3x2 or 2x3

[zoneblue]

Hi again,

Our install is getting closer. I understand that with panel configuration you horse trade cable losses with controller losses. With the classic 150 which will be the better panel solution:

2 strings of 3
3 strings of 2

Specs:
----------
Voc 44.9
Vmp 36.2
Isc 8.87
Imp 8.43
Batterys 24V
Array to controller distance 16m.
Cable size 12mm2 - 18mm2.

Other factors are string fuses for more than 2 strings. Lastly our ELV code rules here get tougher over 120VDC.

Thanks

[Westbranch]

what are the additional costs going 2 x 3?

Going 3  x 2 sounds less complicated  and closer to your bank voltage so less CC losses

[niel]

i think this might have been answered on naws too, but in a 2 string arrangement there won't be a need for each string to have a fuse/circuit breaker as it can be straight up combined. a disconnect would still be a good idea for the combined pv output going to the cc and that could be either a switch or circuit breaker.

[zoneblue]

Im not exactly sure. The country is NZ and i was told that you can install under 120VDC yourself, over that you need a registered electrician. And that there a raft of national standards that must be met.  I am doing the install myself, to save some money, but that doesn't mean that i dont want to wire it up at best practice level regardless. I expect it will probably involve buying the standards, @*#& loads of reading, and getting a sparky to sign it off... Or sucumbing and getting an expert to do the install.

[phonetic]

3x2 wont be a problem with hyperVoc if exceed on cold days..its a moot point ELV or LV..if you dont mind breaking the rules go 3x2..but take care 150 volts  Voc can kill you

[zoneblue]

Yes, that 135V Voc, maybe a bit higher on a cold day, (but never gets below 0C here) is likely to give you a good belt alright.

But what's the expected controller loss at Vmp 108.6V? cf 72.4V? I found one thread where a figure of 2.5% worse  was mentioned.

[Vic]

phonetic's warning is a good one.

DC voltages are usually considerably more dangerous than the same RMS or even peak AC voltage.

DC voltages above about 50  V are can be lethal. Below 50 V DC voltages could be lethal in certain circumstances.  DC can cause muscle contraction that can make it very difficult to remove oneself from the connection.  And a few tens of milliamps of current through the chest can stop the heart,  as I read it.

Please remember to have a very healthy respect for DC voltages in particular.  Vic

[TomW]

Please remember to have a very healthy respect for DC voltages in particular.  Vic

I concur I use a tip from an old sparkie. Try to work with one hand in your pocket. That way you don't get a shock across the chest. I know it is not always possible but it often is. Electricity can be dangerous and even lethal. One blunder, six feet under is what that old sparkie used to say.

Tom

[phonetic]

The LV  or  ELV  (over 120volts DC ) debate is very active on the Australian PV forums for DIY PV stand alone Installs..the rules are there for the lowest commom denominator..to protect DIY Joe public  from electric shock..saying that I think its insulting only Electricains can work on over 120 volts DC..I have a Diploma in electronic Engineering/Telecommunications..and Im not allowed to Install my own PV array if Voc is over 120 volts 
Im a proud owner of a classic 150..using it to the max Voc