Fuses & Charge Controller

[lazza]

HI Forum

I am about to add 6 120W Kyocera panels in 3 series of 2 (24V) to an existing installation, to increase it's power.

The Vsc of the panels are 7,5A, and I am planning to put in a Xantrex C40.

I was trained to put in 4 fuses- two on the positive and negatives of the charge controller input and also two on the postive an negatives of the output of the charge controller before the batteries.........

This seems excessive to me therefore:

Would it be sufficient to just put one fuse on the positive side of the charge controller output?? Or should I install more fuses?

Thanks
Larry

[ggunn]

HI Forum

I am about to add 6 120W Kyocera panels in 3 series of 2 (24V) to an existing installation, to increase it's power.

The Vsc of the panels are 7,5A, and I am planning to put in a Xantrex C40.

I was trained to put in 4 fuses- two on the positive and negatives of the charge controller input and also two on the postive an negatives of the output of the charge controller before the batteries.........

This seems excessive to me therefore:

Would it be sufficient to just put one fuse on the positive side of the charge controller output?? Or should I install more fuses?

Thanks
LarryIf there are more than three PV strings they must be fused separately, but why are you fusing the DC- conductors?

[Cariboocoot]

As a rule you do not fuse the negative conductors of a DC circuit.
You would have one 10 Amp fuse on each positive panel lead and one fuse (at least 30 Amp, 50 Amp for full capacity of the C40) on the positive output of the controller.

Adding more than one fuse to a circuit doesn't make it any safer.

[lazza]

Dunno, it was what was recommended in the installer course I completed a couple of years ago- but doesnt make sense to me. If it doesnt make sense to the forum either, then I will gladly exclude -ve DC fuses from the installation

[ggunn]

Dunno, it was what was recommended in the installer course I completed a couple of years ago- but doesnt make sense to me. If it doesnt make sense to the forum either, then I will gladly exclude -ve DC fuses from the installationI think you may have misunderstood what they were telling you, or they may have been talking about transformerless inverters and/or ungrounded arrays which are so far very minor players in the PV world.

[mike95490]

Dont' buy stuff yet, have you considered series wireing, (gets rid of fuses at the panels) and an MPPT controller ?

[lazza]

Dont' buy stuff yet, have you considered series wireing, (gets rid of fuses at the panels) and an MPPT controller ?

HI .. yes i did consider it and it would be my preferred option, but as the client is very price conscious, and as this is just an addition to an existing system, the % increase in cost of an MPPT system wont be convincing for him. This is the problem with correcting/improving existing systems- but as they say in Spain "Es lo que hay".

Cheers
Larry

[lazza]

I think you may have misunderstood what they were telling you, or they may have been talking about transformerless inverters and/or ungrounded arrays which are so far very minor players in the PV world.

Mmmm dont think so... it is in all the diagrams that we did in the course... talking of which, does anyone know of good software (preferably free) for drawing circuit diagrams for PV systems??

what are transformerless inverters? i suppose that a simple 3kW off-grid system would not have such a type of inverter?