VOC and ISC

[inetdog]

It becomes an Open Circuit in such situations as for example the inverter is switched off, or there is a power cut or perhaps the wires become disconnected etc?

Thanks

Yes, and you are welcome.

Note that a GTI can become switched off by having the mains AC fail or disconnect while still keeping the DC from the panels connected to the GTI.

[mrsolar]

The voltage that the insulation, switches, fuses, CBs and the inverter or charge controller will have to withstand will be the sum of the Voc voltages of the panels in the string as calculated for the lowest expected ambient temperature. (The voltage goes up as the panels get colder.)

You have to use Voc rather than Vmax because you can expect that the circuit will be open at some point. Note that Vmax or Vmp is not the maximum voltage, it is the voltage at which the maximum power is produced.

It becomes an Open Circuit in such situations as for example the inverter is switched off, or there is a power cut or perhaps the wires become disconnected etc?

Thanks

[inetdog]

Thanks inetdog for clearing that up for me. Will I have to do the same with Voc, use this figure instead of Vmax?

The voltage that the insulation, switches, fuses, CBs and the inverter or charge controller will have to withstand will be the sum of the Voc voltages of the panels in the string as calculated for the lowest expected ambient temperature. (The voltage goes up as the panels get colder.)

You have to use Voc rather than Vmax because you can expect that the circuit will be open at some point. Note that Vmax or Vmp is not the maximum voltage, it is the voltage at which the maximum power is produced.

[Naptown]

The National Electrical Code requires that you use the Isc figure from the panels and also multiply that by 125% ( or is it 125% times another 125%??) because it could be a continuous current.
You should read the relevant sections in the NEC on Photovoltaic (PV) systems and then get an electrician to advise you.

it is 125% x 125% or 156%

[mrsolar]

The National Electrical Code requires that you use the Isc figure from the panels and also multiply that by 125% ( or is it 125% times another 125%??) because it could be a continuous current.
You should read the relevant sections in the NEC on Photovoltaic (PV) systems and then get an electrician to advise you.

Thanks inetdog for clearing that up for me. Will I have to do the same with Voc, use this figure instead of Vmax?

[inetdog]

Also the cabling may have to be rated at Isc of 1.65a because the chances of short circuit do exist, eg if someone accidentally short circuited the wires during installation, or water build up, or equipment failure etc rather than 1.25a Imax.

Sorry I am new to this, please be kind.

The National Electrical Code requires that you use the Isc figure from the panels and also multiply that by 125% ( or is it 125% times another 125%??) because it could be a continuous current.
You should read the relevant sections in the NEC on Photovoltaic (PV) systems and then get an electrician to advise you.

[mrsolar]

Grid tie,

To clarify what I meant in the above post I meant 3 panels wired in series to give 231 volts per set x 10 banks.

Also the cabling may have to be rated at Isc of 1.65a because the chances of short circuit do exist, eg if someone accidentally short circuited the wires during installation, or water build up, or equipment failure etc rather than 1.25a Imax.

Sorry I am new to this, please be kind.

[mrsolar]

What exactly will these be used for Off grid? grid tie?

Grid tie,

To clarify what I meant in the above post I meant 3 panels wired in series to give 231 volts per set x 10 banks.

[Naptown]

What exactly will these be used for Off grid? grid tie?

[Sunking]

Wow I would help you but so far you have demonstrated no knowledge of any electrical principle. To start with you will not be connecting 30 panels in series, 5 at most. Sorry but you are a great danger to yourself and have no business doing anything electrical. 30 panels in series would be 3000 volts, enough to blow your arm off in a cloud of black smoke.

But here is my best tip for you. Go to the Northern Arizona Wind & Sun Forum. They will gladly help you burn your house down and sale you all the parts you need to do it.

[mrsolar]

Correct me if I'm wrong, but I am planning on Installing 30 panels with these specs (Rated wattage 100w, Isc 1.65a, Voc 99v, Vmax 77v, Amp max 1.29a)

Am confused as to whether to plan the cabling on the Isc figure of 1.65a in case of short circuit and fire hazard, or do I just go by the 1.29a which each panel puts out? (It will be fused)

I am also confused as to which voltage to go by, 77v Vmax or the 99v VOC.

As an example 30 panels in a series connection of 3 panels in 10 banks of 77v would give me a voltage capacity of 231 volts, and if I used 1.29a this would give a total current capacity of 12.9a (Giving a total of 3000w)

How does Voc or Isc or even the IV curve help me at all?


Thanking you <3