Reverse polarity on sanyo panels

[Coleman]

Hi all
A customer ive quoted recently wants panasonic HIT panels as part of the system and ive never fitted these before, on segens website it says dont reverse the palarity on multible string otherwise you'll destroy the panels, so im a bit reluctunt to fit them as there not the cheepest panel out there!! Has anyone fitted them and had a problem such as this?

 

[moggy1968]

why would you reverse the polarity?
Your system checks before switching on would confirm polarity was correct surely?

 

[sedgy34]

its easy to get it wrong if your using black for +&-

 

[moggy1968]

not if you check the polarity before you connect up

 

[Coleman]

Have you ever reversed the palarity on any of your installs?

 

[moggy1968]

yes, but haven't connected one that was reverse polarity since the first. Learnt my lesson then and always check them now (although happily no damage was done)

 

[Gavin A]

This relates to the bypass diodes, and tbh, I can't see how it's going to be any different for any other panels, other than maybe that the sanyo's are lower ampage, higher voltage panels, so maybe they're set up with lower ampage diodes.

Either way, it should be a worst case scenario situation rather than all the diodes blowing any time 2 strings are connected with one in reverse polarity.

Also, if you test the polarity of the strings before switching the isolator on, then there won't be a problem.

tbh though, you need to be making sure you're labelling up the positive and negative cables properly as you run them as standard, then there shouldn't be this problem anyway.

 

[Coleman]

This relates to the bypass diodes, and tbh, I can't see how it's going to be any different for any other panels, other than maybe that the sanyo's are lower ampage, higher voltage panels, so maybe they're set up with lower ampage diodes.

Either way, it should be a worst case scenario situation rather than all the diodes blowing any time 2 strings are connected with one in reverse polarity.

Also, if you test the polarity of the strings before switching the isolator on, then there won't be a problem.

tbh though, you need to be making sure you're labelling up the positive and negative cables properly as you run them as standard, then there shouldn't be this problem anyway.

Thats a good point thanks!

 

[BBS]

Hello,

Maybe you talk about IEC 61730-2 MST 26.
When there's a short-circuit in a panel (or string cable), all other strings connected to the same junction box will deliver current that becomes reverse in the faulty string.

 

[valet]

Inverter should be able to pick that up? I think Fronius inverters deal with reverse polarity automatically.

 

[BBS]

Hello,

This polarity inversion occurs upstream in the junction box, the inverter cannot deal with.
Even if it occurs between two or more DC inputs of the inverter, the French standards do not recognize electronic protection and require fuses or MCB (that protect only against reverse amperage much greater than string Imp...).

 

[valet]

How the best to protect system from reverse polarity then? I know by marking cables ext....Best solution will be appreciated

 

[Worcester]

That's precisely what string fuses will do. Remember that by their vary nature PV panels are current limiting devices.

 

[Worcester]

On larger arrays it is common practice to include string fuses in the string combiner boxes.
For details and specifications of various string combiner boxes give Andy O'Leary at Sibert a call.

 

[valet]

Thanx boys for that. ...
My system is 10 250w is not that big but it's spread over 3 roofs just don't want mix polarity up. I guess if I mark cables it should help. Cables+/- all black. In worst case scenario what could happen to Panasonic 250w if polarity was wrong when system goes live? Thanx

 

[sedgy34]

It won't work and you could possibly burn out the isolator switch

 

[Worcester]

10 panels in three strinmgs over three roofs - unless your using solaredge or micro-inverters, you'r going to have a problem with start up voltages - what is the proposed string configuration and inverter?

Also please give # of panels, orientation, elevation adn direction of each of the roofs and approx location, and you'll end up with a raneg of design proposals for you to consider!