I'm planning a installation of 27 Sunpower 205BLK panels, and can choose between the Sunpower SPR-5000x (Xantrex GT 5.0, I believe), the 5000m (a SMA Sunnyboy 5000US), or the 5200 (PV Powered unit).

Exposure is southern, so they should be hitting max for a good part of the day.

The inverter will be installed in a garage. I have read some posts about overheating of convection cooled inverters, the SMA has its own fan. But the Xantrex and PVP can be web monitored, and the Xantrex has a remote monitor that will get thrown in to the deal. So what is the best choice? I'd like to avoid fitting an external fan, if possible.

Any advice would be greatly appreciated!

I installed a 3kW Xantrex GT 3.0 system in my garage (two years old now). But, my garage is pretty cool (insulated and under shade trees). I like it here because it is right next to my kitchen door--I just write down the readings every evening--and saved the costs of a computer/cabling and the power required to run the computer (I get about 4,800 kWhrs per year from my system).

The heat sink has never gotten hot enough to prevent me laying my hand on the fins (and my outdoor installation would have been in full sun--so I wanted to avoid this). Your unit at 5kW is larger than mine--so the heat may be more of an issue.

If you garage gets hot--it may be a problem. Some people have added a simple AC fan in the garage pointing at the unit and a lamp timer to turn it on in the afternoons.

For me, I would recommend to avoid any inverter that uses a fan--Fans are mechanical and will eventually fail and they also collect dust (needs cleaning). If that fan is user replaceable (and not too expensive)--perhaps it would not be too bad to have one. If the fan is not easily user replaceable--I would avoid it.

If you are in California and are getting the solar rebate--you will need to check and make sure the unit is approved and what kind of monitoring unit may be required and how much it will cost (the state has made collecting the rebates quite complex now).

-Bill

I run a pair of GT5.0's ... best inverters on the Market IMHO.

You will have no issues as I run a 5.1kw and 5.4kw here and they don't get hot. if your wnating something other than Xantrex, get the SMA, PVPowered is the bottom of the pac, actuall I'm surprised you can even get them and when SunPower started re-selling the Xantrex GT's I was under the impression no PVPower units would be sold.

Thanks for the replies, I was leaning towards the Xantrex due to the feature set and clean output. This information helps.

and another q, if I decide to go with a 24 panel array of 205's, is the 5000x (i.e. GT5.0 still a good selection, with a 3 string 8 panel setup?

Thanks all,

Xantrex has a nice solar array caculator for their Grid Tied inverters here:

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

-Bill

PS: Looks OK... Gives a CEC rated 4,332 watts (14F-95F) for Xantrex GT 5.0 inverter:

Max Imp
1 String 5.1 Adc
2 Strings 10.3 Adc
3 Strings 15.4 Adc
4 Strings 20.5 Adc

Series String Voc-max Vmp-min
7 Modules 368.12 236.91
8 Modules 420.7 270.75
9 Modules 473.29 304.6
10 Modules 525.88 338.44
11 Modules 578.47** 372.28
DC input range 235-600Vdc
DC MPPT range235-550Vdc
* Outside range
** Indicates nearing max Vdc[/i]

Thanks BB,

I checked the Xantrex site, it was a little hard to interpret the data though. I assume that values that do not have cautionary * are OK configurations...?

Basically, yes...

If the voltage is too low, the inverter simply will not operate (typically, very hot, no wind, sunny panels)...

If the voltage is between 550-600 VDC, it will operate, but will not be as efficient (Maximum Power Point Tracking function will not work). Bigger issue is you are near the 600 VDC not to exceed voltage.

Above 600 VDC (open circuit, cold panels), you run the real risk of major damage to your inverter (you can shut off the inverter/panels using the Xantrex master switch--but if somebody forgets--you are snowed out--~poof!)

Solar Guppy (one of the initial designers of the GT inverter series), recommends that you keep your voltages towards the low side of the range as the inverters are most efficient (lower switching losses).

Personally, like like to keep the current low (less (I^2)*R heating losses) and keep the voltage a bit higher.

In reality, keep the voltage somewhere between min and max--and you will be fine.

-Bill

Got it. Thanks!

the 2 configurations I am considering are about 420 - 475 vdc, so that should keep things running decently well.

Thanks again for the replies, this has been very helpful. Great site for solar info.

I would go with the Xantrex. If you have an inverter with a built-in fan & the fan fails, the inverter might get damaged due to overheating. If you add an external fan to an inverter w/o a built-in fan & the fan fails, you won't damage the inverter.

I have a Xantrex GT3.8 with 3960 watts (stc) of panels. The inverter is mounted in my garage, which can get to 100F + in the summer. The hottest inverter temp that I have seen (without using an external fan) is 147F. This is extremely hot to the touch & is very near the point of causing a burn to your skin. It is still within the Xantrex temp operating range (I think that the max is 176F). I added a small (external) fan with a plug-in lamp timer. I have since changed to a thermostat control with a remote mounted sensor. I have secured the sensor to the top of the inverter with heavy foil tape. Now the max temp that I see is 122F. This is the temp that I have set on the thermostat.

http://www.grainger.com/Grainger/items/ ... Item=3ZP77