the $400 additional that it would take to have the latest and greatest when the MX60 could be had for less and will probably perform the same task. -Also, on that note, the average income in our area is only $33,000 per year. Even though we are living slightly above that average, the rest of the country lives MUCH farther above that average. If I did the same job I do now in but in MASS, I would get paid 4 to 5 times what I get here. Even in southern maine, our competition pays double in Portland what I get here in Augusta, and this is the state capitol. Basically this is being scraped together for as little money as possible because we are also putting in a Skystream 3.7 WindTurbine and Repairing our 85 yr old chimney. Need to save every penny we can, but I will refuse to do anything unsafe, even if it takes us a couple months extra to finnish assembly due to money issues. Thanks for everyone's input so far, gets me thinking about issues I haven't thought about yet.

Remember to use an approved anti-oxidant compound when making connections to aluminum wire.

if you are set with the mx60 then i might suggest you to go onto the outback forum and ask them if the connectiions inside are capable of an aluminum wire. you may find what you need on it before posting, but it is large so you may not find it even if it is there. register and ask.
http://www.outbackpower.com/forum/

Thanks for the pointer. I have heard alot of good things about the Outback equipment. But the Xantrex equipment is so new, I dont know if I want to be a Guinea Pig for the latest, greatest, most untested, most unproven tech. Especially when it costs more.... It is tempting though.

Ok Guys, I checked in on the aluminum wire, I "Should" use a terminal block for the adaptation. Now I have a couple more questions.

1.) Is there anyone in particular that I should contact to come an inspect this system once its installed? We are the only people in our town with PVs or Wind Turbines. The town says we dont need construction permits, they also dont have any permits or wind turbines or solar and no electrical inspectors. Central Maine Power also does not Inspect home pv systems. I was told that for a NetMetering contract, just call them and tell them what kind of invertor so they know if it shuts down automatically when the grid goes out. They said they dont have time to inspect them, they will just take us at our word. So aside from the town and the Utility, is there anyone else that would want to inspect this system?

2.) There is a 70' Retractable Ham Radio antenna right next to the arrays (30ft +or-) made of laticework steel no wider than 1.5". At 30ft, and 1.5" wide. Will the steel affect the summer morning output of the arrays greatly? It's Directly East of the Array Position.

Sounds like you have checked with all of the proper people regarding permits/inspections (nobody does electrical/building permits/inspections for just normal home building/remodels?--cool. In my city in California, the old planning commission was just as bad as a city-wide homeowners association)... The last one you may check with is your insurance agent/company if they have any issues (do they require you to use a licensed electrician--for example).

Any shading will cut your solar power output dramatically (in my humble opinion, if you have 2 or more parallel strings, shading even a few cells in a panel runs the risk of dropping close to 100% of the power from the one string).

On the other hand, if these are fixed panels (not tracking), you probably don't generate much power when the sun is due east. It would be better to avoid the shadows of fixed structures (and even power lines) whenever you can--because these are (many times) preventable losses that will add up over 20-30 years of generation. If you have no choice--there is not much you can probably do other than to accept the losses.

-Bill