Too much power

[Ervin R Dilly]

I have 10 panels in series going into a grid tie inverter.My problem is they are producing to many volts for this inverter(MSV 570V)My ? is can I make some of these panels parallel to be able to use them all.All panels are the same.

[Rob Beckers]

What's the maximum input Voltage of the inverter Ervin? Or is that the 570V number you mention? What brand/type are the panels? What's the physical location? The latter matters because panel Voltage goes up as they get colder, so over here we calculate the Voltage for -35 Centigrade (about the same in Fahrenheit), the spec sheet Voltage doesn't count.

If Voltages work out you could do two strings of 5. It depends on those things above though.

-RoB-

[Ervin R Dilly]

ROB,I will try to answer all your?.Tried to upload the picture but I couldnt.Headspace problemName;MX SOLAR,modelMx60-230, Pmax 230 W Vmpp 29.3 V Impp,7.84A Voc 36.8.On 1 ring I disconected 4 panels and getting230 V On string 2 I disconected 3 panels and am getting 320V.This is a clear day and about 48 deg out .Hope this might help.MPPT voltage is 85-550V on the inverter.

[Rob Beckers]

Ervin, those are regular 60-cell panels. Just hook them up as two strings of 5. So two groups of 5 panels, each group of 5 connected in series (positive of one to the negative of the next one, in other words, just click the connectors of 5 panels together). Then connect the two strings of 5 in parallel, so positive to positive, negative to negative. You could use Y-connectors to do that (see https://www.solacity.com/product/multi-contact-mc4-32-0019-pv-azs4/).

That would give you around 180 Volt unloaded, 150 Volt while running under load for the solar array.

-RoB-

[Ervin R Dilly]

Thanks Rob,this is how it is connected now.But is the 150V enough to give me a good return on my input ?My thought was it was better to have more power coming in to produce more going out.Is this wronge thinking?Thanks

[Rob Beckers]

I meant to get back to this yesterday but completely forgot: With 10 panels and an inverter that can do 570V you should be fine connecting them all in series the way they were. I guess your first post threw me off, since you mentioned the Voltage was too high for the inverter, but 10 panels in series won't exceed 440 Volt and that will only be reached on a VERY cold day with the panels you have.

So a single string should be fine. No reason to make it two. If the inverter doesn't work there's something else going on, a string of 10 is well below the maximum input Voltage (if the MPPT range goes up to 570V then it's likely a 600V rated inverter).

-RoB-

[Ervin R Dilly]

Hi Rob,I failed to mention that I have 2 strings of 10 panels each,and if I am correct the inverter can only handle 600V total.Is this correct?Sorry for all the ?s but dont need to lose anouther inverter.

[Rob Beckers]

OK, so it's two strings of 10 connected in parallel then. The inverter can handle 10 panel strings if it can do 600V, you can't destroy it with that.

If you have two inputs in the inverter you'd put each string on its own input. If you only have one input then you parallel them. It is possible that the input current limit of the inverter will kick in and not give you full output (or rather, clip the output power), but you can't destroy the inverter with that either. It will simply limits its input current as needed.

-RoB-

[Ervin R Dilly]

Rob,when I had the panels in excess of 600V.It would give me ARC fault.Would recycle the inverter and things went back to normal for a while,then ARC fault .Called the company and they told me if I put in ti much voltage that it would shut down and give me this fault.I now have finished 2 arrays for each one and I am putting out 180 V per string. which is 360V for the inverter,temp 55 and cloudy.Should this work and be efficient?

[Rob Beckers]

Sounds like you connected strings in series, and not in parallel.

It's not possible to get more than 600 Volt with ten of the 60-cell solar panels as you say you have in a string. The maximum at about -35C (about the same as -35F) would top out at 440 - 450 Volt. We routinely do 13-panel strings of 60-cell panels in a string into a 600V inverter.

In short, something else is going on. The problem isn't 10 panels in a string...

-RoB-

[Ervin R Dilly]

Rob, I agree with you on the string thing but maybe I didnt make myself clear.There is a total of 20 panels going into this inverter.I have 2 separate of 10 panels going in.This inverter can handle 2 inputs.So I think this may help clear this up for you.Sorry for not being that teck,getting to old for this.If I had them in parallel I dont think it would be enough to activate the inverter.Thanks for your help.

[Rob Beckers]

Ervin, as mentioned if you have two inputs it would be one string of 10 per input of course. To be honest, it sounds like you're a bit over your head on this. Why not get a local PV installer to have a look at it? An hour or two of their time would be a good investment.

From what I can tell yours is a very typical and straight forward grid-tie install. With a 600V inverter and 60-cell panels it would be strings of 12 or 13 maximum (depending on panel brand/type), and if you have two inputs you'd use them. Those strings will never exceed the inverter's Voltage rating. Of course inverters can and do break, but it won't be because the string went over-Voltage in a case like this. If you somehow ended up with the two strings in series (i.e. a string of 20 panels) into a 600V inverter that will likely kill said inverter either immediately or on the first cold day when the Voltage goes up.

-RoB-

[Ervin R Dilly]

Ok,thanks for your time ,Rob