Over paneling MPPT, short circuit current too close?

[mickenorlen]

After having contacted a couple of vendors, as well as Victron themselves. This is the somewhat confusing information I got.

Below is reply from Victron's sales dept. I couldn't find a way to get in direct contact with the tech dept.

1. Can we interpret this that the warranty is still valid for PV arrays with short circuit currents up to 30A at STC?

Yes correct , but you need to stay will below this level of course

1. In case the current in rare circumstances would increase above 30A with such an array, e.g. during an over irradiance event, is there an overcurrent protection fuse to safeguard the integrity of the device or would it risk direct damage?

No , as this protection is rated up to 30A , so having a higher current here will result in severe risk for all

From a Vendor, even after I showed him the above reply from Victron:

I will stand my ground with the information already written in my last mail:

“Please do just connect not more than 20A in STC Conditions (as written in the datasheet of the RS48/6000)” !!!

Victron will not answer this “what-if” questions, as all information are written in the manual you already read!

(additional Info you might not have thought about: about 30A are also the maximum current what MC4-connectors can bear (especially if it is a random MC4 and not a very high rated/quality like Evo2), so maybe also think about physical damages due to high current on the connectors and not the RS48/600 itself. In both cases Victron will refuse warranty, as those defects clearly state a “not intended use”)

In the end my interpretation of this is that the warranty and device is designed to hold up for currents up to 30A, but YOU have to be the one to make sure that these currents are not exceeded, which would otherwise be considered a mistake in system design and probably void the warranty.

Regarding the MC4 connectors 30 A limit, there will be 2 separate strings connecting to the 2 MC4 inputs of the tracker, so max current at each connector should only be around 15 A.

The most important takeaway for me is that there is no protection beyond 30A. So I will consider adding some fuses in the future to protect me from any over irradiance events.

 

[pollenface]

Allow oversizing above 130%, is that already checked?

Wonder what folks here would think about a 30A fuse. With 1.56 scaling that is just above the 18A max operating current of the MPPT.

Some folks here overpanel til the cows come home and suffer no ill-effects.

It is my understanding that the Isc limit of an MPPT relates to reverse polarity protection. If you can help yourself to NOT accidentally connect pv in reverse you should be fine

In my monopolized part of the world 132% limit applies to those wanting to claim STCs for government rebates.

 

[Siamac]

I have a similar question.

My MPPT says max 15A.

My panels say ISC 5.99A, max current 5.61A

Can I put 3 strings in parallel?

(voltage is under limit)

 

[sunshine_eggo]

I have a similar question.

My MPPT says max 15A.

My panels say ISC 5.99A, max current 5.61A

Can I put 3 strings in parallel?

(voltage is under limit)

Technically, no. If this is a Victron unit, and you DON'T reverse the polarity, yes. If you reverse the polarity, AND the panels are capable of producing > 15A at that moment, you'll possibly cook the relay that shorts the PV terminals to protect the unit from reverse polarity.

Would I?

Yes.

 

[Siamac]

Technically, no. If this is a Victron unit, and you DON'T reverse the polarity, yes. If you reverse the polarity, AND the panels are capable of producing > 15A at that moment, you'll possibly cook the relay that shorts the PV terminals to protect the unit from reverse polarity.

Would I?

Yes.

Would it change anything if one string is facing south and 2 facing east?

 

[sunshine_eggo]

Would it change anything if one string is facing south and 2 facing east?

Yes. One can argue it's impossible for the 3 panels to exceed 15A Isc.

Again, I would personally go 3P same facing and just make sure I never reversed the polarity.

 

[Siamac]

Yes. One can argue it's impossible for the 3 panels to exceed 15A Isc.

Again, I would personally go 3P same facing and just make sure I never reversed the polarity.

How do you reverse polarity? What does that even mean?

 

[sunshine_eggo]

How do you reverse polarity? What does that even mean?

Connect panel (+) to controller (-) and panel (-) to controller (+) or "backwards"