Switching in and out panels.

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Switching in and out panels.

Postby APR » Sat May 14, 2016 7:45 am

I have 2 strings of panels rated 8.23 amps Imp, one string at around 30 deg south of due east and one string 30 degree north of due west. I would like to parallel these two strings on one MPPT, however, I often see each string putting out +10 amps so a total of plus 20 amps for two parallel strings, and this would potentially damage the inverter as each MPPT is rated 15 amp input. I want to install another string of panels to the west on the second eastern input.

I am looking at the possibility of either manually switching one of the paralleled strings out during that period of the year when the combined amperage of the two strings will exceed 15 amps, or automatically switching out the lower amps producing parallel string by sensing current using a couple of Hall Effect sensors, and reading the sensors and controlling a couple of adequately rated relays with a small processor.

My reason for wanting to do this is that I am not producing enough solar on some days to meet demand, and I am not always able to fully recharge batteries. I also use a power router to direct excess solar generation to the Immersion element HWS, and unless there is excess solar generation, after running the house and charging the batteries, the HWS doesn't get heated.

Is anyone aware of an existing product that will do what I am after?
2 x Goodwe GW5048D-ES Hybrid inverters, 13kW panels, 20kWh LiFePO4
Mk2 PV Router feeding excess solar generation to a 3.6kW 250 ltr HWS
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Re: Switching in and out panels.

Postby Helipos » Sat May 14, 2016 9:40 pm

APR wrote:I have 2 strings of panels rated 8.23 amps Imp, one string at around 30 deg south of due east and one string 30 degree north of due west. I would like to parallel these two strings on one MPPT, however, I often see each string putting out +10 amps so a total of plus 20 amps for two parallel strings, and this would potentially damage the inverter as each MPPT is rated 15 amp input. I want to install another string of panels to the west on the second eastern input.
?


If your inverter is any good it will simply limit the current drawn to some thermal limit of the unit.

What brand and model is it?

Other wise if you really want you could simple pull the breakers for one set of the panels during spring and put them back in Autumn.
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Re: Switching in and out panels.

Postby APR » Sat May 14, 2016 11:07 pm

Helipos wrote:If your inverter is any good it will simply limit the current drawn to some thermal limit of the unit.

I have had communication with the manufacturer, and they have suggested I don't connect the 7kW of panels I propose to parallel into one MPPT. I am happy to do it when insolation is low, but want to minimise the amps to no more than 15 amps when insolation is high.

What brand and model is it?

The inverter is a Goodwe GD5048D-ES Hybrid.

Other wise if you really want you could simple pull the breakers for one set of the panels during spring and put them back in Autumn.

I would be continuously using all panels through the lower insolation months. Through the high insolation months on sunny days I would like to be able to use all panels up to say 9AM, and after say 4PM, and be able to switch from the east panels to the west panels automatically at midday. But, if it was cloudy or overcame I like the idea of both paralleled strings being connected while the total amps from the paralleled strings is under around 15 amps.
2 x Goodwe GW5048D-ES Hybrid inverters, 13kW panels, 20kWh LiFePO4
Mk2 PV Router feeding excess solar generation to a 3.6kW 250 ltr HWS
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Re: Switching in and out panels.

Postby Tracker » Thu May 19, 2016 7:39 pm

..
BUT - lower insolation months are usually the coldest, andI find that I often get near as much in winter as in summer..
..
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Re: Switching in and out panels.

Postby APR » Fri May 20, 2016 12:50 pm

Tracker wrote:..
BUT - lower insolation months are usually the coldest, and I find that I often get near as much in winter as in summer....


That is not been my situation. If my panels were northern facing panels at the right tilt for winter (which they aren't) I would potentially have a lot higher amperage in winter, however, what I am chasing is a flatter generation, not a higher generation peak in the middle of the day. During summer I see combined amperage from the current panels of over 17 amps at 12:30PM DST, but for this month the best day sees total amperage from both panel strings of under 11 amps at 11:40AM.....

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2 x Goodwe GW5048D-ES Hybrid inverters, 13kW panels, 20kWh LiFePO4
Mk2 PV Router feeding excess solar generation to a 3.6kW 250 ltr HWS
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