I am going to increase the output of my system. At present I have 24 ET 185 w panels wired in 8 parallel strings of 3 panels in series. Due to racking considerations I want to add 6 Heliene 72m 310 w panels and rewire to 6 parallel strings of 5 panels in series. Each string would be 4 ETs and 1 Heliene. The ET and Heliene Vmp are 36.29V and 36.77V respectively. I would have to get 2 Classic 250s to permit this configuration. The Imp are 5.11 and 8.43 A respectively. My question is about the amp flow. Does the string amps go to the higher level of the Helienes? Or possibly it is limited by the ETs to the lower amp flow? Maybe it settles out somewhere in between? I am thinking about sizing the fuses for the strings but if the amps does not go to the Heliene lmp rate then I am not going to get the watts out of the panel that it is rated for.
Thanks for any replys.
Will
In a series circuit, the current through each of the components is the same, and the voltage across the circuit is the sum of the voltages across each component. In a parallel circuit, the voltage across each of the components is the same, and the total current is the sum of the currents through each component.
Quote from: WillEert on September 22, 2015, 09:44:34 AM
I am going to increase the output of my system. At present I have 24 ET 185 w panels wired in 8 parallel strings of 3 panels in series. Due to racking considerations I want to add 6 Heliene 72m 310 w panels and rewire to 6 parallel strings of 5 panels in series. Each string would be 4 ETs and 1 Heliene. The ET and Heliene Vmp are 36.29V and 36.77V respectively. I would have to get 2 Classic 250s to permit this configuration. The Imp are 5.11 and 8.43 A respectively. My question is about the amp flow. Does the string amps go to the higher level of the Helienes? Or possibly it is limited by the ETs to the lower amp flow? Maybe it settles out somewhere in between? I am thinking about sizing the fuses for the strings but if the amps does not go to the Heliene lmp rate then I am not going to get the watts out of the panel that it is rated for.
Thanks for any replys.
Will
Hi Will,
When adding PVs:
When adding PVs in SERIES, the Vmp should be within 5%, ideally, and not more than 10% maximum difference. So, if you were adding PVs with that large an Imp difference, you would have the Imp of the PV with the lowest Imp.
For adding PVs in parallel, ideally, one would use a PV with a Vmp within 5% of the other, and not greater than 10% different.
SO, adding those new Heliene PVs in series would seem to be a very poor match, BUT, as an additional parallel string, they would appear to be a very good match.
To add one new PV to each existing string, you should try for a 5% Imp match, IMO.
And, in a perfect world, suppose that if the ETs are Poly, then, the added PVs probably should really be Poly, and the same applies if the ETs are Monos (many would say).
FWIW, Vic
Thanks for the replies to my question. I realized after asking it yesterday that I could wire the new string in parallel which resolves the amp mismatch. It also means I do not have to obtain quite a bit of higher voltage rated BOS equipment which is very good for me. I had been thinking of dc diversion at about 220V into a hot water tank and had not rethought the strings when this proved not possible.
Thanks again.
Will