Overpaneling over a 100% of what a controller can take. Offgrid

[squowse]

Absolutely no problems with overpaneling. I have 3750 watts in panels going to a Growatt 2000w inverter. At mid day, the inverter takes 2200w. It still wouldn't be a problem if I had 10000 watts in panels. The inverter will only take what it needs. The only risk is if somehow the MC4 cable got cut or damaged in such a way that it would cause a short, it would burn up pretty quickly, rather than burn up slowly. But then burning up quickly might be better, since it would be kind of like a fuse.

The short circuit current is Isc. All your wires/cables should be rated for the Isc current or you have a dangerous installation.

This includes the controller. As far as know, only Victron actually specify the max Isc though

 

[littleharbor2]

I had over 80a worth of panels connected to an 18a max SCC. It ran like this for several months.
No issues at all. It just pulled the 18a for most of the day.

Was this a parallel wired array? Series wiring keeps the incoming current at a single panel's current per string and adds voltage.

 

[timselectric]

Sounds like you’re mixing up the PV current and charge current?

No
Overpaneling is about PV current.

 

[timselectric]

Was this a parallel wired array? Series wiring keeps the incoming current at a single panel's current per string and adds voltage.

98 panels
10s8p + 9s2p

 

[timselectric]

If you would prefer it in wattage.
23.7kw connected to a 6kw SCC.

 

[littleharbor2]

98 panels
10s8p + 9s2p

Wow! You aren't messin' around.

 

[timselectric]

Wow! You aren't messin' around.

It was overpaneling to the extreme.
But, it was a good proof of the theory.

 

[squowse]

No
Overpaneling is about PV current

Yes but is the 18A max figure quoted on the PV side or the battery side? If the 18A is max Isc then its voiding the warranty at least. I suspect its on the battery side which is why i said that you are possibly mixing up the PV side and the battery side quoting those 2 figures

 

[squowse]

If you would prefer it in wattage.
23.7kw connected to a 6kw SCC

Where does the max 18A figure come from?

 

[timselectric]

Where does the max 18A figure come from?

Max PV input current.
I'm not sure what you are missing.

 

[timselectric]

Let's try a picture.

 

[squowse]

Let's try a picture.
View attachment 149114

Not seen that marked on the panel before. So you’re happily voiding the warranty? If it malfunctions then the 80A current can burn up the FETs and worse.

The OP charge controller doesnt have that marking anyway. Renogy are a bit vaguer about overpanelling.

 

[timselectric]

Not seen that marked on the panel before. So you’re happily voiding the warranty? If it malfunctions then the 80A current can burn up the FETs and worse.

The OP charge controller doesnt have that marking anyway. Renogy are a bit vaguer about overpanelling.

Not voiding the warranty. That rating is the max it can utilize.
It will never draw more than it can. Unless it fails internally. And that would be covered under warranty. And even then it will never draw more than the 20a fuse on the PV circuit.

 

[pollenface]

80A current can burn up the FETs and worse.

If you connect in reverse polarity, yes. The isc limits are directly related to reverse polarity protection. Every now and then some monkey hooks it up the wrong way

 

[squowse]

Not voiding the warranty. That rating is the max it can utilize.
It will never draw more than it can. Unless it fails internally. And that would be covered under warranty. And even then it will never draw more than the 20a fuse on the PV circuit.

The max pv current it will draw under normal circumstances would surely be dependent on the PV voltage? Best not to rely on the fuse. That won’t blow quick enough to protect the equipment, its to stop the cable melting.

 

[squowse]

If you connect in reverse polarity, yes. The isc limits are directly related to reverse polarity protection. Every now and then some monkey hooks it up the wrong way

Thats one scenario where it matters, there are other malfunctions where the controller wont be protected against massive currents. I’m not sure that figure is the max Isc though. There’s no reference to it on the datasheet

 

[zanydroid]

If there is no explicit spec for max PV watts and max ISC (or other fault current), I don’t see how they can deny a warranty claim. I guess it gets ambiguous if the important spec is explicitly listed in spec table/nameplate vs buried in a “do not exceed” warning written out inside the installation guide.

Personally I think it’s weird that NEC does not provide a calculation for inferring max fault current or PV circuit wattage when not provided by the manufacturer, but it is what it is. They do this for AC consumption equipment.

 

[timselectric]

The max pv current it will draw under normal circumstances would surely be dependent on the PV voltage? Best not to rely on the fuse. That won’t blow quick enough to protect the equipment, its to stop the cable melting.

Well, you can't draw current. If there's no voltage present. But as long as you have the minimum voltage required by the SCC. It can pull its full current.
The fuse is not to protect the equipment. Fuses protect the wiring. But, they will also keep the equipment from melting down after a failure.

 

[zanydroid]

The fuse is not to protect the equipment. Fuses protect the wiring. But, they will also keep the equipment from melting down after a failure.

If AC utilization equipment lists a Max overcircuit protection, you need to respect it. This is typically present in HVAC but not really that common in other appliances.

As alluded to above (and apologies if I've mentioned this at you in other threads), NEC provides a formula for calculating MOCP if it's not on the appliance nameplate, and I don't have any evidence that this is less important to compliance than other parts of NEC.

IMO this is analogous to available fault current and maximum rated interruption.

 

[timselectric]

If AC utilization equipment lists a Max overcircuit protection, you need to respect it. This is typically present in HVAC but not really that common in other appliances.

As alluded to above (and apologies if I've mentioned this at you in other threads), NEC provides a formula for calculating MOCP if it's not on the appliance nameplate, and I don't have any evidence that this is less important to compliance than other parts of NEC.

IMO this is analogous to available fault current and maximum rated interruption.

Solar charge controllers do not require external over current protection. Any additional fuses on Solar circuits are there to protect the panels from each other.