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David Gould avatar image
David Gould asked

Can I use a long cable run

I have an easy solar 48/5000 working well with a few panels. I have the option of connecting another 17 panels to it that are on enphase M215 inverters on the back of each of them, the issue is they are 200 meters away and there is no space to move them closer and refit them. If the panels are running flat out i would get about 14 volts drop, would the two devices work together ok like this? The amount of power i would get if the were running flat out is far more than i need, just like to have the extra for the bad solar days. Anyone got any experience they can share?

wiringenphase
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2 Answers
boekel avatar image
boekel answered ·

That's no problem, off course you want to configure as high as possible in voltage (without going over the limit of the MPPT)

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tilo avatar image
tilo answered ·

The 17 Enphase grid inverters will actually raise the AC voltage by 14V at full power on their side of the 200m AC cable. If your Easysolar AC output voltage is 230V and you add 14V you will have 244V at the Enphase inverters. It depends then on the configuration of the Enphase inverters (the country setting) when they disconnect themselves because of high AC voltage of the grid.

I don´t know if those 17 Enphase inverters synchronize when they disconnect at high AC voltage and shut off all together. That might cause some instability in your system if their full power suddenly is missing.

In case each Enphase decides on its own AC voltage measurement to disconnect, it should be a minor problem, because the 17 inverters will have small AC voltage measurement differences, and after one Enphase inverter disconnects, the voltage will drop and the others keep running (till the next one might drop off etc).

In case you see that the Enphase inverters turn off because of high AC voltage, you might reduce a little the Easysolar AC output voltage, or raise the AC high disconnect voltage in the Enphase inverters if you have access to that setting. Or increase the AC cabling.

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David Gould avatar image David Gould commented ·

Tilo, thanks for the reply. My concern was the enphase units disconnecting as enphase say maximum voltage rise should be 2% which means running 35mm cable at a cost of over a grand. Alterative is to use Victron Energy SmartSolar MPPT Charge Controller 250V/100A, a bonus being I like Victron kit!

Have you, or anyone reading, done long runs from panels?

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tilo avatar image tilo David Gould commented ·

I forgot about this point, sorry. It is true, a fast voltage rise can cause the inverters to disconnect. However this could be handled by configuration. In some country settings the inverter startup speed is limited to 10% of Pmax per minute (for example Germany), and with this setting there will not happen a fast voltage rise. If you don´t have access to the Enphase configuration, it might be a problem.

We have done long cable runs to MPPTs, but not that long. If you don´t mind about "official" design rules to not exceed a certain percentage of energy loss in the cable at maximum current, then I don´t see a problem. You said you don´t need the maximum power, just a support in cloudy days. If you use 6 panels in series (you might get another panel to complete the 3rd string of 6), you can use the minimum cable section that supports the current of 25A which might be between 6 mm2 and 10 mm2.

If you are in an area where lightning occurs, you might add a surge protection near the MPPT, and keep the + and - cables as close together as possible, so that the cable loop has the least surface and thus is inducing less voltage at a lightning strike nearby.

The MPPT is easier and better to integrate than grid inverters, no need to configure frequency control etc., it is more stable.

Would be nice if Victron could add a MPPT model with higher PV voltage, like 500 - 600V, or more.

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tilo avatar image tilo tilo commented ·

I assume those are 60-cell PV panels.

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David Gould avatar image David Gould tilo commented ·

yes, 60 cell pv panels. Agree with the higher voltage as well, have used the morning star before but i'm a bit of a victron groupie!! I will be going for the 250/100 mppt victron unit and just suffer the losses as when it is running flat out I'm not too worried about losses.


thanks

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ejrossouw avatar image ejrossouw tilo commented ·

Not standalone, but may be on the cards yet. Here are some key features of the RS 6000:

Built-in solar charge controller with 450V max PV input. Previously the highest max PV voltage of Victron Energy products was 250V. PV specification limits are 450V, 18A in, 4000Wp

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Phil Gavin avatar image Phil Gavin David Gould commented ·

Another option is using an ac-coupled PV inverter at the Victron end.

Their MPPT's range but can be rated up to 1kV. You would experience minimal transmission losses at higher voltages.


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