Xantrex solar controller question

islandskies

Hi, I'm a solar newbie planning what to buy for my 1st system.

Just a question on the Xantrex solar controller.. I'm a bit confused on the max voltage. The spec sheet says 150VDC max under any condition. What V does that refer to? the open circuit V, or Max V?

I will run a total of 8 205W panels.. So if my understanding is correct in that I can hook up 4 panels (16V nominal/36V open) in series to achieve 64V nominal/144 open. The same for the other 4 panels, then wire both sets up in parallel for total of 64V nominal/144V open to the controller? thanks for any advice.

crewzer

Re: Xantrex solar controller question

The 150 V limit correlates to the temperature-corrected STC Voc. NEC 690-7 provides temperature correction factors. Use the following TCF's for your local morning low temperatures (degrees F):

77 - 50: 100%
49 - 32: 110%
31 - 14: 113%
13 - -4: 117%
-5 - -40: 125%

Choose the TCF that applies to your area and multiply it by your proposed array's STC Voc (144 V?). If the result exceeds 150 V, then the controller could be damaged. Also note that while 150 V may be a unit's absolute limit, the operational limit may be lower. For example, the OutBack MX60's operational input voltage limit is 141 VDC. The unit will disconnect the array if it's higher.

The "Averages" link in a local weather report from www.weather.com is a good source for local temperature data.

Note that the 150 VDC limit is common. It's shared by the MPPT controllers from Apollo, OutBack (MX60 and FM80), and Xantrex, and also by popular PV array DC circuit breakers from OutBack and MidNite.

HTH,
Jim / crewzer

islandskies

Re: Xantrex solar controller question

Thank you crewzer, now it makes more sense to me. Using that temp correction chart, I should be at 100% (77+ degs) thruout the year, if anything, I'll be at a higher temp (80-90F).. so maybe even a tiny bit less than 100%. so its close to 150VDC to the controller. or maybe I should rewire it to 3 panels in series (108V)... OK, now I can order all the stuff this week.

8 - Sharp 205W 16V nominal solar modules
Xantrex XW4024 inverter
Xantrex Solar Controller
8 - Deka 8A8D AGM batteries wired for 24V

Here in the tropics, the sun is killer almost year round.. I cant wait to get it up and running. :cool:

crewzer

Re: Xantrex solar controller question

Using weather data for Andersen AFB, I’d agree that a 100% TCF would appear to be appropriate for your PV array’s Voc calculation. Nonetheless, you still have options for the array configuration and voltages.

As you indicated, wiring three Sharp 205 modules in series would work. You’d need to go with either six or nine modules. A nine-module array might cause the controller to occasionally limit output current to 60 A.

Another option using just the eight modules would be two modules in series with four parallel strings – a “2 x 4” configuration. This configuration would require additional and/or heavier wire between the array and the controller. However, the controller should operate a bit more efficiently in your system with a 24 V battery bank with the lower array voltage than it would in the high-array-voltage “4 x 2” configuration.

Reference module specs: http://solar.sharpusa.com/files/sol_dow_205watt_SS.pdf

Good luck with your project!
Jim / crewzer

mike95490

Re: Xantrex solar controller question

islandskies wrote: »

Using that temp correction chart, I should be at 100% (77+ degs) thruout the year

You mean you never get below 50F, on a cold morning ? Wow.