Well if those Panels are 220 Watts each and you got 21 of them, that comes out to 4620 watts or 4.6Kw. How do they figure that a 3.8 Inverter would handle 4.6kw???

Thats a pretty poor design. The math isn't adding up.


Fred

I'm pretty/very sure the PVPower units are going away and I have heard the GT5.0 will replace the PVPowered 4.4 and 5.2 ... SunPower was the main thrust for the GT 5.0. on the CEC listing, the GT5.0 aka SPR-5000x is listed

http://www.consumerenergycenter.org:80/ ... erters.cgi

Short term, If you can't get a GT5.0/SPR-5000, I would insist the installer put in a second 3.3 unit and power one of the three strings ... The 3.8 + the 3.3 in cost should be similar to the 5.2 anyways.

Take it from someone that know these things inside and out ( both brands ) Stick with the GT's, work with your installer to get a second unit and or find out when the GT5.0/sunpower unit is ready

Untill then make sure you have a large fan on the 3800 , your broiling the poor thing to death in the garage ...

I have a 4.5 STC array, and just a slightly warmer area than magneto does, just north of me in Oxnard.
http://www.mike-burgess.org/images/WiredInverter_c.jpg
I too have an indoor unit (GT3.8) and have a fan / timer with it, as I've expected to be very close to max power in late June.
Fan brought the temp down about 30F
On some cool sunny days recently, I've hit MAX POWER, for short intervals. I'm hopeing that in June, it will be warm enough, the panels will not put out as much power and I'll stay below the limit. The panel/inverter combo was suggested by the system vendor, 22 ea Sharp 208W, 2 strings of 11.
The Xantrex sizer shows me within limits.
If I was able to, I would have added some tilt to my panels, to get them off axis for the summer, but a much better solar angle for the winter, but the racking would have been too expensive.

Here is how they came up with the SPR-4000x inverter for my system.

STC refers to the nameplate which all modules carry (Standard Test Conditions). PTC refers to simulated real-life conditions (Performance Test Conditions). This may help clarify the true wattage available on my system.

So the math shows they have 4050 watts and installed a 3800 watt inverter ...

Also PTC is a generic derating value, since your in a micro-climate cooled by the pacific ocean, your going to be at or above STC most of the year, add another 400 watts minimum ...

You need to have your installer read this thread, it has the correct answers to both WHY its runs the way it does and WHAT needs to be done.

One comment in reading this discussion... although it may essentially be the Xantrex GT3.8 Inverter, the Sunpower SPR-4000x is advertised as a 4000 Watt Inverter which can output 4000 Watts continuous. See www.sunpowercorp.com as well as the CEC Inverter list.

So 21 Sunpower SPR-220 modules (which have a large +/- 8% tolerance) is a 4.054 kW rated system on an advertised 4.0 kW system. The 3 x 7 configuration chosen by the Installer is an approved configuration of Sunpower. Personally, I prefer the 2 x 10 which avoids series fusing.

You can play with the Xantrex GT family sizing tool here:

http://www.xantrex.com/support/gtsizing/disclaimer.asp?lang=eng

Their sizing tool shows that a 3x7 array is over the 3,800 watt rating of the inverter.

The 2x10 is only slightly over the 3,800 watt ratting (61 watts) and, for some reason, does not have the *** disclaimer.

I too would like to skip the fuse installation (fuses tend to be unreliable)--but I would not be too worried by over-sizing the array by 5-10%. I very rarely hit the 3kW output on my array (2949 watt CEC rated with GT 3.0)--usually it is in the 2,500-2,700 watt peak range (SF Bay Area) and very little power would be lost in my area.

However, if you live in a very cold climate with good sun (i.e., mountains with snow)--then you may be wasting some money by oversizing the solar array and hitting the inverter's limits daily.

-Bill

Magneto - any news on resolving the situation ? Are your panels south facing , or on trackers ? they seem to start putting out lots of power , early in the day, noon peak, and output stays high till late/sunset ?

I have 21 Sunpower SPR-220-WHT on 3 strings of 7 mounted on the roof south facing.

They are replacing the 4000x with another one because of the efficiency. As soon as the 5000x comes out they will replace it with that.

snip

Looks like something is happening - did you get a replacement inverter finally?