How many watts ?

9 Posts
Sep 7, 2008 02:02 pm
How many watts ?

Have 2 Kyrocea 130 watt 12 volt wired for 24 volt=260 watts. Hooked up to a Xantrex 35. Want to add a 24 volt 170 watt Sharp panel to the system. Will the Kyrocea 260 watt mimic the 170 watt for a total of 340 watts or will the output be 430 watts ?
220 Posts
Sep 11, 2008 12:25 am
Re: How many watts ?

hi allen,

  looks like you will be in good shape adding that 24v nominal sharp module to that 24v series pair of kyrocea 12v modules. they are all polycrystalline cell technologies (also called multi)- the voc (volts open circuit) and vmp (volts maximun power) are right in there. voc (21.9 x 2)= 43.8v & vmp (17.6 x 2)= 35.2v for those kyrocea 130w combined for 260w series pair. with voc 43.2v & vmp 34.8v for the new Sharp 170w module.

  the expected combined array rating is stc (standard test conditions) of 430 watts. oddly enough we end up back at ~340watts rating when we derate to ptc (pvusa test conditions) sometimes called performance test conditions. (430 x .Cool= 344 watts.
(430 x point eight)
  our "sticker" might look like this.
  voc ~43.6v
  isc 13.67a  (current short circuit) 5.47 + 8.2
  vmp ~35v
  imp  12.29a (current max power)     4.9  + 7.39

  you may already know that how these two strings are combined matters. we want to bring their outputs to an overcurrent protector (fuses or breakers) at a pv combiner box and from there to another breaker (rated at least for the combined output)then to the c35. don't be tempted to try and parallel the outputs right at the modules. lots of reasons why this is bad. the best reason in this case is that our new sharp module has a max fuse rating of only 10 amps and our possible isc is over 13 amps even before the required 1.56 derate factor.

  so the positive and negative from the kyrocea series pair to the pv combiner with a 10amp (or 15amp) breaker on the positive conductor. and the sharp outputs to the combiner with a 10 amp breaker on the positive. and then the combined outputs to another breaker rated to protect that wire run then into the controller. this might be a good time to consider beefing up that wire run from the pv combiner to the controller for future expansion. also don't forget the egc (equipment grounding conductor) all the module frames, steel mounting hardware, and combiner box to the system grounding bus.

  also that sharp module comes with mc connectors. you will need a legnth of mc cable to make the run from the module to the pv combiner. get one cable twice as long as your run and cut it in half and you will have one of each plug male/female and bare ends for the breaker at the pv combiner. i'm sure you know all this. but others might find something useful here.

best of luck to you.
« Last Edit: Sep 11, 2008 12:30 am by david ames »

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